Pik3ca Conditional Knockout mouse models

Pik3ca, the mouse ortholog of PIK3CA, encodes p110 alpha, the class IA PI3K catalytic subunit that heterodimerizes with p85 regulatory subunits and phosphorylates PIP2 to PIP3 downstream of receptor tyrosine kinases and RAS, nucleating PDPK1 and AKT recruitment at the membrane. Oncogenic substitutions cluster in two structural classes with distinct mechanisms: helical domain changes E542K and E545K relieve the p85 nSH2 inhibitory contact, whereas the kinase domain change H1047R alters the membrane-binding interface, and the same alleles cause PIK3CA-related overgrowth spectrum when mosaic. Cre-activated latent knockins such as a lox-stop-lox H1047R allele are therefore standard for modeling dose and timing of activation, kinase-dead knockins isolate lipid kinase output from scaffolding, and conditional nulls test tissue dependence, since germline deletion is embryonic lethal at midgestation. Because p110 beta sustains PIP3 in some lineages, interpret isoform-selective inhibitor studies against compound Pik3ca and Pik3cb genetics.

Tissue restricted knockout of Pik3ca keeps wild type function everywhere else. Breeding is often more robust, and the setup mirrors patient biology where mutations arise in a subset of cells.