STOCK Brca1^tm1Thl/J

Stock number: 036737
Product name: Brca1^flex2, Brca1^co
Research areas: Cancer Research, Research Tools

Description

Exon 2 of the mouse Brca1 gene, encoding the initiator methionine and part of the RING domain, is flanked by loxP sites in these Brca1^flex2 (Brca1^co) mice. Excision of the floxed region results in the expression of a defective, amino-terminally truncated "RINGless" polypeptide that initiates at methionine residue M90 or M99 (Li, 2016). Targeted inactivation in mammary epithelial cells in females results in the development of mammary tumors that resemble the basal-like triple-negative breast tumors of human BRCA1 mutation carriers (Shakya, 2008).

Detailed description

Exon 2 of the mouse Brca1 gene, encoding the initiator methionine and part of the RING domain, is flanked by loxP sites in these Brca1^flex2 (Brca1^co) mice. Homozygous and heterozygous Brca1^flex2 mice develop normally and are fertile. Excision of the floxed region results in the expression of a defective, amino-terminally truncated "RINGless" polypeptide that initiates at methionine residue M90 or M99; expression levels of the truncated protein are similar to those of wildtype.

Widespread Cre recombinase-mediated deletion of exon 2 results in early embryonic lethality. Female mice that undergo targeted inactivation in mammary epithelial cells (via crosses with Wap-cre mice) are viable, but develop mammary tumors that resemble the basal-like triple-negative breast tumors of human BRCA1 mutation carriers. In one experimental study, 35 tumors appeared in 31 of 33 conditional Brca1/Wap^cre/+ females with a latency of T₅₀ of 512 days. (Shakya, 2008)

Development

An FRT-flanked neomycin cassette and loxP site were introduced to intron 1 and a loxP site was placed in intron 2 of the mouse Brca1 gene via homologous recombination in 129Sv-derived embryonic stem (ES) cells. The neomycin cassette was excised through FlpE recombinase, leaving exon 2, encoding the initiator methionine and part of the RING domain, flanked by loxP sites. Resultant mice were backcrossed to C57BL/6 for 3 generations by the donating laboratory. Upon arrival at The Jackson Laboratory, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).

Allele

Symbol: Brca1^tm1Thl
Name: targeted mutation 1, Thomas Ludwig
MGI accession ID: MGI:3790741
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed); No functional change
Marker symbol: Brca1
Marker name: breast cancer 1, early onset
Chromosome: 11
Strain of origin: 129
Molecular note: An frt-flanked neo cassette with a 3' loxP site was inserted upstream of exon 2 and an additional loxP site was inserted downstream of exon 2. This exon encodes most of the RING finger domain.