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L Vilarinho

Publications and source records attributed to L Vilarinho.

At least 19 recordsLinked to original sources
PubMed2006

Congenital disorder of glycosylation type Ia: searching for the origin of common mutations in PMM2.

Congenital Disorders of Glycosylation (CDG) are a group of recessive genetic disorders characterized by hypoglycosylation of glycoproteins. CDG-Ia, the most common type, is caused by mutations in the PMM2 gene, coding for a phosphomannomutase (PMM2; EC 5.4.2.8). The mutational spectrum of PMM2 comprises more than 80 different mutations but one of them, R141H, is particularly interesting due to its high frequency among CDG-Ia patients worldwide. In contrast, other mutations are ethnically or geographically restricted, such as D65Y which is only found in patients of Iberian ancestry. In the present study a population genetic approach was used in an attempt to clarify the origins of two important disease causing mutations: R141H and D65Y. Based on SNP and STR genotypic analysis, we ascertained an association between the R141H substitution and a particular haplotype, suggesting a common origin for all the mutated chromosomes. Similar results were found for D65Y, although the associated haplotype was different from that of R141H, suggesting independent origins for these two mutations. Our results enable us to infer an Iberian origin for the D65Y mutation.

Carbohydrate Metabolism, Inborn Errors↗
PubMed2006

Mutational spectrum of classical galactosaemia in Spain and Portugal.

Classical galactosaemia is an autosomal recessive inherited metabolic disorder due to deficient galactose-1-phosphate uridyltransferase (GALT). Over 180 different base changes and disease-causing mutations have been reported in the GALT gene. Mutation p.Q188R was found to be the most common molecular defect among caucasian classical galactosaemia patients. We have characterized the spectrum of GALT mutations in a group of 51 Spanish families and 32 Portuguese families with this disease. p.Q188R is also the most prevalent mutation in the Spanish and Portuguese population, accounting for 50% and 57.8% of galactosaemic alleles, respectively. An additional 15 mutations were also identified in Spanish patients, four of which were novel: p.D28H, p.S181A, c.658dupG and c.377+53_1059+87del. In the Portuguese population, 11 different mutations were found, three of which were novel: p.R33H, p.P185S, and p.S192G. The differences observed between the genotypes identified in Portuguese and Spanish galactosaemic populations are notable. Only mutations p.Q188R, p.R148Q and c.820+13g>a were identified in both populations. In spite of the geographical proximity of Spain and Portugal, it seems that they have received genetic influences from different populations. The repeated migrations that occurred in the Iberian Peninsula throughout centuries may explain such variability.

Alleles↗
PubMed2006

Overexpression of GAMT restores GAMT activity in primary GAMT-deficient fibroblasts.

Guanidinoacetate methyltransferase deficiency (MIM 601240) is an autosomal recessive disorder of creatine biosynthesis. Patients present with mental retardation, extrapyramidal symptoms, autistic-like behavior, epilepsy, cerebral creatine deficiency and increased levels of guanidinoacetate. So far 15 mutations have been reported, including six missense variants that are highly likely to be pathogenic mutations. To prove that mutations in the GAMT gene are responsible for GAMT deficiency we overexpressed the GAMT open reading frame in GAMT-deficient fibroblasts by stable transfection. In addition, HeLa cells were transiently transfected with the same expression vector. In contrast to mock transfectants transfection of primary GAMT-deficient fibroblasts with wild-type GAMT results in the restoration of GAMT activity as measured by GC-MS using stable isotope labeled substrates. Moreover, the expression of the GAMT-EGFP fusion protein was analyzed by Western blot, confirming the presence of GAMT fusion protein, both in the stable as well as in the transient transfectants. Here, we prove that mutations in the GAMT gene are responsible for GAMT deficiency, since overexpression of the GAMT open reading frame restores GAMT activity in GAMT-deficient fibroblasts. Furthermore, the transient transfection of HeLa cells will be important for functional analysis of variants of unknown consequence (i.e., missense mutations).

Amino Acid Metabolism, Inborn Errors↗
PubMed2006

GAMT deficiency: features, treatment, and outcome in an inborn error of creatine synthesis.

BACKGROUND: Guanidinoactetate methyltransferase (GAMT) deficiency is an autosomal recessive disorder of creatine synthesis. The authors analyzed clinical, biochemical, and molecular findings in 27 patients. METHODS: The authors collected data from questionnaires and literature reports. A score including degree of intellectual disability, epileptic seizures, and movement disorder was developed and used to classify clinical phenotype as severe, moderate, or mild. Score and biochemical data were assessed before and during treatment with oral creatine substitution alone or with additional dietary arginine restriction and ornithine supplementation. RESULTS: Intellectual disability, epileptic seizures, guanidinoacetate accumulation in body fluids, and deficiency of brain creatine were common in all 27 patients. Twelve patients had severe, 12 patients had moderate, and three patients had mild clinical phenotype. Twenty-one of 27 (78%) patients had severe intellectual disability (estimated IQ 20 to 34). There was no obvious correlation between severity of the clinical phenotype, guanidinoacetate accumulation in body fluids, and GAMT mutations. Treatment resulted in almost normalized cerebral creatine levels, reduced guanidinoacetate accumulation, and in improvement of epilepsy and movement disorder, whereas the degree of intellectual disability remained unchanged. CONCLUSION: Guanidinoactetate methyltransferase deficiency should be considered in patients with unexplained intellectual disability, and urinary guanidinoacetate should be determined as an initial diagnostic approach.

Adolescent↗
PubMed2006

Mutational spectrum and linkage disequilibrium patterns at the ornithine transcarbamylase gene (OTC).

Ornithine transcarbamylase (OTC; EC 2.1.3.3) is a hepatic enzyme involved in ammonia elimination via the urea cycle. Since the sequence of the OTC gene was reported many types of mutations continue to be found in OTC deficiency patients, continuing to increase the already wide mutational spectrum known for this gene. In this study we present the clinical, biochemical and molecular features of thirteen late-onset OTC deficiency patients. Mutations were identified in all these patients, among which six were novel point substitutions (L59R, A137P, L148S, Y176L, L186P, and K210N) and one was a 2-bp deletion at exon 4 (341-342delAA). In addition, a de novo genomic deletion of maternal origin encompassing exons 1 to 5 was also identified by the analysis of LD patterns using intragenic polymorphic markers. This work exemplifies the potential value of population genetic studies for the detection of large deletions.

Exons↗
PubMed2005

Molecular studies in Portuguese patients with Smith-Lemli-Opitz syndrome and report of three new mutations in DHCR7.

Smith-Lemli-Opitz syndrome (SLO) is an autosomal recessive disorder characterised by craniofacial dysmorphism, mental retardation, multiple congenital anomalies, and increased levels of 7-dehydrocholesterol (7-DHC) in body tissues and fluids. SLO is caused by mutations in the DHCR7 gene which encodes 7-dehydrocholesterol reductase, the last enzyme of cholesterol biosynthesis pathway. In our investigation, we screened 682 dysmorphic/mentally retarded Portuguese patients for abnormal levels of 7-DHC in blood by UV spectrometry. We identified six unrelated patients with SLO (0.87% of total). Mutational analysis of the DHCR7 gene led to the identification of seven distinct mutations, three of which are new (F174S, H301R, and Q98X). The common IVS8-1G > C and T93M variants together with the H301R accounted for 70% of the all SLO alleles in our population. Our findings contribute to the variegate array of pathological changes in the DHCR7 gene among different European populations.

Child↗
PubMed2005

Novel L2HGDH mutations in 21 patients with L-2-hydroxyglutaric aciduria of Portuguese origin.

We studied 21 patients, from 18 families, with L-2-hydroxyglutaric aciduria (L-2-HGA), a rare neurometabolic disorder with a homogeneous presentation: progressive neurodegeneration with extrapyramidal and cerebellar signs, seizures, and subcortical leukoencephalopathy. Increased levels of L-2-hydroxyglutaric acid in body fluids proved the diagnosis of L-2-HGA in all 21 patients. We analyzed the L-2-HGA gene (L2HGDH), recently found to be mutated in consanguineous families with L-2-HGA, and identified seven novel mutations in 15 families. Three mutations appeared to be particularly prevalent in this Portuguese panel: a frameshift mutation (c.529delC) was detected in 12 out of 30 mutant alleles (40%), a nonsense mutation (c.208C>T; p.Arg70X) in 7/30 alleles (23%), and a missense mutation (c.293A>G; p.His98Arg) in four out of 30 mutant alleles (13%), suggesting that common origin may exist. Furthermore, two novel missense (c.169G>A; p.Gly57Arg, c.1301A>C; p.His434Pro) and two splice error (c.257-2A>G, c.907-2A>G) mutations were found. All the mutations presumably lead to loss-of-function with no relationship between clinical signs, progression of the disease, levels of L-2-HGA and site of the mutation. In the three remaining families, no pathogenic mutations in the L-2-HGA were found, which suggests either alterations in regulatory regions of the gene or of its intervening sequences, compound heterozygosity for large genomic deletion and, or further genetic heterogeneity.

Adolescent↗
PubMed2005

mtDNA single macrodeletions associated with myopathies: absence of haplogroup-related increased risk.

As for any non-recombining genome, any mutation at mtDNA, if not recurrent, appears on a particular haplotype background, allowing its detection by haplogroup association studies. It has been shown that the propensity for occurrence of single macrodeletions at a level beyond the pathological threshold is associated with super-haplogroup U/K. However, in this report, we present evidence for the absence of preferential haplogroup backgrounds for single macrodeletions. We have analysed how haplogroup diagnostic polymorphisms could disrupt direct repeats usually flanking the deleted segment, and we have concluded that for the Common Deletion, no such polymorphisms are observed in humans, but they do occur in other primates. Furthermore, we also report five new single macrodeletions.

Adolescent↗
PubMed2004

Clinical and genetic heterogeneity of branching enzyme deficiency (glycogenosis type IV).

BACKGROUND: Glycogen storage disease type IV (GSD-IV) is a clinically heterogeneous autosomal recessive disorder due to glycogen branching enzyme (GBE) deficiency and resulting in the accumulation of an amylopectin-like polysaccharide. The typical presentation is liver disease of childhood, progressing to lethal cirrhosis. The neuromuscular form of GSD-IV varies in onset (perinatal, congenital, juvenile, or adult) and severity. OBJECTIVE: To identify the molecular bases of different neuromuscular forms of GSD-IV and to establish possible genotype/phenotype correlations. METHODS: Eight patients with GBE deficiency had different neuromuscular presentations: three had fetal akinesia deformation sequence (FADS), three had congenital myopathy, one had juvenile myopathy, and one had combined myopathic and hepatic features. In all patients, the promoter and the entire coding region of the GBE gene at the RNA and genomic level were sequenced. RESULTS: Nine novel mutations were identified, including nonsense, missense, deletion, insertion, and splice-junction mutations. The three cases with FADS were homozygous, whereas all other cases were compound heterozygotes. CONCLUSIONS: This study expands the spectrum of mutations in the GBE gene and confirms that the neuromuscular presentation of GSD-IV is clinically and genetically heterogeneous.

1,4-alpha-Glucan Branching Enzyme↗
PubMed2004

The E37X is a common HMGCL mutation in Portuguese patients with 3-hydroxy-3-methylglutaric CoA lyase deficiency.

3-Hydroxy-3-methylglutaric aciduria (OMIM 246450) is an autosomal recessive inborn error of the final step of leucine catabolic and ketogenic pathways, caused by deficiency of the enzyme 3-hydroxy-3-methylglutaryl CoA lyase (HL, HMGCL, EC 4.1.3.4). Clinically, deficiency of the enzyme results in metabolic acidosis, hyperammonemia, and infantile hypoketotic hypoglycaemia usually presenting during the first year of life with vomiting, lethargy, hypotonia, and sometimes with respiratory distress and coma. HL deficiency is relatively common in Arabic populations but seems to be rare in Europe. Our recent experience suggests that HL deficiency is the most frequent organic aciduria in the Portuguese population. We herein report on the molecular study of the HMGCL gene in 11 cases originated from the Northern area of Portugal. We detected the E37X (c.109G > T) mutation, in 84.1% of the alleles, one allele carried the V168fs(-2) (504_505delCT) and other allele the novel D204N (c.610G > A) mutation. The mutation of the last allele remained unidentified. The relatively high frequency of the "common" HMGCL Portuguese mutation makes useful the development of a rapid and specific molecular confirmation of new cases with HL deficiency in our country.

Acidosis↗
PubMed2003

Mutation analysis in 16 patients with mtDNA depletion.

Sixteen unrelated Southern European patients with the mitochondrial depletion syndrome (MDS) were analyzed for mutations in the TK2 and DGUOK genes. Three novel mutations were identified in TK2 (R183G, R254X, and 142insG). When we analyzed additional genes involved in the dNTPs pool, such as SLC25A19 (DNC) and NT5M (d-NT2), we did not detect mutations. The current study suggest that scanning the TK2, DGUOK, SLC25A19, and NT5M genes is likely to help about 10% of MDS families in terms of genetic counseling. Also, our findings indicate that genotype-phenotype correlations are not straightforward in MDS.

Age of Onset↗
PubMed2003

CblE type of homocystinuria: mild clinical phenotype in two patients homozygous for a novel mutation in the MTRR gene.

Patients with the cblE type of homocystinuria usually present with megaloblastic anaemia, feeding difficulties, developmental delay and cerebral atrophy. We present a 14-year-old Spanish girl (patient 1) and a 10-year-old Portuguese boy (patient 2) with cblE disease and mild clinical phenotype. The main clinical feature in both patients was persistent megaloblastic anaemia observed at 3 years and at 2 months of age, respectively. Diagnosis was made at the ages of 9 and 7 years, respectively, owing to persistent macrocytosis despite cobalamin treatment. Plasma total homocysteine values at diagnosis were 91 micromol/L and 44 micromol/L, respectively, in the absence of methylmalonic aciduria. Neurological and neurophysiological examinations were normal except for two small lesions on brain MRI suggestive of ischaemia and slight abnormalities in somatosensitive evoked potentials. Enzymatic analysis, complementation studies and clearly reduced production of methylcobalamin from 57Co-labelled cyanocobalamin indicated functional methionine synthase reductase deficiency due to the cblE defect. Genetic analysis confirmed that both patients are homozygous for a novel mutation c.1361C>T in the methionine synthase reductase gene leading to a replacement of serine by leucine (S454L) in a highly conserved FAD-binding domain. We propose that homozygosity for this novel mutation may be associated with a mild phenotype, although its long-term deleterious neurological consequences remain possible. Furthermore, we propose that even in the absence of apparent neurological involvement, total homocysteine should be investigated in patients with resistant megaloblastic anaemia to detect possible mild forms of the cblE type of homocystinuria.

Adolescent↗
PubMed2002

Prolidase deficiency with hyperimmunoglobulin E: a case report.

Prolidase deficiency is a rare, inherited disorder characterized by ulceration of the skin, mental retardation, and massive urinary excretion of imidodipeptides. Most patients also have recurrent infections, an unusual facial appearance, and splenomegaly. We describe a girl presenting with chronic dermatitis, recurrent respiratory tract infections since her first months of life, and facial features characteristic of prolidase deficiency. The diagnosis of prolidase deficiency was made at 4.5 months of age. The immunologic study in this patient showed an extreme and progressive increase of total immunoglobulin E (IgE) in serum (reaching the value of 77,600 IU/l) and defective chemotactic function of the neutrophils. Treatment with a hyper-proteic diet supplemented with ascorbic acid, manganese chlorite, and topical proline resulted in reduction of the frequency and severity of the infections and significant improvement of the skin lesions. The authors discuss the immunologic alterations and the favorable evolution with treatment in this patient.

Amino Acid Metabolism, Inborn Errors↗
PubMed2002

Haplotype analysis and phylogeny of ornithine transcarbamylase polymorphisms.

Ornithine transcarbamylase (OT2, EC 2.1.3.3) deficiency, the most common inborn error of urea cycle, is caused by a vast number of point mutations, deletions and insertions in the respective gene. Furthermore, 12 single nucleotide polymorphisms (NSPs) have been described in the OTC gene, four of them causing an amino acid change. We have studied the frequency of these markers in two populations: Portuguese and Mozambican. No significant differences were observed between populations, except for Lys --> Arg in codon 46. Allelic associations between polymorphisms were used to define haplotypic patterns. The three common haplotypes (H1, H2 and H3) show a combined frequency of 95% in Portugal and 87% in Mozambique. One haplotype was found only in Portugal and three are only present in Mozambique, resulting in a higher haplotype diversity. The combined information from the SNPs and the DXS1068 (CA)n repeat was used to outline OTC haplotype phylogeny, which, in conjunction with the population data, allowed us to sketch possible evolutionary pathways although some haplotypes could have arisen by either repeated mutation or recombination.

Alleles↗
PubMed2001

The T9176G mtDNA mutation severely affects ATP production and results in Leigh syndrome.

The authors identified a novel mtDNA mutation (T9176G) in the ATPase 6 gene in a family in which a 10-year-old girl had a severe neurodegenerative disorder, her elder sister had died of Leigh syndrome (LS), and a maternal uncle had a spinocerebellar disorder. Biochemical studies disclosed a reduced rate of ATP synthesis in skin fibroblast cultures from the proposita as the likely explanation of her severe illness. The findings expand the genetic variants associated with LS.

Adenosine Triphosphate↗
PubMed2001

Maternally inherited deafness associated with a T1095C mutation in the mDNA.

Hearing loss is a relatively frequent defect in children with a genetic or predisposition basis in about 50% of cases. Mitochondrial DNA (mtDNA)-associated disorder often present with sensorineural hearing loss (SNHL) either in isolation or as a part of a multisystem disorder in adults but the frequency in pediatric cases is unknown. We analysed deafness-related mtDNA mutations in 80 deaf children to assess the relative frequency of alterations in childhood-onset SNHL. In 16 patients in whom maternal inheritance was possible, we screened for new mutations likely to affect mitochondrial protein synthesis. In one child we detected a novel mutation (T1095C) in the 12S rRNA gene. This mutation fulfils the suggested criteria for definition of a disease-related nucleotide variant. No mutations were found in other patients. Although we cannot exclude the presence of still undefined new mtDNA mutations, our data suggest that mtDNA defect are not common in childhood-onset SNHL.

Base Sequence↗