CNTN6 mutations are risk factors for abnormal auditory sensory perception in autism spectrum disorders

Loss of primary cilia and dopaminergic neuroprotection in pathogenic LRRK2-driven and idiopathic Parkinson's disease

Activating leucine-rich repeat kinase 2 (LRRK2) mutations cause Parkinson's and phosphorylation of Rab10 by pathogenic LRRK2 blocks primary ciliogenesis in cultured cells. In the mouse brain, LRRK2 blockade of primary cilia is highly cell type specific: For example, cholinergic interneurons and astrocytes but not medium spiny neurons of the dorsal striatum lose primary cilia in LRRK2-pathway mutant mice. We show here that the cell type specificity of LRRK2-mediated cilia loss is also seen in human postmortem striatum from patients with LRRK2 pathway mutations and idiopathic Parkinson's. Single nucleus RNA sequencing shows that cilia loss in mouse cholinergic interneurons is accompanied by decreased glial-derived neurotrophic factor transcription, decreasing neuroprotection for dopamine neurons. Nevertheless, LRRK2 expression differences cannot explain the unique vulnerability of cholinergic neurons to LRRK2 kinase as much higher LRRK2 expression is seen in medium spiny neurons that have normal cilia. In parallel with decreased striatal dopaminergic neurite density, LRRK2 G2019S neurons show increased autism-linked CNTN5 adhesion protein expression; glial cells show significant loss of ferritin heavy chain. These data strongly suggest that loss of cilia in specific striatal cell types decreases neuroprotection for dopamine neurons in mice and human Parkinson's.

Molecular mechanism of contactin 2 homophilic interaction

Contactin 2 (CNTN2) is a cell adhesion molecule involved in axon guidance, neuronal migration, and fasciculation. The ectodomains of CNTN1-CNTN6 are composed of six Ig domains (Ig1-Ig6) and four FN domains. Here, we show that CNTN2 forms transient homophilic interactions (KD ∼200 nM). Cryo-EM structures of full-length CNTN2 and CNTN2_Ig1-Ig6 reveal a T-shaped homodimer formed by intertwined, parallel monomers. Unexpectedly, the horseshoe-shaped Ig1-Ig4 headpieces extend their Ig2-Ig3 tips outwards on either side of the homodimer, while Ig4, Ig5, Ig6, and the FN domains form a central stalk. Cross-linking mass spectrometry and cell-based binding assays confirm the 3D assembly of the CNTN2 homodimer. The interface mediating homodimer formation differs between CNTNs, as do the homophilic versus heterophilic interaction mechanisms. The CNTN family thus encodes a versatile molecular platform that supports a very diverse portfolio of protein interactions and that can be leveraged to strategically guide neural circuit development.

Novel genetic loci of inhibitory control in ADHD and healthy children and genetic correlations with ADHD

Cumulative evidence has showed the deficits of inhibitory control in patients with attention deficit hyperactivity disorder (ADHD), which is considered as an endophenotype of ADHD. Genetic study of inhibitory control could advance gene discovery and further facilitate the understanding of ADHD genetic basis, but the studies were limited in both the general population and ADHD patients. To reveal genetic risk variants of inhibitory control and its potential genetic relationship with ADHD, we conducted genome-wide association studies (GWAS) on inhibitory control using three datasets, which included 783 and 957 ADHD patients and 1350 healthy children. Subsequently, we employed polygenic risk scores (PRS) to explore the association of inhibitory control with ADHD and related psychiatric disorders. Firstly, we identified three significant loci for inhibitory control in the healthy dataset, two loci in the case dataset, and one locus in the meta-analysis of three datasets. Besides, we found more risk genes and variants by applying transcriptome-wide association study (TWAS) and conditional FDR method. Then, we constructed a network by connecting the genes identified in our study, leading to the identification of several vital genes. Lastly, we identified a potential relationship between inhibitory control and ADHD and autism by PRS analysis and found the direct and mediated contribution of the identified genetic loci on ADHD symptoms by mediation analysis. In conclusion, we revealed some genetic risk variants associated with inhibitory control and elucidated the benefit of inhibitory control as an endophenotype, providing valuable insights into the mechanisms underlying ADHD.

Loss of primary cilia and dopaminergic neuroprotection in pathogenic LRRK2-driven and idiopathic Parkinson's disease

Activating LRRK2 mutations cause Parkinson's disease. Previously, we showed that cholinergic interneurons and astrocytes but not medium spiny neurons of the dorsal striatum lose primary cilia in LRRK2 mutant mice. Single nucleus RNA sequencing shows that cilia loss in cholinergic interneurons correlates with higher LRRK2 expression and decreased glial derived neurotrophic factor transcription. Nevertheless, much higher LRRK2 expression is seen in medium spiny neurons that have normal cilia in mice and humans. In parallel with decreased striatal dopaminergic neurite density, LRRK2 G2019S neurons show increased autism-linked CNTN5 adhesion protein expression; glial cells show significant loss of ferritin heavy chain. Human striatal tissue from LRRK2 pathway mutation carriers and idiopathic Parkinson's disease show similar cilia loss in cholinergic interneurons and astrocytes and overall loss of such neurons. These data strongly suggest that loss of cilia in specific striatal cell types decreases neuroprotection for dopamine neurons in mice and human Parkinson's disease.

Pathogenetic Insights into Developmental Coordination Disorder Reveal Substantial Overlap with Movement Disorders

Developmental Coordination Disorder (DCD) is a neurodevelopmental condition characterized by non-progressive central motor impairments. Mild movement disorder features have been observed in DCD. Until now, the etiology of DCD has been unclear. Recent studies suggested a genetic substrate in some patients with DCD, but comprehensive knowledge about associated genes and underlying pathogenetic mechanisms is still lacking. In this study, we first identified genes described in the literature in patients with a diagnosis of DCD according to the official diagnostic criteria. Second, we exposed the underlying pathogenetic mechanisms of DCD, by investigating tissue- and temporal gene expression patterns and brain-specific biological mechanisms. Third, we explored putative shared pathogenetic mechanisms between DCD and frequent movement disorders with a known genetic component, including ataxia, chorea, dystonia, and myoclonus. We identified 12 genes associated with DCD in the literature, which are ubiquitously expressed in the central nervous system throughout brain development. These genes are involved in cellular processes, neural signaling, and nervous system development. There was a remarkable overlap (62%) in pathogenetic mechanisms between DCD-associated genes and genes linked with movement disorders. Our findings suggest that some patients might have a genetic etiology of DCD, which could be considered part of a pathogenetic movement disorder spectrum.

Comprehensive Transcriptomic Investigation of Rett Syndrome Reveals Increasing Complexity Trends from Induced Pluripotent Stem Cells to Neurons with Implications for Enriched Pathways

Rett syndrome (RTT) is a rare genetic neurodevelopmental disorder that has no cure apart from symptomatic treatments. While intense research efforts are required to fulfill this unmet need, the fundamental challenge is to obtain sufficient patient data. In this study, we used human transcriptomic data of four different sample types from RTT patients including induced pluripotent stem cells, differentiated neural progenitor cells, differentiated neurons, and postmortem brain tissues with an increasing in vivo-like complexity to unveil specific trends in gene expressions across the samples. Based on DEG analysis, we identified F8A3, CNTN6, RPE65, and COL19A1 to have differential expression levels in three sample types and also observed previously reported genes such as MECP2, FOXG1, CACNA1G, SATB2, GABBR2, MEF2C, KCNJ10, and CUX2 in our study. Considering the significantly enriched pathways for each sample type, we observed a consistent increase in numbers from iPSCs to NEUs where MECP2 displayed profound effects. We also validated our GSEA results by using single-cell RNA-seq data. In WGCNA, we elicited a connection among MECP2, TNRC6A, and HOXA5. Our findings highlight the utility of transcriptomic analyses to determine genes that might lead to therapeutic strategies.

Proteomic characterization of atopic dermatitis blood from infancy to adulthood

BACKGROUND

Patients with atopic dermatitis (AD) have systemic biomarker dysregulation that differs by age group; however, the proteomic characteristics of these age-based changes are unknown.

OBJECTIVE

To profile blood proteins of patients with AD across different age groups versus age-appropriate controls.

METHODS

Using the Olink high-throughput proteomic platform, we profiled 375 serum proteins of 20 infants (age, 0-5 years), 39 children (age, 6-11 years), 21 adolescents (age, 12-17 years), and 20 adults (age, ≥18 years) with moderate-to-severe AD and 83 age-appropriate controls.

RESULTS

Each group presented a distinct systemic proteomic signature. Th2-related proteins were increased in infant AD and further intensified with age through adolescence and adulthood (interleukin 4/CCL13/CCL17). In contrast, Th1 axis down-regulation was detected in infants with AD and gradually reversed to increased Th1 products (interferon γ/CXCL9/CXCL10/CCL2) in patients with AD from childhood to adulthood. Despite their short disease duration, infants already had evidence of systemic inflammation, with significant upregulation of innate immunity (interleukin 17C/ interleukin-1RN), T-cell activation/migration (CCL19), Th2 (CCL13/CCL17), and Th17 (PI3) proteins. Adults with AD present unique upregulation of cardiovascular proteins related to coagulation and diabetes.

LIMITATIONS

Cross-sectional observational study with a single time point.

CONCLUSION

Systemic immune signatures of AD are age-specific beyond the shared Th2 immune activation. These data advocate for precision medicine approaches based on age-specific AD profiles.

Contactin-6-deficient male mice exhibit the abnormal function of the accessory olfactory system and impaired reproductive behavior

INTRODUCTION

Contactin-6 (CNTN6), also known as NB-3, is a neural recognition molecule and a member of the contactin subgroup of the immunoglobulin superfamily. Gene encoding CNTN6 is expressed in many regions of the neural system, including the accessory olfactory bulb (AOB) in mice. We aim to determine the effect of CNTN6 deficiency on the function of the accessory olfactory system (AOS).

METHODS

We examined the effect of CNTN6 deficiency on the reproductive behavior of male mice through behavioral experiments such as urine sniffing and mate preference tests. Staining and electron microscopy were used to observe the gross structure and the circuitry activity of the AOS.

RESULTS

Cntn6 is highly expressed in the vomeronasal organ (VNO) and the AOB, and sparsely expressed in the medial amygdala (MeA) and the medial preoptic area (MPOA), which receive direct and/or indirect projections from the AOB. Behavioral tests to examine reproductive function in mice, which is mostly controlled by the AOS, revealed that Cntn6^-/- adult male mice showed less interest and reduced mating attempts toward estrous female mice in comparison with their Cntn6^+/+ littermates. Although Cntn6^-/- adult male mice displayed no obvious changes in the gross structure of the VNO or AOB, we observed the increased activation of granule cells in the AOB and the lower activation of neurons in the MeA and the MPOA as compared with Cntn6^+/+ adult male mice. Moreover, there were an increased number of synapses between mitral cells and granule cells in the AOB of Cntn6^-/- adult male mice as compared with wild-type controls.

CONCLUSION

These results indicate that CNTN6 deficiency affects the reproductive behavior of male mice, suggesting that CNTN6 participated in normal function of the AOS and its ablation was involved in synapse formation between mitral and granule cells in the AOB, rather than affecting the gross structure of the AOS.

Tackling hypo and hyper sensory processing heterogeneity in autism: From clinical stratification to genetic pathways

As an integral part of autism spectrum symptoms, sensory processing issues including both hypo and hyper sensory sensitivities. These sensory specificities may result from an excitation/inhibition imbalance with a poorly understood of their level of convergence with genetic alterations in GABA-ergic and glutamatergic pathways. In our study, we aimed to characterize the hypo/hyper-sensory profile among autistic individuals. We then explored its link with the burden of deleterious mutations in a subset of individuals with available whole-genome sequencing data. To characterize the hypo/hyper-sensory profile, the differential Short Sensory Profile (dSSP) was defined as a normalized and centralized hypo/hypersensitivity ratio from the Short Sensory Profile (SSP). Including 1136 participants (533 autistic individuals, 210 first-degree relatives, and 267 controls) from two independent study samples (PARIS and LEAP), we observed a statistically significant dSSP mean difference between autistic individuals and controls, driven mostly by a high dSSP variability, with an intermediated profile represented by relatives. Our genetic analysis tended to associate the dSSP and the hyposensitivity with mutations of the GABAergic pathway. The major limitation was the dSSP difficulty to discriminate subjects with a similar quantum of hypo- and hyper-sensory symptoms to those with no such symptoms, resulting both in a similar ratio score of 0. However, the dSSP could be a relevant clinical score, and combined with additional sensory descriptions, genetics and endophenotypic substrates, will improve the exploration of the underlying neurobiological mechanisms of sensory processing differences in autism spectrum.

Prediction Model for Sensory Perception Abnormality in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by heterogeneous clinical phenotypes. Patients often experience abnormal sensory perception, which may further affect the ASD core phenotype, significantly and adversely affecting their quality of life. However, biomarkers for the diagnosis of ASD sensory perception abnormality are currently elusive. We sought to identify potential biomarkers related to ASD sensory perception abnormality to construct a prediction model that could facilitate the early identification of and screening for ASD. Differentially expressed genes in ASD were obtained from the Gene Expression Omnibus database and were screened for genes related to sensory perception abnormality. After enrichment analysis, the random forest method was used to identify disease-characteristic genes. A prediction model was constructed with an artificial neural network. Finally, the results were validated using data from the dorsal root ganglion, cerebral cortex, and striatum of the BTBR T+ Itpr3tf/J (BTBR) ASD mouse model. A total of 1869 differentially expressed genes in ASD were screened, among which 16 genes related to sensory perception abnormality were identified. According to enrichment analysis, these 16 genes were mainly related to actin, cholesterol metabolism, and tight junctions. Using random forest, 15 disease-characteristic genes were screened for model construction. The area under the curve of the training set validation result was 0.999, and for the model function validation, the result was 0.711, indicating high accuracy. The validation of BTBR mice confirmed the reliability of using these disease-characteristic genes for prediction of ASD. In conclusion, we developed a highly accurate model for predicting ASD sensory perception abnormality from 15 disease-characteristic genes. This model provides a new method for the early identification and diagnosis of ASD sensory perception abnormality.

3q29 microduplication syndrome: New evidence for the refinement of the critical region

BACKGROUND

The 3q29 microduplication syndrome is a rare genomic disorder characterized by an extremely variable neurodevelopmental phenotype usually involving a genomic region ranging from 1.6 to 1.76 Mb. A small microduplication of 448.8 Kb containing only two genes was recently described in a patient with a 3q29 microduplication that was proposed as the minimal critical region of overlap of this syndrome.

METHODS

Molecular karyotyping (array-CGH) was performed on DNA extracted from peripheral blood samples using Agilent-California USA Human Genome CGH Microarray 4 × 180 K. The proband and his younger brother were further tested with a next generation sequencing (NGS) panel including genes implicated in autism spectrum disorder and in neurodevelopmental disorders. Quantitative real-time PCR was applied to verify the abnormal array-CGH findings.

RESULTS

Here, we report on a family with two males with neurodevelopmental disorders and an unaffected sibling with a small 3q29 microduplication (432.8 Kb) inherited from an unaffected mother that involves only two genes: DGL1 and BDH1. The proband had an additional intragenic duplication inherited from the unaffected father. Further testing was negative for Fragile X syndrome and for genes implicated in autism spectrum disorder and in neurodevelopmental disorders.

CONCLUSION

To the best of our knowledge, one of the family members here analyzed is the second reported case of a patient carrying a small 3q29 microduplication including only DGL1 and BDH1 genes and without any additional genetic aberration. The recognition of the clinical spectrum in patients with the critical region of overlap associated with the 3q29 duplication syndrome should prove valuable for predicting outcomes and providing more informed genetic counseling to patients with duplications in this region.

Pan-cancer analyses reveal IGSF10 as an immunological and prognostic biomarker

Background: IGSF10 is a member of the immunoglobulin superfamily. Over the previous decade, growing proof has validated definitive correlations between individuals of the immunoglobulin superfamily and human diseases. However, the function of IGSF10 in pan-cancer stays unclear. We aimed to analyze the immunological and prognostic value of IGSF10 in pan-cancer. Methods: We utilized a vary of bioinformatic ways to inspect the function of IGSF10 in pan-cancer, including its correlation with prognosis, immune cell infiltration, tumor mutational burden (TMB), microsatellite instability (MSI), mismatch repair (MMR), DNA methyltransferases, genetic alteration, drug sensitivity, etc. Results: We noticed low expression of IGSF10 in most cancer types. IGSF10 expression in tumor samples correlates with prognosis in most cancers. In most cancer types, IGSF10 expression was strongly related to immune cells infiltration, immune checkpoints, immune modulators, TMB, MSI, MMR, and DNA methyltransferases, among others. Functional enrichment analyses indicated that IGSF10 expression was involved in lymphocyte differentiation, cell molecules adhesion, etc. Furthermore, low IGSF10 expression could increase the drug sensitivity of many drugs. Conclusion: IGSF10 could serve as a novel prognostic marker and attainable immunotherapy target for several malignancies.

Larger pupil dilation to nonsocial sounds in infants with subsequent autism diagnosis

BACKGROUND

Studies of infants with an elevated likelihood of autism spectrum disorder can identify basic developmental processes that are associated with subsequently emerging clinical symptoms. Atypical responsiveness to sounds in infancy is such a potential early marker of autism. Here, we used pupillometry to quantify reactivity to social and nonsocial sounds in infants with a subsequent diagnosis. Previous research suggest that pupil dilation reflects attentional alerting, and link it to the locus coeruleus norepinephrine system.

METHODS

We measured pupil dilation responses to child-directed speech and the sound of running water; sounds infants often hear in their everyday life. The final sample consisted of 99 ten-month-old infants (52 girls), of whom 68 had an elevated likelihood of autism and 31 were typically developing low-likelihood infants. At follow-up (36 months of age), 18 children in the elevated-likelihood group were diagnosed with autism.

RESULTS

Compared to infants without diagnosis, the infants who were subsequently diagnosed with autism had larger pupil dilation when listening to nonsocial sounds, while reactivity to speech was strikingly similar between groups. In the total sample, more pupil dilation to the nonsocial sound was associated with higher levels of autistic symptoms. We also found that on a trial-by-trial basis, across all conditions and groups, more pupil dilation was associated with making fewer gaze shifts.

CONCLUSIONS

This study did not find evidence of atypical pupillary reactivity to child-directed speech early in life in autism. Instead, the results suggest that certain nonsocial sounds elicit atypically strong alerting responses in infants with a subsequent autism diagnosis. These findings may have important theoretical and clinical implications.

Exome sequencing of Japanese schizophrenia multiplex families supports the involvement of calcium ion channels

Background

Most sequencing studies of schizophrenia (SCZ) have focused on de novo genetic variants due to interpretability. However, investigating shared rare variants among patients in the same multiplex family is also important. Relatively large-scale analyses of SCZ multiplex families have been done in Caucasian populations, but whether detected variants are also pathogenic in the Japanese population is unclear because of ethnic differences in rare variants.

Materials and methods

We performed whole-exome sequencing (WES) of 14 Japanese SCZ multiplex families. After quality control and filtering, we identified rare variants shared among affected persons within the same family. A gene ontology (GO) analysis was performed to identify gene categories possibly affected by these candidate variants.

Results

We found 530 variants in 486 genes as potential candidate variants from the 14 SCZ multiplex families examined. The GO analysis demonstrated significant enrichment in calcium channel activity.

Conclusion

This study provides supporting evidence that calcium ion channel activity is involved in SCZ. WES of multiplex families is a potential means of identifying disease-associated rare variants for SCZ.

Prevalence of Decreased Sound Tolerance (Hyperacusis) in Individuals With Autism Spectrum Disorder: A Meta-Analysis

OBJECTIVES

Hyperacusis, defined as decreased tolerance to sound at levels that would not trouble most individuals, is frequently observed in individuals with autism spectrum disorder (ASD). Despite the functional impairment attributable to hyperacusis, little is known about its prevalence or natural history in the ASD population. The objective of this study was to conduct a systematic review and meta-analysis estimating the current and lifetime prevalence of hyperacusis in children, adolescents, and adults with ASD. By precisely estimating the burden of hyperacusis in the ASD population, the present study aims to enhance recognition of this particular symptom of ASD and highlight the need for additional research into the causes, prevention, and treatment of hyperacusis in persons on the spectrum.

DESIGN

We searched PubMed and ProQuest to identify peer-reviewed articles published in English after January 1993. We additionally performed targeted searches of Google Scholar and the gray literature, including studies published through May 2020. Eligible studies included at least 20 individuals with diagnosed ASD of any age and reported data from which the proportion of ASD individuals with current and/or lifetime hyperacusis could be derived. To account for multiple prevalence estimates derived from the same samples, we utilized three-level Bayesian random-effects meta-analyses to estimate the current and lifetime prevalence of hyperacusis. Bayesian meta-regression was used to assess potential moderators of current hyperacusis prevalence. To reduce heterogeneity due to varying definitions of hyperacusis, we performed a sensitivity analysis on the subset of studies that ascertained hyperacusis status using the Autism Diagnostic Interview-Revised (ADI-R), a structured parent interview.

RESULTS

A total of 7783 nonduplicate articles were screened, of which 67 were included in the review and synthesis. Hyperacusis status was ascertained in multiple ways across studies, with 60 articles employing interviews or questionnaires and seven using behavioral observations or objective measures. The mean (range) age of samples in the included studies was 7.88 years (1.00 to 34.89 years). The meta-analysis of interview/questionnaire measures (k(3) = 103, nASD = 13,093) estimated the current and lifetime prevalence of hyperacusis in ASD to be 41.42% (95% CrI, 37.23 to 45.84%) and 60.58% (50.37 to 69.76%), respectively. A sensitivity analysis restricted to prevalence estimates derived from the ADI-R (k(3) = 25, nASD = 5028) produced similar values. The estimate of current hyperacusis prevalence using objective/observational measures (k(3) = 8, nASD = 488) was 27.30% (14.92 to 46.31%). Heterogeneity in the full sample of interview/questionnaire measures was substantial but not significantly explained by any tested moderator. However, prevalence increased sharply with increasing age in studies using the ADI-R (BF10 = 93.10, R2Het = 0.692).

CONCLUSIONS

In this meta-analysis, we found a high prevalence of current and lifetime hyperacusis in individuals with ASD, with a majority of individuals on the autism spectrum experiencing hyperacusis at some point in their lives. The high prevalence of hyperacusis in individuals with ASD across the lifespan highlights the need for further research on sound tolerance in this population and the development of services and/or interventions to reduce the burden of this common symptom.

Hyperacusis in Autism Spectrum Disorders

Hyperacusis is highly prevalent in the autism spectrum disorder (ASD) population. This auditory hypersensitivity can trigger pragmatically atypical reactions that may impact social and academic domains. Objective: The aim of this report is to describe the relationship between decreased sound tolerance disorders and the ASD population. Topics covered: The main topics discussed include (1) assessment and prevalence of hyperacusis in ASD; (2) etiology of hyperacusis in ASD; (3) treatment of hyperacusis in ASD. Conclusions: Knowledge of the assessment and treatment of decreased sound tolerance disorders within the ASD population is growing and changing.

Candidate Genes and Pathways Associated with Gilles de la Tourette Syndrome-Where Are We?

Gilles de la Tourette syndrome (GTS) is a childhood-onset neurodevelopmental and -psychiatric tic-disorder of complex etiology which is often comorbid with obsessive-compulsive disorder (OCD) and/or attention deficit hyperactivity disorder (ADHD). Twin and family studies of GTS individuals have shown a high level of heritability suggesting, that genetic risk factors play an important role in disease etiology. However, the identification of major GTS susceptibility genes has been challenging, presumably due to the complex interplay between several genetic factors and environmental influences, low penetrance of each individual factor, genetic diversity in populations, and the presence of comorbid disorders. To understand the genetic components of GTS etiopathology, we conducted an extensive review of the literature, compiling the candidate susceptibility genes identified through various genetic approaches. Even though several strong candidate genes have hitherto been identified, none of these have turned out to be major susceptibility genes yet.

Familial Psychosis Associated With a Missense Mutation at MACF1 Gene Combined With the Rare Duplications DUP3p26.3 and DUP16q23.3, Affecting the CNTN6 and CDH13 Genes

Psychosis is a highly heritable and heterogeneous psychiatric condition. Its genetic architecture is thought to be the result of the joint effect of common and rare variants. Families with high prevalence are an interesting approach to shed light on the rare variant's contribution without the need of collecting large cohorts. To unravel the genomic architecture of a family enriched for psychosis, with four affected individuals, we applied a system genomic approach based on karyotyping, genotyping by whole-exome sequencing to search for rare single nucleotide variants (SNVs) and SNP array to search for copy-number variants (CNVs). We identified a rare non-synonymous variant, g.39914279 C > G, in the MACF1 gene, segregating with psychosis. Rare variants in the MACF1 gene have been previously detected in SCZ patients. Besides, two rare CNVs, DUP3p26.3 and DUP16q23.3, were also identified in the family affecting relevant genes (CNTN6 and CDH13, respectively). We hypothesize that the co-segregation of these duplications with the rare variant g.39914279 C > G of MACF1 gene precipitated with schizophrenia and schizoaffective disorder.

A review of decreased sound tolerance in autism: Definitions, phenomenology, and potential mechanisms

Atypical behavioral responses to environmental sounds are common in autistic children and adults, with 50-70 % of this population exhibiting decreased sound tolerance (DST) at some point in their lives. This symptom is a source of significant distress and impairment across the lifespan, contributing to anxiety, challenging behaviors, reduced community participation, and school/workplace difficulties. However, relatively little is known about its phenomenology or neurocognitive underpinnings. The present article synthesizes a large body of literature on the phenomenology and pathophysiology of DST-related conditions to generate a comprehensive theoretical account of DST in autism. Notably, we argue against conceptualizing DST as a unified construct, suggesting that it be separated into three phenomenologically distinct conditions: hyperacusis (the perception of everyday sounds as excessively loud or painful), misophonia (an acquired aversive reaction to specific sounds), and phonophobia (a specific phobia of sound), each responsible for a portion of observed DST behaviors. We further elaborate our framework by proposing preliminary neurocognitive models of hyperacusis, misophonia, and phonophobia that incorporate neurophysiologic findings from studies of autism.

Cell Adhesion Molecules Involved in Neurodevelopmental Pathways Implicated in 3p-Deletion Syndrome and Autism Spectrum Disorder

Autism spectrum disorder (ASD) is characterized by impaired social interaction, language delay and repetitive or restrictive behaviors. With increasing prevalence, ASD is currently estimated to affect 0.5–2.0% of the global population. However, its etiology remains unclear due to high genetic and phenotypic heterogeneity. Copy number variations (CNVs) are implicated in several forms of syndromic ASD and have been demonstrated to contribute toward ASD development by altering gene dosage and expression. Increasing evidence points toward the p-arm of chromosome 3 (chromosome 3p) as an ASD risk locus. Deletions occurring at chromosome 3p result in 3p-deletion syndrome (Del3p), a rare genetic disorder characterized by developmental delay, intellectual disability, facial dysmorphisms and often, ASD or ASD-associated behaviors. Therefore, we hypothesize that overlapping molecular mechanisms underlie the pathogenesis of Del3p and ASD. To investigate which genes encoded in chromosome 3p could contribute toward Del3p and ASD, we performed a comprehensive literature review and collated reports investigating the phenotypes of individuals with chromosome 3p CNVs. We observe that high frequencies of CNVs occur in the 3p26.3 region, the terminal cytoband of chromosome 3p. This suggests that CNVs disrupting genes encoded within the 3p26.3 region are likely to contribute toward the neurodevelopmental phenotypes observed in individuals affected by Del3p. The 3p26.3 region contains three consecutive genes encoding closely related neuronal immunoglobulin cell adhesion molecules (IgCAMs): Close Homolog of L1 (CHL1), Contactin-6 (CNTN6), and Contactin-4 (CNTN4). CNVs disrupting these neuronal IgCAMs may contribute toward ASD phenotypes as they have been associated with key roles in neurodevelopment. CHL1, CNTN6, and CNTN4 have been observed to promote neurogenesis and neuronal survival, and regulate neuritogenesis and synaptic function. Furthermore, there is evidence that these neuronal IgCAMs possess overlapping interactomes and participate in common signaling pathways regulating axon guidance. Notably, mouse models deficient for these neuronal IgCAMs do not display strong deficits in axonal migration or behavioral phenotypes, which is in contrast to the pronounced defects in neuritogenesis and axon guidance observed in vitro. This suggests that when CHL1, CNTN6, or CNTN4 function is disrupted by CNVs, other neuronal IgCAMs may suppress behavioral phenotypes by compensating for the loss of function.

Molecules, Mechanisms, and Disorders of Self-Domestication: Keys for Understanding Emotional and Social Communication from an Evolutionary Perspective

The neural crest hypothesis states that the phenotypic features of the domestication syndrome are due to a reduced number or disruption of neural crest cells (NCCs) migration, as these cells differentiate at their final destinations and proliferate into different tissues whose activity is reduced by domestication. Comparing the phenotypic characteristics of modern and prehistoric man, it is clear that during their recent evolutionary past, humans also went through a process of self-domestication with a simultaneous prolongation of the period of socialization. This has led to the development of social abilities and skills, especially language, as well as neoteny. Disorders of neural crest cell development and migration lead to many different conditions such as Waardenburg syndrome, Hirschsprung disease, fetal alcohol syndrome, DiGeorge and Treacher-Collins syndrome, for which the mechanisms are already relatively well-known. However, for others, such as Williams-Beuren syndrome and schizophrenia that have the characteristics of hyperdomestication, and autism spectrum disorders, and 7dupASD syndrome that have the characteristics of hypodomestication, much less is known. Thus, deciphering the biological determinants of disordered self-domestication has great potential for elucidating the normal and disturbed ontogenesis of humans, as well as for the understanding of evolution of mammals in general.

[Pathophysiological mechanisms of autism in children]

Based on the analysis of literature, the authors describe the neuropathophysiological mechanism of the formation of synapses, synaptic transmission and plasticity, which may underlie the pathogenesis of autism. The results of some studies confirm the involvement of aberrant expression of genes and proteins of synaptic contacts, cell adhesion molecules p120ctn, CNTN5, CNTN6, activation of NMDA glutamate, TrkB, p75 receptors, Ca²⁺-input, BDNF, serotonin and testosterone. This leads to an imbalance in the exciting, inhibitory synaptic transmission and forms of synaptic plasticity, including long-term potentiation (LTP) and long-term depression (LTD) at the level of individual neurons and their chains due to suppression of GABA synthesis, expression of its ionotropic and metabotropic receptors, G proteins, NGF, TrkA receptors, a reduction in the number of GABAergic neurons, their contacts and disruption of differentiation. The pathology of the nuclei of the thalamus, especially the reticular nucleus (RN), is associated with a disturbance of the expression of the subunits of metabotropic GABAβ receptors, Ca²⁺ channels, GABA excretion and the work of chlorine transmitters. These failures do not ensure the inhibitory effect of OC on the exciting associative and ventral nuclei of the thalamus, nor modify the incoming information to the cerebral cortex (CC) from these thalamus nuclei, the dentate gyrus of the hippocampus and the nuclei of the reticular formation. Information propagating into the somatosensory and associative regions of CC is not modified by mirror neurons (MN) when performing arbitrary actions, which prevents the formation of an adequate image in the neural networks of the associative cortex and promotes the development of hyperexcitability, irritability, increased visual and auditory sensitivity, anxiety, and the ability to form a holistic image based on the actions of other people.

Prediction of Nephrotoxicity Associated With Cisplatin-Based Chemotherapy in Testicular Cancer Patients

Background

Cisplatin-based chemotherapy may induce nephrotoxicity. This study presents a random forest predictive model that identifies testicular cancer patients at risk of nephrotoxicity before treatment.

Methods

Clinical data and DNA from saliva samples were collected for 433 patients. These were genotyped on Illumina HumanOmniExpressExome-8 v1.2 (964 193 markers). Clinical and genomics-based random forest models generated a risk score for each individual to develop nephrotoxicity defined as a 20% drop in isotopic glomerular filtration rate during chemotherapy. The area under the receiver operating characteristic curve was the primary measure to evaluate models. Sensitivity, specificity, and positive and negative predictive values were used to discuss model clinical utility.

Results

Of 433 patients assessed in this study, 26.8% developed nephrotoxicity after bleomycin-etoposide-cisplatin treatment. Genomic markers found to be associated with nephrotoxicity were located at NAT1, NAT2, and the intergenic region of CNTN6 and CNTN4. These, in addition to previously associated markers located at ERCC1, ERCC2, and SLC22A2, were found to improve predictions in a clinical feature–trained random forest model. Using only clinical data for training the model, an area under the receiver operating characteristic curve of 0.635 (95% confidence interval [CI] = 0.629 to 0.640) was obtained. Retraining the classifier by adding genomics markers increased performance to 0.731 (95% CI = 0.726 to 0.736) and 0.692 (95% CI = 0.688 to 0.696) on the holdout set.

Conclusions

A clinical and genomics-based machine learning algorithm improved the ability to identify patients at risk of nephrotoxicity compared with using clinical variables alone. Novel genetics associations with cisplatin-induced nephrotoxicity were found for NAT1, NAT2, CNTN6, and CNTN4 that require replication in larger studies before application to clinical practice.

Intolerance of loud sounds in childhood: Is there an intergenerational association with grandmaternal smoking in pregnancy?

Recent research using the Avon Longitudinal Study of Parents and Children (ALSPAC) demonstrated an association between maternal grandmother smoking in pregnancy and the autistic traits of impaired social communication and repetitive behaviour in granddaughters but not grandsons, but of paternal grandmother smoking and early development of myopia in the grandchild. Here we investigate whether grandmaternal smoking in pregnancy is associated with intolerance to loud sounds. ALSPAC collected information during the index pregnancy from the study parents on the smoking habits, social and other features of their own parents. Maternal report when the child was aged 6 and 13 included hating loud sounds; at age 11 the child was tested for volume preference for listening to music through headphones. Statistical analysis compared results for grandchildren in relation to whether a parent had been exposed in utero to maternal smoking, adjusted for their grandparents' social and demographic attributes. We hypothesised that there would be sex differences in the effects of grandmaternal prenatal smoking, based on previous intergenerational studies. For 6-year-old children maternal report of intolerance to loud noise was more likely in grandsons if the maternal grandmother had smoked [adjusted odds ratio (AOR) 1.27; 95% confidence interval (CI) 1.03,1.56; P = 0.025], but less likely in girls [AOR 0.82; 95%CI 0.63,1.07] Pinteraction <0.05. If the paternal grandmother had smoked the grandchildren were less likely to be intolerant, especially girls. The objective measure of choice of volume for music through headphones showed that grandsons of both maternal and paternal smoking grandmothers were less likely to choose high volumes compared with granddaughters (P<0.05). In line with our prior hypothesis of sex differences, we showed that grandsons were more intolerant of loud sounds than granddaughters particularly at age 6, and this was confirmed by objective measures at age 11.

The Reeler Mouse: A Translational Model of Human Neurological Conditions, or Simply a Good Tool for Better Understanding Neurodevelopment?

The first description of the Reeler mutation in mouse dates to more than fifty years ago, and later, its causative gene (reln) was discovered in mouse, and its human orthologue (RELN) was demonstrated to be causative of lissencephaly 2 (LIS2) and about 20% of the cases of autosomal-dominant lateral temporal epilepsy (ADLTE). In both human and mice, the gene encodes for a glycoprotein referred to as reelin (Reln) that plays a primary function in neuronal migration during development and synaptic stabilization in adulthood. Besides LIS2 and ADLTE, RELN and/or other genes coding for the proteins of the Reln intracellular cascade have been associated substantially to other conditions such as spinocerebellar ataxia type 7 and 37, VLDLR-associated cerebellar hypoplasia, PAFAH1B1-associated lissencephaly, autism, and schizophrenia. According to their modalities of inheritances and with significant differences among each other, these neuropsychiatric disorders can be modeled in the homozygous (reln^−/−) or heterozygous (reln^+/−) Reeler mouse. The worth of these mice as translational models is discussed, with focus on their construct and face validity. Description of face validity, i.e., the resemblance of phenotypes between the two species, centers onto the histological, neurochemical, and functional observations in the cerebral cortex, hippocampus, and cerebellum of Reeler mice and their human counterparts.

Variable neurodevelopmental and morphological phenotypes of carriers with 12q12 duplications

BACKGROUND

Variable size deletions affecting 12q12 have been found in individuals with neurodevelopmental disorders (NDDs) and distinct facial and physical features. For many genetic loci affected by deletions in individuals with NDDs, reciprocal duplications have been described. However, for the 12q12 region, there are no detailed descriptions of duplication cases in the literature.

METHODS

We report a phenotypic description of a family with monozygotic twins diagnosed with NDDs, carrying a 9 Mb duplication at 12q12, and five other individuals with overlapping duplications ranging from 4.54 Mb up to 15.16 Mb.

RESULTS

The duplication carriers had language delays, cognitive delays, and were diagnosed with autism spectrum disorder. Additionally, distinct facial features (e.g., high foreheads, deeply set eyes, short palpebral fissures, small ears, high nasal bridges, abnormalities of the nose tip, thin lips), large feet, and abnormalities in the digits were noted. We also describe incomplete penetrance of the NDD phenotypes among the individuals with 12q12 duplication.

CONCLUSION

This case series expands our knowledge on this rare genetic aberration and suggests that large 12q12 duplications may increase the risk for developing NDDs.

A large data resource of genomic copy number variation across neurodevelopmental disorders

Copy number variations (CNVs) are implicated across many neurodevelopmental disorders (NDDs) and contribute to their shared genetic etiology. Multiple studies have attempted to identify shared etiology among NDDs, but this is the first genome-wide CNV analysis across autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), schizophrenia (SCZ), and obsessive-compulsive disorder (OCD) at once. Using microarray (Affymetrix CytoScan HD), we genotyped 2,691 subjects diagnosed with an NDD (204 SCZ, 1,838 ASD, 427 ADHD and 222 OCD) and 1,769 family members, mainly parents. We identified rare CNVs, defined as those found in <0.1% of 10,851 population control samples. We found clinically relevant CNVs (broadly defined) in 284 (10.5%) of total subjects, including 22 (10.8%) among subjects with SCZ, 209 (11.4%) with ASD, 40 (9.4%) with ADHD, and 13 (5.6%) with OCD. Among all NDD subjects, we identified 17 (0.63%) with aneuploidies and 115 (4.3%) with known genomic disorder variants. We searched further for genes impacted by different CNVs in multiple disorders. Examples of NDD-associated genes linked across more than one disorder (listed in order of occurrence frequency) are NRXN1, SEH1L, LDLRAD4, GNAL, GNG13, MKRN1, DCTN2, KNDC1, PCMTD2, KIF5A, SYNM, and long non-coding RNAs: AK127244 and PTCHD1-AS. We demonstrated that CNVs impacting the same genes could potentially contribute to the etiology of multiple NDDs. The CNVs identified will serve as a useful resource for both research and diagnostic laboratories for prioritization of variants.

Latrophilin's Social Protein Network

Latrophilins (LPHNs) are adhesion GPCRs that are originally discovered as spider's toxin receptors, but are now known to be involved in brain development and linked to several neuronal and non-neuronal disorders. Latrophilins act in conjunction with other cell adhesion molecules and may play a leading role in its network organization. Here, we focus on the main protein partners of latrophilins, namely teneurins, FLRTs and contactins and summarize their respective temporal and spatial expression patterns, links to neurodevelopmental disorders as well as their structural characteristics. We discuss how more recent insights into the separate cell biological functions of these proteins shed light on the central role of latrophilins in this network. We postulate that latrophilins control the refinement of synaptic properties of specific subtypes of neurons, requiring discrete combinations of proteins.

Decreased Expression of Synaptophysin 1 (SYP1 Major Synaptic Vesicle Protein p38) and Contactin 6 (CNTN6/NB3) in the Cerebellar Vermis of reln Haplodeficient Mice

Reeler heterozygous mice (reln^+/-) are seemingly normal but haplodeficient in reln, a gene implicated in autism. Structural/neurochemical alterations in the reln^+/- brain are subtle and difficult to demonstrate. Therefore, the usefulness of these mice in translational research is still debated. As evidence implicated several synapse-related genes in autism and the cerebellar vermis is structurally altered in the condition, we have investigated the expression of synaptophysin 1 (SYP1) and contactin 6 (CNTN6) within the vermis of reln^+/- mice. Semi-thin plastic sections of the vermis from adult mice of both sexes and different genotypes (reln^+/- and reln^+/+) were processed with an indirect immunofluorescence protocol. Immunofluorescence was quantified on binary images and statistically analyzed. Reln^+/- males displayed a statistically significant reduction of 11.89% in the expression of SYP1 compared to sex-matched wild-type animals, whereas no differences were observed between reln^+/+ and reln^+/- females. In reln^+/- male mice, reductions were particularly evident in the molecular layer: 10.23% less SYP1 than reln^+/+ males and 5.84% < reln^+/+ females. In reln^+/- females, decrease was 9.84% versus reln^+/+ males and 5.43% versus reln^+/+ females. Both reln^+/- males and females showed a stronger decrease in CNTN6 expression throughout all the three cortical layers of the vermis: 17-23% in the granular layer, 24-26% in the Purkinje cell layer, and 9-14% in the molecular layer. Altogether, decrease of vermian SYP1 and CNTN6 in reln^+/- mice displayed patterns compatible with the structural modifications of the autistic cerebellum. Therefore, these mice may be a good model in translational studies.

CNTN6 copy number variations: Uncertain clinical significance in individuals with neurodevelopmental disorders

Copy number variations (CNVs) of the CNTN6 gene - a member of the contactin gene superfamily - have been previously proposed to have an association with neurodevelopmental and autism spectrum disorders. However, no functional evidence has been provided to date and phenotypically normal and mildly affected carriers complicate the interpretation of this aberration. In view of conflicting reports on the pathogenicity of CNVs involving CNTN6 and association with different phenotypes, we, independently, evaluated clinical features of nineteen patients with detected CNV of CNTN6 as part of their clinical microarray analysis at Children's Mercy and Nationwide Children's Hospitals for the period of 2008-2015. The clinical presentations of these patients were variable making it difficult to establish genotype-phenotype correlations. CNVs were inherited in six patients. For thirteen patients, inheritance pattern was not established due to unavailability of parental samples for testing. In three cases CNV was inherited from a healthy parent and in three cases from a parent with neurodevelopmental symptoms. Of the nineteen patients, four had a separate genetic abberation in addition to CNV of the CNTN6 that could independently explain their respective phenotypes. Separately, CNTN6 sequencing was performed on an autism spectrum disorder (ASD) research cohort of 94 children from 80 unrelated families. We found no difference in frequency of rare coding variants between the cohort of patients and controls. We conclude that CNVs involving CNTN6 alone seem to be most likely a neutral variant or a possible modifier rather than a disease-causing variant. Patients with CNVs encompassing CNTN6 could benefit from additional genetic testing since a clinical diagnosis due to a CNV of CNTN6 alone is still questionable.

CNTN5-/+or EHMT2-/+human iPSC-derived neurons from individuals with autism develop hyperactive neuronal networks

Induced pluripotent stem cell (iPSC)-derived neurons are increasingly used to model Autism Spectrum Disorder (ASD), which is clinically and genetically heterogeneous. To study the complex relationship of penetrant and weaker polygenic risk variants to ASD, 'isogenic' iPSC-derived neurons are critical. We developed a set of procedures to control for heterogeneity in reprogramming and differentiation, and generated 53 different iPSC-derived glutamatergic neuronal lines from 25 participants from 12 unrelated families with ASD. Heterozygous de novo and rare-inherited presumed-damaging variants were characterized in ASD risk genes/loci. Combinations of putative etiologic variants (GLI3/KIF21A or EHMT2/UBE2I) in separate families were modeled. We used a multi-electrode array, with patch-clamp recordings, to determine a reproducible synaptic phenotype in 25% of the individuals with ASD (other relevant data on the remaining lines was collected). Our most compelling new results revealed a consistent spontaneous network hyperactivity in neurons deficient for CNTN5 or EHMT2. The biobank of iPSC-derived neurons and accompanying genomic data are available to accelerate ASD research.

Editorial note

This article has been through an editorial process in which authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).

Contactins in the central nervous system: role in health and disease

Contactins are a group of cell adhesion molecules that are mainly expressed in the brain and play pivotal roles in the organization of axonal domains, axonal guidance, neuritogenesis, neuronal development, synapse formation and plasticity, axo-glia interactions and neural regeneration. Contactins comprise a family of six members. Their absence leads to malformed axons and impaired nerve conduction. Contactin mediated protein complex formation is critical for the organization of the axon in early central nervous system development. Mutations and differential expression of contactins have been identified in neuro-developmental or neurological disorders. Taken together, contactins are extensively studied in the context of nervous system development. This review summarizes the physiological roles of all six members of the Contactin family in neurodevelopment as well as their involvement in neurological/neurodevelopmental disorders.

Altered spinogenesis in iPSC-derived cortical neurons from patients with autism carrying de novo SHANK3 mutations

The synaptic protein SHANK3 encodes a multidomain scaffold protein expressed at the postsynaptic density of neuronal excitatory synapses. We previously identified de novo SHANK3 mutations in patients with autism spectrum disorders (ASD) and showed that SHANK3 represents one of the major genes for ASD. Here, we analyzed the pyramidal cortical neurons derived from induced pluripotent stem cells from four patients with ASD carrying SHANK3 de novo truncating mutations. At 40-45 days after the differentiation of neural stem cells, dendritic spines from pyramidal neurons presented variable morphologies: filopodia, thin, stubby and muschroom, as measured in 3D using GFP labeling and immunofluorescence. As compared to three controls, we observed a significant decrease in SHANK3 mRNA levels (less than 50% of controls) in correlation with a significant reduction in dendritic spine densities and whole spine and spine head volumes. These results, obtained through the analysis of de novo SHANK3 mutations in the patients' genomic background, provide further support for the presence of synaptic abnormalities in a subset of patients with ASD.

Clinical and Molecular Characterization of Two Patients with CNTN6 Copy Number Variations

Submicroscopic chromosomal alterations usually involve different protein-coding genes and regulatory elements that are responsible for rare contiguous gene disorders, which complicate the understanding of genotype-phenotype correlations. Chromosome band 3p26.3 contains 3 genes encoding neuronal cell adhesion molecules: CHL1, CNTN6, and CNTN4. We describe 2 boys aged 8 years and 11 years mainly affected by intellectual disability and autism spectrum disorder, who harbor a paternally inherited 3p26.3 microdeletion and a 3p26.3 microduplication, respectively. Both anomalies involved only the CNTN6 gene, which encodes contactin 6, a member of the contactin family (MIM 607220). Contactins show pronounced brain expression and function. Interestingly, phenotypes in reciprocal microdeletions and microduplications of CNTN6 are very similar. In conclusion, our data, added to those reported in the literature, are particularly significant for understanding the pathogenic effect of single gene dosage alterations. As for other recurrent syndromes with variable phenotype, these findings are challenging in genetic counselling because of an evident variable penetrance.

Induced pluripotent stem cells as a tool to study brain circuits in autism-related disorders

The mammalian brain is a very complex organ containing an estimated 200 billion cells in humans. Therefore, studying human brain development has become very challenging given all the data that are available from different approaches, notably genetic studies.Recent pluripotent stem cell methods have given rise to the possibility of modeling neurodevelopmental diseases associated with genetic defects. Fibroblasts from patients have been reprogrammed into pluripotent stem cells to derive appropriate neuronal lineages. They specifically include different subtypes of cortical neurons that are at the core of human-specific cognitive abilities. The use of neurons derived from induced pluripotent stem cells (iPSC) has led to deciphering convergent and pleiotropic neuronal synaptic phenotypes found in neurodevelopmental disorders such as autism spectrum disorders (ASD) and their associated syndromes. In addition to these initial studies, remarkable progress has been made in the field of stem cells, with the major objective of reproducing the in vivo maturation steps of human neurons. Recently, several studies have demonstrated the ability of human progenitors to respond to guidance cues and signals in vivo that can direct neurons to their appropriate sites of differentiation where they become fully mature neurons.We provide a brief overview on research using human iPSC in ASD and associated syndromes and on the current understanding of new theories using the re-implantation of neural precursors in mouse brain.

Cntn6 deficiency impairs allocentric navigation in mice

INTRODUCTION

CNTN6 is an immunoglobulin domain-containing cell adhesion molecule that belongs to the contactin family. It is involved in the development of the nervous system. We aim to determine the effect of Cntn6 deficiency on the allocentric navigation in mice.

METHODS

We recorded the travel distance and escape time of wild-type and Cntn6 mutant male and female mice in the Morris water maze task according to the protocol.

RESULTS

There was hardly any Cntn6 expression in the hippocampus of postnatal day 0 (P0) mice, while obvious Cntn6 expression was present in the hippocampal CA1 region of the P7 mice. During the acquisition period of Morris water maze task (Day 1 to 4), Cntn6-/- male mice failed to shorten the escape time to reach platform on the third day, while the travel distance to platform was not significantly different. There was no significant difference in both escape time and travel distance to the platform among all female subjects. In the probe trial test (Day 5), spatial memory of the female mutant mice was mildly affected, while Cntn6-/- male mice were normal. In the spatial relearning test (Day 7 to 10), Cntn6-/- male mice showed no difference in escape time to the platform compared to the wild-type male mice, while Cntn6 deficient female mice required shorter escape time to travel to the platform on day 7, day 8, and day 10.

CONCLUSIONS

Cntn6 is expressed in the developing hippocampus in mice. Cntn6 deficiency affects spatial learning and memory, indicating that Cntn6 plays a role in the development of hippocampus and affects allocentric navigation of the animals.

Allele-Specific Biased Expression of the CNTN6 Gene in iPS Cell-Derived Neurons from a Patient with Intellectual Disability and 3p26.3 Microduplication Involving the CNTN6 Gene

Copy number variations (CNVs) of the human CNTN6 gene caused by megabase-scale microdeletions or microduplications in the 3p26.3 region are often the cause of neurodevelopmental disorders, including intellectual disability and developmental delay. Surprisingly, patients with different copy numbers of this gene display notable overlapping of neuropsychiatric symptoms. The complexity of the study of human neuropathologies is associated with the inaccessibility of brain material. This problem can be overcome through the use of reprogramming technologies that permit the generation of induced pluripotent stem (iPS) cells from fibroblasts and their subsequent in vitro differentiation into neurons. We obtained a set of iPS cell lines derived from a patient carrier of the CNTN6 gene duplication and from two healthy donors. All iPS cell lines displayed the characteristics of pluripotent cells. Some iPS cell lines derived from the patient and from healthy donors were differentiated in vitro by exogenous expression of the Ngn2 transcription factor or by spontaneous neural differentiation of iPS cells through the neural rosette stage. The obtained neurons showed the characteristics of mature neurons as judged by the presence of neuronal markers and by their electrophysiological characteristics. Analysis of allele-specific expression of the CNTN6 gene in these neuronal cells by droplet digital PCR demonstrated that the level of expression of the duplicated allele was significantly reduced compared to that of the wild-type allele. Importantly, according to the sequencing data, both copies of the CNTN6 gene, which were approximately 1 Mb in size, showed no any additional structural rearrangements.

Mutations in RAB39B in individuals with intellectual disability, autism spectrum disorder, and macrocephaly

Background

Autism spectrum disorder (ASD), a developmental disorder of early childhood onset, affects males four times more frequently than females, suggesting a role for the sex chromosomes. In this study, we describe a family with ASD in which a predicted pathogenic nonsense mutation in the X-chromosome gene RAB39B segregates with ASD phenotype.

Methods

Clinical phenotyping, microarray, and whole genome sequencing (WGS) were performed on the five members of this family. Maternal and female sibling X inactivation ratio was calculated, and phase was investigated. Mutant-induced pluripotent stem cells engineered for an exon 2 nonsense mutation were generated and differentiated into cortical neurons for expression and pathway analyses.

Results

Two males with an inherited RAB39B mutation both presented with macrocephaly, intellectual disability (ID), and ASD. Their female sibling with the same mutation presented with ID and a broad autism phenotype. In contrast, their transmitting mother has no neurodevelopmental diagnosis. Our investigation of phase indicated maternal preferential inactivation of the mutated allele, with no such bias observed in the female sibling. We offer the explanation that this bias in X inactivation may explain the absence of a neurocognitive phenotype in the mother. Our cellular knockout model of RAB39B revealed an impact on expression in differentiated neurons for several genes implicated in brain development and function, supported by our pathway enrichment analysis.

Conclusions

Penetrance for ASD is high among males but more variable among females with RAB39B mutations. A critical role for this gene in brain development and function is demonstrated.

Copy Number Variation in Tourette Syndrome

In the current issue of Neuron, Huang et al. (2017) provide new insights from a consortium study of Tourette syndrome pinpointing copy number variations that are involved in the genomic architecture and implicate genes of interest.

De novo and rare inherited copy-number variations in the hemiplegic form of cerebral palsy

Purpose

Hemiplegia is a subtype of cerebral palsy (CP) in which one side of the body is affected. Our earlier study of unselected children with CP demonstrated de novo and clinically relevant rare inherited genomic copy-number variations (CNVs) in 9.6% of participants. Here, we examined the prevalence and types of CNVs specifically in hemiplegic CP.

Methods

We genotyped 97 unrelated probands with hemiplegic CP and their parents. We compared their CNVs to those of 10,851 population controls, in order to identify rare CNVs (<0.1% frequency) that might be relevant to CP. We also sequenced exomes of “CNV-positive” trios.

Results

We detected de novo CNVs and/or sex chromosome abnormalities in 7/97 (7.2%) of probands, impacting important developmental genes such as GRIK2, LAMA1, DMD, PTPRM, and DIP2C. In 18/97 individuals (18.6%), rare inherited CNVs were found, affecting loci associated with known genomic disorders (17p12, 22q11.21) or involving genes linked to neurodevelopmental disorders.

Conclusion

We found an increased rate of de novo CNVs in the hemiplegic CP subtype (7.2%) compared to controls (1%). This result is similar to that for an unselected CP group. Combined with rare inherited CNVs, the genomic data impacts the understanding of the potential etiology of hemiplegic CP in 23/97 (23.7%) of participants.

Neural Glycosylphosphatidylinositol-Anchored Proteins in Synaptic Specification

Glycosylphosphatidylinositol (GPI)-anchored proteins are a specialized class of lipid-associated neuronal membrane proteins that perform diverse functions in the dynamic control of axon guidance, synaptic adhesion, cytoskeletal remodeling, and localized signal transduction, particularly at lipid raft domains. Recent studies have demonstrated that a subset of GPI-anchored proteins act as critical regulators of synapse development by modulating specific synaptic adhesion pathways via direct interactions with key synapse-organizing proteins. Additional studies have revealed that alteration of these regulatory mechanisms may underlie various brain disorders. In this review, we highlight the emerging role of GPI-anchored proteins as key synapse organizers that aid in shaping the properties of various types of synapses and circuits in mammals.

Rare Copy Number Variants in NRXN1 and CNTN6 Increase Risk for Tourette Syndrome

Tourette syndrome (TS) is a model neuropsychiatric disorder thought to arise from abnormal development and/or maintenance of cortico-striato-thalamo-cortical circuits. TS is highly heritable, but its underlying genetic causes are still elusive, and no genome-wide significant loci have been discovered to date. We analyzed a European ancestry sample of 2,434 TS cases and 4,093 ancestry-matched controls for rare (< 1% frequency) copy-number variants (CNVs) using SNP microarray data. We observed an enrichment of global CNV burden that was prominent for large (> 1 Mb), singleton events (OR = 2.28, 95% CI [1.39-3.79], p = 1.2 × 10-3) and known, pathogenic CNVs (OR = 3.03 [1.85-5.07], p = 1.5 × 10-5). We also identified two individual, genome-wide significant loci, each conferring a substantial increase in TS risk (NRXN1 deletions, OR = 20.3, 95% CI [2.6-156.2]; CNTN6 duplications, OR = 10.1, 95% CI [2.3-45.4]). Approximately 1% of TS cases carry one of these CNVs, indicating that rare structural variation contributes significantly to the genetic architecture of TS.

Structural abnormalities in the primary somatosensory cortex and a normal behavioral profile in Contactin-5 deficient mice

Contactin-5 (Cntn5) is an immunoglobulin cell adhesion molecule that is exclusively expressed in the central nervous system. In view of its association with neurodevelopmental disorders, particularly autism spectrum disorder (ASD), this study focused on Cntn5-positive areas in the forebrain and aimed to explore the morphological and behavioral phenotypes of the Cntn5 null mutant (Cntn5^−/−) mouse in relation to these areas and ASD symptomatology. A newly generated antibody enabled us to elaborately describe the spatial expression pattern of Cntn5 in P7 wild type (Cntn5^+/+) mice. The Cntn5 expression pattern included strong expression in the cerebral cortex, hippocampus and mammillary bodies in addition to described previously brain nuclei of the auditory pathway and the dorsal thalamus. Thinning of the primary somatosensory (S1) cortex was found in Cntn5^−/− mice and ascribed to a misplacement of Cntn5-ablated cells. This phenotype was accompanied by a reduction in the barrel/septa ratio of the S1 barrel field. The structure and morphology of the hippocampus was intact in Cntn5^−/− mice. A set of behavioral experiments including social, exploratory and repetitive behaviors showed that these were unaffected in Cntn5^−/− mice. Taken together, these data demonstrate a selective role of Cntn5 in development of the cerebral cortex without overt behavioral phenotypes.

Intragenic CNTNAP2 Deletions: A Bridge Too Far?

Intragenic deletions of the contactin-associated protein-like 2 gene (CNTNAP2) have been found in patients with Gilles de la Tourette syndrome, intellectual disability (ID), obsessive compulsive disorder, cortical dysplasia-focal epilepsy syndrome, autism, schizophrenia, Pitt-Hopkins syndrome, stuttering, and attention deficit hyperactivity disorder. A variety of molecular mechanisms, such as loss of transcription factor binding sites and perturbation of penetrance and expressivity, have been proposed to account for the phenotypic variability resulting from CNTNAP2 mutations. Deletions of both CNTNAP2 alleles produced truncated proteins lacking the transmembrane or some of the extracellular domains, or no protein at all. This observation can be extended to heterozygous intragenic deletions by assuming that such deletion-containing alleles lead to expression of a Caspr2 protein lacking one or several extracellular domains. Such altered forms of Capr2 proteins will lack the ability to bridge the intercellular space between neurons by binding to partners, such as CNTN1, CNTN2, DLG1, and DLG4. This presumed effect of intragenic deletions of CNTNAP2, and possibly other genes involved in connecting neuronal cells, represents a molecular basis for the postulated neuronal hypoconnectivity in autism and probably other neurodevelopmental disorders, including epilepsy, ID, language impairments and schizophrenia. Thus, CNTNAP2 may represent a paradigmatic case of a gene functioning as a node in a genetic and cellular network governing brain development and acquisition of higher cognitive functions.