MUCOPOLYSACCHARIDOSIS IVA - 4 NEW EXONIC MUTATIONS IN PATIENTS WITH N-ACETYLGALACTOSAMINE-6-SULFATE SULFATASE DEFICIENCY

We report four new mutations in Japanese patients with mucopolysacchar idosis IVA (MPSIVA) who were heterozygous for a common double gene del etion. A nonsense mutation of CAG to TAG at codon 148 in exon 4 was id entified, resulting in a change of Q to a stop codon and three missens e mutations. V (GTC) to A (GCC) at codon 138 in exon 4, P (CCC) to S ( TCC) at codon 151 in exon 5, and P (CCC) to L (CTC) at codon 151 in ex on 5. Introduction of these mutations into the normal GALNS cDNA and t ransient expression in cultured fibroblasts resulted in a significant decrease in the enzyme activity. V138A and Q148X mutations result in c hanges of restriction site, which were analyzed by restriction-enzyme assay. P151S and P151L mutations that did not alter the restriction si te were detected by direct sequencing or allele specific oligohybridiz ation. Detection of the double gene deletion was initially done using Southern blots and was confirmed by PCR. Haplotypes were determined us ing seven polymorphisms to the GALNS locus in families with the double gene deletion. Haplotype analysis showed that the common double gene deletion occurred on a single haplotype, except for some variation in a VNTR-like polymorphism. This finding is consistent with a common fou nder for all individuals with this mutation.