The Pik3r1 locus encodes three proteins (p85α, p55α, and p50α) that arise from alternative transcription initiation sites; and all three transcripts share the last nine exons (exons 7-15). A targeting vector was designed to insert an frt-flanked PGK-neo cassette and a loxP site upstream of exon 7, and a second loxP site downstream of exon 7 of the targeted locus. The donating investigator reports that the construct was electroporated into 129S6/SvEvTac-derived TC-1 embryonic stem (ES) cells, and chimeric mice were bred with C57BL/6NCrl mice to generate the colony. At some point, mutant mice were bred with Flp recombinase-expressing mice (Rosa26-FLP on undisclosed genetic background; see Stock No. 003946) to remove the frt-flanked neo cassette. The resulting p85αloxP mice (with single frt site remaining upstream of the floxed exon 7) were bred together to remove the Rosa26-FLP allele. p85αloxP mice on a mixed genetic background (C57BL/6, 129Sv, FVB/N, and maybe others) were sent to The Jackson Laboratory Repository (see additional information below). Upon arrival, mice were bred to C57BL/6J (Stock No. 000664) for at least one generation to establish the p85αloxP colony.
Prior to arrival at The Jackson Laboratory Repository, p85αloxP mice were also bred with Cre recombinase-expressing mice, conditional EGFP-expressing mice, and Pik3r2 mutant mice (Stock No. 012872); this results in the mixed genetic background (C57BL/6, 129Sv, FVB/N, and maybe others). The donating investigator reports that the mice did not harbor Cre recombinase when they were sent to The Jackson Laboratory Repository. Colony managers here at The Jackson Laboratory Repository will assay the mice (and selectively breed away any unwanted mutant alleles, if necessary) to maintain the p85αloxP colony.
