Targeting frequency for deletion vectors in embryonic stem cells.

We analyzed the gene targeting frequencies and recombination products generated by a series of replacement deletion vectors which target the hprt (hypoxanthine phosphoribosyltransferase) locus in mouse embryonic stem cells. We found that the targeting frequency of a 19.2-kb deletion was comparable to that of a 3-kb deletion or a conventional replacement event in which a 1.7-kb fragment was inserted into the locus. We also observed different integration patterns for these deletion vectors. A result of this finding is that a wide range of genomic deletions in embryonic stem cells is feasible.