Lck Knockout mouse models

Proximal T cell receptor signaling begins with Lck, the mouse ortholog of human LCK, which encodes a Src-family tyrosine kinase anchored to the inner membrane by amino-terminal myristoylation and palmitoylation, with a unique domain that binds the cytoplasmic tails of Cd4 and Cd8, followed by SH3, SH2, and kinase domains; its activity is set by the balance of activating autophosphorylation at Tyr394 and inhibitory Csk-mediated phosphorylation at Tyr505, which Ptprc and Ptpn22 oppose, and once active it phosphorylates CD3 and zeta-chain ITAMs to recruit and activate Zap70. Nulls are viable but show a severe block at the beta-selection checkpoint, so germline deletion is tractable while conditional alleles isolate peripheral T cell requirements from thymic development. A Tyr505 to phenylalanine knockin creates a gain-of-function receptor-proximal kinase, and analog-sensitive gatekeeper mutants permit acute chemical-genetic inhibition on signaling timescales. Fyn substantially compensates, and only Lck and Fyn compound animals fully ablate proximal TCR signaling.

Lck null animals are straightforward to genotype and phenotype when survival is acceptable. They remain a standard background for pharmacology, biomarker, and rescue studies.