The P110*-transgene is a targeting vector designed with (from 5' to 3') a splice acceptor site, a loxP-flanked Neo-STOP cassette, a cDNA sequence encoding P110* (a constituitively active form of mouse P110alpha [Pik3ca; the catalytic subunit of phosphatidylinositol 3-kinase]), an FRT-flanked internal ribosomal entry site-enhanced green fluorescent protein cassette (IRES-EGFP), and bovine polyadenylation signal. This transgene construct was inserted between exons 1 and 2 of the Gt(ROSA)26Sor locus.