Description

Strain Information

Type Congenic; Targeted Mutation; Transgenic; Additional information on Genetically Engineered Mutant Mice. Species laboratory mouse   Donating Investigator Mark Pook,   Brunel University

Description
Mice that are heterozygous for the targeted allele and hemizygous for the transgene are viable and fertile. High levels of human FXN gene product (mRNA or protein) are detected by RT-PCR and Western blot analysis. 40-50% of the endogenous mouse Fxn gene product (protein) is detected by Western blot analysis in mice heterozygous for the targeted mutation alone. The YG8 transgenic founder carries two tandem copies of the human FXN gene with two GAA triplet repeat sequences of 82 and 190 repeats. Mice that are homozygous for the targeted allele and hemizygous for the transgene exhibit an age dependent, tissue specific expansion of the GAA repeat, with expansion accumulation in the CNS (particularly cerebellum), similar to the human pathology. The GAA triplet repeat exhibits intergenerational instability.

This mutant mouse strain may be useful in studies of Friedreich's Ataxia.

Development
These double mutant mice, heterozygous for the targeted mutation and hemizygous for the transgene, were generated by crossing transgenic mice (founder line YG8) with Fxn^tm1Mkn targeted mutant mice.

Drs. Michel Koenig and Helene Puccio generated the Fxn targeted mutation allele by disrupting exon 4 and flanking sequences with a loxP site flanked PGK-neo cassette. The construct was electroporated into 129/Sv derived embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6J blastocysts. The resulting chimeric animals were crossed to C57BL/6J mice, and then backcrossed to C57BL/6J for 5 generations.

The transgenic construct consisting of a 370kb YAC insert that includes the entire human FXN gene with GAA triplet repeat sequences, was injected into fertilized CBA X C57BL/6 hybrid fertilized oocytes. Founder line YG8 was established, carrying 2 tandem copies of the human FXN gene with two GAA trinucleotide repeat sequences of 82 and 190 repeats. Founder animals were bred to wildtype C57BL/6J mice for 5 generations.

The two lines were then crossed to generate the double mutant. The Donating Investigator breeds mice that are heterozygous for the Fxn^tm1Mkn targeted mutation and hemizygous for the YG8 transgene to mice that are heterozygous for the Fxn^tm1Mkn targeted mutation to obtain mice homozygous for the Fxn^tm1Mkn targeted mutation and hemizygous for the YG8 transgene.

Additional Web Information

Congenic Nomenclature
JAX^® NOTES, Fall 2008; 511. The Jackson Laboratory enters partnership to fight Friedreich's Ataxia.

Phenotype

Phenotype Information

View Mammalian Phenotype Terms

Mammalian Phenotype Terms

      assigned by genotype

The following phenotype information may relate to a genetic background differing from this JAX^® Mice strain.

Fxn^tm1Mkn/Fxn^tm1Mkn Tg(FXN)YG8Pook/0

        involves: 129/Sv * C57BL/6 * CBA

• life span-post-weaning/aging
• *normal* life span-post-weaning/aging (MGI Ref ID J:114840)
  • embryonic lethality seen for Fxn-deficient embryos is recued by transgene expression; normal numbers of offspring are recovered and mice show normal lifespans, surviving to at least 2 years of age
• growth/size phenotype
• increased body weight (MGI Ref ID J:114840)
  • significant increase is observed from 9 months of age
• nervous system phenotype
• *normal* nervous system phenotype (MGI Ref ID J:114840)
  • no neuronal histopathology is detected in cerebellar Purkinje cells or granule cells, and no abnormalities in brain or spinal cord regions are seen
• abnormal action potential (MGI Ref ID J:114840)
  • slight decrease in sensory action potential in 20-months old mice is detected, suggesting a mild progressive sensory neuropathy
• abnormal axon morphology (MGI Ref ID J:114840)
  • at 20 months, some axons in lumbar DRG display swelling and secondary demyelination
• abnormal dorsal root ganglion morphology (MGI Ref ID J:114840)
  • in mice >1 year of age, vacuoles are observed within the DRG in the cervical region
  • 16% of cervical DRG sections display vacuoles
• abnormal lumbar dorsal root ganglion morphology (MGI Ref ID J:114840)
  • prominent, giant vacuoles (round, singular or multiple) are observed in large sensory neuronal bodies of DRG in mice between 6 and 12 months, but not in controls; peripheral margination of nucleus in many large neuronal cell bodies with or without vacuoles
  • 70% of lumbar DRG sections examined have vacuoles
• chromatolysis (MGI Ref ID J:114840)
  • some regions of lumbar DRG are devoid of cytoplasmic organelles at 20 months
• neuron degeneration (MGI Ref ID J:114840)
  • degenerating large DRG neurons are detected, with evidence of oxidative stress and mitochondrial dysfunction
• reduced nerve conduction velocity (MGI Ref ID J:114840)
  • slight decrease in sensory nerve conduction velocity in 20-months old mice is detected, suggesting a mild progressive sensory neuropathy
• behavior/neurological phenotype
• hypoactivity (MGI Ref ID J:114840)
  • mice show a significant decrease in locomotor activity in the open field from 6 months of age
• impaired coordination (MGI Ref ID J:114840)
  • reduced rotarod performance is exhibited by mice from 3 months of age
• cardiovascular system phenotype
• abnormal myocardial fiber morphology (MGI Ref ID J:114840)
  • patches of lipofuscin deposition and lysosymes, with accumulation of dispersed free glycogen disrupt regular arrangement of mitochondria within cardiomyocytes at 20 months
• cellular phenotype
• abnormal aerobic energy metabolism (MGI Ref ID J:114840)
  • mitochondrial respiratory chain function is decreased compared to controls
• oxidative stress (MGI Ref ID J:114840)
  • in 6-9 month old animals, levels of oxidized proteins are increased, most significantly in cerebrum and cerebellum, with other significant increases seen in heart and skeletal muscle
  • increased lipid peroxidation is detected in heart samples
• muscle phenotype
• abnormal myocardial fiber morphology (MGI Ref ID J:114840)
  • patches of lipofuscin deposition and lysosymes, with accumulation of dispersed free glycogen disrupt regular arrangement of mitochondria within cardiomyocytes at 20 months
• homeostasis/metabolism phenotype
• abnormal enzyme/coenzyme activity (MGI Ref ID J:114840)
  • aconitase activity is decreased to <70% of wild-type levels

View Research Applications

Research Applications

This mouse can be used to support research in many areas including:

Mouse/Human Gene Homologs

Neurobiology Research
Ataxia (Movement) Defects
Neurodegeneration

Genes & Alleles

Gene & Allele Information

Allele Symbol		Fxntm1Mkn
Allele Name		targeted mutation 1, Michel Koenig
Allele Type		Targeted (knock-out)
Common Name(s)		Frda-; Frdadel4;
Strain of Origin		129/Sv
Gene Symbol and Name		Fxn, frataxin
Chromosome		19
Gene Common Name(s)		CyaY; FA; FARR; FRDA; Frda; Friedreich ataxia; MGC57199; RGD1565754; X25;
Molecular Note		A loxP-flanked PGK-neomycin resistance cassette replaced a genomic DNA fragment containing exon 4, which is highly conserved and often mutated in humans. An additional line was also produced in which the loxP flanked neomycin cassette was removed by Cremediated recombination, but no distinction was made between these alleles in the original reference. From J:90098: The presence of a human FRDA transgene in hemizygous form in a Frdatm1Mkn homozygous null background rescues the embryonic lethal phenotype and complements for the loss of endogenous mouse frataxin. [MGI Ref ID J:62185]
Allele Symbol		Tg(FXN)YG8Pook
Allele Name		transgene insertion YG8, Mark A Pook
Allele Type		Transgenic (random, expressed)
Common Name(s)		YG8;
Strain of Origin		CBA x C57BL/6
Expressed Gene		FXN, frataxin, human
Promoter		FXN, frataxin, human
General Note		Line YG22 exhibits slightly greater age-related repeat instability, with a bias toward repeat expansion.
Molecular Note		The transgenic construct consists of a 370kb YAC insert that includes the entire human FXN gene with GAA triplet repeat sequences, and was injected into fertilized CBA X C57BL/6 hybrid fertilized oocytes. Founder line YG8 was established, carrying 2 tandem copies of the human FXN gene with two GAA trinucleotide repeat sequences of 82 and 190 repeats. A second line YG22 was also generated. This line showed a reduced transmission rate of 21%. One copy of the FXN gene was detected, and contains a single 190GAA repeat sequence. [MGI Ref ID J:91581]

Genotyping

Genotyping Information

Genotyping Protocols

Fxn^tm1Mkn, STD PCR, vers. 1

Helpful Links

Optimizing PCR Protocols

References

References

Selected Reference(s)

Al-Mahdawi S; Pinto RM; Ruddle P; Carroll C; Webster Z; Pook M. 2004. GAA repeat instability in Friedreich ataxia YAC transgenic mice. Genomics 84(2):301-10. [PubMed: 15233994]  [MGI Ref ID J:91581]

Al-Mahdawi S; Pinto RM; Varshney D; Lawrence L; Lowrie MB; Hughes S; Webster Z; Blake J; Cooper JM; King R; Pook MA. 2006. GAA repeat expansion mutation mouse models of Friedreich ataxia exhibit oxidative stress leading to progressive neuronal and cardiac pathology. Genomics 88(5):580-90. [PubMed: 16919418]  [MGI Ref ID J:114840]

Cossee M; Puccio H; Gansmuller A; Koutnikova H; Dierich A; LeMeur M; Fischbeck K; Dolle P; Koenig M. 2000. Inactivation of the Friedreich ataxia mouse gene leads to early embryonic lethality without iron accumulation. Hum Mol Genet 9(8):1219-26. [PubMed: 10767347]  [MGI Ref ID J:62185]

Additional References

Fxn^tm1Mkn related

Miranda CJ; Santos MM; Ohshima K; Smith J; Li L; Bunting M; Cossee M; Koenig M; Sequeiros J; Kaplan J; Pandolfo M. 2002. Frataxin knockin mouse. FEBS Lett 512(1-3):291-7. [PubMed: 11852098]  [MGI Ref ID J:109164]

Santos MM; Miranda CJ; Levy JE; Montross LK; Cossee M; Sequeiros J; Andrews N; Koenig M; Pandolfo M. 2003. Iron metabolism in mice with partial frataxin deficiency. Cerebellum 2(2):146-53. [PubMed: 12880182]  [MGI Ref ID J:112348]

Sarsero JP; Li L; Holloway TP; Voullaire L; Gazeas S; Fowler KJ; Kirby DM; Thorburn DR; Galle A; Cheema S; Koenig M; Williamson R; Ioannou PA. 2004. Human BAC-mediated rescue of the Friedreich ataxia knockout mutation in transgenic mice. Mamm Genome 15(5):370-82. [PubMed: 15170226]  [MGI Ref ID J:90098]

Health & husbandry

Health & Colony Maintenance Information

Colony Maintenance

Breeding & Husbandry	When maintaining a live colony, these mice can be bred as heterozygotes for the targeted mutation and hemizygotes for the transgene.

Purchasing information

Pricing, Supply Level & Notes, Controls, General Terms & Conditions

 

This strain is currently Under Development for Distribution Colony.
To register your interest in this strain go to the Strain Interest Form.

Estimated Available for Sale Date:

Please note: Estimated available for sale dates are provided to keep customers better informed on strains under development. Please note that our Colony Managers routinely monitor the target date and edit it based on breeding performance and other factors. The length of time it takes to make a new strain available for sale depends on genotype, age, number of animals sent by the Donating Investigator, breeding performance, additional strain development (backcrossing, making homozygous), and anticipated demand for the strain/interest registered.

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Supply Details

Standard Supply	Under Development for Distribution Colony
Supply Notes	This strain is included in the Induced Mutant Resource Colony collection.

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The Jackson Laboratory has rigorous genetic quality control and mutant gene genotyping programs to ensure the genetic background of JAX^® Mice strains as well as the genotypes of strains with identified molecular mutations. JAX^® Mice strains are only made available to researchers after meeting our standards. However, the phenotype of each strain may not be fully characterized and/or captured in the strain data sheets. Therefore, we cannot guarantee a strain's phenotype will meet all expectations. To ensure that JAX^® Mice will meet the needs of individual research projects or when requesting a strain that is new to your research, we suggest ordering and performing tests on a small number of mice to determine suitability for your particular project.

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