The prune mutation, discovered among G3 progeny of an ENU-mutagenized male mouse, corresponds to a T-to-G transversion at nucleotide position 3938 of the gene (Genbank: NM__021877), in exon 18 of 20 total exons. It results in replacement of a highly-conserved tyrosine by aspartic acid at amino acid 1082 of the protein (Y1082D).