B6.129(FVB)-Gabra1^tm1Geh/J

Stock number: 004318
Product name: Gabra-1 floxed
Research areas: Neurobiology Research, Research Tools

Description

These floxed mutant mice possess loxP sites flanking the second transmembrane domain of the Gabra1 gene. This strain may be useful for generating conditional mutations in applications related to development of cerebellar neurons.

Detailed description

These mice possess loxP sites flanking the second transmembrane domain of the gamma-aminobutyric acid (GABA) A receptor, subunit alpha 1 (Gabra1) gene. GABA is an inhibitory neurotransmitter in the nervous system which helps regulate neuronal excitability. Mice that are homozygous for this floxed Gabra1 allele are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities. When used in conjunction with a Cre recombinase-expressing strain, this strain is useful in generating tissue-specific mutants of Gabra1.

For example, when these mice are bred to B6.C-Tg(CMV-cre)1Cgn/J mice (Stock No. 006054) expressing cre in all tissues, the resulting double mutant mice exhibit sex-dependent decreased survival after P19, decreased body mass, EEG spike-wave discharges, and seizures. Heterozygotes display an intermediate decrease in body mass and survival.

In an attempt to offer alleles on well-characterized or multiple genetic backgrounds, alleles are frequently moved to a genetic background different from that on which an allele was first characterized. This is the case for the strain above. It should be noted that the phenotype could vary from that originally described. We will modify the strain description if necessary as published results become available.

Of note, several strains bearing gamma-aminobutyric acid (GABA-A) receptor mutations are available from this donating investigator (Dr. Gregg Homanics, University of Pittsburgh), including Gabra1 (Stock No. 004318), Gabra4 (Stock No. 006874), Gabra6 (Stock No. 002710), Gabrb3 (Stock No. 002711), Gabrd (Stock No. 003725), and Gabrg2 (Stock No. 003137).

Development

A targeting vector was constructed containing a selectable marker cassette (Neo/Tk) flanked by loxP sites. The loxP-flanked cassette was placed approximately 0.6 kb 5' of an exon encoding nucleotides 1307-1509 of the gamma-aminobutyric acid (GABA) A receptor, subunit alpha 1 (Gabra1) gene. A third loxP- site was placed approximately 0.8 kb 3' of the same exon. The construct was electroporated into 129X1/SvJ x 129S1/Sv-derived R1 embryonic stem (ES) cells. Correctly targeted ES cells were transiently transfected with a supercoiled cre expression plasmid for the purpose of removing the selectable marker cassette. ES cells that had successfully undergone Cre recombination and no longer retained the cassette but did retain the loxP-flanked exon (F) were injected in C57BL/6J blastocysts. The resulting chimeric animals were crossed to C57BL/6 mice and subsequently made homozygous (F/F). The homozygotes were bred to an actin-Cre general deleter on an FVB/N genetic background. Selected mice that were heterozygous for the flanked exon (F/+) and lacked the cre transgene were obtained and crossed to C57BL/6 animals.

Allele

Symbol: Gabra1^tm1Geh
Name: targeted mutation 1, Gregg E Homanics
MGI accession ID: MGI:2137418
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed); No functional change
Marker symbol: Gabra1
Marker name: gamma-aminobutyric acid (GABA) A receptor, subunit alpha 1
Chromosome: 11
Strain of origin: (129X1/SvJ x 129S1/Sv)F1-Kitl⁺
Molecular note: A loxP flanked neomycin and thymidine kinase cassette was inserted 5' to sequences corresponding to nucleotides 1307-1509, and a single loxP site was inserted 3' to these sequences. The loxP flanked neomycin selection cassette was removed in ES cells by transient Cre recombinase expression prior to the production of chimeric mice, leaving a single loxP site in place of the cassette.