Mutation analysis and carrier detection of Hunter syndrome

Hunter syndrome, mucopolysaccharidosis type II (MPS II, MIM 309900), is an X-linked lysosomal storage disorder due to a deficiency of iduronate-2-sulfatase (IDS, EC 3.1.6.13) activity. The IDS cDNA sequence and genomic exon/intron sequences have been characterized. In the present investigation, 8 patients with IDS deficiency enzymatically diagnosed by us were used for molecular analysis. Total cellular RNA was isolated from cultured skin fibroblasts and DNA was isolated from cultured skin fibroblasts or leukocytes of the patients and controls. A RT-PCR sequencing method and an exon-by exon PCR amplification of the IDS gene were used for mutation analysis. Six new mutations, from the 8 patients, have been identified: A346V (GCC to GTC) in exon VIII coexistent with T146T silent mutation and a two-nucleotide insertion at codon 423 (CCC to CCCCC) in exon IX coexistent with T146T were found in two patients with a mild Hunter phenotype; S71R (AGC to AGA) in exon II, L279X (TTA to TGA) in exon VI, 406delCT (CTT to --T) in exon IX, and 407delTT (TTT to T--) in exon IX were found in 4 unrelated cases. All mutations detected by RT-PCR sequencing were confirmed by restriction enzyme assay and PCR analysis of the genomic DNA sequence.more » The mutation L279X eliminated an Mse I site from the mutant allele. Carrier detection for this mutation revealed that the mother of the proband was a carrier; however, neither her mother nor any of her sisters were carriers and none of her brothers were affected. We postulate that the mutation probably originated from a germline mutation. Our studies support previous findings that a large proportion of MPS II families result from new mutations. The RT-PCR sequencing and exon-by-exon PCR method has proven to be a practical approach for mutation analysis and carrier detection in families with an affected MPS II.« less