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Husbandry

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Husbandry

Are there any recommendations on how to maintain aggressive mice?

Some strains of mice are inherently more aggressive than others. Signs of aggression in communally housed mice may range from patchy hair loss and whisker eating to swollen or bloody bite marks, particularly on the ears, tail, back, feet and genital areas. In some instances the wounds are severe enough to cause death of the weaker animal.

Male mice tend to be more aggressive than female mice. Aggression can occur if sexually mature male mice are housed together. If the males have been housed as a group from a young age, aggression is less likely to happen.

If aggression occurs in a cage of males, verify the gender of each animal to make sure that no females have inadvertently been placed in the cage.

The dominant animal in a cage is frequently identified by the lack of fight wounds. Removing this animal may, at least temporarily, resolve the problem. In other cases, individual housing of the animals may be needed to control the situation and avoid harm to the mice. Mice are social animals and ideally they should not be housed singly unless necessary.

Avoid overcrowding, however; consult your facility manager for housing guidelines. A comprehensive study of floor space requirements for young adult male and female C57BL/6J mice conducted at The Jackson Laboratory suggests that 5.6 in 2 (ca. 36 cm 2) per mouse is sufficient for that strain (Smith, 2004). This density is approximately twice that recommended in the Guide for the Care and Use of Laboratory Animals (Institute of Laboratory Animal Resources, 1996), but some recommendations in the Guide are based on professional judgment rather than scientific study. Individual strains may vary in their requirements. Try not to house just two animals in a cage. If several animals are kept together, it can help to diffuse aggressive acts by the dominant animal rather than have it focused on a single subordinate. (Emond, 2003)

Providing environmental enrichment (e.g. nesting materials, NestPaks (WF Fisher and Son, Inc., Somerville, NJ), Shepherd Shacks (Shepherd Specialty Papers, Watertown, TN), etc.) to divert the energies and activities of the animals can also be helpful.

Mice use scent, primarily in urine, to mark territories and establish/indicate dominance. Avoid cross-contaminating dirty litter between cages to avoid stimulating aggression and be aware that scents can be transferred as you handle several consecutive cages. When introducing mice that are unfamiliar with each other, this is best done in clean cage that is new to both animals. Inbred mice of the same gender, bearing the same genetic scent signature, will often get along better than outbred mice or inbred mice of different genetic backgrounds. ( Hurst, 2005).

Very rarely do males show aggression towards litters; they generally assist in parenting. It may be necessary in some cases, however, to remove the male from the cage as soon as the females are visibly pregnant. For some strains, housing two breeding females along with a male can help improve the viability of pups that need to be housed along with an aggressive male. Artificial means of reproduction may provide other options.

References for additional reading:
  • Alopecia in C57BL/6J and Related Strains. JAX Notes #431. 1987 http://jaxmice.jax.org/library/notes/431a.html
  • Ambrose N, Morton DB. The Use of Cage Enrichment to Reduce Male Mouse Aggression. Journal of Applied Animal Welfare Science, 3(2): 117-125. 2000
  • Emond, M et al. Social Conflict Reduction Program for Male Mice. Contemp Topics 42(5):24-26. 2003
  • Hurst, J. Making sense of scents: reducing aggression and uncontrolled variation in laboratory mice. NC3Rs 2:1-8. 2005 http://www.nc3rs.org.uk/downloaddoc.asp?id=230
  • Institute of Laboratory Animal Resources. Guide for the care and use of laboratory animals. National Academy Press, Washington, D.C. 1996.
  • Singleton, G.R., and Hay, D.A. A genetic study of male social aggression in wild and laboratory mice. Behav Genet. 12, 435-448. 1982
  • Smith AL, Mabus SL, Muir C, Woo Y. Effects of housing density and cage floor space on three strains of young adult inbred mice. Comp Med. 55(4):368-76. 2005
  • Smith AL, Mabus SL, Stockwell JD, Muir C.Effects of housing density and cage floor space on C57BL/6J mice. Comp Med. 54(6):656-63. 2004

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Do C57BL/6J (Stock number 000664) mice ever have white hairs in their coat?

C57BL/6J mice will, on occasion, show individual white hairs mixed in their black coat. This is accepted as a strain characteristic and these animals are not culled from our colony. A white tip at the end of the tail is also not uncommon. Animals showing white spotting (larger areas of white hairs) on their bodies would not be considered normal and would be removed from the colony.

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How can I improve the breeding performance of my mice?

Some mice, including the C57BL/6J inbred strain, are very susceptible to environmental stress. Breeding difficulties may be overcome in this strain and others by examining the overall mouse room conditions and trying to minimize exposure to sudden noises, excess handling, and vibrations from equipment in adjoining rooms. Often, extending the light/dark cycle from 12/12 to 14/10 can improve performance.

As well, dietary fat content and nutritional makeup affects the overall health of the mice and also their reproductive performance. The Jackson Laboratory has had success with mice maintained on NIH 31 6% feed from Purina Mills. Another factor to consider is that reproductive performance generally decreases with age. We recommend replacing older breeders (i.e., greater than 8 months of age) with young mice (i.e., 6-8 weeks of age) on a routine basis. If breeder pairs do not produce progeny within 6-8 weeks, try switching males and female pairs. If females are not caring for their young and environmental stress has been minimized, then consider fostering the litter to a proven surrogate mother.

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How can I reduce the amount of variability when measuring glucose values in mice?

Blood glucose levels fluctuate when mice are exposed to changes in their environment. These changes can be acute or chronic. Glucose levels may vary substantially within a group of same-aged mice (± 3 days) and upon repeat sampling of an individual mouse. It is therefore important to minimize the handling stress that mice are exposed to and develop a standardized protocol that decreases variability and allows accurate replication.
The following guidelines may help eliminate some variability in glucose levels.

  • Allow mice to acclimate to the investigator's environment for at least one week, preferably two, prior to glucose sampling. This will allow the mice to recover from any shipping stress (shipping stress can be reduced by utilizing a truck route), and adapt to their new surroundings which may include changes in diet, bedding, mode of water administration, housing density, and health status. It is also helpful to have the new technicians handle the mice periodically prior to sampling.
  • Properly train animal care technicians to allow expeditious sampling. An experienced technician should be capable of sampling blood within 10 seconds of grasping the mouse without causing excessive commotion. It is important to look at the glucose data to determine if there is a pattern of variability depending on the first vs. the last mouse sampled in a cage.
  • Blood samplings should always be done at the same time of day since there are diurnal fluctuations. Most investigators sample glucose levels two to four hours after the onset of the light cycle.
  • Samplings should be done on the same day(s) of the week, as glucose levels may vary depending on the day of the week. Glucose variability across the week is primarily due to changes in what mice are exposed to on any one day (e.g. box changes, weekend vs. weekday traffic in the animal room).

When establishing a protocol as well as comparing glucose values to those reported in the literature, it is important to remember that: (1) plasma glucose values in mice range up to 30% higher than the corresponding whole blood glucose values from the same mice; (2) glucose values vary depending on the amount of fat and sucrose in the diet; slight changes in fat content can have significant effects; (3) glucose values vary depending on how they are analyzed (e.g. glucometer, glucose analyzer, kit); (4) glucose values vary depending on how the sample is drawn (e.g. retro-orbital vs. tail vein sampling  vs. terminal sampling); and (5) glucose values may vary depending on the number of times mice have been serial sampled.

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How can male mice be distinguished from female mice?

The anogenital distance (the distance between the anus and external genitalia) is longer in males (left) than in females (right). Males also have scrotal sacs that contain the testes.

photo courtesy of
Dr. Kathleen Pritchett

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How do you adapt JAX® Mice to automatic watering systems?

JAX® Mice are maintained in a variety of caging systems at The Jackson Laboratory, all of which use bottles as the water source. Some institutions receiving JAX® Mice use automatic watering systems. Most of the time, JAX® Mice adapt to this new system without difficulty. However, in some cases, animal care technicians or researchers may notice rapid weight loss, dehydration, or failure to eat. If mice are not drinking, they tend to stop eating, creating additional problems. It is important to closely monitor all recently received mice to ensure they are adapting to their new environment. Any visible problems need to be corrected quickly to assure the health and well being of the mice. The following are some suggestions for mice experiencing difficulty adjusting to an automatic watering system:

  • Tap the water valve so that a small bead of water forms on the surface. Most mice will find this water and realize that this is their new water source.
  • If mice don't find the watering valve, place a water bottle on the cage or put a small container of water in the bottom of the cage. Alternatively, transfer mice to a cage with a water bottle for a short period of time. After a few days, remove the alternate water source and make another attempt at adapting the mice to the automatic watering system.
  • Place semi-moist food or a gel pack in the cage until the mice locate the water nozzle. Very young or recently weaned mice (i.e., shipped within 24 hours of weaning) may be more prone to experiencing problems adjusting to a new watering system. The ability to adapt may also be strain dependent. For instance, anecdotal evidence suggests that some NZB/BlNJ mice experience difficulty adapting to a new water source.

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How should I foster a litter?

Newborn litters are sometimes fostered onto nursing surrogate mothers for a variety of reasons. The following is a compilation of comments, suggestions and proven techniques that can be used to successfully foster a litter. It is important to note that techniques used to ensure the foster mother will accept the new pups vary and the method that works best may depend upon individual preferences and the reason for fostering.

  • The first step in fostering is the selection of a suitable foster mother. Try to choose a mother that has success- fully weaned a litter in the recent past. For best results it is important to match the age of the litter to be fostered with the age of the foster mother's natural litter. The foster mother's litter should be a different coat color than the litter to be fostered so the pups can be separated at weaning. If, however, the entire natural litter is removed and replaced with the foster litter this is not necessary. Always be sure the foster mother has finished delivering her young before using her as a foster mother because sometimes one or two pups may be born up to 6 hours after the majority of pups are born.

  • It is critical to have the foster litter size equivalent to the natural litter size. If the litter to be fostered is especially large (i.e., more than 10 pups) then the litter may need to be divided and given to two foster mothers. A change in litter size of ± 2 or more pups can affect the milk supply of the foster mother.

    • It is best to keep the foster mother in her cage, remove the natural litter, then add the foster litter to the cage. The foster mother and her foster litter can be transferred to a clean cage the next day. During the first 24 hours, avoid disturbing the foster mother and her new foster litter, but periodically check to ensure that the foster mother is caring for the new litter.

    • An alternative approach to transferring a litter is to remove the entire nest containing the foster mother's natural litter. Place the nest under a heat lamp or some source of heat. Next place the foster litter in the nest, then gently mingle pups from the natural and foster litters together to spread scent. Rub feces from the foster mother on the backs of the foster pups. When the foster mother cleans the foster pups, she will most likely accept the pups as her own. Place the nest with the foster pups back in the cage of the foster mother.

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What animal identification systems can be used for mice? Where can equipment and supplies be obtained?

Identification systems

Several systems are available for individually identifying research mice. Depending on the circumstances, either temporary or permanent methods may be used.

Temporary identification

Several methods are particularly well suited for identifying cage mates. A felt tip marker may be used for marking an ear or tail: such marks usually disappear in 1-2 days. Food coloring may be used to dye a patch of fur: such marks generally last for 1-2 weeks but can be used only on albino and light colored mice. A patch of fur on the back or side of the mouse may be shaved: such marks generally last 1-4 weeks (depending on stage of the hair cycle) and can be used on any color mouse.

Permanent identification

Methods for permanently identifying mice include ear punching, ear tagging, tattooing, and subcutaneously implanting a numerically coded microchip.

Ear punching, commonly used for identification of rodents, involves using a special punch to either produce a small (0.5-2 mm) notch near the edge or to punch a hole in the middle of the ear. The holes and notches are placed according to a predetermined code (Dickie 1975; Ingalis 1980; Stark and Ostrow 1991). Before using an ear punch, it should be tested to make sure it works properly, and the cutting edge should be disinfected. The punched out ear tissue may be sufficient to perform PCR genotyping. Mice do not need to be anesthetized to be ear punched. Ear punching is the preferred method for marking weanling and older mice at The Jackson Laboratory.

Ear tagging involves using a special applicator to place an "earring" or metal tag with an identification number in the pinna of a mouse's ear. Because tags are relatively large and mouse ears develop quickly, ear tagging is suitable only for weanling and older mice. The applicator tip and ear tags should be disinfected before they are used. Ear tags may be troublesome to a mouse, and sometimes they fall or tear out.

Tattooing is the preferred method for identifying neonatal mice. The tattoo is placed on a toe or tail. Tattoos may also be used to mark weanling and older mice. The tattoo is placed on the tail, toe, or ear. While being tattooed, neonatal mice are manually restrained; older mice are either placed in a restraining device or sedated. Before you tattoo a mouse, disinfect its skin and the tattoo needles. Use pigment approved by the United States Food and Drug Administration.

Subcutaneously implanting a microchip is another method of permanently identifying a mouse. Microchips are about the size of a grain of rice and transmit a unique alphanumeric code for each mouse. The codes are easily distinguished from one another by a computer. Because the implants are relatively large, they are not recommended for newborns, but they are acceptable for identifying weanlings and adults. Before being implanted, mice are either sedated or anesthetized. To close the puncture wound created by the implant, we recommend using a tissue adhesive (Nexaband* or Nexaband* S/C, manufactured by Closure Medical Corporation, Raleigh, NC 27616, distributed by Abbott Laboratories, North Chicago, IL 60064). Sutures or wound clips are not recommended. Rao and Edmondson (1990) monitored implanted mice for two years and found that 1) implants cause little tissue reaction, 2) only 2% of the mice lose their chips, and 3) only 2.8% of the chips fail.

Resources for Instruments

Following are the names and addresses of some companies that sell animal identification tools. Other companies may also sell them. Links to non-Jackson Laboratory sites does not represent endorsement by The Jackson Laboratory.

Ear punches

Ear tags (model 1005-1)

  • National Band and Tag Company, 721 York St., PO Box 430, Newport, Kentucky, 41072-0430 (1-800-261-TAGS). (This manufacturer can stamp up to four number-letter combinations on one side of a tag, or a total of six numbers that extend around the bend of the tag.)
  • Kent Scientific Corporation, 1116 Litchfield Street, Torrington, CT 06790

Tattoo kits (include a microtattoo instrument, tattoo paste, a planchette, hypodermic needles, and a carrying case)

Microchips

References

Dickie, MM. 1975. Keeping Records. In: Green EL, editor. Biology of the Laboratory Mouse. New York, New York: Dover Publications; 706 p.

Ingalis, JK. 1980. Introduction to Laboratory Animal Science and Technology. New York, New York: Pergamon Press; 323 p.

Rao GH, J Edmondson. 1990. Tissue reaction to an implantable identification device in mice. Toxicologic Pathology 18:412-16.

Stark, DM and ME Ostrow, editors. 1991. AALAS training manual series, vol 1: assistant laboratory animal technician. Tennessee: Cordova; 186 p.

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What is the best method for establishing timed matings?

For more productive timed matings, it is best to use females that are in estrus. A table explaining how to identify female mice in estrus is included in the following text, as well as in other references.

Manipulating the Mouse Embryo: A Laboratory Manual, 3rd ed.

Andras Nagy, Marina Gertsenstein, Kristina Vintersten, and Richard Behringer. 2003.
Cold Spring Harbor Laboratory Press.
ISBN 0-87969-574-9

In our facility, we set up timed matings in the following manner. Trios (2 females and one male per cage) are established on Monday, and checking for vaginal plugs is performed on each subsequent morning. Since most matings occur at the midpoint of the dark cycle, it is important to check for plugs as early in the morning as possible, before the plugs dissolve. Plugged females are then removed from the cage, and the date noted on the female's new cage card. The day the plug is found is considered to be gestational day 0. Although a vaginal plug is a sign that mating has occurred, it is not a guarantee of pregnancy. There is some variability of the plug:pregnancy rate by strain.

Unplugged females remain with the male until a vaginal plus is identified. As the mouse estrus cycle is 4-6 days long, most of the females should be plugged by the end of the week. Females that are not plugged are removed from the male's cage on Friday morning. Males are given a week to "rest" and will be re-mated the second week.

Recommendations from our technicians for timed matings are:

  1. Mate two females with a male at a time.
  2. Use 8-15 week old females. Younger females are better.
  3. House females together so their estrus cycles will be synchronous, but do not house more than 10 females per cage prior to setting up the mating trios, since group housing females can lead to a suppression of the estrus cycle. Follow your institution's ACUC protocols when establishing cages for the females.
  4. Have the stud males set out in their own cage for at least two weeks prior to mating. Older males are better, use proven males when possible.

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What strategies are recommended for managing allergies to laboratory animals?

Animal care personnel, researchers, and technicians who work with laboratory animals are often at risk of developing allergies. Considered a common and significant occupational disease, laboratory animal allergy (LAA) has been observed to affect as many as one-third of personnel exposed to animals and may lead to serious health consequences if not managed appropriately.

Carolyn Reeb-Whitaker, Senior Research Assistant with The Jackson Laboratory Allergy Research Group, and Fuzz Harrison, Industrial Hygienist at the Laboratory, recently published an overview of LAA that includes recommended strategies and methods to help manage the problem. (Reeb-Whitaker and Harrison, 1999).

Simply put, an allergy can be described as an abnormal sensitivity to a substance (an allergen) that is normally tolerated by exposed individuals and generally considered harmless. Allergic reactions may include contact urticaria (skin redness or itchiness, welts, hives), allergic conjunctivitis and rhinitis (sneezing, itchiness, nasal drainage, nasal congestion), asthma, and the spectrum of anaphylactic reactions.

Allergenic proteins found in common laboratory animals such as mice are present in urine, hair, dander, saliva, and serum. Urine is the most significant source of allergen in the mouse.

Humans are exposed to animal allergens primarily through the air (inhalation) and skin contact. A less common yet significant route of exposure is animal bites (saliva), which can elicit anaphylaxis in hypersensitive individuals. Multiple factors influence the risk of developing LAA including individual genetic susceptibility, and the intensity, duration, and frequency of exposure.

Medical evaluation of employees prior to contact with laboratory animals as well as ongoing medical surveillance, is recommended. Timely screening can identify individuals at higher risk of developing LAA and allow the employer to educate individuals about the risks of LAA and develop a control strategy prior to onset of allergic symptoms. Ongoing medical surveillance is crucial in order to identify individuals who have become allergic, to provide appropriate medical support, and to monitor status. An effective medical surveillance program, coupled with environmental monitoring, is fundamental for characterizing and quantifying the scope (and cost) of the problem.

Employee education and training is an important factor for reducing the risk of allergy development. Once an allergic individual becomes symptomatic, controlling exposure may not be adequate or feasible to manage symptoms. Although only about 10% of allergic individuals develop asthma, people with severe allergic symptoms ultimately may have to be reassigned to new positions which eliminate exposure to animals.

Reducing exposure to animal allergens has proven to reduce symptoms and to decrease the incidence of LAA. The following recommendations include strategies and methods that should be considered for managing LAA and for weighing costs and feasibility against the negative health, morale, and financial impact of LAA.

Personal Protective Equipment and Personal Hygiene
  • Change of clothes prior to entering the animal room and the use of laboratory coats, scrubs, hair bonnets, shoe covers, and gloves.
  • Use of respiratory protection as necessary and appropriate examples include the half-face disposable mask (dust/mist), half-face or full-face mask with HEPA filter, and the air helmet or air hat (powered air-purifying respirator, or PAPR).
  • Shower facilities for workers to use after removing protective equip ment and prior to leaving work.
  • Handwashing after handling any animals and prior to leaving animal room.
Engineering Controls
  • Validation of room ventilation performance for effectiveness in removing airborne contaminants.
  • Use of local exhaust ventilation for cage changing and mouse handling (fume hood, laminar flow cabinet, etc.).
  • Installation of air locks or suitable barriers to separate facility zones (i.e., animal facility, laboratory research, and administrative).
  • Effective humidity control in the animal room.
  • Use of ventilated caging systems to reduce ambient allergen levels.
Administrative Controls and Work Practices
  • Establishment of animal room density limits based on ventilation capacity.
  • Use of filter cage tops for conventional, non-ventilated cages.
  • Implementation of wet cleaning methods (floors, walls, fixtures, equipment, and animal racks) and vacuuming.
  • Reduction of dry-broom sweeping. Minimization of animal transport.
  • Use of covered carriers containing fresh bedding when transporting animals.
  • Alternative bedding (low dust, non-contact, etc.).
  • Implementation of a comprehensive employee education and training program for LAA.
Reference

Authors in bold indicate Jackson Laboratory scientists

  • Reeb-Whitaker CK, Harrison DJF. 1999. Practical management strategies for laboratory animal allergy. Lab Animal 28:25-30.

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What techniques can I use to obtain mouse fetuses of a known gestational age?

The "Ask the Vet" feature answers questions frequently asked of Jackson Laboratory veterinarians and technical support personnel. If you have a question, send it to one of our technical support personnel at micetech@jax.org.

The question in this issue is:

"What techniques can I use to obtain mouse fetuses of a known gestational age?"

Timed pregnancies in mice can be set up in two ways: 1) use vaginal cytology to determine the stage of a mouse's estrous cycle and the appropriate time for mating; and/or 2) check females for vaginal plugs to determine if mating has occurred.

Evaluating vaginal cytology
To obtain a vaginal specimen for determining the stage of the estrous cycle, insert a moistened cotton-tipped swab into the vaginal opening of a manually-restrained mouse. Most commercially available swabs are too large to fit easily into the vaginal opening of an average-sized mouse, but a swab of the appropriate size can be made by wrapping a small amount of sterile cotton wool around the blunt end of a toothpick. Rotate the swab gently but firmly within the mouse's vagina, taking care to maintain contact with the vaginal wall. After removing the swab, wipe it on a clean glass microscope slide to transfer the vaginal specimen to the slide. Allow the slide to air dry, then apply a 0.1% aqueous solution of methylene blue to stain the vaginal material. After the stain dries, examine the specimen under a microscope. The stage of estrous can be determined by the types and relative numbers of cells present:

  • If the mouse is in diestrus, you will see mostly polymorphonuclear leukocytes (PMNs) and some epithelial cells.
  • If the mouse is in proestrus, you will see mostly nucleated and cornified epithelial cells. You will see some PMNs if the mouse is in early proestrus.
  • If the mouse is in estrus, you will see mostly cornified epithelial cells. You may see a few nucleated cells if the mouse is in early estrus.
  • If the mouse is in metestrus, you will see mostly cornified epithelial cells and PMNs and some nucleated epithelial cells.

Both mating and ovulation typically (but not invariably) occur during estrus, which generally occurs approximately six hours after the onset of the dark period and lasts 12-14 hours. For timed breeding, place the female with a male during the proestrus phase. To verify that mating has occurred, check the female for a vaginal plug the next morning (see below).

Checking for vaginal plugs
Although evaluating vaginal cytology is commonly used to determine the best time for breeding in some domestic species (such as dogs), it is not as practical for mice because they have a very short estrous cycle (4-5 days total). A more practical approach for mice is to simply place the male and female together, then check the female early the following morning for a vaginal plug. The plug is made of coagulated secretions from the coagulating and vesicular glands of the male. It generally fills the female's vagina and persists for 8-24 hours after breeding. To see the plug, lift the female by the base of her tail and examine her vaginal opening for a whitish mass. It may be difficult to see, especially if you are less experienced in this procedure. You may see it better if you spread the lips of the vulva slightly with a cotton-tipped swab or the blunt end of a flat toothpick. If there is no plug, leave the female with the male and check her each morning until you see a plug.

If you need large numbers of timed pregnant females, you can take advantage of the influence of pheromones and social factors on the estrous cycle. House the females in large groups with no males nearby. By doing this, diestrus is prolonged and estrus is suppressed, a phenomenon known as the Whitten effect. Because pheromones from male mice can interfere with this effect, olfactory stimulation of the group-housed females by male mice must be prevented. When the females are placed with males (typically 1-3 females per male) the estrous cycle of most females will restart within three days. To identify those that have mated, examine them daily for a vaginal plug.

The presence of a vaginal plug does not guarantee pregnancy: it only indicates that sexual activity occurred. The likelihood of pregnancy after mating varies with the mouse strain and with the phase of the estrous cycle when mating occurs. For most strains, the rate of pregnancy is highest among estrus-suppressed females with vaginal plugs found the third day after being placed with a male. As examples, whereas the rate of pregnancy is ~100% and 44% respectively for C3H/HeJ and BALB/cJ females with plugs found on the third day, it is only 62% and 31% respectively for those with plugs found on the fifth day. In contrast, whereas the rate of pregnancy for C57BL/6J females is only 39% for those with plugs found on the third day, it is 69% for those with plugs found on the fourth day.

If the plugged female is pregnant, the first day of gestation is considered to be the day after the plug is found

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Ordering Mice & Services

Do I need to be a current customer to order JAX® Mice or Services?

The Jackson Laboratory requires all new customers to complete a New Customer Account Form as a condition of receiving mice products and services. This process ensures that customers are billed correctly, agree to our Conditions of Use and General Terms of Sale, and have the appropriate staff and housing to properly care for mice.

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Do you have forms for requesting literature, submitting a new strain, requesting technical help, and placing order requests?

The following online web forms are available for use by customers:

Also available are the following services:

 

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For which strains may I purchase time pregnant females?

Timed pregnant females are only available from the following inbred strains: A/J, AKR/J, BALB/cByJ, BALB/cJ, CBA/J, C57BL/6J, C3H/HeJ, C3HeB/FeJ, DBA/2J, SJL/J.

Identification by vaginal plug, 0 to 10 days of gestation (pregnancy not guaranteed).

Identification by palpation, 11 to 15 days of gestation (pregnancy guaranteed).

To reduce stress, we recommend shipping pregnant mice between the 11th and 15th day of gestation. Shipment methods and delivery timing may limit some options.

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If I receive mice from The Jackson Laboratory, may I send these mice or their progeny to collaborators at another institution or any third party?

Under our Product Use Limitation statement, any recipient of mice from The Jackson Laboratory agrees that the mice and their descendants, if any, will not be bred for sale nor distributed to any third parties outside the recipient's institution and will be used solely for research purposes. Acceptance of mice shall be deemed agreement to these terms.

Occasionally, The Jackson Laboratory allows distribution of JAX® Mice to a third party. A Material Transfer Agreement is required for all such transactions. For information about Material Transfer Agreements call Customer Service at 800.422.MICE or 207.288.5845. Alternatively, you may send your inquiry by e-mail to orderquest@jax.org.

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What information is available on ordering JAX Mice?

The Mice Orders section of this site contains information about:

For specific information about any of the over 3000 unique strains of JAX Mice, see the Strain Information section.

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What information is available on the International Cooperative Relationship with Charles River for supplying JAX® Mice?

In July 2001, The Jackson Laboratory and Charles River Laboratories International, Inc., through its wholly-owned subsidiary Charles River Laboratories, Inc., entered into an international cooperative relationship to supply The Jackson Laboratory's JAX® Mice to biomedical researchers located in European and Pacific Rim countries.

The Jackson Laboratory distributes directly to researchers from any country but strongly encourages researchers in Europe and Asia to order JAX® Mice through Charles River organizations.

More details and information about this agreement are available in the Mice Orders section of this site.

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What is involved in bringing in a strain for distribution by The Jackson Laboratory? What factors affect the time frame from acceptance to distribution?

The process of transferring a strain from a principal investigator’s laboratory to The Jackson Laboratory for distribution is complex. Essentially, three phases are involved: (1) candidate strain submission, review and acceptance; (2) importation, rederivation and genotyping; and (3) colony development, expansion and distribution.

Phase 1: Candidate Strain Submission, Review, and Acceptance

During this phase, investigators interested in donating a new strain submit information on strain characteristics, strain history, breeding performance, and genotyping as well as relevant publications that describe the phenotype and potential research applications. The Genetic Resource Committee at The Jackson Laboratory then reviews the submission and selects specific strains for distribution.

Once a strain has been selected for distribution, The Jackson Laboratory then negotiates any necessary licensing agreements with the originating institution. When all legal issues are resolved, we formally accept the strain. Delays during this phase are primarily due to legal negotiations.

As a final step in phase one, the investigator ships breeder pairs or a few mice to The Jackson Laboratory’s importation facility.

Phase 2: Importation, Rederivation, and Genotyping

Once the mice have been received at The Jackson Laboratory, the mice are transferred into isolators for breeding. Progeny from the original mice sent by the investigator are rederived by either hysterectomy or embryo transfer. The time period required to move mice through this phase depends on the genotype, sex, and number of mice provided as well as the breeding performance and the genotyping method(s) used.

Strains in Phase 2 are categorized as “Under Development - Not Yet Available�. Scientists can register their interest in these strains using a Web-accessible form.

The goal of this phase is to develop a “starter colony� of mice, free of detectable pathogens and with the correct genotype. Prior to moving into the next phase, the starter colony mice must be tested to validate both health status and genotype. Often, genotyping methods must be developed or optimized to confirm the genotype of progeny mice prior to release to breeding colonies. Genotyping methods development can delay release of progeny into the next phase but is absolutely essential in ensuring genetic quality of JAX® Mice.

Other activities that occur during Phase 2 but do NOT delay distribution of the strain

As a standard procedure, we preserve all strains for long term storage by cryopreservation of sperm or embryos. For some selected strains on mixed genetic backgrounds, a few progeny from the starter colonies will be transferred into a backcrossing program to develop congenic strains on stable, inbred genetic backgrounds. The cryopreservation and backcrossing activities are partially supported by the National Institutes of Health and are conducted as services to the research community but do not delay distribution of the strain.

Phase 3: Colony Development, Expansion, and Distribution

Starter colony mice, confirmed as pathogen free and of correct genotype, are then transferred from our importation facility into breeding facilities. During this phase, we optimize strain-specific breeding strategies.

The period of time required to move the strain through this phase depends on the need for developing any specialized husbandry protocols and on the size of a distribution colony needed to meet the anticipated demand. If a large colony is required then the initial progeny are used primarily as breeders to build the colony which can delay distribution by several months. As well, the genotype of mice bred for distribution directly affects the role of colony expansion. Homozygous colonies can be expanded more rapidly than heterozygous colonies.

Once a colony has reached a size to meet anticipated demand and all breeding and quality testing methods are optimized, the strain is released for distribution. Distribution of a new strain is on a first come, first serve basis. Investigators who have registered their interest in a particular strain by contacting our Customer Service Department or by using our on-line new strain interest form are contacted first to allow these individuals to place an order. Following this notification, the new strain will is made publicly available.

Factors Affecting Time Frame

Moving a new strain through these phases typically requires 6 to 12 months. As described above, this process is influenced by several key factors including:

  • The legal restrictions imposed by the originating institution and resultant negotiations.
  • The genotype, sex, and number of mice originally provided by the investigator.
  • The need for methods development, including optimizing a breeding scheme, husbandry protocols, breeding performance, and genotyping.
  • Progeny mortality due to severe or lethal mutations.
The Role of Biology

It is important to consider the biology of the mouse throughout this process. Mice are required to go through several generations of breeding during importation, colony development, and expansion. If an “ideal� female mouse (e.g. a standard, easy-to-breed inbred mouse on a defined genetic background) is bred at 6 weeks of age and gives birth by 9 weeks of age, the progeny will be ready for breeding in another 6 weeks.

In the best case scenario, the absolute minimum amount of time to create a starter colony of mice, based on biology alone, is 12 weeks. However, most cases are not ideal, and the original mice sent by investigators usually need to produce several litters to obtain enough mice, of the correct genotype, for a starter colony. Once a starter colony is transferred into a breeding facility, it is likely that these mice will need to undergo additional generations of breeding prior to distribution. The need for additional generations to build a distribution colony typically adds another three to six months to the strain development and expansion time.

New Technologies

Recognizing the fast pace of modern biomedical research, we continually investigate and assess new options and technologies to accelerate the rate of importing and distributing many new strains as quickly as possible.

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What services does The Jackson Laboratory provide?

JAX® Services are based on our long-standing expertise in successfully breeding laboratory mice under the highest standards of animal health and genetic purity.

Services include:

A full list of services is available at the JAX® Services section of this site.

For over seventy years, scientists at The Jackson Laboratory have been conducting mouse-based biomedical research. As a result, we have accumulated a tremendous wealth of information related to husbandry, genetics and biology associated with selecting and using laboratory mice in research. We also obtain new knowledge as we provide custom mouse breeding and related support services that is used in our research and the development of additional mouse models.

The cumulative knowledge of The Laboratory is shared with researchers around the world through our scientific presentations, technical information services, web-accessible databases, printed literature and publications, and training programs.

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Why is it necessary to specify whether you need individual mice or breeder pairs when placing an order?

Genotypes of individual mice and breeder pairs for transgenic mice and mice with targeted mutations (“knockouts”), and mice with spontaneous mutations are indicated in the JAX® Mice Catalog, Price List and in the JAX® Mice Database.

The genotype of the affected mutant mouse, either homozygote for recessive mutations or heterozygote or hemizygote for semi-dominant and dominant mutations, and transgenics, frequently differs from the genotype of the breeder pair for the same strain. This difference results from the breeding scheme required to produce progeny carrying the desired mutation.

When placing an order, please specify whether you need individual mice for experimental purposes or breeder pairs to propagate the mutation at your facility. This clarification will ensure that you receive mice of the correct genotype for your purposes.

For a small number of strains we are able to provide more than one combination of genotypes to make up a breeder pair. Breeder pairs for the albino 2J strain, C57BL/6J-Tyrc-2J/+ (Stock No. 000058), are offered as heterozygote x homozygote or homozygote x homozygote. The heterozygote x homozygote breeder pair will produce a phenotypically normal littermate control (Tyrc-2J/+). C57BL/6J mice (Stock No. 000664) may be used as controls for the homozygote x homozygote breeder pair. Please specify the desired genotype when placing an order if more than one genotype combination is indicated.

The Jackson Laboratory provides affected mutant mice whenever possible; however, for some mutations, homozygotes die in utero, perinatally, or are too fragile to ship. The individual mouse genotype for these strains is designated “hetero- zygote only-affected mutant not available”. If homozygous mice are required for these strains, the investigator must purchase breeder pairs to produce the affected mutant mice.

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Why is the expected delivery 1 to 3 months for most Level 4 strains?

The Jackson Laboratory functions as a mouse strain repository for the scientific community. The size of a colony is based on customer demand. Level 4 colonies are low demand strains, so they are maintained in small numbers of breeding pairs. This approach enables us to keep more low demand strains as breeding colonies. When researchers order these mice, additional breeding may be required to fill the customer order and to maintain our colony. In addition, many level 4 colonies are not maintained homozygously, and progeny must be genotyped before they can be shipped.

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Will you please provide information on the filters used in the new shipping container?

The Jackson Laboratory is highly committed to both the genetic integrity and the health quality of JAX® Mice. As part of this commitment, we have designed and engineered a state of the art shipping container in response to feedback from our customers. All JAX® Mice are packed in our autoclave sterilized shipping containers within the isolators or barrier facilities in which they are raised. The filters in the shipping containers play an important role in restricting the exposure of mice to undesirable infectious agents in transit. Filters are white spunbond media containing 100% #5 polypropylene, sonic welded to the shipping container for optimum quality and performance.

Physical Properties
Basis Weight: 2.25 oz/sq yd
Nominal Thickness (1 ply): 17 mils
Air Permeability: 125 cfm/sq ft
Mullen Burst: 125 psi
Grab Tensile: MD 45 lbs, CD 40 lbs

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Additional Information

Do you have cross-reference information on former and new gene symbols?

The JAX Mice Catalog contains several useful appendices, and among those is a helpful cross-reference chart of former gene/allele symbols to cloned gene symbols.

This information is available from this Web site in a PDF file (7 pages).

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Do you have definitions for types of JAX Mice (e.g. inbreds, hybrids, transgenics, etc.)?

Refer to the pages below for definitions:

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How do I select the proper 129 strain to use as a control for my knockout created using a 129-derived ES cell line?

In order to choose the best 129 control strain for your knockout, you need to know what ES cell line was used to generate your knockout. The two references listed below contain useful information that can help to determine which 129 strain to use as a control. The Simpson et al. (1997) reference describes the history of 129 substrains and ES cell lines. Catalog numbers for 129 strains are available from The Jackson Laboratory are given as well. The Festing et al. (1999) reference lists the revised nomenclature for 129 substrains.

Simpson EM, Linder CC, Sargent EE, Davisson MT, Mobraaten LE, Sharp JJ. 1997. Genetic variation among 129 substrains and its importance for targeted mutagenesis in mice. Nat Genet 16:19-27. [PubMed: 9140391]

Festing MF, Simpson EM, Davisson MT, Mobraaten LE. 1999. Revised nomenclature for strain 129 mice. Mamm Genome 10:836. [PubMed: 10430671]

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How do I submit my strain for distribution by The Jackson Laboratory?

Submission forms are available at the Genetic Resources Committee web page.

The Genetic Resources Committee (GRC) is an in-house committee that meets monthly. The GRC discuss which submitted strains The Jackson Laboratory should import. Due to the large number of mutants being created and identified by the scientific community, the submission process has become somewhat competitive. Resources permit us to accept only 80 to 100 strains each year.

The major criteria assessed by the Genetic Resources Committee are:

  1. Utility of the strain
  2. Publications
  3. Demand

The GRC depends heavily upon published references. Please include only those publications that actually describe the construction, characterization and use of the mouse. Should you have an in-press/submitted or in-preparation manuscript, please fax it.

The information regarding strain construction, breeding and background strain should be as complete as possible because of the need to supply the same information to researchers interested in the mice.

All materials are treated confidentially. If you should have any additional questions or would like clarification of any of the requested fields on the submission form, please don't hesitate to contact Steve Rockwood:

Stephen Rockwood
Strain Acquisition Coordinator
Induced Mutant Resource
The Jackson Laboratory
600 Main Street
Bar Harbor, Maine 04609 USA
Tel: 207-288-6437
Fax: 207-288-6150

Sponsored Strain Distribution - The Jackson Laboratory offers a convenient way for investigators to distribute their novel mouse strains to the worldwide research community. Through our Sponsored Strain Distribution program, donating investigators pay a low up-front cost to cover the cost of importation, cryopreservation, curation and distribution of their strain. Each donated strain will be cryopreserved and recovered (for quality assurance), assigned a stock number and proper genetic nomenclature, and made available for sale to the public through JAX® Mice literature and our web site.

 

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How much blood can I take from a mouse without endangering its health? How much can I take as a terminal procedure?

The amount of blood you can safely withdraw depends on the size of the mouse, how frequently you sample its blood, and whether or not you give it fluids afterwards. Below are some guidelines for single samples, multiple samples, and exsanguination.

Single sample - Most animals go into shock if 25-30% of their blood volume is rapidly removed; over 50% die if 30-40% is removed; and nearly all die if more than 40% is removed (Walcott 1945; Smith and Hamlin 1977; Waynforth and Flecknell 1992; Kristensen and Feldman 1995). For most species, the blood volume in milliliters is approximately 6-8% of their body weight (BW) in gm, or 55-80 ml/kg BW. However, this relationship varies significantly among species. In general, without fluid replacement, approximately 10% of the total blood volume (0.75% of BW) can be safely removed at one time; with fluid replacement, up to 15% (approximately 1.5% of BW) can be removed (Smith and Hamlin 1977; McGuill and Rowan 1989; Authement 1992; Waynforth and Flecknell 1992).

The average total blood volume of a mouse is about 77-80 ml/kg (0.077-0.080 ml/gm) (Mitruka and Rawnsley 1981; Harkness and Wagner 1989). Without fluid replacement, approximately 0.007-0.008 ml of blood/gm BW can be safely withdrawn (about 0.18-0.2 ml of blood from a 25-gm mouse); with fluid replacement, approximately 0.014-0.016 ml blood/gm BW can be withdrawn (about 0.35-0.4 ml blood from a 25-gm mouse). Generally, replacement fluids are given subcutaneously and should be warmed beforehand.

Multiple samples-If multiple samples must be taken at short intervals, smaller volumes should be removed each time. The issue is not fluid loss: although blood volume is rapidly replaced following acute blood loss (Fettman 1985), other blood components may not be restored for several weeks (Jain 1986; McGuill and Rowan 1989; Waynforth and Flecknell 1992). For this reason, the quantity of blood withdrawn per week should not exceed 7.5% of the total blood volume, or 10% of the total blood volume every two weeks (McGuill and Rowan 1989). Ideally, if a mouse will have large amounts of blood (i.e., approaching the recommended maximum) withdrawn more than three times at intervals of two weeks or less, its hematocrit and/or hemoglobin should be monitored. If deficits are found in these parameters, sampling volume and/or frequency should be reduced.

If samples are withdrawn weekly, approximately 0.006 ml of blood per gm BW can be taken; if withdrawn every other week, approximately 0.008 ml blood/gm BW can be taken. For a 25-gm mouse this corresponds to 0.15 ml per week or 0.2 ml every two weeks. For repeated sampling at intervals of three weeks or less, fluid replacement will not allow safe removal of larger volumes at a time.

To maintain the optimal health and physiological stability of a mouse, blood volume withdrawn (whether repeatedly or only once) should be limited to the lower end of the suggested range. Higher end volumes should be withdrawn only if necessary and only from mice in peak health. The amount of blood that can be safely removed from sick, severely stressed, or otherwise abnormal mice is less (perhaps even below the suggested ranges) than that which can be taken from a healthy, minimally-stressed mouse.

Exsanguination - Under ideal conditions, a skilled person can obtain approximately 50-75% of a mouse's total blood volume (3-4% of BW) by exsanguination. This amounts to 0.04-0.06 ml blood/gm BW, or 1.0-1.5 ml blood from a 25 gm mouse. The best yields are obtained if the blood is removed slowly and steadily so that the heart is kept beating as long as possible. The total volume of blood cells obtained can be increased by giving the mouse fluids during bleeding to maintain its blood pressure. This is best accomplished by using a vascular catheter to alternate between blood withdrawal and fluid administration. (Note: Exsanguination is distressful and should be performed only on anesthetized mice.)

References

Authement JM. 1992. Blood transfusion therapy. In: DiBartola SP, editor. Fluid therapy in small animal practice. Philadelphia: W.B. Saunders Company; 720 p.

Fettman MJ. 1985. Hypertonic crystalloid solutions for treating hemorrhagic shock. Compend Contin Educ Pract Vet 7:915-20.

Harkness JE, Wagner JE. 1989. Biology and husbandry. In: Harkness JE, Wagner JE, editors. The biology and medicine of rabbits and rodents, 3rd ed. Philadelphia: Lea & Febiger; 372 p.

Jain NC. 1986. Schalm's Veterinary Hematology. Philadelphia: Lea & Febiger; 1221 p.

Kristensen AT, Feldman BF. 1995. Blood banking and transfusion medicine. In: Ettinger SJ, Feldman EC, editors. Textbook of veterinary internal medicine, 4th ed. Philadelphia: W.B. Saunders Company; 2145 p.

McGuill MW, Rowan AN. 1989. Biological effects of blood loss: implications for sampling volumes and techniques. ILAR News 31:5-20

Mitruka BM, Rawnsley HM. 1981. Clinical, biochemical and hematological reference values in normal experimental animals and normal humans. New York: Masson Publishing; 413 p.

Smith CR, Hamlin RL. 1977. Circulatory shock. In: Swenson MJ, editor. Dukes' physiology of domestic animals. 9th ed. Ithaca, NY: Cornell University Press; 914 p.

Walcott WW. 1945. Blood volume in experimental hemorrhagic shock. Am J Physiol 143:247.

Waynforth HB, Flecknell PA. 1992. Anesthesia and postoperative care. In: Waynforth HB, Flecknell PA, editors. Experimental and surgical technique in the rat, 2nd ed. LondonL Academic Press; 382 p.

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If I'm reading a reference that mentions C57BL/6 mice, is it safe to assume they are referring to C57BL/6J mice?

The "J" in C57BL/6J is the laboratory code for The Jackson Laboratory. These laboratory codes are added to strain names to indicate the potential for genetic drift that may arise as a result of maintaining colonies independently. If a lab code is not added to the end of a strain name, it is always a good idea to contact the primary investigator for additional information on the source of the animals used in their studies. Laboratory codes are registered with the Institute for Laboratory Animal Resources (ILAR). The ILAR Web site is accessible at: http://dels.nas.edu/ilar.

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What is the impact of the Nnt deletion in C57BL/6J mice? 

The C57BL/6J male mouse has been the paradigm strain for studies of high fat diet-induced obesity (DIO).  A recent report (see abstract below) indicates that this strain's low insulin secretion in response to acute glucose challenge is attributable to a mutation in the NAD nucleotide transhydrogenase gene (Nnt, Chromosome 13).  This finding raises the question as to whether this mutation is a major factor in the strain's high sensitivity to DIO.  This seems unlikely because C57BL/6N, which expresses a wildtype Nnt gene, reportedly is also DIO-sensitive.  Moreover, males of certain other Nnt-intact strains, such as NON/ShiLtJ (formerly NON/LtJ), show even greater DIO responsiveness than do C57BL/6J males.  The Jackson Laboratory currently has a study in progress to compare the DIO responsiveness of C57BL/6J and C57BL/6N males in the same vivarium.

In a general sense, such deletions are often found as a result of intensively studying a mouse strain, especially a strain with a sequenced genome. Likewise, similar mutations or deletions may be found in other B6 sublines once they are sequenced and/or studied with greater rigor.

Reference

Freeman HC, Hugill A, Dear NT, Ascroft FM, Cox RD. 2006. Deletion of nicotinamide nucleotide transhydrogenase: a new quantitive trait locus accounting for glucose intolerance in C57BL/6J mice. Diabetes 55:2153-2156 PubMed: [16804088]

Please contact our Technical Information Services group if you have additional questions or concerns (e-mail: micetech@jax.org or call: 1-207-288-5845.)

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May I purchase B6 (C57BL/6J) embryonic stem (ES) cells from The Jackson Laboratory?

In keeping with the institution's interest in distributing such resources, The Jackson Laboratory has deposited its B6 ES cell line in the National Stem Cell Resource maintained at ATCC. The Stem Cell Resource link is under 'About Us' on the ATCC home page navigation bar, or can be directly accessed at this link.

The specific line submitted to and distributed by ATCC is clonal embryonic stem cell line #693 ES C57BL/6, which was derived from a strain C57BL/6J (B6) mouse blastocyst (BioTechniques publication is attached). Information on ordering that cell line from ATCC is available at:

www.atcc.org/common/catalog/numSearch/numResults.cfm?atccNum=SCRC-1002

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What does the term "hemizygous" mean?

The term "hemizygous" is used synonymously with the term "heterozygous" for mouse transgenes. "Hemizygous" is defined as having unpaired genes in an otherwise diploid cell.

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What information do you have on The Jackson Laboratory's Induced Mutant Resource?

The Induced Mutant Resource at The Jackson Laboratory contains information about JAX® GEMM® strains with transgenes or with targeted (i.e., "knockout") or chemically-induced mutations (NOTE: this strain information is also available in the JAX® Mice Database). This site also has information on submitting new strains and general information on the Induced Mutant Resource.

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What information is available on controls?

Refer to the links below for important considerations when choosing controls for experiments involving mouse types listed below.

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What information is available on disease models?

The JAX® Mice database contains research application information about many of our strains. For a disease area / research area specific view of information & resources, we recommend the Research Models section of this Web site. There you will find information on JAX® Mice that can be used to support research in many areas including apoptosis, cancer, cardiovascular biology, immunology & inflammation, neurobiology, type 1 & type 2 diabetes and several others.

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What is the definition of "Tested" and "Untested" breeder pairs?

For some strains of mice carrying spontaneous mutations, heterozygous breeder pairs are identified by progeny testing rather than DNA typing. Progeny testing involves observing affected pups from breeder pairs of an unverified genotype. Mice proven to be heterozygous by breeding are sold as "tested" breeder pairs and may have produced one or more litters prior to distribution. "Untested" breeder pairs (noted by +/? x +/?) are of unknown genotype; these mice have not been bred prior to distribution. The purchase of more than one breeder pair is recommended to assure carriers of the spontaneous mutation of interest. Both untested and tested breeder pairs should produce progeny, the question is whether or not they produce affected pups. The best strategy for determining the genotype of a mouse with an unknown genotype (+/?) is to mate it to a known heterozygote (+/-) (e.g. mate an untested male or female with a tested male or female). Generally, if no homozygous mutant mice appear within 20 pups, the untested mouse is considered +/+. If an untested breeder pair produced affected mutant mice, then you now have two "tested" breeder pair.

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What is The Jackson Laboratory's Position on Use-Licenses for Mouse Strains?

The Jackson Laboratory makes every effort to accept and distribute mouse strains that are unencumbered by license restrictions. However, some institutions that create genetically engineered strains or that have developed patented technology that is used to create genetically engineered mice require that users obtain use-licenses. To expedite distribution of new strains, we request that users work directly with the institutions requiring licenses to obtain user licenses. Specific patented technologies requiring licenses include the following:

  • “OncoMouse™” Technology (E.I. duPont de Nemours and Company)
  • “Cre-lox” Technology (DuPont Pharmaceuticals Company)
  • “TET-System” Technology (TET Systems Holding).

We also supply M.I.T. originated p53 “knockout” mice (Trp53tm1Tyj), which require: 1) a license from Taconic Farms, which has licensed the Baylor College of Medicine patent (Donehower); and 2) a license from E.I. duPont de Neumors and Company for use of OncoMouse™ Technology. For more information on licensing, please call Customer Service at 800-422-MICE (800-422-6423) or 207-288-5845.

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What is the meaning of "?/+" as a genotype?

For many strains carrying recessive spontaneous mutations, a molecular assay that may distinguish wildtype and heterozygous mice is not used for genotyping. Rather, phenotypic characteristics are used to identify homozygous mutants, and those mice that do not exhibit the phenotype are identified as ?/+, where "+" is the indication for a wildtype allele and "?" indicates that the remaining allele is unknown. A ?/+ mouse may be heterozygous or wildtype at the gene of interest.

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What technical information resources are available?

The Strain Information section of this Web site outlines the technical information resources available with links to information both on this Web site and external sites useful to the scientific community.

For a list of research resources available from The Jackson Laboratory research community, see the Research Resources Web site.

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Where are the genotyping protocols located?

Genotyping protocols are located in the Genetic resources & information section of Research & resource initiatives on this website. You can get there by selecting the Research & resource initiatives drop-down menu from The Jackson Laboratory home page. On that menu, the genetic resources & information link is toward the bottom of the list. Genotyping protocols are located on the resulting page. You can search the protocol list via Stock Number or Gene Symbol.

Direct link to Genotyping Protocols for JAX®Mice

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Where can I find information on mouse strain nomenclature?

Helpful hints for understanding JAX® Mice strain names are available on our web site. See the Mouse Nomenclature Home Page on the Mouse Genome Informatics web site for the complete guides to mouse nomenclature and for additional help understanding gene and strain nomenclature.

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Where can I find information on the major histocompatibility loci carried by JAX Mice strains?

A table which lists both the H2 haplotypes for individual strains and the alleles associated with the loci of the MHC is available on our website.

This chart is also printed in the appendices of the JAX® Mice catalog.

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Why do diagnostic tests for microorganisms sometimes produce false positive results?

Despite rigorous testing and optimization of routine diagnostic serological tests, false positive results may occur. Certain inbred strains (e.g.MRL/MpJ) and mice carrying specific genetic mutations (e.g. lymphoproliferation, Faslpr, and generalized lymphoproliferative disease, Faslgld) are prone to the development of autoimmune disorders making them especially susceptible to misdiagnosis. These strains produce large quantities of autoantibodies that circulate in the blood and produce nonspecific tissue reactions, which often produce false positive results in serological tests.

In addition to serological testing, PCR is becoming more widely used as a diagnostic test method for microorganisms. Although the extreme sensitivity of PCR is often viewed as a test benefit, it also can create ambiguous results. Due to the power and sensitivity of PCR, the validity of test results depends greatly on the availability of appropriate control DNA samples (both positive and negative) for proper interpretation of the results. Although PCR diagnostic tests are becoming more routine in use, many have not been thoroughly evaluated for sensitivity and efficacy in distinguishing different organisms.

The Jackson Laboratory is committed to setting quality standards in animal care and to providing investigators with genetically defined mice of the highest health status. JAX® Mice are extensively monitored using both serological and some PCR methods for a large number of agents. For a complete list please refer to Table 3.1 in our JAX® Mice Catalog or in the Animal Health section of this site. The Jackson Laboratory also supports an ongoing program in optimizing new methods for diagnostic testing.

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Why do some mice have multiple genetic mutations within the same strain?

For a variety of reasons, many of the mice with spontaneous mutations contain multiple genetic mutations within the same strain. In some cases this is because a mutation is propagated with the aid of a mutation affecting coat color. In the strain carrying the diabetes mutation, C57BLKS/J-m +/+ Leprdb(Stock No. 000642), Leprdb is maintained in repulsion with the closely linked coat color marker misty, (m). The mating system used produces three genotypes which are phenotypically distinguishable:

  • + Leprdb/+ Leprdb fat and black
  • m +/+ Leprdb lean and black
  • m +/ m + lean and misty (dark grey)

An example of multiple mutations carried within the same strain is the JE/Le a/a f/f je/+ ru/ru strain (Stock No. 000259). JE/Le mice are homozygous for nonagouti (a) flexed-tail (f), and ruby-eye (ru) but the strain is maintained heterozygous for the neurological mutation, jerker (je).

Most investigators purchase JE/Le mice to study the jerker mutation. The Jackson Laboratory supplies both individual mice homozygous for the je mutation and breeder pairs heterozygous for jerker. These mice will also be homozygous for a, f, and ru mutations.

An investigator interested in the ruby-eye mutation can also order JE/Le mice by the same stock number. The breeder pair would be homozygous for not only the desired ru mutation but would also be a/a f/f and je/+ because all these mutations are inherent in the JE/Le strain.

Strains carrying multiple mutations are listed in our JAX® Mice Catalog under each gene symbol and allele name that is carried in the strain. We have listed the genotype of the individual mouse and breeder pairs for each specific genetic mutation. Please be sure to specify not only the stock number of the strain but also the genetic mutation (by gene symbol) that you desire. This will ensure that you receive mice of the correct genotype.

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Why does The Jackson Laboratory cryopreserve so many mouse strains?

With over 3000 mouse strains available, The Jackson Laboratory does not have enough mouse room space to keep each strain as a live colony. Therefore, the strains with the lowest demand are cryopreserved as frozen embryos and/or sperm.

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Embryo Information - Training

Are there books that may help me learn embryo transfer?

Yes: "Manipulating the Mouse Embryo," available from Cold Spring Harbor Laboratory Press.

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Do you know where I could receive training for thawing straws and transferring embryos?

We highly recommend that you attend an Embryo Handling Workshop. There, you will learn how to thaw and transfer embryos. Furthermore, you will receive additional support when you return to your lab. The workshops are held in May and September at The Jackson Laboratory. See our listing of current courses for more details.

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How will attending an Embryo Handling Workshop help me?

We will teach you how to collect, thaw, and transfer embryos, and we will give you additional help and support when you return to your lab. See our Courses and Conferences Web site for details on upcoming Embryo Handling Workshops.

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Would someone from The Jackson Laboratory talk me through the embryo transfer procedure on the phone?

No. If you need help with transferring embryos, we strongly recommend that you take the Embryo Handling Workshop offered here. See our Courses and Conferences Web site for details.

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Embryo Information - Receiving

Can I use the shipper to store my embryos until I am ready to transfer my embryos?

No. The dry shipper is for transport only. Embryos should be transferred to a permanent storage container immediately.

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Do I need a liquid nitrogen supply at my facility?

Yes. You will need to transfer samples to a permanent storage container.

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We have received a shipper to send our embryos to The Jackson Laboratory. Do we have to fill it with Liquid Nitrogen before sending it?

No. The shipper is pre-charged with liquid nitrogen. Simply put your embryos in the shipper, and make sure the embryo information is attached to it.

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How do I know the dry shipper has not been opened or tampered with in transit?

The security ties, plastic wire ties on the outside and inside catches of the container, should still be in place when the shipper arrives.

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How long can the samples be exposed to air when moving them to a storage vessel from the dry shipper?

No more than 5 seconds for straws and 30 seconds for vials.

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I received a shipper with my samples enclosed, but where is the information about what I received?

An envelope in the lid of the dry shipper contains all the information you need. If it is missing, please email jaxservices@jax.org.

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There is no liquid nitrogen in the shipping container. Will my samples still be OK?

The shipping container is a "dry shipper:" the liquid nitrogen is in the walls. Your samples are quite safe, but move them to a permanent storage container immediately.

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What do I do with the dry shipper when my samples have been removed?

Please return it within 7 days to:

The Jackson Laboratory
Importation / Kurt Christiansen
600 Main Street
Bar Harbor, ME 04609

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Embryo Information - Transfer

Can I culture my embryos before transferring them into the uterus?

We don't recommend it. Transfer them immediately after they thaw.

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Can I get practice embryos from The Jackson Laboratory before I order important strains?

Yes. We can supply practice embryos on request. Email jaxservices@jax.org.

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Do you guarantee that we will recover mice from your frozen embryos?

No. We guarantee that we have successfully recovered all the strains available for sale, but we cannot guarantee that you will have similar results.

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How long can I wait between thawing embryos and transferring them?

Transfer two-cell embryos within an hour of thawing them. You can thaw eight-cell embryos and keep them in a refrigerator for 3-4 hours before you transfer them.

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Is timing critical when thawing embryos?

Yes. You should follow the protocol carefully.

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Should I transfer all the embryos I recover?

If you are not experienced in grading embryos, you should transfer all of them-- even the ones that are not perfect.

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Should I transfer embryos to a 0.5- or a 2.5-day pseudopregnant female?

Transfer 2-, 4-, and 8-cell embryos to a 0.5-day pseudopregnant female. A 2.5-day pseudopregnant female is used for transferring blastocysts.

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Should my facility have a pseudo colony?

Ideally, yes, but you can vasectomize males and start your own.

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If I do not recover any live mice from the practice straws, should I request more practice straws?

Yes. Please do not thaw out any strains received until you have successfully recovered the practice embryos. Email jaxservices@jax.org.

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What media do I need to thaw embryos?

PBS for thawing vials and M2 for thawing straws. You will find the information on our web page, "Cryopreservation Media Preparation."

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What strain do you use for pseudopregnant females?

Many hybrids and outbreds can be used successfully to make pseudopregnant female mice. We use CByB6F1/J (Stock number: 100009) animals.

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Gene Mapping Service

What strains can I use for the mapping cross?

The Jackson Laboratory SNP markers have been tested against 103 commonly used inbred strains. Any of these strains can be used in a mapping cross. We recommend that the two strains used be as unrelated as is practical, to increase the potential marker density. We have pre-established marker panels for some of the more commonly used strain combinations, such as C57BL/6J and 129S1/SvImJ, C57BL/6J and DBA/2J, DBA/2J and BALB/cJ and many more. We can develop new marker panels for other strain combinations as needed.

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How do I determine whether an F2 or an N2 would be used for mapping in my project?

The differences in these two approaches are subtle. Both work well for mapping. If you have a recessive mutation that breeds well and have no major limitation in your mouse box space, you can breed F1xF1 and collect enough F2 animals to get 10 or more affected mice (about 40 offspring, best bred from several F1 intercross mating pairs to assure plenty of affected F2 homozygotes). If box space is limited, and you have a good supply of homozygous mutant parental animals, by producing an N2 (F1 backcrossed to affected parent) about one half instead of one quarter of the offspring will be affected homozygous mutant mice usable for the genome scan. Nevertheless, ultimately more offspring will need to be bred to get the same map resolution.

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How many markers do you look at for the first scan, how many markers for the second scan?

We may use 80-100 markers in the genome wide scan, and then select 4-8 additional markers to refine the position. If higher resolution is requested, we can add more markers in the candidate interval up to the number of markers from our set that are polymorphic with the particular strain combination in your cross.

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If I don't have the total number of samples you suggest (20 for a F2 and 40 for an N2), can you still map my gene?

Yes, though we may not be able to narrow the region as much as we could with the requested number of samples. Please contact us to discuss this situation.

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Should I send you processed DNA or tail samples?

We prefer to prepare DNA from your tail samples. Please send tissues on dry ice, individually labeled with your animal id numbers. If you want to or have already prepared DNA from your mice, we can test your DNA preps in our system, and, if they work well, we can use them for the mapping. Highly purified and correctly quantitated DNA is more likely to work.

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If I extract my own DNA, what method and storage buffer should I use?

A 2 mm tail snip should yield enough DNA for analysis. The Qiagen extraction kit or another comparable extraction method is preferred. The ideal DNA Concentration is ~100-200ng/ul. DNA should be stored in 10mMTrisHCl or ddH20 (Tris EDTA (TE) should NOT BE USED as a storage buffer).

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Why do you request the shipment of all samples for the project at one time?

Shipping all samples at the same time saves you shipping costs and it reduces our costs of processing your samples.

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What types of mapping projects would not be appropriate with this method?

The method for mapping single gene traits will not work if the phenotype is being contributed to by multiple unlinked loci. Another reason for mapping failure would be if multiple similar or related phenotypes are segregating in the cross and being lumped together for mapping. Cases of severely reduced penetrance can also prevent discovery of the underlying gene location. If you need help in determining if any of these issues may be affecting your cross, please inquire before submitting a project.

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Can you identify multi-integrated transgenes?

Please be aware that transgenes can integrate into multiple locations. While we do have the capability to identify a multi-integrated transgene, we will not be able to refine the location of the transgene. If our analysis indicates that the transgene has integrated into multiple locations, we will be sure to contact you immediately.

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When would you recommend additional breeding for a mapping project?

The answer depends on your goal. To simply check to see if the new mutation is likely to be a remutation at a previously known locus or at a novel site, lower resolution may satisfy this need. If you plan to positionally clone or identify the exact sequence change that has caused the mutation, more animals will be needed to generate a higher resolution map. 40 meioses (20 F2 or 40 N2) give a maximum theoretical map resolution of 1/40 or 2.5 cM (roughly equivalent to 5 MB genome wide average). This may be sufficient to rule out previously identified genes and to identify flanking molecular markers that may be useful in future refining of the map position. It is not necessary to have a large number of animals for a single mapping run, as the most useful markers identified on a few animals can always be run later on additional animals as they become available. It is important, however, to set up enough breeding pairs to anticipate future mapping resolution needs.

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