This is a spontaneous mutation that arose at the Clinical Research Centre. The molecular mutation is a small genomic deletion that removes exons 11-14. RT-PCR and sequencing analysis demonstrated that a shorter transcript that spliced exon 10 to exon 15 was expressed. This in-frame mutant transcript is prediced to encode a protein lacking the majority of the small cytoplasmic loop including a phosphatase motif and the fifth transmembrane domain.