STOCK Fxn^tm1Mkn Tg(FXN)YG8Pook/J

Stock number: 008398
Product name: YG8 rescue mice (YG8R)
Strain synonyms: YG8R
Research areas: Mouse/Human Gene Homologs, Neurobiology Research

Description

Mice that are homozygous for the Fxn^tm1Mkn (frataxin) targeted allele and hemizygous for the Tg(FXN)YG8Pook (frataxin, human) transgene, display an age dependent, tissue specific expansion of the GAA repeat, with expansion accumulation in the CNS (particularly cerebellum), similar to the human pathology of Friedreich's Ataxia.

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Detailed 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.

Importation of this model was supported by the Friedreich's Ataxia Research Alliance (FARA).

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-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.

SNP (single nucleotide polymorphism) analysis performed by The Jackson Laboratory revealed that this strain was on a mixed genetic background.

Allele

Symbol: Tg(FXN)YG8Pook
Name: transgene insertion YG8, Mark A Pook
MGI accession ID: MGI:3797739
Generation method: Transgenic
Attributes: Inserted expressed sequence; Humanized sequence
Marker symbol: Tg(FXN)YG8Pook
Marker name: transgene insertion YG8, Mark A Pook
Chromosome: UN
Strain of origin: CBA x C57BL/6
Expressed genes: FXN,frataxin,human
Site of expression: The human FXN YAC transgene contains the promoter and coding regions of human FXN with GAA trinucleotide sequence repeats. Individual strains at The Jackson Laboratory have specific variants of this this transgene. See Detailed Description section for greater detail of transgene insertion site, copy number, GAA repeat values and expression levels.
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. This line displayed a transmission rate of 52% to offspring.
General note: Line YG22 exhibits slightly greater age-related repeat instability, with a bias toward repeat expansion.

Allele

Symbol: Fxn^tm1Mkn
Name: targeted mutation 1, Michel Koenig
MGI accession ID: MGI:2177162
Generation method: Targeted
Attributes: Null/Knockout
Marker symbol: Fxn
Marker name: frataxin
Chromosome: 19
Strain of origin: 129/Sv
Expressed genes: Fxn,frataxin,mouse, laboratory
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 Cre mediated 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 Frda^tm1Mkn homozygous null background rescues the embryonic lethal phenotype and complements for the loss of endogenous mouse frataxin.