A 1.8kb neomycin resistance cassette replaced parts of exon 2 and 4, all of exon 3, and all of introns 2 and 3. Northern blots of submandibular gland homogenates from homozygous mutant mice showed no detectable full-length Aqp5 transcripts. Immunocytochemistry of the salivary glands from homozygous mutant mice showed no detectable Aqp5 protein. (J:56302)