Targeting of the T-cell receptor zeta-chain gene in embryonic stem cells: strategies for generating multiple mutations in a single gene.

The T-cell receptor zeta chain is a member of a family of related proteins that play a critical role in coupling cell-surface receptors to intracellular signaling pathways. To study the role of zeta chain in T-cell ontogeny, we generated targeted mutations of the zeta-chain gene in murine embryonic stem cells. The mutant alleles are predicted to result either in a null phenotype or in the synthesis of a truncated protein capable of supporting T-cell-receptor surface expression but deficient in transmembrane signaling. Both of these targeting events were recovered in a single electroporation experiment with either coelectroporation or a combination deletion/truncation construct. Our results suggest that similar approaches could be used to generate multiple single mutations, modifications of more than one site within a gene, or subtle alterations that rely upon coconversion with the selectable marker gene.