Browsing by Author "Pineda, M."
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- Molecular analysis of the GNPTAB and GNPTG genes in 13 patients with mucolipidosis type II or type III - identification of eight novel mutationsPublication . Encarnação, Marisa; Lacerda, Lúcia; Costa, Roberto; Prata, Maria João; Coutinho, Maria Francisca; Ribeiro, Helena; Lopes, Lurdes; Pineda, M.; Ignatius, J.; Galvez, H.; Mustonen, A.; Vieira, P.; Lima, Margarida Reis; Alves, SandraMucolipidosis II (ML II) and mucolipidosis III (ML III) are diseases in which the activity of the uridine diphosphate (UDP)-N-acetylglucosamine:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase (GlcNAc-phosphotransferase) is absent or reduced, respectively. In the absence of mannose phosphorylation, trafficking of lysosomal hydrolases to the lysosome is impaired. In these diseases, mistargeted lysosomal hydrolases are secreted into the blood, resulting in lysosomal deficiency of many hydrolases and a storage-disease phenotype. GlcNAc-phosphotransferase is a multimeric transmembrane enzyme composed of three subunits (alpha, beta and gamma) encoded by two genes -GNPTAB and GNPTG. Defects in GNPTAB result in ML II and III whereas mutations in GNPTG were only found in ML III patients. We have performed a molecular analysis of the GNPTAB and GNPTG genes in 13 mucolipidosis II and III patients (10 Portuguese, one Finnish, one Spanish of Arab origin and one Indian). Mutations were identified by the study of both cDNA and gDNA. The GNPTAB and GNPTG mRNA expressions were determined by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). The study led to the identification of 11 different mutations. Eight of these mutations are novel, six in the GNPTAB gene [c.121delG (V41FfsX42), c.440delC (A147AfsX5), c.2249_50insA (N750KfsX8), c.242G>T (W81L), c.1208T>C (I403T) and c.1999G>T (p.E667X)] and two in the GNPTG gene [c.610-1G>T and c.639delT (F213LfsX7)]. With regard to the mRNA expression studies, the values obtained by qRT-PCR indicate the possible existence of feedback regulation mechanisms between alpha/beta and the gamma subunits.
- Molecular characterization of five patients with homocystinuria due to severe methylenetetrahydrofolate reductase deficiencyPublication . Urreizti, R.; Moya-García, A. A.; Pino-Ángeles, A.; Cozar, M.; Langkilde, A.; Fanhoe, U.; Esteves, C.; Arribas, J.; Vilaseca, M.A.; Pérez-Dueñas, B.; Pineda, M.; González, V.; Artuch, R.; Baldellou, A.; Vilarinho, L.; Fowler, B.; Ribes, A.; Sánchez-Jiménez, F.; Grinberg, D.; Balcells, S.Methylenetetrahydrofolate reductase (MTHFR) plays a major role in folate metabolism. Disturbed function of the enzyme results in hyperhomocysteinemia and causes severe vascular and neurological disorders and developmental delay. Five patients suspected of having non-classical homocystinuria due to MTHFR deficiency were examined with respect to their symptoms, MTHFR enzyme activity and genotypes of the MTHFR gene. All patients presented symptoms of severe central nervous system disease. Two patients died, at the ages of 15 months and 14 years. One patient is currently 32 years old, and is being treated with betaine and folinic acid. The other two patients, with an early diagnosis and a severe course of the disease, are currently improving under treatment. MTHFR enzyme activity in the fibroblasts of four of the patients was practically undetectable. We found four novel mutations, three of which were missense changes c.664G>T (p.V218L), c.1316T>C (p.F435S) and c.1733T>G (p.V574G), and the fourth was the 1-bp deletion c.1780delC (p.L590CfsX72). We also found the previously reported nonsense mutation c.1420G>T (p.E470X). All the patients were homozygous. Molecular modelling of the double mutant allele (p.V218L; p.A222V) revealed that affinity for FAD was not affected in this mutant. For the p.E470X mutation, the evidence pointed to nonsense-mediated mRNA decay. In general, genotype–phenotype analysis predicts milder outcomes for patients with missense changes than for those in which mutations led to severe alterations of the MTHFR protein.