Genetic analysis of a child with early onset neurodevelopmental disorder with involuntary movement and a literature review / 中华医学遗传学杂志

OBJECTIVE@#To explore the clinical phenotype and genetic basis of a child with early onset neurodevelopmental disorder with involuntary movement (NEDIM).@*METHODS@#A child who presented at Department of Neurology of Hunan Children's Hospital on October 8, 2020 was selected as the study subject. Clinical data of the child were collected. Genomic DNA was extracted from peripheral blood samples of the child and his parents. Whole exome sequencing (WES) was carried out for the child. Candidate variant was verified by Sanger sequencing and bioinformatic analysis. Relevant literature was searched from the CNKI, PubMed and Google Scholar databases to summarize the clinical phenotypes and genetic variants of the patients.@*RESULTS@#This child was a 3-year-and-3-month boy with involuntary trembling of limbs and motor and language delay. WES revealed that the child has harbored a c.626G>A (p.Arg209His) variant of the GNAO1 gene. Sanger sequencing confirmed that neither of his parents has carried the same variant. The variant had been reported in HGMD and ClinVar databases, but not in the dbSNP, ExAC and 1000 Genomes databases. Prediction with SIFT, PolyPhen-2, and Mutation Taster online software suggested that the variant may be deleterious to the protein function. By UniProt database analysis, the encode amino acid is highly conserved among various species. Prediction with Modeller and PyMOL software indicated that the variant may affect the function of GαO protein. Based on the guideline of the American College of Medical Genetics and Genomics (ACMG), the variant was rated as pathogenic.@*CONCLUSION@#The GNAO1 gene c.626G>A (p.Arg209His) variant probably underlay the NEDIM in this child. Above finding has expanded the phenotypic spectrum of GNAO1 gene c.626G>A (p.Arg209His) variant and provided a reference for clinical diagnosis and genetic counseling.

RhoGEF Trio Regulates Radial Migration of Projection Neurons via Its Distinct Domains / 神经科学通报·英文版

The radial migration of cortical pyramidal neurons (PNs) during corticogenesis is necessary for establishing a multilayered cerebral cortex. Neuronal migration defects are considered a critical etiology of neurodevelopmental disorders, including autism spectrum disorders (ASDs), schizophrenia, epilepsy, and intellectual disability (ID). TRIO is a high-risk candidate gene for ASDs and ID. However, its role in embryonic radial migration and the etiology of ASDs and ID are not fully understood. In this study, we found that the in vivo conditional knockout or in utero knockout of Trio in excitatory precursors in the neocortex caused aberrant polarity and halted the migration of late-born PNs. Further investigation of the underlying mechanism revealed that the interaction of the Trio N-terminal SH3 domain with Myosin X mediated the adherence of migrating neurons to radial glial fibers through regulating the membrane location of neuronal cadherin (N-cadherin). Also, independent or synergistic overexpression of RAC1 and RHOA showed different phenotypic recoveries of the abnormal neuronal migration by affecting the morphological transition and/or the glial fiber-dependent locomotion. Taken together, our findings clarify a novel mechanism of Trio in regulating N-cadherin cell surface expression via the interaction of Myosin X with its N-terminal SH3 domain. These results suggest the vital roles of the guanine nucleotide exchange factor 1 (GEF1) and GEF2 domains in regulating radial migration by activating their Rho GTPase effectors in both distinct and cooperative manners, which might be associated with the abnormal phenotypes in neurodevelopmental disorders.

Loss of O-GlcNAcylation on MeCP2 at Threonine 203 Leads to Neurodevelopmental Disorders / 神经科学通报·英文版

Mutations of the X-linked methyl-CpG-binding protein 2 (MECP2) gene in humans are responsible for most cases of Rett syndrome (RTT), an X-linked progressive neurological disorder. While genome-wide screens in clinical trials have revealed several putative RTT-associated mutations in MECP2, their causal relevance regarding the functional regulation of MeCP2 at the etiologic sites at the protein level requires more evidence. In this study, we demonstrated that MeCP2 was dynamically modified by O-linked-β-N-acetylglucosamine (O-GlcNAc) at threonine 203 (T203), an etiologic site in RTT patients. Disruption of the O-GlcNAcylation of MeCP2 specifically at T203 impaired dendrite development and spine maturation in cultured hippocampal neurons, and disrupted neuronal migration, dendritic spine morphogenesis, and caused dysfunction of synaptic transmission in the developing and juvenile mouse cerebral cortex. Mechanistically, genetic disruption of O-GlcNAcylation at T203 on MeCP2 decreased the neuronal activity-induced induction of Bdnf transcription. Our study highlights the critical role of MeCP2 T203 O-GlcNAcylation in neural development and synaptic transmission potentially via brain-derived neurotrophic factor.

La neuroanatomía y neurofisiología en la comprensión de los trastornos del espectro autista / Neuroanatomy and neurophysiology in the study of autism spectrum disorders

Introducción: Los trastornos de espectro autista se caracterizan por presentar un déficit en la interacción y comunicación social con presencia de patrones repetitivos y restrictivos de comportamiento, intereses y actividades. En ellos estarían implicadas causas genéticas, ambientales y del desarrollo del sistema nervioso central. Un mayor conocimiento de la neuroanatomía y la neurofisiología ayudaría a comprender mejor este trastorno del neurodesarrollo. Objetivo: Profundizar en el conocimiento neuroanatómico y neurofisiológico de los trastornos del espectro autista. Métodos: Se realizó una búsqueda bibliográfica acerca del tema en las bases de datos LILACS, Scopus, SciELO, Pubmed, Medigraphic. Se escogieron 13 documentos, todos correspondientes a artículos originales que abordan el tema desde diferentes aristas. De los documentos, dos fueron localizados en Scopus, uno en Pubmed, cuatro en Medigrafhic, dos en LILACS y cuatro en SciELO. Resultados: Los trastornos de espectro autista se producen por una alteración estructural y funcional de la corteza cerebral. Los estudios de neuroimágenes han demostrado las alteraciones estructurales, fundamentalmente en la corteza prefrontal y sus conexiones, principal región encefálica implicada en la regulación de la conducta social. Las técnicas de secuenciación genómica de nueva generación muestran el origen genético en casos donde los estudios previamente señalados han resultado ser normales. Conclusiones: La profundización del conocimiento neuroanatómico y neurofisiológico de los trastornos de espectro autista permiten comprenderlos mejor(AU)

Introduction: Autism spectrum disorders are characterized by social deficits and communication difficulties, as well as restrictive, repetitive behavior patterns, interests and activities. Their causes may be genetic, environmental or related to the development of the central nervous system. Broader knowledge about neuroanatomy and neurophysiology could lead to a better understanding of this neurodevelopmental disorder. Objective: Gain insight into the neuroanatomy and neurophysiology of autism spectrum disorders. Methods: A bibliographic search about the topic was conducted in the databases LILACS, Scopus, SciELO, Pubmed and Medigraphic. A total 13 documents were selected, all of which were original papers approaching the topic from different perspectives. Two of the documents were obtained from Scopus, one from Pubmed, four from Medigraphic, two from LILACS and four from SciELO. Results: Autism spectrum disorders are caused by a structural and functional alteration of the cerebral cortex. Neuroimaging studies have shown the structural alterations, which mainly occur in the prefrontal cortex and its connections, the principal encephalic region involved in social behavior regulation. New generation genomic sequencing techniques reveal a genetic origin in cases where previous studies have been normal. Conclusions: Broader knowledge about the neuroanatomy and neurophysiology of autism spectrum disorders lead to their better understanding(AU)

A review on the genetic mechanism of chromatin remodeling in children with neurodevelopmental disorders / 中国当代儿科杂志

Neural development is regulated by both external environment and internal signals, and in addition to transcription factors, epigenetic modifications also play an important role. By focusing on the genetic mechanism of ATP-dependent chromatin remodeling in children with neurodevelopmental disorders, this article elaborates on the effect of four chromatin remodeling complexes on neurogenesis and the development and maturation of neurons and neuroglial cells and introduces the clinical research advances in neurodevelopmental disorders.

Genómica de los trastornos del desarrollo neurológico / Genomics of neurodevelopmental disorders

Introduction: Neurodevelopmental disorders (NDD) are featured by a delay in the acquisition of motor functions, cognitive abilities and speech, or combined deficits in these areas with the onset before the age of 5 years. Genetic causes account for approximately a half of all NDD cases. Objective: to describe alterations of the genome implied in neurodevelopmental disorders and some aspects of their genetic counseling. Methods: Bibliographic search in Medline, Pubmed, Scielo, LILACS and Cochrane, emphasizing in the last five years, the relationship between the various genetic factors that may be involved in neurodevelopmental disorders. Results: Multiple genetic factors are involved in neurodevelopmental disorders, from gross ones such as chromosomal aneuploidies to more subtle ones such as variations in the number of copies in the genome. Special emphasis is placed on microdeletion-micro duplication syndromes as a relatively frequent cause of NDDs and their probable mechanisms of formation are explained. Final Considerations: Genetic aberrations are found in at least 30-50 percent of children with NDD. Conventional karyotyping allows the detection of chromosomal aberrations encompassing more than 5-7 Mb, which represent 5-10 percent of causative genome rearrangements in NDD. Molecular karyotyping (e.g. SNP array/array CGH) can significantly improve the yield in patients with NDD and congenital malformations(AU)

Introducción: Los trastornos del neurodesarrollo están caracterizados por retardo en la adquisición de las funciones motoras, habilidades cognitivas para el habla o el déficit combinado en estas áreas; se presenta en niños menores de 5 años de edad. Las causas genéticas están implicadas en más de la mitad de los pacientes con estos trastornos Objetivo: Examinar las alteraciones del genoma implicados en los trastornos del neurodesarrollo y algunos aspectos de su asesoramiento genético. Métodos: Búsqueda bibliográfica en Medline, Pubmed, Scielo, LILACS y Cochrane con énfasis en los últimos cinco años, acerca de la relación entre los variados factores genéticos que pueden estar involucrados en los trastornos del neurodesarrollo. Resultados: Los factores genéticos involucrados pueden ser groseros como las aneuploidías cromosómicas hasta los más sutiles como las variaciones en el número de copias en el genoma. Se describen los síndromes de microdeleción-micro duplicación como una causa relativamente frecuente de los trastornos del neurodesarrollo y se explican sus probables mecanismos de formación. Se relacionan las aneuploidías cromosómicas y las variaciones en el número de copia como causas de estos trastornos. Consideraciones finales . Las aberraciones genéticas se encuentran en 30-50 por ciento de los niños con trastornos del neurodesarrollo. El cariotipo convencional permite la detección de aberraciones cromosómicas que abarcan más de 5-7 Mb, lo que representa 5-10 por ciento de los reordenamientos genómicos causales en estos trastornos. El cariotipo molecular (por ejemplo, una matriz de SNP/ CGH de matriz) puede mejorar significativamente la certeza del diagnóstico en pacientes con trastornos del neurodesarrollo y malformaciones congénitas(AU)

Estudios genéticos y neurodesarrollo: De la utilidad al modelo genético / Genetic studies and neurodevelopment. From effectiveness to genetic models]

Los avances en la genética han podido apoyar la sospecha que aportaba la experiencia clínica sobre el gran componente hereditario de la mayor parte de estos trastornos del neurodesarrollo (TND). Los estudios iniciales de heredabilidad, ligamiento o asociación evidenciaron desde los inicios la gran contribución de la variación genotípica a la clínica en general, y a los TND en particular. No debe obviarse la utilidad de los estudios genéticos en el ejercicio clínico, encaminados al diagnóstico etiológico. La mayor parte de los mismos están protocolizados en el estudio de trastornos como la discapacidad intelectual y el autismo; dentro de éstos, la hibridación por arrays cromosómicos ha aportado una mayor rentabilidad diagnóstica respecto a técnicas citogenéticas históricas (3 vs. 10% respectivamente). Sin embargo, la irrupción y rentabilidad de técnicas de genética molecular por secuenciación, particularmente la exómica y genómica en trío, analizando a padres, (tasas diagnósticas del 30-50%), están condicionando la modificación de los algoritmos genéticos en el diagnóstico de trastornos graves del neurodesarrollo. El mayor conocimiento de variantes causales de discapacidad intelectual y autismo está igualmente modificando los modelos teóricos poligénicos establecidos hasta la fecha.

Advances in genetics have been able to support the clinical suspicion on the large hereditary component of most of these neurodevelopmental disorders (NDD). Initial studies on heritability, linkage or association showed from the beginning the great contribution of genotypic variation to the clinic in general, and to NDD in particular. The effectiveness of genetic studies in clinical practice, targeted to aetiological diagnosis, should not be ignored. Most of these are protocolized in the study of disorders such as intellectual disability and autism; within these, the array comparative genomic hybridization have supported a greater diagnostic effectiveness with respect to historical cytogenetic techniques (3 vs. 10% respectively). However, the irruption and success of molecular genetic sequencing techniques, particularly the exome and genome in trio, analyzing the parents (diagnostic rates of 30-50%), are conditioning the modification of the genetic algorithms in the diagnosis of different NDD. The greater knowledge of causal variants in intellectual disability and autism is also modifying the polygenic theoretical models established to date.

Microarreglos cromosómicos en 236 pacientes chilenos con trastornos del neurodesarrollo y anomalías congénitas / Microarrays in 236 patients with neurodevelopmental disorders and congenital abnormalities

Background: In 20% of neurodevelopmental disorders (NDD) and congenital abnormalities (CA) the cause would be a genomic imbalance detectable only by chromosomal microarrays (CMA). Aim: To analyze the results of CMA performed at the INTA Laboratory of Molecular Cytogenetics, during a period of four years in patients with NDD or CA. Material and Methods: Retrospective study that included all CMA reports of Chilean patients. Age, sex, clinical diagnosis and origin were analyzed, as well as the characteristics of the finding. The percentage of cases diagnosed by CMA was calculated considering all patients with pathogenic (PV) or probably pathogenic variants (VLP). Finally, we studied the association between patients' characteristics and a positive CMA outcome. Results: A total of 236 reports were analyzed. The median age was 5.41 (range 2.25-9.33) years, and 59% were men. Ninety chromosomal imbalances were found, which corresponded mainly to deletions (53.3%), with a median size of 1.662 (range 0.553-6.673) Megabases. The diagnostic rate of CMA in Chilean patients from all over the country was 19.2%. There was a close relationship between the patient's sex and the detection of VLP/VP (p = 0.034). Conclusions: Our diagnostic rate and the association between female sex and a higher percentage of diagnosed cases are concordant with other international studies. Therefore, CMA is a valid diagnostic tool in the Chilean population.