B6(Cg)-Nr6a1^{tm1c(EUCOMM)Wtsi}/J

Stock number: 023803
Research areas: Research Tools

Description

This mutant strain carries a floxed allele of the Nr6a1 (nuclear receptor subfamily 6, group A, member 1; also called Gcnf) gene. Cre-mediated recombination can be carried out to create a knockout allele in which exon 7, encoding the beginning of the ligand binding domain, is deleted.

Detailed description

Nr6a1 (nuclear receptor subfamily 6, group A, member 1; also called Gcnf) is expressed in fetal ovarian cells, peaking at embryonic day 14.5 (E14.5). Both somatic stem cells and embryonic stem cells require NR6A1 to silence the activities of Pou5f1 (POU domain, class 5, transcription factor 1; also called Oct4) and Nanog (Nanog homeobox) in the transition from pluripotent to differentiated cell state. Interestingly, the gene is not required for this process in fetal ovarian germ cells and it is not required for initiation of meiosis and oogenesis.

Exon 7 of the Nr6a1 gene, encoding the beginning of the ligand binding domain, is flanked by loxP sites in this mutant strain. Homozygous floxed animals are phenotypically normal for gross morphology, behavior, fertility, and viability.

Cre-mediated recombination can be carried out to produce a knockout allele in which exon 7 is deleted. Crosses with tamoxifen-inducible UBC-cre/ERT2 mice (e.g. Stock No. 008085) produce a widespread knockout of the gene. Homozygous knockout embryos die prenatally and display reduced size, impaired neural tube closure, and failure to turn from the lordotic to the fetal position.

Development

This floxed allele of Nr6a1 (called Gcnf) is derived from embryonic stem (ES) cells made by the EUCOMM (European Conditional Mouse Mutagenesis) Project, Wellcome Trust Sanger Institute. The original targeting vector incorporated a cassette containing a splice acceptor (SA) and internal ribosome entry site (IRES) upstream of a lacZ reporter gene followed by a polyadenylation (pA) signal. A selection cassette followed, consisting of a neomycin resistance gene (neo) driven by an autonomous promoter (hBactP) and pA signal. Both cassettes, separated by a loxP site, were flanked by FRT sites within the intron 6 region. Additionally, loxP sites were introduced on either side of exon 7 which encodes the ligand-binding domain. The mutation was created in C57BL/6NTac-derived JM8.F6 embryonic stem (ES) cells. The original targeted allele is reflected in Stock No. 023804.

After Flp-mediated recombination through crosses with ACTB-FLPe mice (e.g. Stock No. 005703), the IRES-lacZ and neomycin cassettes were removed, leaving exon 7 of the gene flanked by loxP sites. This strain was maintained on a C57BL/6NTac genetic background by the donating laboratory. Upon arrival at The Jackson Laboratory, mice were rederived with C57BL/6NJ (see Stock No. 005304)

In 2014, a 32 SNP (single nucleotide polymorphism) panel analysis, with 27 markers covering all 19 chromosomes and the X chromosome, as well as 5 markers that distinguish between the C57BL/6J and C57BL/6N substrains, was performed on the first generation rederived living colony at The Jackson Laboratory Repository. While the 27 markers throughout the genome suggested a C57BL/6 genetic background, 3 of 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating in some mice (chromosomes 8 [~15.2 Mbp], 13 [~41.0 Mbp] and 15 [~57 Mbp]). These data suggest that the mice sent to The Jackson Laboratory Repository were on a mixed C57BL/6J;C57BL/6N genetic background.

Allele

Symbol: Nr6a1^{tm1c(EUCOMM)Wtsi}
Name: targeted mutation 1c, Wellcome Trust Sanger Institute
MGI accession ID: MGI:5510737
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed)
Marker symbol: Nr6a1
Marker name: nuclear receptor subfamily 6, group A, member 1
Chromosome: 2
Strain of origin: C57BL/6N
Molecular note: The L1L2_Bact_P cassette was inserted at position 38743429 of Chromosome 2 upstream of the critical exon 7 (Build GRCm38). The cassette is composed of an FRT site followed by lacZ sequence and a loxP site. This first loxP site is followed by neomycin resistance gene under the control of the human beta-actin promoter, SV40 polyA, a second FRT site and a second loxP site. A third loxP site is inserted downstream of the targeted exon 7 at position 38742577. The critical exon 7 is thus flanked by loxP sites. A "conditional ready" (floxed) allele can be created by flp recombinase expression in mice carrying this allele. Subsequent cre expression results in a knockout mouse. If cre expression occurs without flp expression, a reporter knockout mouse will be created. Further information on targeting strategies used for this and other IKMC alleles can be found at http://www.informatics.jax.org/mgihome/nomen/IKMC_schematics.shtml. Flp-mediated recombination removed the reporter and neomycin resistance cassette and left exon 7 floxed.
General note: Cell line EPD0105_6_D03 was successfully used to make chimeric mice. Germline transmission was accomplished. J:101977