B6.Cg-Pvalb^tm1(cre)Arbr Fxn^em2.1Lutzy/J

Stock number: 030218
Product name: Fxn^null::PV-Cre
Strain synonyms: B6 Pvalb-IRES-Cre;Fxn^null
Research areas: Neurobiology Research, Research Tools

Description

Fxn^null::PV-Cre mice harbor a frataxin global knockout allele and a Pvalb knock-in allele directing Cre recombinase expression to parvalbumin-expressing neurons. These mice are a parental control used to generate the progressive ataxia mouse line Fxn^flox/null::PV-Cre (Stock No. 029721), and may be useful in studying Friedreich's Ataxia.

Mice that are heterozygous for the Fxn^em2.1Lutzy allele and heterozygous or homozygous for the Pvalb^tm1(cre)Arbr allele are phenotypically normal.

Detailed description

The Fxn gene encodes mitochondrial frataxin protein which is involved in mitochondrial iron transport and respiration regulation. Mutations in this gene have been associated with Friedreich's Ataxia. These mice carry the Pvalb^tm1(cre)Arbr allele, expressing Cre recombinase in parvalbumin-expressing neurons, and the Fxn^null (global Fxn knock-out; Fxn^em2.1Lutzy) allele. This double mutant strain is designed to generate mice that are heterozygous for the Fxn^null (global knock-out Fxn) allele with cre expression in parvalbumin-expressing neurons. Mice that are heterozygous for the Fxn^em2.1Lutzy allele and heterozygous or homozygous for the Pvalb^tm1(cre)Arbr allele are phenotypically normal.

Of note, parvalbumin is expressed in sperm. However, characterization of Pvalb^tm1(cre)Arbr (aka Pv^cre or Pvalb-IRES-Cre) mice performed by The Jackson Laboratory Genetic Resource Science group reports no Cre expression in spermatids, and Pvalb^tm1(cre)Arbr did not exhibit germline recombination in multiple crosses from different labs - see Stock No. 017320 Detailed Description for more information.

Development

These Fxn^null::PV-Cre mice (Stock No. 030218) harbor a global null allele of mouse frataxin Fxn^null (Fxn^em2.1Lutzy; from Stock No. 028040) and the PV-Cre knock-in allele Pvalb^tm1(cre)Arbr (Pvalb promoter driving Cre recombinase expression; from Stock No. 017320). 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 knockout 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 knockout allele are available as Stock No. 028040.

The PV-Cre knock-in allele was designed by Dr. Silvia Arber (Friedrich Miescher Institute) to have an IRES-Cre-pA targeting cassette (containing an internal ribosome entry site (IRES), a Cre recombinase coding sequence, a TK-Neo-Hygro sequence and polyadenylation site sequence) inserted into the 3' UTR of exon 5 of the parvalbumin locus (Pvalb).

Allele

Symbol: Pvalb^tm1(cre)Arbr
Name: targeted mutation 1, Silvia Arber
MGI accession ID: MGI:3590684
Generation method: Targeted
Attributes: Recombinase-expressing
Synonyms: (PV-CRE#32)SA-09; Parvalbumin-IRES-Cre; Parv-Cre; Prvlb-CRE; Pv^Cre(Arbr); PV^cre; PV^IRES-Cre; Pvalb^Cre; PVCre; PV-Cre; Pv-ires-Cre
Marker symbol: Pvalb
Marker name: parvalbumin
Marker synonyms: D22S749; PALB1; Parv; PV; Pva
Chromosome: 15
Strain of origin: 129P2/OlaHsd
Expressed genes: cre,cre recombinase,bacteriophage P1
Site of expression: most neurons that express parvalbumin including interneurons in the brain and proprioceptive afferent sensory neurons in the dorsal root ganglia
Molecular note: An IRES-cre-pA cassette was inserted into the 3' UTR of exon 5.

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
Marker synonyms: CyaY; FA; FARR; FRDA; RGD1565754; X25
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.