A C1184T transition was inserted into exon 3 to create an A386V substitution in the eighth transmembrane domain. A neo was inserted into intron 2. Northern blot of mutant skin samples indicated that the presence of the neo caused impaired splicing of exon 2 to exon 3, with an abnormal band comprising ~40 and 60% of the total transcript in hetero- and homozygous animals, respectively.