The mutation has been identified as an G-to-A transition (C-to-T on forward strand) at coding nucleotide position 1456 in exon 8, that results in replacement of glycine with arginine at amino acid position 486 (p.G486R), in the predicted transmembrane domain of the protein. The mutation does not prevent membrane insertion, but it shifts the entire transmembrane region approximately four amino acids toward the N-terminus.