A novel p.E276K IDUA mutation decreasing α-L-iduronidase activity causes mucopolysaccharidosis type I.

PURPOSE: To characterize the pathogenic mutations causing mucopolysaccharidosis type I (MPS I) in two Thai patients: one with Hurler syndrome (MPS IH), the most severe form, and the other with Scheie syndrome (MPS IS), the mildest. Both presented with distinctive phenotype including corneal clouding. METHODS: The entire coding regions of the α-L-iduronidase (IDUA) gene were amplified by PCR and sequenced. Functional characterization of the mutant IDUA was determined by transient transfection of the construct into COS-7 cells. RESULTS: Mutation analyses revealed that the MPS IH patient was homozygous for a previously reported mutation, c.252insC, while the MPS IS patient was found to harbor a novel c.826G>A (p.E276K) mutation. The novel p.E276K mutation was not detected in 100 unaffected ethnic-matched control chromosomes. In addition, the glutamic acid residue at codon 276 was located at a well conserved residue. Transient transfection of the p.E276K construct revealed a significant reduction of IDUA activity compared to that of the wild-type IDUA suggesting it as a disease-causing mutation. CONCLUSIONS: This study reports a novel mutation, expanding the mutational spectrum for MPS I.

External Quality Assessment Scheme for HIV-1 Drug-Resistance Genotyping in Thailand.

The efficacy of antiretroviral (ARV) therapy can be compromised by the emergence and transmission of HIV-1 drug-resistant strains. HIV-1 drug-resistance (DR) genotypic testing thus plays an important role in the selection of optimal treatment regimens for HIV-infected individuals. Given the complexities of the testing procedures and the variety of approaches used, there is considerable potential for results to vary between laboratories. In Thailand, the national External Quality Assessment (EQA) scheme assesses the DR genotype testing performance of laboratories. Here, we evaluated the performance of laboratories in nucleotide sequencing and compared drug-resistance-associated mutations (DRMs) in the HIV-1 protease (PR) and reverse transcriptase (RT) genes during 2010-2015. The EQA samples in the 12 panels showed predominance for the CRF01_AE (85%) and subtype B (15%). Fourteen laboratory datasets were generated: eight using TruGene (TG), two using ViroSeq (VS), and four using in-house (IH) assays. All IH and VS laboratories had penalty scores <7, whereas five of the eight TG laboratories had fluctuating penalty scores. Moreover, seven and six TG laboratories could not amplify the two identical samples, 10B and 10E samples, or the CRF01_AE. Our findings demonstrate the requirement for laboratory participation in the ongoing EQA program and the optimization of kit assays using CRF01_AE samples. Our results also indicate that one advantage of participation is that the laboratories can monitor and investigate the source of laboratory errors.