A gene trap vector pPAT containing intron 1 and the splicing acceptor from Fyn, lacZ-pA, Ampr, PGK-neo and the splicing donor from Fyn was inserted at the 3' end of the endogenous gene. Northern blot of mutant mice indicated no wild-type transcripts present in brain, testis or kidney, but showed evidence of fusion transcripts between the neo and the 3' end of Rab3ip. RT-PCR of mutant kidney and testis confirmed lack of wild-type transcript. (J:29606)