Eight week old A/J male mice were treated weekly for three weeks with ENU. After several weeks of recovery, mice were crossed to C57BL/6 females with or without a lacZ reporter. Resulting females were backrossed to their fathers and subjected to phenotype screening. A 42 bp insertion was found after exon 63 due to a T to C mutation at the exon 63 distal splice junction. Five amino acids and a stop codon were added and the 33 terminal amino acids were lost.