scholarly journals Impaired development of neocortical circuits contributes to the neurological alterations in DYRK1A haploinsufficiency syndrome

2018 ◽  
Author(s):  
Juan Arranz ◽  
Elisa Balducci ◽  
Krisztina Arató ◽  
Gentzane Sánchez-Elexpuru ◽  
Sònia Najas ◽  
...  
Keyword(s):  
Biochemical Characterization ◽  
Catalytic Domain ◽  
De Novo ◽  
Epileptic Activity ◽  
Autism Spectrum ◽  
Repetitive Behaviors ◽  
Mutant Mice ◽  
Chromosome 21 ◽  
Missense Mutations ◽  
Human Pathology

ABSTRACTAutism spectrum disorders are early onset neurodevelopmental disorders characterized by deficits in social communication and restricted repetitive behaviors, yet they are quite heterogeneous in terms of their genetic basis and phenotypic manifestations. Recently, de novo pathogenic mutations in DYRK1A, a chromosome 21 gene associated to neuropathological traits of Down syndrome, have been identified in patients presenting a recognizable syndrome included in the autism spectrum. These mutations produce DYRK1A kinases with partial or complete absence of the catalytic domain, or they represent missense mutations located within this domain. Here, we undertook an extensive biochemical characterization of the DYRK1A missense mutations reported to date and show that most of them, but not all, result in enzymatically dead DYRK1A proteins. We also show that haploinsufficient Dyrk1a+/- mutant mice mirror the neurological traits associated with the human pathology, such as defective social interactions, stereotypic behaviors and epileptic activity. These mutant mice present altered proportions of excitatory and inhibitory neocortical neurons and synapses. Moreover, we provide evidence that alterations in the production of cortical excitatory neurons are contributing to these defects. Indeed, by the end of the neurogenic period, the expression of developmental regulated genes involved in neuron differentiation and/or activity is altered. Therefore, our data indicate that altered neocortical neurogenesis could critically affect the formation of cortical circuits, thereby contributing to the neuropathological changes in DYRK1A haploinsufficiency syndrome.

scholarly journals Sex-dependent role for EPHB2 in brain development and autism-associated behavior

2021 ◽  
Author(s):  
Ahlem Assali ◽  
Jennifer Y. Cho ◽  
Evgeny Tsvetkov ◽  
Abha R. Gupta ◽  
Christopher W. Cowan
Keyword(s):  
Pyramidal Neurons ◽  
De Novo ◽  
Repetitive Behavior ◽  
Autism Spectrum ◽  
Repetitive Behaviors ◽  
Male Mice ◽  
Sensory Sensitivity ◽  
Hyperactivity Disorder ◽  
Specific Effects ◽  
Layer V

AbstractAutism spectrum disorder (ASD) is characterized by impairments in social communication and interaction and restricted, repetitive behaviors. It is frequently associated with comorbidities, such as attention-deficit hyperactivity disorder, altered sensory sensitivity, and intellectual disability. A de novo nonsense mutation in EPHB2 (Q857X) was discovered in a female patient with ASD [13], revealing EPHB2 as a candidate ASD risk gene. EPHB2 is a receptor tyrosine kinase implicated in axon guidance, synaptogenesis, and synaptic plasticity, positioning it as a plausible contributor to the pathophysiology of ASD and related disorders. In this study, we show that the Q857X mutation produced a truncated protein lacking forward signaling and that global disruption of one EphB2 allele (EphB2+/−) in mice produced several behavioral phenotypes reminiscent of ASD and common associated symptoms. EphB2+/− female, but not male, mice displayed increased repetitive behavior, motor hyperactivity, and learning and memory deficits, revealing sex-specific effects of EPHB2 hypofunction. Moreover, we observed a significant increase in the intrinsic excitability, but not excitatory/inhibitory ratio, of motor cortex layer V pyramidal neurons in EphB2+/− female, but not male, mice, suggesting a possible mechanism by which EPHB2 hypofunction may contribute to sex-specific motor-related phenotypes. Together, our findings suggest that EPHB2 hypofunction, particularly in females, is sufficient to produce ASD-associated behaviors and altered cortical functions in mice.

scholarly journals SENP1 in the retrosplenial agranular cortex regulates core autistic-like symptoms in mice

2021 ◽  
Author(s):  
Kan Yang ◽  
Yuhan Shi ◽  
Xiujuan Du ◽  
Yuefang Zhang ◽  
Shifang Shan ◽  
...  
Keyword(s):  
Social Interaction ◽  
De Novo ◽  
Fragile X ◽  
Neurodevelopmental Disorder ◽  
Autism Spectrum ◽  
Repetitive Behaviors ◽  
Genetic Components ◽  
Truncating Mutation ◽  
Synaptic Functions ◽  
Core Symptoms

AbstractAutism spectrum disorder (ASD) is a highly heritable complex neurodevelopmental disorder. While the core symptoms of ASD are defects of social interaction and repetitive behaviors, over 50% of ASD patients have comorbidity of intellectual disabilities (ID) or developmental delay (DD), raising the question whether there are genetic components and neural circuits specific for core symptoms of ASD. Here, by focusing on ASD patients who do not show compound ID or DD, we identified a de novo heterozygous gene-truncating mutation of the Sentrin-specific peptidase1 (SENP1) gene, coding the small ubiquitin-like modifiers (SUMO) deconjugating enzyme, as a potentially new candidate gene for ASD. We found that Senp1 haploinsufficient mice exhibited core symptoms of autism such as deficits in social interaction and repetitive behaviors, but normal learning and memory ability. Moreover, we found that the inhibitory and excitatory synaptic functions were severely affected in the retrosplenial agranular (RSA) cortex of Senp1 haploinsufficient mice. Lack of Senp1 led to over SUMOylation and degradation of fragile X mental retardation protein (FMRP) proteins, which is coded by the FMR1 gene, also implicated in syndromic autism. Importantly, re-introducing SENP1 or FMRP specifically in RSA fully rescued the defects of synaptic functions and core autistic-like symptoms of Senp1 haploinsufficient mice. Taken together, these results elucidate that disruption of the SENP1-FMRP regulatory axis in the RSA may cause core autistic symptoms, which further provide a candidate brain region for therapeutic intervene of ASD by neural modulation approaches.

scholarly journals Varying intolerance of gene pathways to mutational classes explain genetic convergence across neuropsychiatric disorders

2016 ◽  
Author(s):  
Shahar Shohat ◽  
Eyal Ben-David ◽  
Sagiv Shifman
Keyword(s):  
Gene Expression ◽  
Genome Wide Association Study ◽  
De Novo ◽  
Expression Patterns ◽  
Neuropsychiatric Disorders ◽  
Autism Spectrum ◽  
Specific Gene ◽  
Missense Mutations ◽  
Loss Of Function ◽  
Brain Gene Expression

AbstractGenetic susceptibility to Intellectual disability (ID), autism spectrum disorder (ASD) and schizophrenia (SCZ) often arises from mutations in the same genes, suggesting that they share common mechanisms. We studied genes with de novo mutations in the three disorders and genes implicated by SCZ genome-wide association study (GWAS). Using biological annotations and brain gene expression, we show that mutation class explains enrichment patterns more than specific disorder. Genes with loss of function mutations and genes with missense mutations were enriched with different pathways, shared with genes intolerant to mutations. Specific gene expression patterns were found for each disorder. ID genes were preferentially expressed in fetal cortex, ASD genes also in fetal cerebellum and striatum, and genes associated with SCZ were most significantly enriched in adolescent cortex. Our study suggests that convergence across neuropsychiatric disorders stems from vulnerable pathways to genetic variations, but spatiotemporal activity of genes contributes to specific phenotypes.

scholarly journals Translational animal models of autism and neurodevelopmental disorders

2012 ◽  
Vol 14 (3) ◽  
pp. 293-305 ◽  
Keyword(s):  
Mouse Models ◽  
De Novo ◽  
Single Gene ◽  
Neurodevelopmental Disorder ◽  
Gene Mutations ◽  
Autism Spectrum ◽  
Repetitive Behaviors ◽  
Restricted Interests ◽  
Homologous Genes ◽  
Biological Outcomes

Autism is a neurodevelopmental disorder whose diagnosis is based on three behavioral criteria: unusual reciprocal social interactions, deficits in communication, and stereotyped repetitive behaviors with restricted interests. A large number of de novo single gene mutations and chromosomal deletions are associated with autism spectrum disorders. Based on the strong genetic evidence, mice with targeted mutations in homologous genes have been generated as translational research tools. Mouse models of autism have revealed behavioral and biological outcomes of mutations in risk genes. The field is now poised to employ the most robust phenotypes in the most replicable mouse models for preclinical screening of novel therapeutics.

scholarly journals Genome Wide Variant Analysis of Simplex Autism Families with an Integrative Clinical-Bioinformatics Pipeline

2015 ◽  
Author(s):  
Laura T Jiménez-Barrón ◽  
Jason A O'Rawe ◽  
Yiyang Wu ◽  
Margaret Yoon ◽  
Han Fang ◽  
...  
Keyword(s):  
Whole Genome Sequencing ◽  
Genome Sequencing ◽  
De Novo ◽  
Autism Spectrum ◽  
Repetitive Behaviors ◽  
Whole Genome ◽  
Sequencing Data ◽  
Bioinformatics Pipeline ◽  
Bioinformatics Tools ◽  
Genome Wide

Autism spectrum disorders (ASD) are a group of developmental disabilities that affect social interaction, communication and are characterized by repetitive behaviors. There is now a large body of evidence that suggests a complex role of genetics in ASD, in which many different loci are involved. Although many current population scale genomic studies have been demonstrably fruitful, these studies generally focus on analyzing a limited part of the genome or use a limited set of bioinformatics tools. These limitations preclude the analysis of genome-wide perturbations that may contribute to the development and severity of ASD-related phenotypes. To overcome these limitations, we have developed and utilized an integrative clinical and bioinformatics pipeline for generating a more complete and reliable set of genomic variants for downstream analyses. Our study focuses on the analysis of three simplex autism families consisting of one affected child, unaffected parents, and one unaffected sibling. All members were clinically evaluated and widely phenotyped. Genotyping arrays and whole genome sequencing were performed on each member, and the resulting sequencing data were analyzed using a variety of available bioinformatics tools. We searched for rare variants of putative functional impact that were found to be segregating according to de-novo, autosomal recessive, x-linked, mitochondrial and compound heterozygote transmission models. The resulting candidate variants included three small heterozygous CNVs, a rare heterozygous de novo nonsense mutation in MYBBP1A located within exon 1, and a novel de novo missense variant in LAMB3. Our work demonstrates how more comprehensive analyses that include rich clinical data and whole genome sequencing data can generate reliable results for use in downstream investigations. We are moving to implement our framework for the analysis and study of larger cohorts of families, where statistical rigor can accompany genetic findings.

scholarly journals Mice harboring a SCA28 patient mutation in AFG3L2 develop late-onset ataxia associated with enhanced mitochondrial proteotoxicity.

2018 ◽  
Author(s):  
Cecilia Mancini ◽  
Eriola Hoxha ◽  
Luisa Iommarini ◽  
Alessandro Brussino ◽  
Uwe Richter ◽  
...  
Keyword(s):  
Network Formation ◽  
De Novo ◽  
Neurodegenerative Disorder ◽  
Late Onset ◽  
Mitochondrial Protein ◽  
Atp Synthesis ◽  
Protein Translation ◽  
Mutant Mice ◽  
Mitochondrial Morphology ◽  
Missense Mutations

Spinocerebellar ataxia 28 is an autosomal dominant neurodegenerative disorder caused by missense mutations affecting the proteolytic domain of AFG3L2, a major component of the mitochondrial m-AAA protease. However, little is known of the underlying pathogenetic mechanisms or how to treat patients with SCA28. Currently available Afg3l2 mutant mice harbour deletions that lead to severe, early-onset neurological phenotypes that do not faithfully reproduce the late-onset and slowly progressing SCA28 phenotype. Here we describe production and detailed analysis of a new knock-in murine model harbouring an Afg3l2 allele carrying the p.Met665Arg patient-derived mutation. Heterozygous mutant mice developed normally but signs of ataxia were detectable by beam test at 18 months. Cerebellar pathology was negative; electrophysiological analysis showed increased spontaneous firing in Purkinje cells from heterozygous mutants with respect to wild-type controls, although not statistically significant. As homozygous mutants died perinatally with evidence of cardiac atrophy, for each genotype we generated mouse embryonic fibroblasts (MEFs) to investigate mitochondrial function. MEFs from mutant mice showed altered mitochondrial bioenergetics, with decreased basal oxygen consumption rate, ATP synthesis and mitochondrial membrane potential. Mitochondrial network formation and morphology was also altered, in line with greatly reduced expression of Opa1 fusogenic protein L-isoforms. The mitochondrial alterations observed in MEFs were also detected in cerebella of 18-month-old heterozygous mutants, suggesting they may be a hallmark of disease. Pharmacological inhibition of de novo mitochondrial protein translation with chloramphenicol caused reversal of mitochondrial morphology in homozygous mutant MEFs, supporting the relevance of mitochondrial proteotoxicity for SCA28 pathogenesis and therapy development.

scholarly journals Evolutionary Action of de novo Missense Variants across Pathways Prioritizes Genes Linked to Autism and Predicts Patient Phenotypic Severity

2017 ◽  
Author(s):  
Amanda Koire ◽  
Christie Buchovecky ◽  
Panagiotis Katsonis ◽  
Young Won Kim ◽  
Stephen J. Wilson ◽  
...  
Keyword(s):  
Autism Spectrum Disorder ◽  
Synaptic Transmission ◽  
De Novo ◽  
Missense Variant ◽  
Autism Spectrum ◽  
Spectrum Disorder ◽  
Integrative Approach ◽  
Missense Mutations ◽  
Functional Impact ◽  
Missense Variants

AbstractThe pathogenicity of individual de novo missense mutations in autism spectrum disorder remains difficult to validate. Here we asked in 2,384 probands whether these variants exhibited collective functional impact biases across pathways. As measured with Evolutionary Action (EA) in 368 gene groupings, we found significant biases in axonogenesis, synaptic transmission, and other neurodevelopmental pathways. Strikingly, both de novo and inherited missense variants in prioritized genes correlated with patient IQ. This general integrative approach thus detects missense variants most likely to contribute to autism pathogenesis and is the first, to our knowledge, to link missense variant impact to autism phenotypic severity.

The Autism Spectrum

2018 ◽  
pp. 243-260
Author(s):  
Marco Del Giudice
Keyword(s):  
Risk Factors ◽  
De Novo ◽  
Autism Spectrum ◽  
Repetitive Behaviors ◽  
Evolutionary Models ◽  
De Novo Mutations ◽  
Life History Variation ◽  
New Directions ◽  
Developmental Features

The chapter discusses autism spectrum disorder (ASD). Autism is defined by a triad of symptoms: impairments in social interaction, impairments in communication, and restricted/repetitive behaviors and interests. After an overview of this disorder, its developmental features, and the main risk factors identified in the epidemiological literature, the chapter critically reviews existing evolutionary models and suggests new directions for research. The final section applies the criteria developed earlier in the book to classify the disorder within the fast-slow-defense (FSD) model and identify functionally distinct subtypes. The author proposes to distinguish between a slow spectrum subtype with normal or high IQ and a major role of common alleles (S-ASD) and a subtype unrelated to life history variation, with high rates of intellectual disability and a major role of rare and de novo mutations (O-ASD).

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