The murine mutation dominant white spotting (W) is in the proto-oncogene, c-kit. The receptor tyrosine kinase encoded by this gene has pleiotropic effects on murine development including hemopoietic cells, pigment cells, and germ cells. In this study, mutation in W homozygous mouse was identified as a single base substitution (GT-AT) at the 5′-splice donor site of the exon which encodes the transmembrane domain. Two types of aberrant exon skipping resulted from this mutation, occurred in a tissue specific manner. Either transcript lost the exon coding for transmembrane region and therefore the product might not be functional for signal transduction. Any unusual cryptic splice sites were not activated by this mutation as betaglobin gene in beta-thalassaemia. In addition, twelve base pair sequence of the 3′-end of the exon prior to the exon coding for transmembrane domain was found to be alternatively spllced. These findings should provide the genetic base for not only the receptor function but the splicing mechanism.