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1.
Artigo em Inglês | MEDLINE | ID: mdl-34524739

RESUMO

Exome sequencing (ES) has revolutionized rare disease management, yet only ˜25%-30% of patients receive a molecular diagnosis. A limiting factor is the quality of available phenotypic data. Here, we describe how deep clinicopathological phenotyping yielded a molecular diagnosis for a 19-year-old proband with muscular dystrophy and negative clinical ES. Deep phenotypic analysis identified two critical data points: (1) the absence of emerin protein in muscle biopsy and (2) clinical features consistent with Emery-Dreifuss muscular dystrophy. Sequencing data analysis uncovered an ultra-rare, intronic variant in EMD, the gene encoding emerin. The variant, NM_000117.3: c.188-6A > G, is predicted to impact splicing by in silico tools. This case thus illustrates how better integration of clinicopathologic data into ES analysis can enhance diagnostic yield with implications for clinical practice.

2.
Genet Med ; 2021 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-34385670

RESUMO

PURPOSE: Alternative splicing plays a critical role in mouse neurodevelopment, regulating neurogenesis, cortical lamination, and synaptogenesis, yet few human neurodevelopmental disorders are known to result from pathogenic variation in splicing regulator genes. Nuclear Speckle Splicing Regulator Protein 1 (NSRP1) is a ubiquitously expressed splicing regulator not known to underlie a Mendelian disorder. METHODS: Exome sequencing and rare variant family-based genomics was performed as a part of the Baylor-Hopkins Center for Mendelian Genomics Initiative. Additional families were identified via GeneMatcher. RESULTS: We identified six patients from three unrelated families with homozygous loss-of-function variants in NSRP1. Clinical features include developmental delay, epilepsy, variable microcephaly (Z-scores -0.95 to -5.60), hypotonia, and spastic cerebral palsy. Brain abnormalities included simplified gyral pattern, underopercularization, and/or vermian hypoplasia. Molecular analysis identified three pathogenic NSRP1 predicted loss-of-function variant alleles: c.1359_1362delAAAG (p.Glu455AlafsTer20), c.1272dupG (p.Lys425GlufsTer5), and c.52C>T (p.Gln18Ter). The two frameshift variants result in a premature termination codon in the last exon, and the mutant transcripts are predicted to escape nonsense mediated decay and cause loss of a C-terminal nuclear localization signal required for NSRP1 function. CONCLUSION: We establish NSRP1 as a gene for a severe autosomal recessive neurodevelopmental disease trait characterized by developmental delay, epilepsy, microcephaly, and spastic cerebral palsy.

4.
Pediatr Neurol ; 121: 20-25, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34126318

RESUMO

BACKGROUND: Neonatal cerebral sinus venous thrombosis (CSVT) causes high morbidity and mortality. Factors associated with either favorable or unfavorable long-term outcomes have not been clearly established. This study aimed to determine the factors involved in long-term neurological outcomes in patients with neonatal CSVT. METHODS: This was a retrospective cohort study of patients with neonatal CSVT at a single institution. Clinical factors associated with long-term neurological outcomes were examined. RESULTS: A total of 67 patients met study inclusion criteria for radiologically confirmed neonatal CSVT. The mean patient follow-up duration was four years (range one week to 16 years, median six years). We observed a favorable neurological outcome defined by a pediatric stroke outcome measures (PSOM) score of 0 to 0.5 in 26 (53%) of osurviving patients at follow-up. An unfavorable neurological outcome as defined by PSOM score >0.5 was observed in 23 survivors (47%). Death was reported in 18 (27%) patients, of which 10 patients died due to direct complications of CSVT. Congential heart disease and genetic disease were associated with significantly increased odds for all-cause death. Cardiorespiratory failure and altered mental status during the initial neurological examination were significantly associated with increased odds of death due to CSVT. Among surviving patients, higher PSOM scores were associated with premature birth (i.e., gestational age < 37 weeks), traumatic birth, site of thrombosis in the straight sinus, site of thrombosis in the internal cerebral veins, and hemorrhagic infarct. In contrast, lower PSOM scores were associated with a normal neurological examination at presentation, thrombosis in only superficial sinuses, and hemorrhage without infarct. There was no statistically significant association between the type and duration of CSVT treatment. CONCLUSIONS: The major factors influencing outcome of neonates following CSVT included comorbid medical conditions, abnormal neurological examination at presentation, location of venous thrombosis, and type of cerebral injury. These results can help guide further studies in neonatal CSVT aiming to decrease morbidity and mortality with the goal of improving long-term neurological outcomes.

5.
Am J Hum Genet ; 108(7): 1301-1317, 2021 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-34038740

RESUMO

Human C2orf69 is an evolutionarily conserved gene whose function is unknown. Here, we report eight unrelated families from which 20 children presented with a fatal syndrome consisting of severe autoinflammation and progredient leukoencephalopathy with recurrent seizures; 12 of these subjects, whose DNA was available, segregated homozygous loss-of-function C2orf69 variants. C2ORF69 bears homology to esterase enzymes, and orthologs can be found in most eukaryotic genomes, including that of unicellular phytoplankton. We found that endogenous C2ORF69 (1) is loosely bound to mitochondria, (2) affects mitochondrial membrane potential and oxidative respiration in cultured neurons, and (3) controls the levels of the glycogen branching enzyme 1 (GBE1) consistent with a glycogen-storage-associated mitochondriopathy. We show that CRISPR-Cas9-mediated inactivation of zebrafish C2orf69 results in lethality by 8 months of age due to spontaneous epileptic seizures, which is preceded by persistent brain inflammation. Collectively, our results delineate an autoinflammatory Mendelian disorder of C2orf69 deficiency that disrupts the development/homeostasis of the immune and central nervous systems.


Assuntos
Encefalite/genética , Doenças Mitocondriais/genética , Animais , Evolução Biológica , Sistemas CRISPR-Cas , Linhagem Celular , Encefalite/mortalidade , Feminino , Genes Recessivos , Glicogênio/metabolismo , Humanos , Inflamação/genética , Masculino , Proteínas de Membrana/genética , Doenças Mitocondriais/mortalidade , Linhagem , Convulsões/genética , Convulsões/mortalidade , Peixe-Zebra/genética
7.
Am J Hum Genet ; 108(6): 1069-1082, 2021 06 03.
Artigo em Inglês | MEDLINE | ID: mdl-34022130

RESUMO

BCAS3 microtubule-associated cell migration factor (BCAS3) is a large, highly conserved cytoskeletal protein previously proposed to be critical in angiogenesis and implicated in human embryogenesis and tumorigenesis. Here, we established BCAS3 loss-of-function variants as causative for a neurodevelopmental disorder. We report 15 individuals from eight unrelated families with germline bi-allelic loss-of-function variants in BCAS3. All probands share a global developmental delay accompanied by pyramidal tract involvement, microcephaly, short stature, strabismus, dysmorphic facial features, and seizures. The human phenotype is less severe compared with the Bcas3 knockout mouse model and cannot be explained by angiogenic defects alone. Consistent with being loss-of-function alleles, we observed absence of BCAS3 in probands' primary fibroblasts. By comparing the transcriptomic and proteomic data based on probands' fibroblasts with those of the knockout mouse model, we identified similar dysregulated pathways resulting from over-representation analysis, while the dysregulation of some proposed key interactors could not be confirmed. Together with the results from a tissue-specific Drosophila loss-of-function model, we demonstrate a vital role for BCAS3 in neural tissue development.


Assuntos
Mutação com Perda de Função , Perda de Heterozigosidade , Proteínas de Neoplasias/genética , Transtornos do Neurodesenvolvimento/etiologia , Adolescente , Adulto , Animais , Movimento Celular , Criança , Pré-Escolar , Drosophila , Feminino , Fibroblastos/metabolismo , Fibroblastos/patologia , Humanos , Lactente , Masculino , Camundongos , Camundongos Knockout , Proteínas de Neoplasias/metabolismo , Transtornos do Neurodesenvolvimento/metabolismo , Transtornos do Neurodesenvolvimento/patologia , Linhagem , Proteoma/análise , Adulto Jovem
8.
Am J Med Genet A ; 185(7): 1972-1980, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33797191

RESUMO

Biallelic loss-of-function (LoF) of SLC13A5 (solute carrier family 13, member 5) induced deficiency in sodium/citrate transporter (NaCT) causes autosomal recessive developmental epileptic encephalopathy 25 with hypoplastic amelogenesis imperfecta (DEE25; MIM #615905). Many pathogenic SLC13A5 single nucleotide variants (SNVs) and small indels have been described; however, no cases with copy number variants (CNVs) have been sufficiently investigated. We describe a consanguineous Iraqi family harboring an 88.5 kb homozygous deletion including SLC13A5 in Chr17p13.1. The three affected male siblings exhibit neonatal-onset epilepsy with fever-sensitivity, recurrent status epilepticus, global developmental delay/intellectual disability (GDD/ID), and other variable neurological findings as shared phenotypical features of DEE25. Two of the three affected subjects exhibit hypoplastic amelogenesis imperfecta (AI), while the proband shows no evidence of dental abnormalities or AI at 2 years of age with apparently unaffected primary dentition. Characterization of the genomic architecture at this locus revealed evidence for genomic instability generated by an Alu/Alu-mediated rearrangement; confirmed by break-point junction Sanger sequencing. This multiplex family from a distinct population elucidates the phenotypic consequence of complete LoF of SLC13A5 and illustrates the importance of read-depth-based CNV detection in comprehensive exome sequencing analysis to solve cases that otherwise remain molecularly unsolved.

9.
Am J Med Genet A ; 185(4): 1288-1293, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33544954

RESUMO

Alkylated DNA repair protein AlkB homolog 8 (ALKBH8) is a member of the AlkB family of dioxygenases. ALKBH8 is a methyltransferase of the highly variable wobble nucleoside position in the anticodon loop of tRNA and thus plays a critical role in tRNA modification by preserving codon recognition and preventing errors in amino acid incorporation during translation. Moreover, its activity catalyzes uridine modifications that are proposed to be critical for accurate protein translation. Previously, two distinct homozygous truncating variants in the final exon of ALKBH8 were described in two unrelated large Saudi Arabian kindreds with intellectual developmental disorder and autosomal recessive 71 (MRT71) syndrome (MIM# 618504). Here, we report a third family-of Egyptian descent-harboring a novel homozygous frame-shift variant in the last exon of ALKBH8. Two affected siblings in this family exhibit global developmental delay and intellectual disability as shared characteristic features of MRT71 syndrome, and we further characterize their observed dysmorphic features and brain MRI findings. This description of a third family with a truncating ALKBH8 variant from a distinct population broadens the phenotypic and genotypic spectrum of MRT71 syndrome, affirms that perturbations in tRNA biogenesis can contribute to neurogenetic disease traits, and firmly establishes ALKBH8 as a novel neurodevelopmental disease gene.


Assuntos
Homólogo AlkB 8 da RNAt Metiltransferase/genética , Encéfalo/diagnóstico por imagem , Predisposição Genética para Doença , Transtornos do Neurodesenvolvimento/genética , Adolescente , Encéfalo/patologia , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Imageamento por Ressonância Magnética , Masculino , Transtornos do Neurodesenvolvimento/diagnóstico por imagem , Transtornos do Neurodesenvolvimento/patologia , Linhagem
10.
Ann Neurol ; 89(4): 828-833, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33443317

RESUMO

The Mediator multiprotein complex functions as a regulator of RNA polymerase II-catalyzed gene transcription. In this study, exome sequencing detected biallelic putative disease-causing variants in MED27, encoding Mediator complex subunit 27, in 16 patients from 11 families with a novel neurodevelopmental syndrome. Patient phenotypes are highly homogeneous, including global developmental delay, intellectual disability, axial hypotonia with distal spasticity, dystonic movements, and cerebellar hypoplasia. Seizures and cataracts were noted in severely affected individuals. Identification of multiple patients with biallelic MED27 variants supports the critical role of MED27 in normal human neural development, particularly for the cerebellum. ANN NEUROL 2021;89:828-833.


Assuntos
Cerebelo/anormalidades , Deficiências do Desenvolvimento/genética , Distonia/genética , Complexo Mediador/genética , Malformações do Sistema Nervoso/genética , Adolescente , Adulto , Sequência de Aminoácidos , Catarata/genética , Criança , Pré-Escolar , Epilepsia/genética , Variação Genética , Humanos , Lactente , Fenótipo , Sequenciamento Completo do Exoma
11.
J Pediatr Gastroenterol Nutr ; 72(3): 354-360, 2021 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-32969958

RESUMO

OBJECTIVES: We report the development and validation of a tool to assess gastrointestinal health in Rett syndrome (RTT). We hypothesized that the Gastrointestinal Health Questionnaire (GHQ) is a valid clinical outcomes measure of gastrointestinal health in RTT. PATIENTS AND METHODS: We used parent interviews, surveys, and literature review to generate a questionnaire related to gastrointestinal health and function, mood and behaviors, and parental concerns for individuals with RTT. Parents of affected and unaffected individuals provided responses to the GHQ, assessed the relevance and importance of statements, and completed 5 surveys related to gastrointestinal health, child-related mood and behaviors, and parent concerns. We used multivariate item analysis, 2-sample t tests, and correlations to assess the validity of the GHQ. RESULTS: We documented acceptable internal consistency of statements related to gastrointestinal health and function (Cronbach-α = 0.91), RTT-related mood and behaviors (Cronbach-α = 0.89), and parent concerns (Cronbach-α = 0.95) in the GHQ. We documented favorable external validity based on differences in response scores between parents of affected and unaffected individuals (P < 0.001) and correlations in parental response scores between the GHQ and 5 validated questionnaires addressing similar issues (P < 0.001). CONCLUSION: The GHQ is a valid tool for the assessment of gastrointestinal health in RTT and offers the opportunity to field test the safety and efficacy of novel drug therapies in clinical trials for individuals affected with this disorder.


Assuntos
Síndrome de Rett , Criança , Trato Gastrointestinal , Nível de Saúde , Humanos , Pais , Reprodutibilidade dos Testes , Síndrome de Rett/diagnóstico , Inquéritos e Questionários
12.
Muscle Nerve ; 63(3): 304-310, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33146414

RESUMO

BACKGROUND: The diagnosis of uncommon pediatric neuromuscular disease (NMD) is challenging due to genetic and phenotypic heterogeneity, yet is important to guide treatment, prognosis, and recurrence risk. Patients with diagnostically challenging presentations typically undergo extensive testing with variable molecular diagnostic yield. Given the advancement in next generation sequencing (NGS), we investigated the value of clinical whole exome sequencing (ES) in uncommon pediatric NMD. METHODS: A retrospective cohort study of 106 pediatric NMD patients with a combination of ES, chromosomal microarray (CMA), and candidate gene testing was completed at a large tertiary referral center. RESULTS: A molecular diagnosis was achieved in 37/79 (46%) patients with ES, 4/44 (9%) patients with CMA, and 15/74 (20%) patients with candidate gene testing. In 2/79 (3%) patients, a dual molecular diagnosis explaining the neuromuscular disease process was identified. A total of 42 patients (53%) who received ES remained without a molecular diagnosis at the conclusion of the study. CONCLUSIONS: Due to NGS, molecular diagnostic yield of rare neurological diseases is at an all-time high. We show that ES has a higher diagnostic rate compared to other genetic tests in a complex pediatric neuromuscular disease cohort and should be considered early in the diagnostic journey for select NMD patients with challenging presentations in which a clinical diagnosis is not evident.


Assuntos
Doenças Neuromusculares/diagnóstico , Sequenciamento Completo do Exoma , Adolescente , Biópsia , Criança , Pré-Escolar , Estudos de Coortes , Eletromiografia , Feminino , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Lactente , Recém-Nascido , Masculino , Análise em Microsséries , Miopatias Mitocondriais/diagnóstico , Miopatias Mitocondriais/genética , Miopatias Mitocondriais/patologia , Técnicas de Diagnóstico Molecular , Distrofias Musculares/diagnóstico , Distrofias Musculares/genética , Distrofias Musculares/patologia , Distrofia Muscular do Cíngulo dos Membros/diagnóstico , Distrofia Muscular do Cíngulo dos Membros/genética , Distrofia Muscular do Cíngulo dos Membros/patologia , Miopatia da Parte Central/diagnóstico , Miopatia da Parte Central/genética , Miopatia da Parte Central/patologia , Miosite/diagnóstico , Miosite/genética , Miosite/patologia , Condução Nervosa , Doenças Neuromusculares/genética , Doenças Neuromusculares/patologia , Estudos Retrospectivos , Análise de Sequência de DNA , Atrofias Musculares Espinais da Infância/diagnóstico , Atrofias Musculares Espinais da Infância/genética , Atrofias Musculares Espinais da Infância/patologia , Ataxias Espinocerebelares/diagnóstico , Ataxias Espinocerebelares/genética , Ataxias Espinocerebelares/patologia
15.
Hum Mutat ; 41(12): 2094-2104, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32935419

RESUMO

KIF1A is a molecular motor for membrane-bound cargo important to the development and survival of sensory neurons. KIF1A dysfunction has been associated with several Mendelian disorders with a spectrum of overlapping phenotypes, ranging from spastic paraplegia to intellectual disability. We present a novel pathogenic in-frame deletion in the KIF1A molecular motor domain inherited by two affected siblings from an unaffected mother with apparent germline mosaicism. We identified eight additional cases with heterozygous, pathogenic KIF1A variants ascertained from a local data lake. Our data provide evidence for the expansion of KIF1A-associated phenotypes to include hip subluxation and dystonia as well as phenotypes observed in only a single case: gelastic cataplexy, coxa valga, and double collecting system. We review the literature and suggest that KIF1A dysfunction is better understood as a single neuromuscular disorder with variable involvement of other organ systems than a set of discrete disorders converging at a single locus.

16.
Nat Commun ; 11(1): 4625, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32934225

RESUMO

A hallmark of neurodegeneration is defective protein quality control. The E3 ligase Listerin (LTN1/Ltn1) acts in a specialized protein quality control pathway-Ribosome-associated Quality Control (RQC)-by mediating proteolytic targeting of incomplete polypeptides produced by ribosome stalling, and Ltn1 mutation leads to neurodegeneration in mice. Whether neurodegeneration results from defective RQC and whether defective RQC contributes to human disease have remained unknown. Here we show that three independently-generated mouse models with mutations in a different component of the RQC complex, NEMF/Rqc2, develop progressive motor neuron degeneration. Equivalent mutations in yeast Rqc2 selectively interfere with its ability to modify aberrant translation products with C-terminal tails which assist with RQC-mediated protein degradation, suggesting a pathomechanism. Finally, we identify NEMF mutations expected to interfere with function in patients from seven families presenting juvenile neuromuscular disease. These uncover NEMF's role in translational homeostasis in the nervous system and implicate RQC dysfunction in causing neurodegeneration.


Assuntos
Doenças Neuromusculares/metabolismo , Ribossomos/metabolismo , Sequência de Aminoácidos , Animais , Feminino , Humanos , Masculino , Camundongos , Camundongos Knockout , Mutação , Doenças Neuromusculares/genética , Doenças Neuromusculares/patologia , Proteólise , Proteínas de Ligação a RNA/química , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismo , Ribossomos/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/química , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Alinhamento de Sequência
17.
Kidney Int ; 98(4): 1020-1030, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32450157

RESUMO

Congenital anomalies of the kidney and urinary tract (CAKUTs) are the most common cause of chronic kidney disease in children. Human 16p11.2 deletions have been associated with CAKUT, but the responsible molecular mechanism remains to be illuminated. To explore this, we investigated 102 carriers of 16p11.2 deletion from multi-center cohorts, among which we retrospectively ascertained kidney morphologic and functional data from 37 individuals (12 Chinese and 25 Caucasian/Hispanic). Significantly higher CAKUT rates were observed in 16p11.2 deletion carriers (about 25% in Chinese and 16% in Caucasian/Hispanic) than those found in the non-clinically ascertained general populations (about 1/1000 found at autopsy). Furthermore, we identified seven additional individuals with heterozygous loss-of-function variants in TBX6, a gene that maps to the 16p11.2 region. Four of these seven cases showed obvious CAKUT. To further investigate the role of TBX6 in kidney development, we engineered mice with mutated Tbx6 alleles. The Tbx6 heterozygous null (i.e., loss-of-function) mutant (Tbx6+/‒) resulted in 13% solitary kidneys. Remarkably, this incidence increased to 29% in a compound heterozygous model (Tbx6mh/‒) that reduced Tbx6 gene dosage to below haploinsufficiency, by combining the null allele with a novel mild hypomorphic allele (mh). Renal hypoplasia was also frequently observed in these Tbx6-mutated mouse models. Thus, our findings in patients and mice establish TBX6 as a novel gene involved in CAKUT and its gene dosage insufficiency as a potential driver for kidney defects observed in the 16p11.2 microdeletion syndrome.


Assuntos
Escoliose , Animais , Humanos , Rim , Camundongos , Estudos Retrospectivos , Proteínas com Domínio T/genética , Anormalidades Urogenitais , Refluxo Vesicoureteral
18.
Eur J Hum Genet ; 28(9): 1243-1264, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32376988

RESUMO

Previously we reported the identification of a homozygous COL27A1 (c.2089G>C; p.Gly697Arg) missense variant and proposed it as a founder allele in Puerto Rico segregating with Steel syndrome (STLS, MIM #615155); a rare osteochondrodysplasia characterized by short stature, congenital bilateral hip dysplasia, carpal coalitions, and scoliosis. We now report segregation of this variant in five probands from the initial clinical report defining the syndrome and an additional family of Puerto Rican descent with multiple affected adult individuals. We modeled the orthologous variant in murine Col27a1 and found it recapitulates some of the major Steel syndrome associated skeletal features including reduced body length, scoliosis, and a more rounded skull shape. Characterization of the in vivo murine model shows abnormal collagen deposition in the extracellular matrix and disorganization of the proliferative zone of the growth plate. We report additional COL27A1 pathogenic variant alleles identified in unrelated consanguineous Turkish kindreds suggesting Clan Genomics and identity-by-descent homozygosity contributing to disease in this population. The hypothesis that carrier states for this autosomal recessive osteochondrodysplasia may contribute to common complex traits is further explored in a large clinical population cohort. Our findings augment our understanding of COL27A1 biology and its role in skeletal development; and expand the functional allelic architecture in this gene underlying both rare and common disease phenotypes.


Assuntos
Anormalidades Múltiplas/genética , Colágenos Fibrilares/genética , Efeito Fundador , Luxação do Quadril/genética , Escoliose/genética , Anormalidades Múltiplas/patologia , Adolescente , Animais , Desenvolvimento Ósseo , Criança , Pré-Escolar , Consanguinidade , Matriz Extracelular/metabolismo , Matriz Extracelular/patologia , Feminino , Colágenos Fibrilares/metabolismo , Frequência do Gene , Luxação do Quadril/patologia , Homozigoto , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Mutação , Linhagem , Escoliose/patologia , Síndrome
19.
Ann Clin Transl Neurol ; 7(5): 610-627, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32286009

RESUMO

OBJECTIVE: Defects in ion channels and neurotransmitter receptors are implicated in developmental and epileptic encephalopathy (DEE). Metabotropic glutamate receptor 7 (mGluR7), encoded by GRM7, is a presynaptic G-protein-coupled glutamate receptor critical for synaptic transmission. We previously proposed GRM7 as a candidate disease gene in two families with neurodevelopmental disorders (NDDs). One additional family has been published since. Here, we describe three additional families with GRM7 biallelic variants and deeply characterize the associated clinical neurological and electrophysiological phenotype and molecular data in 11 affected individuals from six unrelated families. METHODS: Exome sequencing and family-based rare variant analyses on a cohort of 220 consanguineous families with NDDs revealed three families with GRM7 biallelic variants; three additional families were identified through literature search and collaboration with a clinical molecular laboratory. RESULTS: We compared the observed clinical features and variants of 11 affected individuals from the six unrelated families. Identified novel deleterious variants included two homozygous missense variants (c.2671G>A:p.Glu891Lys and c.1973G>A:p.Arg685Gln) and one homozygous stop-gain variant (c.1975C>T:p.Arg659Ter). Developmental delay, neonatal- or infantile-onset epilepsy, and microcephaly were universal. Three individuals had hypothalamic-pituitary-axis dysfunction without pituitary structural abnormality. Neuroimaging showed cerebral atrophy and hypomyelination in a majority of cases. Two siblings demonstrated progressive loss of myelination by 2 years in both and an acquired microcephaly pattern in one. Five individuals died in early or late childhood. CONCLUSION: Detailed clinical characterization of 11 individuals from six unrelated families demonstrates that rare biallelic GRM7 pathogenic variants can cause DEEs, microcephaly, hypomyelination, and cerebral atrophy.


Assuntos
Epilepsia/genética , Microcefalia/genética , Transtornos do Neurodesenvolvimento/genética , Receptores de Glutamato Metabotrópico/genética , Adolescente , Alelos , Atrofia/genética , Atrofia/patologia , Criança , Pré-Escolar , Estudos de Coortes , Consanguinidade , Epilepsia/patologia , Epilepsia/fisiopatologia , Feminino , Humanos , Lactente , Masculino , Microcefalia/patologia , Microcefalia/fisiopatologia , Transtornos do Neurodesenvolvimento/patologia , Transtornos do Neurodesenvolvimento/fisiopatologia , Linhagem , Fenótipo , Sequenciamento Completo do Exoma
20.
Brain ; 143(1): 112-130, 2020 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-31794024

RESUMO

The conserved transport protein particle (TRAPP) complexes regulate key trafficking events and are required for autophagy. TRAPPC4, like its yeast Trs23 orthologue, is a core component of the TRAPP complexes and one of the essential subunits for guanine nucleotide exchange factor activity for Rab1 GTPase. Pathogenic variants in specific TRAPP subunits are associated with neurological disorders. We undertook exome sequencing in three unrelated families of Caucasian, Turkish and French-Canadian ethnicities with seven affected children that showed features of early-onset seizures, developmental delay, microcephaly, sensorineural deafness, spastic quadriparesis and progressive cortical and cerebellar atrophy in an effort to determine the genetic aetiology underlying neurodevelopmental disorders. All seven affected subjects shared the same identical rare, homozygous, potentially pathogenic variant in a non-canonical, well-conserved splice site within TRAPPC4 (hg19:chr11:g.118890966A>G; TRAPPC4: NM_016146.5; c.454+3A>G). Single nucleotide polymorphism array analysis revealed there was no haplotype shared between the tested Turkish and Caucasian families suggestive of a variant hotspot region rather than a founder effect. In silico analysis predicted the variant to cause aberrant splicing. Consistent with this, experimental evidence showed both a reduction in full-length transcript levels and an increase in levels of a shorter transcript missing exon 3, suggestive of an incompletely penetrant splice defect. TRAPPC4 protein levels were significantly reduced whilst levels of other TRAPP complex subunits remained unaffected. Native polyacrylamide gel electrophoresis and size exclusion chromatography demonstrated a defect in TRAPP complex assembly and/or stability. Intracellular trafficking through the Golgi using the marker protein VSVG-GFP-ts045 demonstrated significantly delayed entry into and exit from the Golgi in fibroblasts derived from one of the affected subjects. Lentiviral expression of wild-type TRAPPC4 in these fibroblasts restored trafficking, suggesting that the trafficking defect was due to reduced TRAPPC4 levels. Consistent with the recent association of the TRAPP complex with autophagy, we found that the fibroblasts had a basal autophagy defect and a delay in autophagic flux, possibly due to unsealed autophagosomes. These results were validated using a yeast trs23 temperature sensitive variant that exhibits constitutive and stress-induced autophagic defects at permissive temperature and a secretory defect at restrictive temperature. In summary we provide strong evidence for pathogenicity of this variant in a member of the core TRAPP subunit, TRAPPC4 that associates with vesicular trafficking and autophagy defects. This is the first report of a TRAPPC4 variant, and our findings add to the growing number of TRAPP-associated neurological disorders.


Assuntos
Autofagia/genética , Anormalidades Craniofaciais/genética , Fibroblastos/metabolismo , Proteínas do Tecido Nervoso/genética , Transtornos do Neurodesenvolvimento/genética , Proteínas de Transporte Vesicular/genética , Atrofia , Cerebelo/diagnóstico por imagem , Cerebelo/patologia , Córtex Cerebral/diagnóstico por imagem , Córtex Cerebral/patologia , Criança , Pré-Escolar , Anormalidades Craniofaciais/diagnóstico por imagem , Surdez/genética , Surdez/fisiopatologia , Deficiências do Desenvolvimento/genética , Deficiências do Desenvolvimento/fisiopatologia , Epilepsia/genética , Epilepsia/fisiopatologia , Feminino , Perda Auditiva Neurossensorial/genética , Perda Auditiva Neurossensorial/fisiopatologia , Humanos , Lactente , Recém-Nascido , Deficiência Intelectual/genética , Deficiência Intelectual/fisiopatologia , Masculino , Microcefalia/genética , Microcefalia/fisiopatologia , Microscopia de Fluorescência , Espasticidade Muscular/genética , Espasticidade Muscular/fisiopatologia , Transtornos do Neurodesenvolvimento/fisiopatologia , Linhagem , Quadriplegia/genética , Quadriplegia/fisiopatologia , Sítios de Splice de RNA/genética , Síndrome
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