Molecular analysis of the iduronate-2-sulfatase gene in Thai patients with Hunter syndrome.

Molecular defects in the gene encoding the enzyme iduronate-2-sulfatase (IDS) result in Hunter disease (mucopolysaccharidosis type II, MPS II). To determine the molecular basis of MPS II in Thailand, the IDS gene was analysed in 20 Thai patients with Hunter syndrome from 18 unrelated families. A total of 19 different mutations, including 9 missense mutations, 3 nonsense mutations, 3 splice site alterations, 1 deletion, 2 indels, and 1 rearrangement were identified, 8 of which were novel (p.R101C, p.D148V, p.G224A, p.K227E, p.E254X, p.W337X, c.440_442delinsTT and c.720_731delinsTTTCAGATGTTCTCCCCAG). Evaluation of the IDS activity of two hemizygous variants identified in the same patient, p.R101C and p.R468Q, by expression of IDS with the individual mutations in COS 7 cells indicated that only the p.R468Q mutation affected IDS protein activity. Two exonic mutations, c.257C>T (p.P86L) and c.418G>A, were found to activate multiple cryptic splice sites, resulting in aberrantly spliced transcripts. Thus, MPS II in Thailand is caused by a diverse set of defects affecting both IDS protein production and activity.

Molecular characterization of type 3 (neuronopathic) Gaucher disease in Thai patients.

Gaucher disease is an autosomal recessive lysosomal storage disorder due to deficiency of the lysosomal enzyme glucocerebrosidase. Three clinical phenotypes, type 1, nonneuronopathic; and types 2 and 3, acute and subacute neuronopathic are recognized. The incidence of Gaucher disease in the Thai population is unknown, but likely under-diagnosed. We performed molecular analysis in four patients, from three sibships, with type 3 Gaucher disease. Four mutant glucocerebrosidase (GBA) alleles were identified including two novel splice site mutations, IVS6-1G>C and IVS9-3C>G; both are predicted to result in truncated protein products, p.F255fsX256, and p.K464fsX487 and p.S463fsX480, respectively. One patient, homozygous for the L444P point mutation, had a "Norbottnian-like" phenotype, with more severe visceral involvement, kyphosis, barreled chest, and no neurological involvement other than supranuclear gaze palsy. These molecular studies of neuronopathic Gaucher disease will provide additional genotype-phenotype correlation particularly in non-Caucasian population.

Mitochondrial DNA mutations in a patient with sex reversal and clinical features consistent with Fraser syndrome.

We describe a 20-year-old 46,XY woman, with clinical findings of Fraser syndrome and three mitochondrial DNA (mtDNA) mutations of Leber hereditary optic neuropathy. The patient had microphthalmia, blindness, widely spaced nipples, bifid ureter, syndactyly of the toes, and mental retardation. Sonography showed the presence of a uterus and intra-abdominal gonads. The proband was screened for mtDNA mutations because of chronic gastrointestinal pseudo-obstruction, urinary tract dysmotility, seizures, mental retardation and persistent macrocytosis, as well as the intermittent elevation of methylmalonic acid. Analysis of point mutations by multiplex polymerase chain reaction and allele-specific oligonucleotide dot-blot hybridization revealed three homoplasmic mtDNA mutations, T14484C, T4216C, and T3394C. This represents a unique case with sex reversal, Fraser-like syndrome, and mitochondrial disease.