An EcoRI site in exon 8 was converted to a stop codon and a PGK-neo selection cassette replaced the terminal part of exon 8 along with intron 8. This resulted in loss of the coding region for amino acids 584 - 670 encoding transmembrane segments 4 and 5 and a small part of the putative pore domain. RT-PCR analysis detected a shorter transcript in which all of exon 8 was skipped resulting in a frameshift and stop codon at position 2 of exon 9. Western blot analysis confirmed absence of expression in the submandibular glands of homozygous mice. (J:127118, J:127788)