This phenotypic mutant was identified in an ENU mutagenesis screen at the Baylor College of Medicine. The molecular lesion is a T-to-A transversion mutation in the second dinucleotide of the intron 9 splice donor. Splicing of the normal trancript is reduced to 20-30% and an aberrant transcript using a cryptic site is expressed. While a small amount of wild-type protein is expressed, the aberrent transcript is predicted to express a mutant protein that lacks 2 amino acids from the sixth WD40 repeat. This mutation is hypomorphic.