The mutation in jck mice has been identified as a double nucleotide substitution (c.1341G>T and c.1343G>T). While c.1341G>T is a silent mutation in the last base of the leucine codon at position 447, the c.133G>T mutation in the second base of evolutionary conserved glycine codon 448 in the C-terminal domain of the protein results in it changing to valine (p.G448V).