RESUMO
BACKGROUND AND AIMS: Brugada syndrome (BrS) is an inherited arrhythmia with a higher disease prevalence and more lethal arrhythmic events in Asians than in Europeans. Genome-wide association studies (GWAS) have revealed its polygenic architecture mainly in European populations. The aim of this study was to identify novel BrS-associated loci and to compare allelic effects across ancestries. METHODS: A GWAS was conducted in Japanese participants, involving 940 cases and 1634 controls, followed by a cross-ancestry meta-analysis of Japanese and European GWAS (total of 3760 cases and 11 635 controls). The novel loci were characterized by fine-mapping, gene expression, and splicing quantitative trait associations in the human heart. RESULTS: The Japanese-specific GWAS identified one novel locus near ZSCAN20 (P = 1.0 × 10-8), and the cross-ancestry meta-analysis identified 17 association signals, including six novel loci. The effect directions of the 17 lead variants were consistent (94.1%; P for sign test = 2.7 × 10-4), and their allelic effects were highly correlated across ancestries (Pearson's R = .91; P = 2.9 × 10-7). The genetic risk score derived from the BrS GWAS of European ancestry was significantly associated with the risk of BrS in the Japanese population [odds ratio 2.12 (95% confidence interval 1.94-2.31); P = 1.2 × 10-61], suggesting a shared genetic architecture across ancestries. Functional characterization revealed that a lead variant in CAMK2D promotes alternative splicing, resulting in an isoform switch of calmodulin kinase II-δ, favouring a pro-inflammatory/pro-death pathway. CONCLUSIONS: This study demonstrates novel susceptibility loci implicating potentially novel pathogenesis underlying BrS. Despite differences in clinical expressivity and epidemiology, the polygenic architecture of BrS was substantially shared across ancestries.
Assuntos
Síndrome de Brugada , Predisposição Genética para Doença , Estudo de Associação Genômica Ampla , Humanos , Síndrome de Brugada/genética , Japão/epidemiologia , Masculino , Europa (Continente)/epidemiologia , Predisposição Genética para Doença/genética , Feminino , População Branca/genética , Pessoa de Meia-Idade , Povo Asiático/genética , Estudos de Casos e Controles , Adulto , Polimorfismo de Nucleotídeo Único/genéticaRESUMO
Intellectual disability (ID) is a neurodevelopmental disorder frequently caused by monogenic defects. In this study, we collected 14 SEMA6B heterozygous variants in 16 unrelated patients referred for ID to different centers. Whereas, until now, SEMA6B variants have mainly been reported in patients with progressive myoclonic epilepsy, our study indicates that the clinical spectrum is wider and also includes non-syndromic ID without epilepsy or myoclonus. To assess the pathogenicity of these variants, selected mutated forms of Sema6b were overexpressed in Human Embryonic Kidney 293T (HEK293T) cells and in primary neuronal cultures. shRNAs targeting Sema6b were also used in neuronal cultures to measure the impact of the decreased Sema6b expression on morphogenesis and synaptogenesis. The overexpression of some variants leads to a subcellular mislocalization of SEMA6B protein in HEK293T cells and to a reduced spine density owing to loss of mature spines in neuronal cultures. Sema6b knockdown also impairs spine density and spine maturation. In addition, we conducted in vivo rescue experiments in chicken embryos with the selected mutated forms of Sema6b expressed in commissural neurons after knockdown of endogenous SEMA6B. We observed that expression of these variants in commissural neurons fails to rescue the normal axon pathway. In conclusion, identification of SEMA6B variants in patients presenting with an overlapping phenotype with ID and functional studies highlight the important role of SEMA6B in neuronal development, notably in spine formation and maturation and in axon guidance. This study adds SEMA6B to the list of ID-related genes.
Assuntos
Epilepsia , Deficiência Intelectual , Semaforinas , Animais , Orientação de Axônios , Embrião de Galinha , Espinhas Dendríticas , Epilepsia/genética , Células HEK293 , Humanos , Deficiência Intelectual/genética , Semaforinas/genéticaRESUMO
The collapsin response mediator protein (CRMP) family proteins are intracellular mediators of neurotrophic factors regulating neurite structure/spine formation and are essential for dendrite patterning and directional axonal pathfinding during brain developmental processes. Among this family, CRMP5/DPYSL5 plays a significant role in neuronal migration, axonal guidance, dendrite outgrowth, and synapse formation by interacting with microtubules. Here, we report the identification of missense mutations in DPYSL5 in nine individuals with brain malformations, including corpus callosum agenesis and/or posterior fossa abnormalities, associated with variable degrees of intellectual disability. A recurrent de novo p.Glu41Lys variant was found in eight unrelated patients, and a p.Gly47Arg variant was identified in one individual from the first family reported with Ritscher-Schinzel syndrome. Functional analyses of the two missense mutations revealed impaired dendritic outgrowth processes in young developing hippocampal primary neuronal cultures. We further demonstrated that these mutations, both located in the same loop on the surface of DPYSL5 monomers and oligomers, reduced the interaction of DPYSL5 with neuronal cytoskeleton-associated proteins MAP2 and ßIII-tubulin. Our findings collectively indicate that the p.Glu41Lys and p.Gly47Arg variants impair DPYSL5 function on dendritic outgrowth regulation by preventing the formation of the ternary complex with MAP2 and ßIII-tubulin, ultimately leading to abnormal brain development. This study adds DPYSL5 to the list of genes implicated in brain malformation and in neurodevelopmental disorders.
Assuntos
Agenesia do Corpo Caloso/genética , Cerebelo/anormalidades , Mutação de Sentido Incorreto/genética , Transtornos do Neurodesenvolvimento/genética , Adulto , Agenesia do Corpo Caloso/diagnóstico por imagem , Cerebelo/diagnóstico por imagem , Criança , Pré-Escolar , Feminino , Humanos , Hidrolases/química , Hidrolases/genética , Deficiência Intelectual/diagnóstico por imagem , Deficiência Intelectual/genética , Masculino , Proteínas Associadas aos Microtúbulos/química , Proteínas Associadas aos Microtúbulos/genética , Proteínas Associadas aos Microtúbulos/metabolismo , Modelos Moleculares , Transtornos do Neurodesenvolvimento/diagnóstico por imagem , Tubulina (Proteína)/metabolismo , Adulto JovemRESUMO
BACKGROUND: In first-degree relatives of patients with aneurysmal subarachnoid hemorrhage (aSAH), the risk of an intracranial aneurysm can be predicted at initial screening but not at follow-up screening. We aimed to develop a model for predicting the probability of a new intracranial aneurysm after initial screening in people with a positive family history of aSAH. METHODS: In a prospective study, we obtained data from follow-up screening for aneurysms of 499 subjects with ≥2 affected first-degree relatives. Screening took place at the University Medical Center Utrecht, the Netherlands, and the University Hospital of Nantes, France. We studied associations between potential predictors and the presence of aneurysms using Cox regression analysis and the predictive performance at 5, 10, and 15 years after initial screening using C statistics and calibration plots, while correcting for overfitting. RESULTS: In 5050 person-years of follow-up, intracranial aneurysms were found in 52 subjects. The risk of aneurysm at 5 years was 2% to 12%, at 10 years, 4% to 28%, and at 15 years, 7% to 40%. Predictors were female sex, history of intracranial aneurysms/aneurysmal subarachnoid hemorrhage, and older age. The sex, previous history of intracranial aneurysm/aSAH, older age score had a C statistic of 0.70 (95% CI, 0.61-0.78) at 5 years, 0.71 (95% CI, 0.64-0.78) at 10 years, and 0.70 (95% CI, 0.63-0.76) at 15 years and showed good calibration. CONCLUSIONS: The sex, previous history of intracranial aneurysm/aSAH, older age score provides risk estimates for finding new intracranial aneurysms at 5, 10, and 15 years after initial screening, based on 3 easily retrievable predictors; this can help to define a personalized screening strategy after initial screening in people with a positive family history for aSAH.
Assuntos
Aneurisma Intracraniano , Hemorragia Subaracnóidea , Humanos , Feminino , Masculino , Aneurisma Intracraniano/epidemiologia , Aneurisma Intracraniano/genética , Aneurisma Intracraniano/diagnóstico , Hemorragia Subaracnóidea/epidemiologia , Hemorragia Subaracnóidea/genética , Hemorragia Subaracnóidea/diagnóstico , Seguimentos , Estudos Prospectivos , Fatores de RiscoRESUMO
[Figure: see text].
Assuntos
Arritmias Cardíacas/genética , Proteínas Associadas aos Microtúbulos/metabolismo , Miócitos Cardíacos/metabolismo , Canal de Sódio Disparado por Voltagem NAV1.5/metabolismo , Potenciais de Ação , Animais , Arritmias Cardíacas/metabolismo , Células Cultivadas , Glicogênio Sintase Quinase 3 beta/metabolismo , Células HEK293 , Humanos , Mutação com Perda de Função , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Proteínas Associadas aos Microtúbulos/genética , Miócitos Cardíacos/fisiologia , Canal de Sódio Disparado por Voltagem NAV1.5/genética , Transporte Proteico , Peixe-ZebraRESUMO
Bardet-Biedl syndrome (BBS) is an autosomal recessive ciliopathy that affects multiple organs, leading to retinitis pigmentosa, polydactyly, obesity, renal anomalies, cognitive impairment, and hypogonadism. Until now, biallelic pathogenic variants have been identified in at least 24 genes delineating the genetic heterogeneity of BBS. Among those, BBS5 is a minor contributor to the mutation load and is one of the eight subunits forming the BBSome, a protein complex implied in protein trafficking within the cilia. This study reports on a European BBS5 patient with a severe BBS phenotype. Genetic analysis was performed using multiple next-generation sequencing (NGS) tests (targeted exome, TES and whole exome, WES), and biallelic pathogenic variants could only be identified using whole-genome sequencing (WGS), including a previously missed large deletion of the first exons. Despite the absence of family samples, the biallelic status of the variants was confirmed. The BBS5 protein's impact was confirmed on the patient's cells (presence/absence and size of the cilium) and ciliary function (Sonic Hedgehog pathway). This study highlights the importance of WGS and the challenge of reliable structural variant detection in patients' genetic explorations as well as functional tests to assess a variant's pathogenicity.
Assuntos
Síndrome de Bardet-Biedl , Polidactilia , Humanos , Síndrome de Bardet-Biedl/genética , Síndrome de Bardet-Biedl/patologia , Proteínas do Citoesqueleto/genética , Proteínas Hedgehog/genética , Mutação , Fenótipo , Proteínas de Ligação a Fosfato/genética , Transporte Proteico , Masculino , Pré-EscolarRESUMO
Arrhythmogenic cardiomyopathy with right dominant form (ACR) is a rare heritable cardiac cardiomyopathy disorder associated with sudden cardiac death. Pathogenic variants (PVs) in desmosomal genes have been causally related to ACR in 40% of cases. Other genes encoding nondesmosomal proteins have been described in ACR, but their contribution in this pathology is still debated. A panel of 71 genes associated with inherited cardiopathies was screened in an ACR population of 172 probands and 856 individuals from the general population. PVs and uncertain significance variants (VUS) have been identified in 36% and 18.6% of patients, respectively. Among the cardiopathy-associated genes, burden tests show a significant enrichment in PV and VUS only for desmosomal genes PKP2 (plakophilin-2), DSP (desmoplakin), DSC2 (desmocollin-2), and DSG2 (desmoglein-2). Importantly, VUS may account for 15% of ACR cases and should then be considered for molecular diagnosis. Among the other genes, no evidence of enrichment was detected, suggesting an extreme caution in the interpretation of these genetic variations without associated functional or segregation data. Genotype-phenotype correlation points to (1) a more severe and earlier onset of the disease in PV and VUS carriers, underlying the importance to carry out presymptomatic diagnosis in relatives and (2) to a more prevalent left ventricular dysfunction in DSP variant carriers.
Assuntos
Displasia Arritmogênica Ventricular Direita , Displasia Arritmogênica Ventricular Direita/diagnóstico , Displasia Arritmogênica Ventricular Direita/genética , Displasia Arritmogênica Ventricular Direita/metabolismo , Desmossomos/genética , Desmossomos/metabolismo , Estudos de Associação Genética , Heterozigoto , Humanos , Placofilinas/genética , Placofilinas/metabolismoRESUMO
BACKGROUND: Persons with a positive family history of aneurysmal subarachnoid hemorrhage are at increased risk of aneurysmal subarachnoid hemorrhage. Preventive screening for intracranial aneurysms (IAs) in these persons is cost-effective but not very efficient. We aimed to develop and externally validate a model for predicting the probability of an IA at first screening in persons with a positive family history of aneurysmal subarachnoid hemorrhage. METHODS: For model development, we studied results from initial screening for IA in 660 prospectively collected persons with ≥2 affected first-degree relatives screened at the University Medical Center Utrecht. For validation, we studied results from 258 prospectively collected persons screened in the University Hospital of Nantes. We assessed potential predictors of IA presence in multivariable logistic regression analysis. Predictive performance was assessed with the C statistic and a calibration plot and corrected for overfitting. RESULTS: IA were present in 79 (12%) persons in the development cohort. Predictors were number of affected relatives, age, smoking, and hypertension (NASH). The NASH score had a C statistic of 0.68 (95% CI, 0.62-0.74) and showed good calibration in the development data. Predicted probabilities of an IA at first screening varied from 5% in persons aged 20 to 30 years with two affected relatives, without hypertension who never smoked, up to 36% in persons aged 60 to 70 years with ≥3 affected relatives, who have hypertension and smoke(d). In the external validation data IA were present in 67 (26%) persons, the model had a C statistic of 0.64 (95% CI, 0.57-0.71) and slightly underestimated IAs risk. CONCLUSIONS: For persons with ≥2 affected first-degree relatives, the NASH score improves current predictions and provides risk estimates for an IA at first screening between 5% and 36% based on 4 easily retrievable predictors. With the information such persons can now make a better informed decision about whether or not to undergo preventive screening.
Assuntos
Hipertensão , Aneurisma Intracraniano , Hepatopatia Gordurosa não Alcoólica , Hemorragia Subaracnóidea , Humanos , Hipertensão/complicações , Hipertensão/epidemiologia , Aneurisma Intracraniano/complicações , Fatores de Risco , Fumar/epidemiologia , Hemorragia Subaracnóidea/diagnósticoRESUMO
Variants in genes encoding ribosomal proteins have thus far been associated with Diamond-Blackfan anemia, a rare inherited bone marrow failure, and isolated congenital asplenia. Here, we report one de novo missense variant and three de novo splice variants in RPL13, which encodes ribosomal protein RPL13 (also called eL13), in four unrelated individuals with a rare bone dysplasia causing severe short stature. The three splice variants (c.477+1G>T, c.477+1G>A, and c.477+2 T>C) result in partial intron retention, which leads to an 18-amino acid insertion. In contrast to observations from Diamond-Blackfan anemia, we detected no evidence of significant pre-rRNA processing disturbance in cells derived from two affected individuals. Consistently, we showed that the insertion-containing protein is stably expressed and incorporated into 60S subunits similar to the wild-type protein. Erythroid proliferation in culture and ribosome profile on sucrose gradient are modified, suggesting a change in translation dynamics. We also provide evidence that RPL13 is present at high levels in chondrocytes and osteoblasts in mouse growth plates. Taken together, we show that the identified RPL13 variants cause a human ribosomopathy defined by a rare skeletal dysplasia, and we highlight the role of this ribosomal protein in bone development.
Assuntos
Doenças do Desenvolvimento Ósseo/genética , Nanismo/genética , Mutação de Sentido Incorreto/genética , Proteínas de Neoplasias/genética , Proteínas Ribossômicas/genética , Anemia de Diamond-Blackfan/genética , Animais , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BLRESUMO
OBJECTIVE: Primary hypobetalipoproteinemia is characterized by LDL-C (low-density lipoprotein cholesterol) concentrations below the fifth percentile. Primary hypobetalipoproteinemia mostly results from heterozygous mutations in the APOB (apolipoprotein B) and PCSK9 genes, and a polygenic origin is hypothesized in the remaining cases. Hypobetalipoproteinemia patients present an increased risk of nonalcoholic fatty liver disease and steatohepatitis. Here, we compared hepatic alterations between monogenic, polygenic, and primary hypobetalipoproteinemia of unknown cause. Approach and Results: Targeted next-generation sequencing was performed in a cohort of 111 patients with hypobetalipoproteinemia to assess monogenic and polygenic origins using an LDL-C-dedicated polygenic risk score. Forty patients (36%) had monogenic hypobetalipoproteinemia, 38 (34%) had polygenic hypobetalipoproteinemia, and 33 subjects (30%) had hypobetalipoproteinemia from an unknown cause. Patients with monogenic hypobetalipoproteinemia had lower LDL-C and apolipoprotein B plasma levels compared with those with polygenic hypobetalipoproteinemia. Liver function was assessed by hepatic ultrasonography and liver enzymes levels. Fifty-nine percent of patients with primary hypobetalipoproteinemia presented with liver steatosis, whereas 21% had increased alanine aminotransferase suggestive of liver injury. Monogenic hypobetalipoproteinemia was also associated with an increased prevalence of liver steatosis (81% versus 29%, P<0.001) and liver injury (47% versus 0%) compared with polygenic hypobetalipoproteinemia. CONCLUSIONS: This study highlights the importance of genetic diagnosis in the clinical care of primary hypobetalipoproteinemia patients. It shows for the first time that a polygenic origin of hypobetalipoproteinemia is associated with a lower risk of liver steatosis and liver injury versus monogenic hypobetalipoproteinemia. Thus, polygenic risk score is a useful tool to establish a more personalized follow-up of primary hypobetalipoproteinemia patients.
Assuntos
Apolipoproteína B-100/genética , LDL-Colesterol/sangue , Hipobetalipoproteinemias/genética , Herança Multifatorial , Mutação , Hepatopatia Gordurosa não Alcoólica/etiologia , Pró-Proteína Convertase 9/genética , Adulto , Biomarcadores/sangue , Regulação para Baixo , Feminino , Predisposição Genética para Doença , Humanos , Hipobetalipoproteinemias/sangue , Hipobetalipoproteinemias/complicações , Hipobetalipoproteinemias/diagnóstico , Masculino , Hepatopatia Gordurosa não Alcoólica/diagnóstico por imagem , Fenótipo , Estudos Retrospectivos , Medição de Risco , Fatores de Risco , Adulto JovemRESUMO
Intracranial aneurysms (IAs) are acquired cerebrovascular abnormalities characterized by localized dilation and wall thinning in intracranial arteries, possibly leading to subarachnoid hemorrhage and severe outcome in case of rupture. Here, we identified one rare nonsense variant (c.1378A>T) in the last exon of ANGPTL6 (Angiopoietin-Like 6)-which encodes a circulating pro-angiogenic factor mainly secreted from the liver-shared by the four tested affected members of a large pedigree with multiple IA-affected case subjects. We showed a 50% reduction of ANGPTL6 serum concentration in individuals heterozygous for the c.1378A>T allele (p.Lys460Ter) compared to relatives homozygous for the normal allele, probably due to the non-secretion of the truncated protein produced by the c.1378A>T transcripts. Sequencing ANGPTL6 in a series of 94 additional index case subjects with familial IA identified three other rare coding variants in five case subjects. Overall, we detected a significant enrichment (p = 0.023) in rare coding variants within this gene among the 95 index case subjects with familial IA, compared to a reference population of 404 individuals with French ancestry. Among the 6 recruited families, 12 out of 13 (92%) individuals carrying IA also carry such variants in ANGPTL6, versus 15 out of 41 (37%) unaffected ones. We observed a higher rate of individuals with a history of high blood pressure among affected versus healthy individuals carrying ANGPTL6 variants, suggesting that ANGPTL6 could trigger cerebrovascular lesions when combined with other risk factors such as hypertension. Altogether, our results indicate that rare coding variants in ANGPTL6 are causally related to familial forms of IA.
Assuntos
Proteínas Semelhantes a Angiopoietina/genética , Predisposição Genética para Doença , Aneurisma Intracraniano/genética , Mutação/genética , Fases de Leitura Aberta/genética , Proteína 6 Semelhante a Angiopoietina , Proteínas Semelhantes a Angiopoietina/sangue , Células Cultivadas , Códon sem Sentido/genética , Família , Feminino , Células HEK293 , Humanos , Aneurisma Intracraniano/sangue , Masculino , Pessoa de Meia-Idade , Linhagem , Fatores de RiscoRESUMO
Bardet-Biedl syndrome (BBS) is a ciliopathy characterized by retinitis pigmentosa, obesity, polydactyly, cognitive impairment and renal failure. Pathogenic variants in 24 genes account for the molecular basis of >80% of cases. Toward saturated discovery of the mutational basis of the disorder, we carefully explored our cohorts and identified a hominid-specific SINE-R/VNTR/Alu type F (SVA-F) insertion in exon 13 of BBS1 in eight families. In six families, the repeat insertion was found in trans with c.1169 T > G, p.Met390Arg and in two families the insertion was found in addition to other recessive BBS loci. Whole genome sequencing, de novo assembly and SNP array analysis were performed to characterize the genomic event. This insertion is extremely rare in the general population (found in 8 alleles of 8 BBS cases but not in >10 800 control individuals from gnomAD-SV) and due to a founder effect. Its 2435 bp sequence contains hallmarks of LINE1 mediated retrotransposition. Functional studies with patient-derived cell lines confirmed that the BBS1 SVA-F is deleterious as evidenced by a significant depletion of both mRNA and protein levels. Such findings highlight the importance of dedicated bioinformatics pipelines to identify all types of variation.
Assuntos
Síndrome de Bardet-Biedl/genética , Proteínas Associadas aos Microtúbulos/genética , Retroelementos , Estudos de Coortes , Feminino , Efeito Fundador , Frequência do Gene , Humanos , Masculino , Mutagênese Insercional , Linhagem , Sequenciamento Completo do GenomaRESUMO
BACKGROUND AND PURPOSE: The ever-growing availability of imaging led to increasing incidentally discovered unruptured intracranial aneurysms (UIAs). We leveraged machine-learning techniques and advanced statistical methods to provide new insights into rupture intracranial aneurysm (RIA) risks. METHODS: We analysed the characteristics of 2505 patients with intracranial aneurysms (IA) discovered between 2016 and 2019. Baseline characteristics, familial history of IA, tobacco and alcohol consumption, pharmacological treatments before the IA diagnosis, cardiovascular risk factors and comorbidities, headaches, allergy and atopy, IA location, absolute IA size and adjusted size ratio (aSR) were analysed with a multivariable logistic regression (MLR) model. A random forest (RF) method globally assessed the risk factors and evaluated the predictive capacity of a multivariate model. RESULTS: Among 994 patients with RIA (39.7%) and 1511 patients with UIA (60.3 %), the MLR showed that IA location appeared to be the most significant factor associated with RIA (OR, 95% CI: internal carotid artery, reference; middle cerebral artery, 2.72, 2.02-3.58; anterior cerebral artery, 4.99, 3.61-6.92; posterior circulation arteries, 6.05, 4.41-8.33). Size and aSR were not significant factors associated with RIA in the MLR model and antiplatelet-treatment intake patients were less likely to have RIA (OR: 0.74; 95% CI: 0.55-0.98). IA location, age, following by aSR were the best predictors of RIA using the RF model. CONCLUSIONS: The location of IA is the most consistent parameter associated with RIA. The use of 'artificial intelligence' RF helps to re-evaluate the contribution and selection of each risk factor in the multivariate model.
Assuntos
Aneurisma Roto/etiologia , Aneurisma Intracraniano/complicações , Fatores Etários , Idoso , Algoritmos , Aneurisma Roto/prevenção & controle , Feminino , Humanos , Aneurisma Intracraniano/diagnóstico por imagem , Aneurisma Intracraniano/patologia , Aprendizado de Máquina , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Neuroimagem , Fatores de Risco , Tomografia Computadorizada por Raios XRESUMO
AIMS: In 2003, an Australian woman was convicted by a jury of smothering and killing her four children over a 10-year period. Each child died suddenly and unexpectedly during a sleep period, at ages ranging from 19 days to 18 months. In 2019 we were asked to investigate if a genetic cause could explain the children's deaths as part of an inquiry into the mother's convictions. METHODS AND RESULTS: Whole genomes or exomes of the mother and her four children were sequenced. Functional analysis of a novel CALM2 variant was performed by measuring Ca2+-binding affinity, interaction with calcium channels and channel function. We found two children had a novel calmodulin variant (CALM2 G114R) that was inherited maternally. Three genes (CALM1-3) encode identical calmodulin proteins. A variant in the corresponding residue of CALM3 (G114W) was recently reported in a child who died suddenly at age 4 and a sibling who suffered a cardiac arrest at age 5. We show that CALM2 G114R impairs calmodulin's ability to bind calcium and regulate two pivotal calcium channels (CaV1.2 and RyR2) involved in cardiac excitation contraction coupling. The deleterious effects of G114R are similar to those produced by G114W and N98S, which are considered arrhythmogenic and cause sudden cardiac death in children. CONCLUSION: A novel functional calmodulin variant (G114R) predicted to cause idiopathic ventricular fibrillation, catecholaminergic polymorphic ventricular tachycardia, or mild long QT syndrome was present in two children. A fatal arrhythmic event may have been triggered by their intercurrent infections. Thus, calmodulinopathy emerges as a reasonable explanation for a natural cause of their deaths.
Assuntos
Infanticídio , Taquicardia Ventricular , Arritmias Cardíacas , Austrália , Criança , Pré-Escolar , Morte Súbita Cardíaca/etiologia , Feminino , Humanos , Lactente , Canal de Liberação de Cálcio do Receptor de Rianodina , Taquicardia Ventricular/diagnóstico , Taquicardia Ventricular/genéticaRESUMO
Chuvash polycythemia is an autosomal recessive form of erythrocytosis associated with a homozygous p.Arg200Trp mutation in the von Hippel-Lindau (VHL) gene. Since this discovery, additional VHL mutations have been identified in patients with congenital erythrocytosis, in a homozygous or compound-heterozygous state. VHL is a major tumor suppressor gene, mutations in which were first described in patients presenting with VHL disease, which is characterized by the development of highly vascularized tumors. Here, we identify a new VHL cryptic exon (termed E1') deep in intron 1 that is naturally expressed in many tissues. More importantly, we identify mutations in E1' in 7 families with erythrocytosis (1 homozygous case and 6 compound-heterozygous cases with a mutation in E1' in addition to a mutation in VHL coding sequences) and in 1 large family with typical VHL disease but without any alteration in the other VHL exons. In this study, we show that the mutations induced a dysregulation of VHL splicing with excessive retention of E1' and were associated with a downregulation of VHL protein expression. In addition, we demonstrate a pathogenic role for synonymous mutations in VHL exon 2 that altered splicing through E2-skipping in 5 families with erythrocytosis or VHL disease. In all the studied cases, the mutations differentially affected splicing, correlating with phenotype severity. This study demonstrates that cryptic exon retention and exon skipping are new VHL alterations and reveals a novel complex splicing regulation of the VHL gene. These findings open new avenues for diagnosis and research regarding the VHL-related hypoxia-signaling pathway.
Assuntos
Éxons , Predisposição Genética para Doença , Mutação , Policitemia/genética , Splicing de RNA , Proteína Supressora de Tumor Von Hippel-Lindau/genética , Doença de von Hippel-Lindau/genética , Adolescente , Adulto , Criança , Feminino , Heterozigoto , Humanos , Masculino , Pessoa de Meia-Idade , Linhagem , Policitemia/classificação , Policitemia/patologia , Adulto Jovem , Doença de von Hippel-Lindau/patologiaRESUMO
AIMS: The Brugada syndrome (BrS) is an inherited cardiac disorder predisposing to ventricular arrhythmias. Despite considerable efforts, its genetic basis and cellular mechanisms remain largely unknown. The objective of this study was to identify a new susceptibility gene for BrS through familial investigation. METHODS AND RESULTS: Whole-exome sequencing performed in a three-generation pedigree with five affected members allowed the identification of one rare non-synonymous substitution (p.R211H) in RRAD, the gene encoding the RAD GTPase, carried by all affected members of the family. Three additional rare missense variants were found in 3/186 unrelated index cases. We detected higher levels of RRAD transcripts in subepicardium than in subendocardium in human heart, and in the right ventricle outflow tract compared to the other cardiac compartments in mice. The p.R211H variant was then subjected to electrophysiological and structural investigations in human cardiomyocytes derived from induced pluripotent stem cells (iPSC-CMs). Cardiomyocytes derived from induced pluripotent stem cells from two affected family members exhibited reduced action potential upstroke velocity, prolonged action potentials and increased incidence of early afterdepolarizations, with decreased Na+ peak current amplitude and increased Na+ persistent current amplitude, as well as abnormal distribution of actin and less focal adhesions, compared with intra-familial control iPSC-CMs Insertion of p.R211H-RRAD variant in control iPSCs by genome editing confirmed these results. In addition, iPSC-CMs from affected patients exhibited a decreased L-type Ca2+ current amplitude. CONCLUSION: This study identified a potential new BrS-susceptibility gene, RRAD. Cardiomyocytes derived from induced pluripotent stem cells expressing RRAD variant recapitulated single-cell electrophysiological features of BrS, including altered Na+ current, as well as cytoskeleton disturbances.
Assuntos
Síndrome de Brugada/genética , Mutação de Sentido Incorreto , Miócitos Cardíacos/patologia , Proteínas ras/genética , Potenciais de Ação/genética , Adulto , Síndrome de Brugada/patologia , Síndrome de Brugada/fisiopatologia , Citoesqueleto/genética , Citoesqueleto/patologia , Feminino , Marcadores Genéticos , Predisposição Genética para Doença , Humanos , Masculino , Miócitos Cardíacos/fisiologiaRESUMO
Sudden unexpected death in infancy occurs in apparently healthy infants and remains largely unexplained despite thorough investigation. The vast majority of cases are sporadic. Here we report seven individuals from three families affected by sudden and unexpected cardiac arrest between 4 and 20 months of age. Whole-exome sequencing revealed compound heterozygous missense mutations in PPA2 in affected infants of each family. PPA2 encodes the mitochondrial pyrophosphatase, which hydrolyzes inorganic pyrophosphate into two phosphates. This is an essential activity for many biosynthetic reactions and for energy metabolism of the cell. We show that deletion of the orthologous gene in yeast (ppa2Δ) compromises cell viability due to the loss of mitochondria. Expression of wild-type human PPA2, but not PPA2 containing the mutations identified in affected individuals, preserves mitochondrial function in ppa2Δ yeast. Using a regulatable (doxycycline-repressible) gene expression system, we found that the pathogenic PPA2 mutations rapidly inactivate the mitochondrial energy transducing system and prevent the maintenance of a sufficient electrical potential across the inner membrane, which explains the subsequent disappearance of mitochondria from the mutant yeast cells. Altogether these data demonstrate that PPA2 is an essential gene in yeast and that biallelic mutations in PPA2 cause a mitochondrial disease leading to sudden cardiac arrest in infants.
Assuntos
Alelos , Morte Súbita Cardíaca/etiologia , Pirofosfatase Inorgânica/genética , Proteínas Mitocondriais/genética , Mutação/genética , Morte Súbita Cardíaca/patologia , Difosfatos , Exoma/genética , Feminino , Deleção de Genes , Genes Essenciais/genética , Teste de Complementação Genética , Heterozigoto , Humanos , Lactente , Pirofosfatase Inorgânica/metabolismo , Masculino , Potencial da Membrana Mitocondrial/genética , Viabilidade Microbiana , Mitocôndrias/enzimologia , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Proteínas Mitocondriais/metabolismo , Mutação de Sentido Incorreto , Bombas de Próton/deficiência , Bombas de Próton/genética , Bombas de Próton/metabolismo , Saccharomyces cerevisiae/citologia , Saccharomyces cerevisiae/enzimologia , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismoRESUMO
Motivation: Reformatting and filtering bioinformatics files are common tasks for bioinformaticians. Standard Linux tools and specific programs are usually used to perform such tasks but there is still a gap between using these tools and the programming interface of some existing libraries. Results: In this study, we developed a set of tools namely bioalcidae, samjs and vcffilterjs that reformat or filter files using a JavaScript engine or a pure java expression and taking advantage of the java API for high-throughput sequencing data (htsjdk). Availability and implementation: https://github.com/lindenb/jvarkit. Contact: pierre.lindenbaum@univ-nantes.fr.
Assuntos
Biologia Computacional/métodos , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Armazenamento e Recuperação da Informação/métodos , Software , Análise de Sequência de DNA/métodosRESUMO
PURPOSE: Lanosterol synthase (LSS) gene was initially described in families with extensive congenital cataracts. Recently, a study has highlighted LSS associated with hypotrichosis simplex. We expanded the phenotypic spectrum of LSS to a recessive neuroectodermal syndrome formerly named alopecia with mental retardation (APMR) syndrome. It is a rare autosomal recessive condition characterized by hypotrichosis and intellectual disability (ID) or developmental delay (DD), frequently associated with early-onset epilepsy and other dermatological features. METHODS: Through a multicenter international collaborative study, we identified LSS pathogenic variants in APMR individuals either by exome sequencing or LSS Sanger sequencing. Splicing defects were assessed by transcript analysis and minigene assay. RESULTS: We reported ten APMR individuals from six unrelated families with biallelic variants in LSS. We additionally identified one affected individual with a single rare variant in LSS and an allelic imbalance suggesting a second event. Among the identified variants, two were truncating, seven were missense, and two were splicing variants. Quantification of cholesterol and its precursors did not reveal noticeable imbalance. CONCLUSION: In the cholesterol biosynthesis pathway, lanosterol synthase leads to the cyclization of (S)-2,3-oxidosqualene into lanosterol. Our data suggest LSS as a major gene causing a rare recessive neuroectodermal syndrome.
Assuntos
Alopecia/genética , Colesterol/metabolismo , Deficiências do Desenvolvimento/genética , Deficiência Intelectual/genética , Transferases Intramoleculares/genética , Idade de Início , Alopecia/complicações , Alopecia/patologia , Criança , Pré-Escolar , Colesterol/genética , Deficiências do Desenvolvimento/complicações , Deficiências do Desenvolvimento/patologia , Epilepsia/complicações , Epilepsia/genética , Epilepsia/patologia , Feminino , Humanos , Lactente , Deficiência Intelectual/complicações , Deficiência Intelectual/patologia , Lanosterol/genética , Lanosterol/metabolismo , Masculino , Mutação , Linhagem , Fenótipo , Esqualeno/análogos & derivados , Esqualeno/metabolismo , Sequenciamento do ExomaRESUMO
Aims: QT prolongation during mental stress test (MST) has been associated with familial idiopathic ventricular fibrillation. In long QT syndrome (LQTS), up to 30% of mutation carriers have normal QT duration. Our aim was to assess the QT response during MST, and its accuracy in the diagnosis of concealed LQTS. Methods and results: All patients who are carrier of a KCNQ1 or KCNH2 mutations without QT prolongation were enrolled. A control group was constituted of patients with negative exercise and epinephrine tests. Electrocardiogram were recorded at rest and at the maximum heart rate during MST and reviewed by two physicians. Among the 70 patients enrolled (median age 41±2.1 years, 46% male), 36 were mutation carrier for LQTS (20 KCNQ1 and 16 KCNH2), and 34 were controls. KCNQ1 and KCNH2 mutation carriers presented a longer QT interval at baseline [405(389; 416) and 421 (394; 434) ms, respectively] compared with the controls [361(338; 375)ms; P < 0.0001]. QT duration during MST varied by 9 (4; 18) ms in KCNQ1, 3 (-6; 16) ms in KCNH2, and by -22 (-29; -17) ms in controls (P < 0.0001). These QT variations were independent of heart rate (P < 0.3751). Receiver operating characteristic curve analysis identified a cut-off value of QT variation superior to -11 ms as best predictor of LQTS. It provided 97% sensitivity and 97% specificity of QT prolongation in the diagnosis of LQTS. Conclusion: We identified a paradoxical response of the QT interval during MST in LQTS. Easy to assess, MST may be efficient to unmask concealed LQTS in patients at risk of this pathology.