ENU mutagenesis induced a T to A transversion in exon 4 that results in the amino acid substitution of asparagine for isoleucine at position 604 (I604N). This mutation, located in the extracellular KL2 domain, is predicted to impair protein stability; in vitro expression analysis in COS-7 cells revealed endoplasmic reticulum retention of the mutant protein. (J:229255)