Browsing by Author "Duarte, ST"
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- AP4S1 Splice-Site Mutation in a Case of Spastic Paraplegia Type 52 with PolymicrogyriaPublication . Carmona, S; Marecos, C; Amorim, M; Ferreira, AC; Conceição, C; Brás, J; Duarte, ST; Guerreiro, RHereditary spastic paraplegias (HSPs) are a group of rare inherited neurodegenerative disorders that result from primary retrograde dysfunction of the long descending fibers of the corticospinal tract, causing lower limb spasticity and muscular weakness. This group of diseases has a heterogeneous clinical presentation. An extensive list of associated genes, different inheritance patterns, and ages at onset have been reported in HSPs.1 Spastic paraplegia type 52 (SPG52) is an autosomal recessive disease caused by AP4S mutations. The disease is characterized by neonatal hypotonia that progresses to hypertonia and spasticity in early childhood, developmental delay, mental retardation, and poor or absent speech. Febrile or afebrile seizures may also occur.
- De Novo Truncating Mutations in WASF1 Cause Intellectual Disability with SeizuresPublication . Ito, Y; Carss, KJ; Duarte, ST; Hartley, T; Keren, B; Kurian, MA; Marey, I; Charles, P; Mendonça, C; Nava, C; Pfundt, R; Sanchis-Juan, A; van Bokhoven, H; van Essen, A; van Ravenswaaij-Arts, C; Boycott, KM; Kernohan, KD; Dyack, S; Raymond, FLNext-generation sequencing has been invaluable in the elucidation of the genetic etiology of many subtypes of intellectual disability in recent years. Here, using exome sequencing and whole-genome sequencing, we identified three de novo truncating mutations in WAS protein family member 1 (WASF1) in five unrelated individuals with moderate to profound intellectual disability with autistic features and seizures. WASF1, also known as WAVE1, is part of the WAVE complex and acts as a mediator between Rac-GTPase and actin to induce actin polymerization. The three mutations connected by Matchmaker Exchange were c.1516C>T (p.Arg506Ter), which occurs in three unrelated individuals, c.1558C>T (p.Gln520Ter), and c.1482delinsGCCAGG (p.Ile494MetfsTer23). All three variants are predicted to partially or fully disrupt the C-terminal actin-binding WCA domain. Functional studies using fibroblast cells from two affected individuals with the c.1516C>T mutation showed a truncated WASF1 and a defect in actin remodeling. This study provides evidence that de novo heterozygous mutations in WASF1 cause a rare form of intellectual disability.
- Dominant and Recessive RYR1 Mutations in Adults with Core Lesions and Mild Muscle SymptomsPublication . Duarte, ST; Oliveira, J; Santos, R; Pereira, P; Barroso, C; Conceição, I; Evangelista, TINTRODUCTION: Ryanodine receptor gene (RYR1) mutations have been associated with central core disease (CCD), multiminicore/minicore/multicore disease (MmD), and susceptibility to malignant hyperthermia (MH). METHODS: Patients with muscle symptoms in adulthood, who had features compatible with CCD/MmD, underwent clinical, histological, and genetic (RYR1 and SEPN1 genes) evaluations. Published cases of CCD and MmD with adult onset were also reviewed. RESULTS: Eight patients fulfilled the criteria for further analysis. Five RYR1 mutations, 4 of them unreported, were detected in 3 patients. Compound heterozygosity was proven in 1 case. CONCLUSIONS: To our knowledge, this is the only report of adult onset associated with recessive RYR1 mutations and central core/multiminicores on muscle biopsy. Although adult patients with CCD, MmD, and minimally symptomatic MH with abnormal muscle biopsy findings usually have a mild clinical course, differential diagnosis and carrier screening is crucial for prevention of potentially life-threatening reactions to general anesthesia.
- Impairment of Adenosinergic System in Rett syndrome: Novel Therapeutic Target to Boost BDNF SignallingPublication . Miranda-Lourenço, C; Duarte, ST; Palminha, C; Gaspar, C; Rodrigues, TM; Magalhães-Cardoso, T; Rei, N; Colino-Oliveira, M; Gomes, R; Ferreira, S; Rosa, J; Xapelli, S; Armstrong, J; García-Cazorla, A; Correia-de-Sá, P; Sebastião, AM; Diógenes, MJRett syndrome (RTT; OMIM#312750) is mainly caused by mutations in the X-linked MECP2 gene (methyl-CpG-binding protein 2 gene; OMIM*300005), which leads to impairments in the brain-derived neurotrophic factor (BDNF) signalling. The boost of BDNF mediated effects would be a significant breakthrough but it has been hampered by the difficulty to administer BDNF to the central nervous system. Adenosine, an endogenous neuromodulator, may accomplish that role since through A2AR it potentiates BDNF synaptic actions in healthy animals. We thus characterized several hallmarks of the adenosinergic and BDNF signalling in RTT and explored whether A2AR activation could boost BDNF actions. For this study, the RTT animal model, the Mecp2 knockout (Mecp2-/y) (B6.129P2 (C)-Mecp2tm1.1Bird/J) mouse was used. Whenever possible, parallel data was also obtained from post-mortem brain samples from one RTT patient. Ex vivo extracellular recordings of field excitatory post-synaptic potentials in CA1 hippocampal area were performed to evaluate synaptic transmission and long-term potentiation (LTP). RT-PCR was used to assess mRNA levels and Western Blot or radioligand binding assays were performed to evaluate protein levels. Changes in cortical and hippocampal adenosine content were assessed by liquid chromatography with diode array detection (LC/DAD). Hippocampal ex vivo experiments revealed that the facilitatory actions of BDNF upon LTP is absent in Mecp2-/y mice and that TrkB full-length (TrkB-FL) receptor levels are significantly decreased. Extracts of the hippocampus and cortex of Mecp2-/y mice revealed less adenosine amount as well as less A2AR protein levels when compared to WT littermates, which may partially explain the deficits in adenosinergic tonus in these animals. Remarkably, the lack of BDNF effect on hippocampal LTP in Mecp2-/y mice was overcome by selective activation of A2AR with CGS21680. Overall, in Mecp2-/y mice there is an impairment on adenosinergic system and BDNF signalling. These findings set the stage for adenosine-based pharmacological therapeutic strategies for RTT, highlighting A2AR as a therapeutic target in this devastating pathology.
- Loss of Hierarchical Imprinting Regulation at the Prader-Willi/Angelman Syndrome Locus in Human iPSCsPublication . Pólvora-Brandão, D; Joaquim, M; Godinho, I; Aprile, D; Álvaro, AR; Onofre, I; Raposo, AC; Pereira de Almeida, L; Duarte, ST; da Rocha, STThe human chr15q11-q13 imprinted cluster is linked to several disorders, including Prader-Willi (PWS) and Angelman (AS) syndromes. Recently, disease modeling approaches based on induced pluripotent stem cells (iPSCs) have been used to study these syndromes. A concern regarding the use of these cells for imprinted disease modeling is the numerous imprinting defects found in many iPSCs. Here, by reprogramming skin fibroblasts from a control and AS individuals, we generated several iPSC lines and addressed the stability of imprinting status across the PWS/AS domain. We focused on three important regulatory DNA elements which are all differentially methylated regions (DMRs), methylated on the maternal allele: the PWS imprinting center (PWS-IC), which is a germline DMR and the somatic NDN and MKRN3 DMRs, hierarchically controlled by PWS-IC. Normal PWS-IC methylation pattern was maintained in most iPSC lines; however, loss of maternal methylation in one out of five control iPSC lines resulted in a monoallelic to biallelic switch for many imprinted genes in this domain. Surprisingly, MKRN3 DMR was found aberrantly hypermethylated in all control and AS iPSCs, regardless of the methylation status of the PWS-IC master regulator. This suggests a loss of hierarchical control of imprinting at PWS/AS region. We confirmed these results in established iPSC lines derived using different reprogramming procedures. Overall, we show that hierarchy of imprinting control in donor cells might not apply to iPSCs, accounting for their spectrum of imprinting alterations. Such differences in imprinting regulation should be taken into consideration for the use of iPSCs in disease modeling.
- Structural Analysis of Pathogenic Missense Mutations in GABRA2 and Identification of a Novel de Novo Variant in the Desensitization GatePublication . Sanchis-Juan, A; Hasenahuer, MA; Baker, JA; McTague, A; Barwick, K; Kurian, MA; Duarte, ST; Carss, KJ; Thornton, J; Raymond, FLBackground: Cys-loop receptors control neuronal excitability in the brain and their dysfunction results in numerous neurological disorders. Recently, six missense variants in GABRA2, a member of this family, have been associated with early infantile epileptic encephalopathy (EIEE). We identified a novel de novo missense variant in GABRA2 in a patient with EIEE and performed protein structural analysis of the seven variants. Methods: The novel variant was identified by trio whole-genome sequencing. We performed protein structural analysis of the seven variants, and compared them to previously reported pathogenic mutations at equivalent positions in other Cys-loop receptors. Additionally, we studied the distribution of disease-associated variants in the transmembrane helices of these proteins. Results: The seven variants are in the transmembrane domain, either close to the desensitization gate, the activation gate, or in inter-subunit interfaces. Six of them have pathogenic mutations at equivalent positions in other Cys-loop receptors, emphasizing the importance of these residues. Also, pathogenic mutations are more common in the pore-lining helix, consistent with this region being highly constrained for variation in control populations. Conclusion: Our study reports a novel pathogenic variant in GABRA2, characterizes the regions where pathogenic mutations are in the transmembrane helices, and underscores the value of considering sequence, evolutionary, and structural information as a strategy for variant interpretation of novel missense mutations.
- Undetectable Levels of CSF Amyloid-β Peptide in a Patient with 17β-Hydroxysteroid Dehydrogenase DeficiencyPublication . Ortez, C; Villar, C; Fons, C; Duarte, ST; Pérez, A; García-Villoria, J; Ribes, A; Ormazábal, A; Casado, M; Campistol, Jaume; Vilaseca, MA; García-Cazorla, A17β-hydroxysteroid dehydrogenase 10 (HSD10) deficiency is a rare X-linked inborn error of isoleucine catabolism. Although this protein has been genetically implicated in Alzheimer's disease pathogenesis, studies of amyloid-β peptide (Aβ) in patients with HSD10 deficiency have not been previously reported. We found, in a severely affected child with HSD10 deficiency, undetectable levels of Aβ in the cerebrospinal fluid, together with low expression of brain-derived neurotrophic factor, α-synuclein, and serotonin metabolites. Confirmation of these findings in other patients would help elucidating mechanisms of synaptic dysfunction in this disease, and highlight the role of Aβ in both early and late periods of life.