The Jackson Laboratory's Center for New Mouse Models of Heart, Lung, Blood, and Sleep Disorders
JAX® NOTES Issue 503, Fall 2006
The Jackson Laboratory's Center for New Mouse Models of Heart, Lung, Blood, and Sleep (HLBS) Disorders is one of five Programs for Genomic Applications (PGAs) established in September, 2000, by the National Heart, Lung, and Blood Institute to advance functional genomic research. Since its inception in October, 2000, The Jackson Laboratory HLBS Center has enjoyed significant success. This article summarizes some of its accomplishments, benefits to the scientific community, and importance to improving human health.
Producing New Mouse Models of Heart, Lung, Blood, and Sleep Disorders
One of the objectives of the HLBS Center is to develop new mouse models of heart, lung, blood, and sleep disorders. To accomplish this objective, the Center uses a phenotype-driven approach: Instead of seeking to characterize the phenotypic manifestations of known genes, it seeks to understand the genetic basis for known phenotypes. The Center draws its phenotypes from two sources: 1) chemically-induced mutant mice and 2) the 40 widely used and genetically diverse inbred strains of the Mouse Phenome Project (MPP).
The Center generates chemically-induced mutant mice at its mutagenesis facility, using N-ethyl-N-nitrosourea (ENU) and C57BL/6J (B6) mice as the mutagen and strain of choice. ENU is well tolerated by mice and causes point mutations at a high rate. Specifically, it makes "A" DNA bases look like "G" bases, causing them to pair with "C" bases instead of with "T" bases. These mistakes are perpetuated with each DNA replication, potentially affecting the functions of mutated genes. The mutations partly or completely delete a gene's function, augment its function, or make it perform an opposing function. The B6 strain was chosen because it is healthy, widely used, and well characterized.
The Center's mutagenesis protocol is designed to capture ENU-induced point mutations in a population of third generation (G3) mutants on a B6 background. Briefly, B6 males are mutagenized to produce G0 males, which then become infertile for about 10 weeks. When they are fertile again, G0 males are mated to B6 females to produce G1 mice, each representing one mutated genome containing 30-60 mutations. G1 males are mated to B6 females to produce G2 mice. G2 females are mated to their G1 grandfathers to produce G3 mice. Except at the ENU-induced point mutations, the G3 mutants are coisogenic to B6 mice.
Once G3 mice are produced, they are efficiently and systematically screened for heart, lung, blood, and sleep disorders. The state-of-the art, non-invasive, high throughput screen (designed by Jackson Laboratory scientists) is the first robust method for non-invasively assessing sleep patterns in mice.
When phenotypically deviant G3 mice are detected, they are tested for heritability and mode of inheritance. Although many mutagenesis facilities screen only for dominant mutations, the HLBS Center mutants are screened for both recessive and dominant mutations (view procedural details). To date, the Center has established heritability of deviants for the following phenotypes: hypertension, leukocytosis, thrombocytopenia, tachycardia and bradycardia, low HDL, high HDL, hypocholesterolemia, hypercholesterolemia, low fibrinogen, hyperglycemia, obesity, and low bone density.
In addition to establishing and distributing live lines of new mutants, the Center cryopreserves embryos, extracts and makes DNA available from, and maps as many of the alleles responsible for each mutant line as possible.
Publishing and Distributing Information and Mutants
The Center publishes its protocols and results on its Web site. Mutants are posted for distribution as soon as heritability is confirmed and lines are established. Posted information for each mutant includes date of birth, sex, phenotype description, chromosomal location and inheritance pattern (if known) of the mutation, and availability. New mutants are available to the public for the cost of shipping only. Instructions for ordering are on the Center's Web site.
To date, the Center has identified 400 phenotypic deviants, 80 of which have been proven heritable. Approximately 180 lines are maintained at three stages of development: not yet proven heritable, heritable and available to ship, heritable and in the process of being mapped.
Mapping the Mutant Alleles Responsible for Heart, Lung, Blood, and Sleep Disorders
The Center maps as many of the alleles that underlie the pathophysiology of the mutants as possible. To accomplish this, it analyzes the progeny of F2 intercrosses between a mutant and an inbred strain in which the average value of the phenotype of interest differs from that of the mutant by greater than two standard deviations. So far, it has mapped loci associated with the following phenotypes: leukocytosis (two), neutrophilia, thrombocytopenia (two), leucopenia (two), high cholesterol, low HDL (two), hyperglycemia, low fibrinogen, and obesity. For more detailed information about these mutants and a "Mapped Mutant Matrix" view this link.
In a related endeavor, the Center constructs and publishes phenotype-specific genome maps. These are graphic representations of all quantitative trait loci (QTLs) and candidate genes currently associated with cardiovascular, respiratory, sleep, obesity, and related phenotypes. So far, it has published mouse QTL maps for several phenotypes, including hypertension, atherosclerosis susceptibility, HDL cholesterol levels, LDL cholesterol levels, and triglyceride levels. View these maps. Many of the maps are linked to resource tables that include chromosome locations, mouse crosses, statistical significances, and references for each QTL. The Center has also constructed and published tables of human QTL data for the same phenotypes. Other QTL maps and linked tables are forthcoming.
Comprehensively Characterizing the Heart, Lung, Blood, and Sleep Phenotypes of the Mouse Phenome Strains
A second source of the Center's phenotypes is the panel of Mouse Phenome strains. As a participant in the Mouse Phenome Project (MPP), the Center is in the process of comprehensively characterizing the heart, lung, blood, and sleep phenotypes of these strains. This is allowing scientists to choose the strains most appropriate to cross for identifying QTLs associated with cardiovascular, respiratory, and related phenotypes. HLBS and MPP participants have already characterized coagulation, heart rate, blood pressure, electrocardiogram, plasma lipid, atherosclerosis susceptibility (pathogen-accelerated and pathogen-free), airway hyperreactivity, and related phenotypes for some or all Phenome strains. Their data are published and publicly accessible in the Mouse Phenome Database (MPD). Additionally, the Center has carried out QTL crosses for baseline peripheral blood counts, HDL levels, and disordered sleep.
Providing Educational and Training Opportunities to the Scientific Community
Another of the Center's objectives is to provide the scientific community with training and education opportunities through courses and workshops. One of the most successful of these is the highly acclaimed "Genetic Approaches in Complex Heart, Lung, and Blood Diseases" course. Two others include the "Short Course on Complex Trait Analysis" and the "Workshop on Phenotyping New Mouse Models for Heart, Lung, Blood, and Sleep Disorders." Details on content and registration for these courses can be found at The Jackson Laboratory Courses and Conferences Web site.
The HLBS Center has improved The Jackson Laboratory's Visiting Investigator Program (VIP) by inviting outside investigators to the Laboratory to 1) collaborate with Laboratory scientists to conduct heart, lung, blood, and sleep research and 2) enhance the Laboratory's research environment. A particularly successful program involved Dr. Cecilia Lo of the National Heart, Lung, and Blood Institute. Over a four-year period, two of Dr. Lo's postdoctoral fellows performed non-invasive fetal ultrasound in over 10,000 mouse fetuses in the HLBS Center's barrier facility. They found many mutants, each with at least one major congenital cardiovascular defect. The alleles for these defects are in the process of being mapped, and the underlying genes will be identified shortly thereafter (seven mutations have already been mapped, and two novel functional mutations identified). The project has revealed that a wide range of human congenital cardiovascular anomalies have a genetic basis. For more details about and instructions for applying to the Center's VIP, see the Center's Web site.
In summary, the new research tools provided by the HLBS Center are accelerating the pace and improving the quality of cardiovascular, respiratory, and related research. As the similarities between mice and humans become increasingly more evident, the applications of these tools should greatly improve human health.
The Director of The Jackson Laboratory HLBS Center is Luanne Peters, Ph.D. Component Principal Investigators are: Karen Svenson, M.S., Phenotyping and Mutagenesis; Beverly Paigen, Ph.D., QTL analysis; Carol Bult, Ph.D., Bioinformatics; John Macauley, Ph.D., Education; Gary Churchill, Ph.D., Statistical Analysis; and Molly Bogue, Ph.D., Director of the Mouse Phenome Database.
References of Interest
Chu V, Otero JM, Lopez O, Morgan JP, Amende I, Hampton TG. 2001. Method for non-invasively recording electrocardiograms in conscious mice. BMC Physiol 1:6.
Galante RJ, Metaxes D, Lu S, Lian J, Zhang L, Pack AI. 2003. Can direct digital video analysis of mice be used as a non-invasive high throughput phenotyping strategy to estimate durations of sleep and wake? Sleep 26:A418.
Peters LL, Lambert AJ, Zhang W, Churchill GA, Brugnara C, Platt OS. 2006. Quantitative trait loci for baseline erythroid traits. Mamm Genome 17:298-309.
Peters LL, Cheever EM, Ellis HR, Magnani PA, Svenson KL, Von Smith R, Bogue MA. 2002. Large-scale, high-throughput screening for coagulation and hematologic phenotypes in mice. Physiol Genomics 11:185-93.
Svenson KL, Bogue MA, Peters LL. 2003. Identifying new mouse models of cardiovascular disease: a review of high-throughput screens of mutagenized and inbred strains. J Appl Physiol 94:1650-9.
