[Genomic analysis of Japanese patients with adult-type metachromatic leukodystrophy]

We performed the genomic analysis of arylsulfatase A (ASA) gene in five Japanese patients with adult-type metachromatic leukodystrophy (MLD) including two sibling cases. Sequencing of amino acid coding region of ASA gene of proband case of family A disclosed 426Pro (CCG)-->Leu (CTG) mutation, which was reported to be frequently found in Caucasian patients with late-onset MLD. We developed mismatch primer PCR/RFLP method for detection of this mutation. If 426Pro-->Leu mutation exists in genomic DNA, Pst I site is newly created by PCR with a 3'-primer mismatched at one nucleotide. Genomic analysis of family A members using this method revealed that younger patient was homozygote of 426Pro-->Leu mutation and patient's parents and her younger brother were heterozygotes, which were confirmed by sequencing of exon 8 of ASA gene. Screening of this mutation using mismatch primer PCR/RFLP method was performed in one sibling case and one autopsy case. This point mutation was found in the sibling case. These results showed the possibility of world-wide spread of 426Pro-->Leu mutation in late-onset MLD patients and usefulness of our mismatch primer PCR/RFLP method for screening of this mutation.