A stop codon was introduced at position 292 to shorten the protein by 7 residues, 2 of which are in the essential domain. Expression and sequence analysis showed message to be transcribed and processed properly in homozygous mutant mice. RT-PCR analysis revealed levels of transcript to be approximately 15% of those in wild-type mice. Further analysis showed that transcription of the antisense gene was unaffected by the targeting event. (J:41161)