G - Genética
Permanent URI for this community
Browse
Browsing G - Genética by Issue Date
Now showing 1 - 10 of 19
Results Per Page
Sort Options
- Genes, Crianças e Pediatras IVPublication . Soares, G.; Pimentel, I.; Dias, C.; Pinto-Basto, J.; Martins, M.; Fortuna, A.; Reis-Lima, M.
- Genes, Crianças e Pediatras IIIPublication . Dias, C.; Soares, G.; Pinto-Basto, J.; Fortuna, A.; Martins, M.; Reis-Lima, M.; Fonseca, F.
- Genes, Crianças e Pediatras IIPublication . Pinto-Basto, J.; Soares, G:; Dias, C.; Martins, M.; Fortuna, A.; Barbot, J.; Reis-Lima, M.
- Genes, Crianças e PediatrasPublication . Soares, G.; Dias, C.; Martins, M.; Fortuna, A.; Reis-Lima, M.; Álvares, S.
- Genes, Crianças e Pediatras 2005 IIPublication . Dias, C.; Martins, M.; Rocha, M.; Soares, G.; Pinto-Basto, J.; Gonçalves, S.; Carrilho, I.; Fortuna, A.; Reis-Lima, M.
- A nonsense mutation in the LIMP-2 gene associated with progressive myoclonic epilepsy and nephrotic syndromePublication . Balreira, A.; Gaspar, P.; Caiola, D.; Chaves, J.; Beirão, I.; Lima, J.; Azevedo, J.; Miranda, M.Abstract The main clinical features of two siblings from a consanguineous marriage were progressive myoclonic epilepsy without intellectual impairment and a nephrotic syndrome with a strong accumulation of C1q in capillary loops and mesangium of kidney. The biochemical analysis of one of the patients revealed a normal beta-glucocerebrosidase activity in leukocytes, but a severe enzymatic deficiency in cultured skin fibroblasts. This deficiency suggested a defect in the intracellular sorting pathway of this enzyme. The sequence analysis of the gene encoding LIMP-2 (SCARB2), the sorting receptor for beta-glucocerebrosidase, confirmed this hypothesis. A homozygous nonsense mutation in codon 178 of SCARB2 was found in the patient, whereas her healthy parents were heterozygous for the mutation. Besides lacking immunodetectable LIMP-2, patient fibroblasts also had decreased amounts of beta-glucocerebrosidase, which was mainly located in the endoplasmic reticulum, as assessed by its sensitivity to Endo H. This is the first report of a mutation in the SCARB2 gene associated with a human disease, which, contrary to earlier proposals, shares no features with Charcot-Marie-Tooth disease both at the clinical and neurophysiological levels.
- Expanding the MTM1 mutational spectrum: novel variants including the first multi-exonic duplication and development of a locus-specific databasePublication . Oliveira, J.; Oliveira, M.; Kress, W.; Taipa, R.; Melo-Pires, M.; Hilbert, P.; Baxter, P.; Santos, M.; Buermans, H.; den Dunnen, J.; Santos, R.Myotubular myopathy (MIM#310400), the X-linked form of Centronuclear myopathy (CNM) is mainly characterized by neonatal hypotonia and inability to maintain unassisted respiration. The MTM1 gene, responsible for this disease, encodes myotubularin - a lipidic phosphatase involved in vesicle trafficking regulation and maturation. Recently, it was shown that myotubularin interacts with desmin, being a major regulator of intermediate filaments. We report the development of a locus-specific database for MTM1 using the Leiden Open Variation database software (http://www.lovd.nl/MTM1), with data collated for 474 mutations identified in 472 patients (by June 2012). Among the entries are a total of 25 new mutations, including a large deletion encompassing introns 2-15. During database implementation it was noticed that no large duplications had been reported. We tested a group of eight uncharacterized CNM patients for this specific type of mutation, by multiple ligation-dependent probe amplification (MLPA) analysis. A large duplication spanning exons 1-5 was identified in a boy with a mild phenotype, with results pointing toward possible somatic mosaicism. Further characterization revealed that this duplication causes an in-frame deletion at the mRNA level (r.343_444del). Results obtained with a next generation sequencing approach suggested that the duplication extends into the neighboring MAMLD1 gene and subsequent cDNA analysis detected the presence of a MTM1/MAMLD1 fusion transcript. A complex rearrangement involving the duplication of exon 10 has since been reported, with detection also enabled by MLPA analysis. It is thus conceivable that large duplications in MTM1 may account for a number of CNM cases that have remained genetically unresolved.
- Phenotypic and functional consequences of haploinsufficiency of genes from exocyst and retinoic acid pathway due to a recurrent microdeletion of 2p13.2Publication . Wen, J.; Lopes, F.; Soares, G.; Farrell, S.; Nelson, C.; Qiao, Y.; Martell, S.; Badukke, C.; Bessa, C.; Ylstra, B.; Lewis, S.; Isoherranen, N.; Maciel, P.; Rajcan-Separovic, E.Background Rare, recurrent genomic imbalances facilitate the association of genotype with abnormalities at the “whole body” level. However, at the cellular level, the functional consequences of recurrent genomic abnormalities and how they can be linked to the phenotype are much less investigated. Method and results We report an example of a functional analysis of two genes from a new, overlapping microdeletion of 2p13.2 region (from 72,140,702-72,924,626). The subjects shared intellectual disability (ID), language delay, hyperactivity, facial asymmetry, ear malformations, and vertebral and/or craniofacial abnormalities. The overlapping region included two genes, EXOC6B and CYP26B1, which are involved in exocytosis/Notch signaling and retinoic acid (RA) metabolism, respectively, and are of critical importance for early morphogenesis, symmetry as well as craniofacial, skeleton and brain development. The abnormal function of EXOC6B was documented in patient lymphoblasts by its reduced expression and with perturbed expression of Notch signaling pathway genes HES1 and RBPJ, previously noted to be the consequence of EXOC6B dysfunction in animal and cell line models. Similarly, the function of CYP26B1 was affected by the deletion since the retinoic acid induced expression of this gene in patient lymphoblasts was significantly lower compared to controls (8% of controls). Conclusion Haploinsufficiency of CYP26B1 and EXOC6B genes involved in retinoic acid and exocyst/Notch signaling pathways, respectively, has not been reported previously in humans. The developmental anomalies and phenotypic features of our subjects are in keeping with the dysfunction of these genes, considering their known role. Documenting their dysfunction at the cellular level in patient cells enhanced our understanding of biological processes which contribute to the clinical phenotype.
- Sindrome de X frágil: pessoas, contextos & percursosPublication . Franco, V.; Martins, M.; Jorge, P.; Ferreira, F.; Bertão, A.; Apolónio, A.; Pires, H.; Melo, M.; Albuquerque, C.; Cunha, M.; Carmona, C.; Costa, T.; Reis, S.; Jiménez, S.
- Newborn screening for medium-chain acyl-CoA dehydrogenase deficiency: regional experience and high incidence of carnitine deficiencyPublication . Couce, M.; Sánchez-Pintos, P.; Diogo, L.; Leão-Teles, E.; Martins, E.; Santos, H.; Amor Bueno, M.; Delgado-Pecellín, C.; Castiñeiras, D.; Cocho, J.; García-Villoria, J.; Ribes, A.; Fraga, J.; Rocha, HBackground Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is the most common inherited defect in the mitochondrial fatty acid oxidation pathway, resulting in significant morbidity and mortality in undiagnosed patients. Newborn screening (NBS) has considerably improved MCADD outcome, but the risk of complication remains in some patients. The aim of this study was to evaluate the relationship between genotype, biochemical parameters and clinical data at diagnosis and during follow-up, in order to optimize monitoring of these patients. Methods We carried out a multicenter study in southwest Europe, of MCADD patients detected by NBS. Evaluated NBS data included free carnitine (C0) and the acylcarnitines C8, C10, C10:1 together with C8/C2 and C8/C10 ratios, clinical presentation parameters and genotype, in 45 patients. Follow-up data included C0 levels, duration of carnitine supplementation and occurrence of metabolic crises. Results C8/C2 ratio and C8 were the most accurate biomarkers of MCADD in NBS. We found a high number of patients homozygous for the prevalent c.985A > G mutation (75%). Moreover, in these patients C8, C8/C10 and C8/C2 were higher than in patients with other genotypes, while median value of C0 was significantly lower (23 μmol/L vs 36 μmol/L). The average follow-up period was 43 months. To keep carnitine levels within the normal range, carnitine supplementation was required in 82% of patients, and for a longer period in patients homozygotes for the c.985A>G mutation than in patients with other genotypes (average 31 vs 18 months). Even with treatment, median C0 levels remained lower in homozygous patients than in those with other genotypes (14 μmol/L vs 22 μmol/L). Two patients died and another three suffered a metabolic crisis, all of whom were homozygous for the c.985 A>G mutation. Conclusions Our data show a direct association between homozygosity for c.985A>G and lower carnitine values at diagnosis, and a higher dose of carnitine supplementation for maintenance within the normal range. This study contributes to a better understanding of the relationship between genotype and phenotype in newborn patients with MCADD detected through screening which could be useful in improving follow-up strategies and clinical outcome.