A large 13,080 bp deletion begins at nucleotide 1616 in intron 10 and extends to nucleotide 1959 in the 3' downstream sequence beyond exon 18. Exon 10 is then spliced to a cryptic "exon 11M" 4213 bp downstream of the deletion breakpoint. Exon 11M is, in turn, spliced to a second cryptic "exon 12M" located 830 bp downstream of exon 11M. The resulting 1724 nucleotide transcript is predicted to code for a 457 amino acid mutant protein.