Sequence analysis on RT-PCR products of mRNA revealed that exon 21 was spliced to exon 23 in frame. The entire coding sequence of exon 22 was absent in mice homozygous for the av6J allele. Protein encoded by this allele would be lacking the extracellular cadherin protein domain due to the loss of 47 amino acids. An allelism test confirmed that the mutation was a new mutation of Pcdh15.