Serviço de Genética
Permanent URI for this community
Browse
Browsing Serviço de Genética by Issue Date
Now showing 1 - 10 of 22
Results Per Page
Sort Options
- 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.
- MAN1B1 Deficiency: An Unexpected CDG-IIPublication . Rymen, D.; Peanne, R.; Millón, M.; Race, V.; Sturiale, L.; Garozzo, D.; Mills, P.; Clayton, P.; Asteggiano, C.; Quelhas, D.; Cansu, A.; Martins, E.; Nassogne, M.; Gonc¸alves-Rocha, M.; Topaloglu, H.; Jaeken, J.; Foulquier, F.; Matthijs, G.Congenital disorders of glycosylation (CDG) are a group of rare metabolic diseases, due to impaired protein and lipid glycosylation. In the present study, exome sequencing was used to identify MAN1B1 as the culprit gene in an unsolved CDG-II patient. Subsequently, 6 additional cases with MAN1B1-CDG were found. All individuals presented slight facial dysmorphism, psychomotor retardation and truncal obesity. Generally, MAN1B1 is believed to be an ER resident alpha-1,2-mannosidase acting as a key factor in glycoprotein quality control by targeting misfolded proteins for ER-associated degradation (ERAD). However, recent studies indicated a Golgi localization of the endogenous MAN1B1, suggesting a more complex role for MAN1B1 in quality control. We were able to confirm that MAN1B1 is indeed localized to the Golgi complex instead of the ER. Furthermore, we observed an altered Golgi morphology in all patients' cells, with marked dilatation and fragmentation. We hypothesize that part of the phenotype is associated to this Golgi disruption. In conclusion, we linked mutations in MAN1B1 to a Golgi glycosylation disorder. Additionally, our results support the recent findings on MAN1B1 localization. However, more work is needed to pinpoint the exact function of MAN1B1 in glycoprotein quality control, and to understand the pathophysiology of its deficiency.
- 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.
- A 26-Year Experience in Chorionic Villus Sampling Prenatal Genetic DiagnosisPublication . Jorge, P.; Mota-Freitas, M.; Santos, R.; Silva, M.; Soares, G.; Fortuna, A.Abstract: This report describes the trends of chorionic villus sampling (CVS) referred for prenatal genetic diagnosis in the past two and a half decades in a Portuguese Center. Our cohort of 491 CVS was mostly performed by the transcervical method at the 12th gestational week. Data collected within the framework of this study relate to the following: sampling method, referral reason versus abnormality and incidence of procedure-related pregnancy loss, that declined to about 0.5% over the last 15 years. The year 2000 represented a change in referral reasons for chorionic tissue collection, shifting from almost exclusively for cytogenetic testing to an increasing number of molecular tests for monogenic disorders. Herein, success rates as well as cytogenetic and/or molecular DNA results are presented. These latter include not only tests for several monogenic disorders, but also aneuploidy and maternal cell contamination screening. This retrospective analysis reiterates that CVS is a safe and reliable first trimester technique for prenatal diagnosis in high genetic risk pregnancies.
- Unraveling the pathogenesis of ARX polyalanine tract variants using a clinical and molecular interfacing approachPublication . Marques, I.; Sá, J.; Soares, G.; Mota, M.; Pinheiro, C.; Aguiar, L.; Amado, M.; Soares, C.; Calado, A.; Dias, P.; Sousa, A.; Fortuna, A.; Santos, R.; Howell, K.; Ryan, M.; Leventer, R.; Sachdev, R.; Catford, R.; Friend, K; Mattiske, T.; Shoubridge, C.; Jorge, P.The Aristaless-related homeobox (ARX) gene is implicated in intellectual disability with the most frequent pathogenic mutations leading to expansions of the first two polyalanine tracts. Here, we describe analysis of the ARX gene outlining the approaches in the Australian and Portuguese setting, using an integrated clinical and molecular strategy. We report variants in the ARX gene detected in 19 patients belonging to 17 families. Seven pathogenic variants, being expansion mutations in both polyalanine tract 1 and tract 2, were identifyed, including a novel mutation in polyalanine tract 1 that expands the first tract to 20 alanines. This precise number of alanines is sufficient to cause pathogenicity when expanded in polyalanine tract 2. Five cases presented a probably non-pathogenic variant, including the novel HGVS: c.441_455del, classified as unlikely disease causing, consistent with reports that suggest that in frame deletions in polyalanine stretches of ARX rarely cause intellectual disability. In addition, we identified five cases with a variant of unclear pathogenic significance. Owing to the inconsistent ARX variants description, publications were reviewed and ARX variant classifications were standardized and detailed unambiguously according to recommendations of the Human Genome Variation Society. In the absence of a pathognomonic clinical feature, we propose that molecular analysis of the ARX gene should be included in routine diagnostic practice in individuals with either nonsyndromic or syndromic intellectual disability. A definitive diagnosis of ARX-related disorders is crucial for an adequate clinical follow-up and accurate genetic counseling of at-risk family members.
- Whole Gene Deletion of EBF3 Supporting Haploinsufficiency of This Gene as a Mechanism of Neurodevelopmental DiseasePublication . Lopes, F.; Soares, G.; Gonçalves-Rocha, M.; Pinto-Basto, J.; Maciel, P.Mutations in early B cell factor 3 (EBF3) were recently described in patients with a neurodevelopmental disorder (NDD) that includes developmental delay/intellectual disability, ataxia, hypotonia, speech impairment, strabismus, genitourinary abnormalities, and mild facial dysmorphisms. Several large 10q terminal and interstitial deletions affecting many genes and including EBF3 have been described in the literature. However, small deletions (<1 MB) affecting almost exclusively EBF3 are not commonly reported. We performed array comparative genomic hybridization (aCGH) (Agilent 180K) and quantitative PCR analysis in a female patient with intellectual disability. A clinical comparison between our patient and overlapping cases reported in the literature was also made. The patient carries a de novo 600 Kb deletion at 10q26.3 affecting the MGMT, EBF3, and GLRX genes. The patient has severe intellectual disability, language impairment, conductive hearing loss, hypotonia, vision alterations, triangular face, short stature, and behavior problems. This presentation overlaps that reported for patients carrying EBF3 heterozygous point mutations, as well as literature reports of patients carrying large 10qter deletions. Our results and the literature review suggest that EBF3 haploinsufficiency is a key contributor to the common aspects of the phenotype presented by patients bearing point mutations and indels in this gene, given that deletions affecting the entire gene (alone or in addition to other genes) are causative of a similar syndrome, including intellectual disability (ID) with associated neurological symptoms and particular facial dysmorphisms.
- Mutations in the X-linked ATP6AP2 cause a glycosylation disorder with autophagic defectsPublication . Rujano, M.; Cannata Serio, M.; Panasyuk, G.; Péanne, R.; Reunert, J.; Rymen, D.; Hauser, V.; Park, J.; Freisinger, P.; Souche, E.; Guida, M.; Maier, E.; Wada, Y.; Jäger, S.; Krogan, N.; Kretz, O.; Nobre, S.; Garcia, P.; Quelhas, D.; Bird, T.; Raskind, W.; Schwake, M.; Duvet, S.; Foulquier, F.; Matthijs, G.; Marquardt, T.; Simons, M.The biogenesis of the multi-subunit vacuolar-type H+-ATPase (V-ATPase) is initiated in the endoplasmic reticulum with the assembly of the proton pore V0, which is controlled by a group of assembly factors. Here, we identify two hemizygous missense mutations in the extracellular domain of the accessory V-ATPase subunit ATP6AP2 (also known as the [pro]renin receptor) responsible for a glycosylation disorder with liver disease, immunodeficiency, cutis laxa, and psychomotor impairment. We show that ATP6AP2 deficiency in the mouse liver caused hypoglycosylation of serum proteins and autophagy defects. The introduction of one of the missense mutations into Drosophila led to reduced survival and altered lipid metabolism. We further demonstrate that in the liver-like fat body, the autophagic dysregulation was associated with defects in lysosomal acidification and mammalian target of rapamycin (mTOR) signaling. Finally, both ATP6AP2 mutations impaired protein stability and the interaction with ATP6AP1, a member of the V0 assembly complex. Collectively, our data suggest that the missense mutations in ATP6AP2 lead to impaired V-ATPase assembly and subsequent defects in glycosylation and autophagy.
- International practices in the dietary management of fructose 1-6 biphosphatase deficiencyPublication . Pinto, A.; Alfadhel, M.; Akroyd, R.; Atik Altınok, Y.; Bernabei, S.; Bernstein, L.; Bruni, G.; Caine, G.; Cameron, E.; Carruthers, R.; Cochrane, B.; Daly, A.; de Boer, F.; Delaunay, S.; Dianin, A.; Dixon, M.; Drogari, E.; Dubois, S.; Evans, S.; Gribben, J.; Gugelmo, G.; Heidenborg, C.; Hunjan, I.; Kok, I.; Kumru, B.; Liguori, A.; Mayr, D.; Megdad, E.; Meyer, U.; Oliveira, R.; Pal, A.; Pozzoli, A.; Pretese, R.; Rocha, J.; Rosenbaum-Fabian, S.; Serrano-Nieto, J.; Sjoqvist, E.; Timmer, C.; White, L.; van den Hurk, T.; van Rijn, M.; Zweers, H.; Ziadlou, M.; MacDonald, A.Background: In fructose 1,6 bisphosphatase (FBPase) deficiency, management aims to prevent hypoglycaemia and lactic acidosis by avoiding prolonged fasting, particularly during febrile illness. Although the need for an emergency regimen to avoid metabolic decompensation is well established at times of illness, there is uncertainty about the need for other dietary management strategies such as sucrose or fructose restriction. We assessed international differences in the dietary management of FBPase deficiency. Methods: A cross-sectional questionnaire (13 questions) was emailed to all members of the Society for the Study of Inborn Errors of Metabolism (SSIEM) and a wide database of inherited metabolic disorder dietitians. Results: Thirty-six centres reported the dietary prescriptions of 126 patients with FBPase deficiency. Patients' age at questionnaire completion was: 1-10y, 46% (n = 58), 11-16y, 21% (n = 27), and >16y, 33% (n = 41). Diagnostic age was: <1y, 36% (n = 46); 1-10y, 59% (n = 74); 11-16y, 3% (n = 4); and >16y, 2% (n = 2). Seventy-five per cent of centres advocated dietary restrictions. This included restriction of: high sucrose foods only (n = 7 centres, 19%); fruit and sugary foods (n = 4, 11%); fruit, vegetables and sugary foods (n = 13, 36%). Twenty-five per cent of centres (n = 9), advised no dietary restrictions when patients were well. A higher percentage of patients aged >16y rather than ≤16y were prescribed dietary restrictions: patients aged 1-10y, 67% (n = 39/58), 11-16y, 63% (n = 17/27) and >16y, 85% (n = 35/41). Patients classified as having a normal fasting tolerance increased with age from 30% in 1-10y, to 36% in 11-16y, and 58% in >16y, but it was unclear if fasting tolerance was biochemically proven. Twenty centres (56%) routinely prescribed uncooked cornstarch (UCCS) to limit overnight fasting in 47 patients regardless of their actual fasting tolerance (37%). All centres advocated an emergency regimen mainly based on glucose polymer for illness management. Conclusions: Although all patients were prescribed an emergency regimen for illness, use of sucrose and fructose restricted diets with UCCS supplementation varied widely. Restrictions did not relax with age. International guidelines are necessary to help direct future dietary management of FBPase deficiency.
- Classical fragile-X phenotype in a female infant disclosed by comprehensive genomic studiesPublication . Jorge, P.; Garcia, E.; Gonçalves, A.; Marques, I.; Maia, N.; Rodrigues, B.; Santos, H.; Fonseca, J.; Soares, G.; Correia, C.; Reis-Lima, M.; Cirigliano, V.; Santos, R.BACKGROUND: We describe a female infant with Fragile-X syndrome, with a fully expanded FMR1 allele and preferential inactivation of the homologous X-chromosome carrying a de novo deletion. This unusual and rare case demonstrates the importance of a detailed genomic approach, the absence of which could be misguiding, and calls for reflection on the current clinical and diagnostic workup for developmental disabilities. CASE PRESENTATION: We present a female infant, referred for genetic testing due to psychomotor developmental delay without specific dysmorphic features or relevant family history. FMR1 mutation screening revealed a methylated full mutation and a normal but inactive FMR1 allele, which led to further investigation. Complete skewing of X-chromosome inactivation towards the paternally-inherited normal-sized FMR1 allele was found. No pathogenic variants were identified in the XIST promoter. Microarray analysis revealed a 439 kb deletion at Xq28, in a region known to be associated with extreme skewing of X-chromosome inactivation. CONCLUSIONS: Overall results enable us to conclude that the developmental delay is the cumulative result of a methylated FMR1 full mutation on the active X-chromosome and the inactivation of the other homologue carrying the de novo 439 kb deletion. Our findings should be taken into consideration in future guidelines for the diagnostic workup on the diagnosis of intellectual disabilities, particularly in female infant cases.
- Genotype-phenotype correlations and BH4 estimated responsiveness in patients with phenylketonuria from Rio de Janeiro, Southeast BrazilPublication . Vieira Neto, Eduardo; Laranjeira, F.; Quelhas, D.; Ribeiro, I.; Seabra, A.; Mineiro, N.; Carvalho, L.; Lacerda, L.; Ribeiro, M.Background: Genetic heterogeneity and compound heterozygosis give rise to a continuous spectrum of phenylalanine hydroxylase deficiency and metabolic phenotypes in phenylketonuria (PKU). The most used parameters for evaluating phenotype in PKU are pretreatment phenylalanine (Phe) levels, tolerance for dietary Phe, and Phe overloading test. Phenotype can vary from a "classic" (severe) form to mild hyperphenylalaninemia, which does not require dietary treatment. A subset of patients is responsive to treatment by the cofactor tetrahydrobiopterin (BH4 ). Genotypes of PKU patients from Rio de Janeiro, Brazil, were compared to predicted and observed phenotypes. Genotype-based estimations of responsiveness to BH4 were also conducted. Methods: Phenotype was defined by pretreatment Phe levels. A standard prediction system based on arbitrary assigned values was employed to measure genotype-phenotype concordance. Patients were also estimated as BH4 -responders according to the responsiveness previously reported for their mutations and genotypes. Results: A 48.3% concordance rate between genotype-predicted and observed phenotypes was found. When the predicted phenotypes included those reported at the BIOPKU database, the concordance rate reached 77%. A total of 18 genotypes from 30 patients (29.4%) were estimated as of potential or probable BH4 responsiveness. Inconsistencies were observed in genotypic combinations including the common "moderate" mutations p.R261Q, p.V388M, and p.I65T and the mild mutations p.L48S, p.R68S, and p.L249F. Conclusion: The high discordance rate between genotype-predicted and observed metabolic phenotypes in this study seems to be due partially to the high frequency of the so-called "moderate" common mutations, p.R261Q, p.V388M, and p.I65T, which are reported to be associated to erratic or more severe than expected metabolic phenotypes. Although our results of BH4 estimated responsiveness must be regarded as tentative, it should be emphasized that genotyping and genotype-phenotype association studies are important in selecting patients to be offered a BH4 overload test, especially in low-resource settings like Brazil.
- «
- 1 (current)
- 2
- 3
- »