A spontaneous C-to-T mutation was identified that is a single base pair substitution in exon 4 generating a nonsense mutation in which the glutamine at amino acid 87 is mutated to a premature stop codon (Q87X) and results in a truncated protein lacking 18 amino acids at its C terminus. The mutation occurred spontaneously on a mixed background consisting of 129S6/SvEvTac, C57BL/6 and DBA/2. (J:271219)