A 1.1 kb sequence containing 365 bp upstream of the predicted translational start site of exon 1 and 696 bp downstream of the exon 1 splice donor site was replaced with a PGKneo selection cassette. The deleted sequence was common to both known transcripts. Northern blot of mutant brains suggested that the allele may not have been a null as overexposure to probes demonstrated transcripts at ~7% of wild-type levels. (J:72166)