This phenotypic mutant was identified in an ENU mutagenesis screen at the Baylor College of Medicine. A T-to-A point mutation occurs two base pairs after exon 6, resulting in alteration of a consensus splice donor sequence. RT-PCR and sequencing showed that the mutation results in aberrant splicing of the transcript. A noncomplementation test with a knockout allele confirmed that the mutation in this gene is responsible for the mutant phenotype.