B6.Cg-Fxn^em2.1Lutzy Tg(Ckmm-cre)5Khn/J

Stock number: 029100
Product name: Fxn^null::MCK-Cre
Research areas: Cardiovascular Research, Developmental Biology Research, Neurobiology Research, Research Tools

Description

Fxn^null::MCK-Cre mice harbor a frataxin global knock-out allele and a cardiac/skeletal muscle-specific Cre recombinase transgene. When heterozygous for Fxn^null and hemizygous or homozygous for MCK-Cre, these double mutant mice are "phenotypically normal" and are a parental control used to generate the progressive cardiomyopathy mouse line Fxn^flox/null::MCK-Cre (Stock No. 029720) - which is useful in studying Friedreich's Ataxia.

Detailed description

Fxn^null::MCK-Cre mice harbor a frataxin global knock-out allele Fxn^null (Fxn^em2.1Lutzy) and the MCK-Cre transgene (Tg(Ckmm-cre)5Khn) that has Cre recombinase expression directed to cardiac and skeletal muscle. When heterozygous for the Fxn^null allele and hemizygous or homozygous for the MCK-Cre transgene, these double mutant mice are "phenotypically normal" and only used as a parental strain to generate the early-onset cardiomyopathy model of Friedreich's Ataxia, Fxn^flox/null::MCK-Cre (Stock No. 029720).

When singly heterozygous for the frataxin global null allele, mice are viable and fertile with normal lifespan. Mice homozygous for the frataxin global null allele are embryonic lethal - regardless of presence or absence of the MCK-Cre transgene.

When singly hemizygous or homozygous for the MCK-Cre transgene, mice are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities.

Development

These Fxn^null::MCK-Cre mice (Stock No. 029100) harbor a global null allele of mouse frataxin Fxn^null (Fxn^em2.1Lutzy; from Stock No. 028040) and the MCK-Cre transgene with the Ckmm promoter driving Cre recombinase expression (Tg(Ckmm-cre)5Khn; from Stock No. 006475). Each component is described below.

The frataxin floxed exon 2 allele Fxn^flox (Fxn^em2Lutzy) was made by Dr. Cat Lutz at The Jackson Laboratory using CRISPR/cas9 endonuclease-mediated genome editing. Plasmids encoding a signal guide RNA designed to introduce loxP sites flanking exon 2 in the Fxn gene and the CRISPR/cas9 nuclease were introduced into the cytoplasm C57BL/6J-derived fertilized eggs with well recognized pronuclei. Correctly targeted embryos were transferred to pseudopregnant females. Correctly targeted pups were identified by sequencing and PCR. Mice from founder 466 were further bred to C57BL/6J inbred mice (Stock No. 000664) to develop the frataxin floxed exon 2 colony as Stock No. 028520.

To generate the global knock-out allele Fxn^null (Fxn^em2.1Lutzy), male mice carrying the floxed exon 2 allele (from Stock No. 028520) were bred to female B6N.Cg-Tg(Sox2-cre)1Amc/J (Stock No. 014094). The resulting mice (exon 2 deleted from germline) were further bred to C57BL/6J to breed out the Cre recombinase transgene. Heterozygous intercrosses were performed to confirm the embryonic lethality of the null allele. Mice heterozygous for this frataxin global knock-out allele are available as Stock No. 028040. Fxn^null mice from Stock No. 028040 were used to generate Stock No. 029100.

The Tg(Ckmm-cre) transgene (MCK-Cre) was designed by Dr. C. Ronald Kahn (Joslin Diabetes Center) to have a Cre recombinase cDNA sequence (with a SV-40 large T antigen nuclear localization signal and polyA signal) inserted in place of the translation initiation site of the Ckm gene. C57BL/6-congenic MCK-Cre line 5 mice from Stock No. 006475 were used to generate Stock No. 029100.

Allele

Symbol: Tg(Ckmm-cre)5Khn
Name: transgene insertion 5, C Ronald Kahn
MGI accession ID: MGI:2182095
Generation method: Transgenic
Attributes: Recombinase-expressing
Marker symbol: Tg(Ckmm-cre)5Khn
Marker name: transgene insertion 5, C Ronald Kahn
Chromosome: UN
Strain of origin: FVB
Expressed genes: cre,cre recombinase,bacteriophage P1
Site of expression: skeletal and cardiac muscle
Molecular note: A 6.5 kb genomic DNA fragment of the Ckmm gene containing the promoter and enhancer 1, untranslated exon 1, 3kb of intron 1 including the enhancer 2 region, and the first 16 bp of exon 2 drives expression of a modified cre with an SV40 large T antigen nuclear localization signal. Expression is directed to the heart and skeletal muscle.

Allele

Symbol: Fxn^em2.1Lutzy
Name: endonuclease-mediated mutation 2.1, Cathy Lutz
MGI accession ID: MGI:5825278
Generation method: Endonuclease-mediated
Attributes: Null/Knockout
Marker symbol: Fxn
Marker name: frataxin
Chromosome: 19
Strain of origin: C57BL/6J
Site of expression: Cardiac and skeletal muscle.
Molecular note: CRISPR/Cas9 genome editing was used to introduce loxP sites flanking exon 2. Cre-mediated recombination removed exon 2.