scholarly journals Systematic phenomics analysis of ASD-associated genes reveals shared functions and parallel networks underlying reversible impairments in habituation learning

2019 ◽  
Author(s):  
Troy A. McDiarmid ◽  
Manuel Belmadani ◽  
Joseph Liang ◽  
Fabian Meili ◽  
Eleanor A. Mathews ◽  
...  
Keyword(s):  
Vision System ◽  
Missense Variant ◽  
Autism Spectrum ◽  
Loss Of Function ◽  
C Elegans ◽  
Learning Impairments ◽  
Functional Assays ◽  
Epistasis Analysis ◽  
Parallel Networks

SUMMARYA major challenge facing the genetics of Autism Spectrum Disorders (ASD) is the large and growing number of candidate risk genes and gene variants of unknown functional significance. Here, we used Caenorhabditis elegans to systematically functionally characterize ASD-associated genes in vivo. Using our custom machine vision system we quantified 26 phenotypes spanning morphology, locomotion, tactile sensitivity, and habituation learning in 87 strains each carrying a mutation in an ortholog of an ASD-associated gene. We identified hundreds of novel genotype-phenotype relationships ranging from severe developmental delays and uncoordinated movement to subtle deficits in sensory and learning behaviors. We clustered genes by similarity in phenomic profiles and used epistasis analysis to discover parallel networks centered on CHD8•chd-7 and NLGN3•nlg-1 that underlie mechanosensory hyper-responsivity and impaired habituation learning. We then leveraged our data for in vivo functional assays to gauge missense variant effect. Expression of wild-type NLG-1 in nlg-1 mutant C. elegans rescued their sensory and learning impairments. Testing the rescuing ability of all conserved ASD-associated neuroligin variants revealed varied partial loss-of-function despite proper subcellular localization. Finally, we used CRISPR-Cas9 auxin inducible degradation to determine that phenotypic abnormalities caused by developmental loss of NLG-1 can be reversed by adult expression. This work charts the phenotypic landscape of ASD-associated genes, offers novel in vivo variant functional assays, and potential therapeutic targets for ASD.

scholarly journals Systematic phenomics analysis of autism-associated genes reveals parallel networks underlying reversible impairments in habituation

2019 ◽  
Vol 117 (1) ◽  
pp. 656-667 ◽  
Author(s):  
Troy A. McDiarmid ◽  
Manuel Belmadani ◽  
Joseph Liang ◽  
Fabian Meili ◽  
Eleanor A. Mathews ◽  
...  
Keyword(s):  
Vision System ◽  
Missense Variant ◽  
Autism Spectrum ◽  
Loss Of Function ◽  
C Elegans ◽  
Learning Impairments ◽  
Functional Assays ◽  
Epistasis Analysis ◽  
Parallel Networks

A major challenge facing the genetics of autism spectrum disorders (ASDs) is the large and growing number of candidate risk genes and gene variants of unknown functional significance. Here, we usedCaenorhabditis elegansto systematically functionally characterize ASD-associated genes in vivo. Using our custom machine vision system, we quantified 26 phenotypes spanning morphology, locomotion, tactile sensitivity, and habituation learning in 135 strains each carrying a mutation in an ortholog of an ASD-associated gene. We identified hundreds of genotype–phenotype relationships ranging from severe developmental delays and uncoordinated movement to subtle deficits in sensory and learning behaviors. We clustered genes by similarity in phenomic profiles and used epistasis analysis to discover parallel networks centered onCHD8•chd-7andNLGN3•nlg-1that underlie mechanosensory hyperresponsivity and impaired habituation learning. We then leveraged our data for in vivo functional assays to gauge missense variant effect. Expression of wild-type NLG-1 innlg-1mutantC. elegansrescued their sensory and learning impairments. Testing the rescuing ability of conserved ASD-associated neuroligin variants revealed varied partial loss of function despite proper subcellular localization. Finally, we used CRISPR-Cas9 auxin-inducible degradation to determine that phenotypic abnormalities caused by developmental loss of NLG-1 can be reversed by adult expression. This work charts the phenotypic landscape of ASD-associated genes, offers in vivo variant functional assays, and potential therapeutic targets for ASD.

scholarly journals UBE3A-mediated PTPA ubiquitination and degradation regulate PP2A activity and dendritic spine morphology

2019 ◽  
Vol 116 (25) ◽  
pp. 12500-12505 ◽  
Author(s):  
Jie Wang ◽  
Sen-Sen Lou ◽  
Tingting Wang ◽  
Rong-Jie Wu ◽  
Guangying Li ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Dendritic Spine ◽  
Isotope Labeling ◽  
Neurodevelopmental Disorder ◽  
Critical Role ◽  
Motor Impairment ◽  
Autism Spectrum ◽  
Loss Of Function ◽  
Pp2a Activity

Deficiency in the E3 ubiquitin ligase UBE3A leads to the neurodevelopmental disorder Angelman syndrome (AS), while additional dosage of UBE3A is linked to autism spectrum disorder. The mechanisms underlying the downstream effects of UBE3A gain or loss of function in these neurodevelopmental disorders are still not well understood, and effective treatments are lacking. Here, using stable-isotope labeling of amino acids in mammals and ubiquitination assays, we identify PTPA, an activator of protein phosphatase 2A (PP2A), as a bona fide ubiquitin ligase substrate of UBE3A. Maternal loss of Ube3a (Ube3am−/p+) increased PTPA level, promoted PP2A holoenzyme assembly, and elevated PP2A activity, while maternal 15q11–13 duplication containing Ube3a down-regulated PTPA level and lowered PP2A activity. Reducing PTPA level in vivo restored the defects in dendritic spine maturation in Ube3am−/p+ mice. Moreover, pharmacological inhibition of PP2A activity with the small molecule LB-100 alleviated both reduction in excitatory synaptic transmission and motor impairment in Ube3am−/p+ mice. Together, our results implicate a critical role of UBE3A-PTPA-PP2A signaling in the pathogenesis of UBE3A-related disorders and suggest that PP2A-based drugs could be potential therapeutic candidates for treatment of UBE3A-related disorders.

scholarly journals Haploinsufficiency of autism candidate gene NUAK1 impairs cortical development and behavior

2018 ◽  
Author(s):  
Virginie Courchet ◽  
Amanda J Roberts ◽  
Peggy Del Carmine ◽  
Tommy L. Lewis ◽  
Franck Polleux ◽  
...  
Keyword(s):  
Social Preference ◽  
De Novo ◽  
Sensorimotor Gating ◽  
Learning Task ◽  
Autism Spectrum ◽  
Dominant Negative ◽  
Loss Of Function ◽  
Cortical Connectivity

SUMMARYRecently, numerous rare de novo mutations have been identified in children diagnosed with autism spectrum disorders (ASD). However, despite the predicted loss-of-function nature of some of these de novo mutations, the affected individuals are heterozygous carriers, which would suggest that most of these candidate genes are haploinsufficient and/or that these mutations lead to expression of dominant-negative forms of the protein. Here, we tested this hypothesis with the gene Nuak1, recently identified as a candidate ASD gene and that we previously identified for its role in the development of cortical connectivity. We report that Nuak1 is happloinsufficient in mice in regard to its function in cortical axon branching in vitro and in vivo. Nuak1+/− mice show a combination of abnormal behavioral traits ranging from defective memory consolidation in a spatial learning task, defects in social novelty (but not social preference) and abnormal sensorimotor gating and prepulse inhibition of the startle response. Overall, our results demonstrate that Nuak1 haploinsufficiency leads to defects in the development of cortical connectivity and a complex array of behavorial deficits compatible with ASD, intellectual disability and schizophrenia.

scholarly journals Pharmacological and functional similarities of the human neuropeptide Y system in C. elegans challenges phylogenetic views on the FLP/NPR system

2019 ◽  
Vol 17 (1) ◽  
Author(s):  
Miron Mikhailowitsch Gershkovich ◽  
Victoria Elisabeth Groß ◽  
Anette Kaiser ◽  
Simone Prömel
Keyword(s):  
Neuropeptide Y ◽  
Pharmacological Study ◽  
Receptor Activation ◽  
Cross Reactivity ◽  
Model Organisms ◽  
Loss Of Function ◽  
C Elegans ◽  
Molecular Studies

Abstract Background The neuropeptide Y system affects various processes, among others food intake, and is frequently discussed in the context of targeting obesity. Studies in model organisms are indispensable to enable molecular studies in a physiological context. Although the NPY system is evolutionarily conserved in all bilaterians, in the widely used model Caenorhabditis elegans there is controversy on the existence of NPY orthologous molecules. While the FMRFamide-like peptide (FLP)/Neuropeptide receptor-Resemblance (NPR) system in the nematode was initially suggested to be orthologous to the mammalian NPY system, later global phylogenetic studies indicate that FLP/NPR is protostome-specific. Methods We performed a comprehensive pharmacological study of the FLP/NPR system in transfected cells in vitro, and tested for functional substitution in C. elegans knockout strains. Further, we phenotypically compared different flp loss-of-function strains. Differences between groups were compared by ANOVA and post-hoc testing (Dunnett, Bonferroni). Results Our pharmacological analysis of the FLP/NPR system including formerly functionally uncharacterized NPY-like peptides from C. elegans demonstrates that G protein-coupling and ligand requirements for receptor activation are similar to the human NPY system. In vitro and in vivo analyses show cross-reactivity of NPY with the FLP/NPR system manifesting in the ability of the human GPCRs to functionally substitute FLP/NPR signaling in vivo. The high pharmacological/functional similarities enabled us to identify C. elegans FLP-14 as a key molecule in avoidance behavior. Conclusions Our data demonstrate the pharmacological and functional similarities of human NPY and C. elegans NPR systems. This adds a novel perspective to current phylogenetic reconstructions of the neuropeptide Y system. NPY and NPR receptors are pharmacologically so similar that the human receptors can functionally compensate for the C. elegans ones, suggesting orthologous relationships. This is also underlined by the presence of NPY-like peptides and parallels in peptide requirements for receptor activation. Further, the results presented here highlight the potential of this knowledge for physiological as well as molecular studies on neuropeptide GPCRs such as the NPY system in the future.

scholarly journals Reduced prefrontal synaptic connectivity and disturbed oscillatory population dynamics in the CNTNAP2 model of autism

2018 ◽  
Author(s):  
Maria T. Lazaro ◽  
Jiannis Taxidis ◽  
Tristan Shuman ◽  
Iris Bachmutsky ◽  
Taruna Ikrar ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Phase Locking ◽  
Autism Spectrum ◽  
Repetitive Behaviors ◽  
Neuronal Firing ◽  
Inhibitory Neurons ◽  
Loss Of Function ◽  
Knock Out ◽  
Synaptic Inputs

ABSTRACTLoss of function mutations in CNTNAP2 cause a syndromic form of autism spectrum disorder (ASD) in humans and produce social deficits, repetitive behaviors, and seizures in mice. Yet, the functional effects of these mutations at the cellular and circuit level remain elusive. Using laser scanning photostimulation, whole-cell recordings, and electron microscopy, we found a dramatic decrease in functional excitatory and inhibitory synaptic inputs in L2/3 medial prefrontal cortex (mPFC) of Cntnap2 knock-out (KO) mice. In accordance with decreased synaptic input, KO mice displayed reduced spine and synapse densities, despite normal intrinsic excitability and dendritic complexity. To determine how this decrease in synaptic inputs alters coordination of neuronal firing patterns in vivo, we recorded mPFC local field potentials (LFP) and unit spiking in head-fixed mice during locomotion and rest. In KO mice, LFP power was not significantly altered at all tested frequencies, but inhibitory neurons showed delayed phase-firing and reduced phase-locking to delta and theta oscillations during locomotion. Excitatory neurons showed similar changes but only to delta oscillations. These findings suggest that profound ASD-related alterations in synaptic inputs can yield perturbed temporal coordination of cortical ensembles.

scholarly journals Kirrel3-mediated synapse formation is attenuated by disease-associated missense variants

2019 ◽  
Author(s):  
Matthew R. Taylor ◽  
E. Anne Martin ◽  
Brooke Sinnen ◽  
Rajdeep Trilokekar ◽  
Emmanuelle Ranza ◽  
...  
Keyword(s):  
Autism Spectrum Disorder ◽  
Intellectual Disability ◽  
Synapse Formation ◽  
Autism Spectrum ◽  
Spectrum Disorder ◽  
Cellular Interactions ◽  
Loss Of Function ◽  
Wild Type ◽  
Missense Variants

ABSTRACTMissense variants in Kirrel3 are repeatedly identified as risk factors for autism spectrum disorder and intellectual disability but it has not been reported if or how these variants disrupt Kirrel3 function. Previously, we studied Kirrel3 loss-of-function using knockout mice and showed that Kirrel3 is a synaptic adhesion molecule necessary to form one specific type of hippocampal synapse in vivo. Here, we developed a new gain-of-function assay for Kirrel3 and find that wild-type Kirrel3 induces synapse formation selectively between Kirrel3-expressing cells via homophilic, trans-cellular binding. We tested six disease-associated Kirrel3 missense variants and find that five attenuate this synaptogenic function. All variants tested traffic to the cell surface and localize to synapses similar to wild-type Kirrel3. Two tested variants lack homophilic trans-cellular binding, which likely accounts for their reduced synaptogenic function. Interestingly, we also identified variants that bind in trans but cannot induce synapses, indicating Kirrel3 trans-cellular binding is necessary but not sufficient for its synaptogenic function. Collectively, these results suggest Kirrel3 functions as a synaptogenic, cell-recognition molecule, and this function is attenuated by missense variants associated with autism spectrum disorder and intellectual disability. Thus, we provide critical insight to Kirrel3 function in typical brain development and the consequences of missense variants associated with autism spectrum disorder and intellectual disability.SIGNIFICANCE STATEMENTHere, we advance our understanding of mechanisms mediating target-specific synapse formation by providing evidence that Kirrel3 trans-cellular interactions mediate contact recognition and signaling to promote synapse development. Moreover, this is the first study to test the effects of disease-associated Kirrel3 missense variants on synapse formation, and thereby, provides a framework to understand the etiology of complex neurodevelopmental disorders arising from rare missense variants in synaptic genes.

scholarly journals The critical role of ASD-related gene CNTNAP3 in regulating synaptic development and social behavior in mice

2018 ◽  
Author(s):  
Da-li Tong ◽  
Rui-guo Chen ◽  
Yu-lan Lu ◽  
Wei-ke Li ◽  
Yue-fang Zhang ◽  
...  
Keyword(s):  
Critical Role ◽  
Autism Spectrum ◽  
Repetitive Behaviors ◽  
Inhibitory Synapses ◽  
Scaffolding Proteins ◽  
Loss Of Function ◽  
Chinese Han

AbstractAccumulated genetic evidences indicate that the contactin associated protein-like (CNTNAP) family is implicated in autism spectrum disorders (ASD). In this study, we identified genetic mutations in the CNTNAP3 gene from Chinese Han ASD cohorts and Simons Simplex Collections. We found that CNTNAP3 interacted with synaptic adhesion proteins Neuroligin1 and Neuroligin2, as well as scaffolding proteins PSD95 and Gephyrin. Significantly, we found that CNTNAP3 played an opposite role in controlling the development of excitatory and inhibitory synapses in vitro and in vivo, in which ASD mutants exhibited loss-of-function effects. In this study, we showed that Cntnap3-null mice exhibited deficits in social interaction, spatial learning and prominent repetitive behaviors. These evidences elucidate the pivotal role of CNTNAP3 in synapse development and social behaviors, providing the mechanistic insights for ASD.

scholarly journals ATP13A2-mediated endo-lysosomal polyamine export counters mitochondrial oxidative stress

2020 ◽  
Vol 117 (49) ◽  
pp. 31198-31207
Author(s):  
Stephanie Vrijsen ◽  
Laura Besora-Casals ◽  
Sarah van Veen ◽  
Jeffrey Zielich ◽  
Chris Van den Haute ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Stress Response ◽  
Antioxidant Properties ◽  
Loss Of Function ◽  
Mitochondrial Oxidative Stress ◽  
C Elegans ◽  
Polyamine Transport ◽  
Exogenous Spermine ◽  
The Impact

Recessive loss-of-function mutations inATP13A2(PARK9) are associated with a spectrum of neurodegenerative disorders, including Parkinson’s disease (PD). We recently revealed that the late endo-lysosomal transporter ATP13A2 pumps polyamines like spermine into the cytosol, whereas ATP13A2 dysfunction causes lysosomal polyamine accumulation and rupture. Here, we investigate how ATP13A2 provides protection against mitochondrial toxins such as rotenone, an environmental PD risk factor. Rotenone promoted mitochondrial-generated superoxide (MitoROS), which was exacerbated by ATP13A2 deficiency in SH-SY5Y cells and patient-derived fibroblasts, disturbing mitochondrial functionality and inducing toxicity and cell death. Moreover, ATP13A2 knockdown induced an ATF4-CHOP-dependent stress response following rotenone exposure. MitoROS and ATF4-CHOP were blocked by MitoTEMPO, a mitochondrial antioxidant, suggesting that the impact of ATP13A2 on MitoROS may relate to the antioxidant properties of spermine. Pharmacological inhibition of intracellular polyamine synthesis with α-difluoromethylornithine (DFMO) also increased MitoROS and ATF4 when ATP13A2 was deficient. The polyamine transport activity of ATP13A2 was required for lowering rotenone/DFMO-induced MitoROS, whereas exogenous spermine quenched rotenone-induced MitoROS via ATP13A2. Interestingly, fluorescently labeled spermine uptake in the mitochondria dropped as a consequence of ATP13A2 transport deficiency. Our cellular observations were recapitulated in vivo, in aCaenorhabditis elegansstrain deficient in the ATP13A2 orthologcatp-6. These animals exhibited a basal elevated MitoROS level, mitochondrial dysfunction, and enhanced stress response regulated byatfs-1, theC. elegansortholog of ATF4, causing hypersensitivity to rotenone, which was reversible with MitoTEMPO. Together, our study reveals a conserved cell protective pathway that counters mitochondrial oxidative stress via ATP13A2-mediated lysosomal spermine export.

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