The sequence at the intron exon boundary between intron 14 and exon 15 was modified from TCTCCCCACAG GCA TCC CGA CGC to TCTCCAG ACA GGC ATC TAG GCGC. These nucleotide substitutions alter the splice acceptor site and result in amino acid substitutions plus the formation of a stop codon that prevents the translation of the remaining 43 amino acids. 90% of transcripts utilize the alternative splice acceptor site while 10% utilize the endogenous splice acceptor site and produce full-length transcripts.