An 841 bp deletion spans from the proximal promoter region into intron 1. A 41 bp insertion, of which the first 39 bp are a duplication of intron 1 sequence downstream of the deletion site, takes the place of the deleted sequence. The deleted exon 1 contains the translation start site. RT-PCR indicates that aberrant transripts, containing intron 1 sequence, are transcribed from this allele.