Contactins in the neurobiology of autism

Mechanistic insights and therapeutic approaches in tic disorders: The distinctive role of ethnomedicine and modern medical interventions

Tic disorders (TDs) are a class of neurodevelopmental disorders that have received considerable scientific attention. The genesis of TDs is increasingly understood as a complex interplay of neurobiological, genetic, and immunological factors. Animal model studies have elucidated the pathophysiology of TDs, paving the way for innovative therapeutic approaches. This review provides a comprehensive analysis of the etiologic basis, experimental framework, and treatment strategies for TDs, highlighting the contributions of ethnomedicine and modern medicine. Our synthesis aims to deepen the understanding of the disease and spur the development of superior treatments. In addition, we present new insights and hypotheses for the future management of TDs, emphasizing the need for continued research into their etiology and progression, as well as the pursuit of more effective therapies. We advocate personalized, holistic care strategies that focus on symptom relief and improving patients' quality of life. Overall, this review provides a critical compendium for TD researchers and practitioners to help navigate the complexities of these disorders.

Linking genomic and proteomic signatures to brain amyloid burden: insights from GR@ACE/DEGESCO

Alzheimer's disease (AD) is a complex disease with a strong genetic component, yet many genetic risk factors remain unknown. We combined genome-wide association studies (GWAS) on amyloid endophenotypes measured in cerebrospinal fluid (CSF) and positron emission tomography (PET) as surrogates of amyloid pathology, which may provide insights into the underlying biology of the disease. We performed a meta-GWAS of CSF Aβ42 and PET measures combining six independent cohorts (n = 2,076). Given the opposite beta direction of Aβ phenotypes in CSF and PET measures, only genetic signals showing opposite directions were considered for analysis (n = 376,599). We explored the amyloidosis signature in the CSF proteome using SOMAscan proteomics (ACE cohort, n = 1,008), connected it with GWAS loci modulating amyloidosis and performed an enrichment analysis of overlapping hits. Finally, we compared our results with a large meta-analysis using publicly available datasets in CSF (n = 13,409) and PET (n = 13,116). After filtering the meta-GWAS, we observed genome-wide significance in the rs429358-APOE locus and annotated nine suggestive hits. We replicated the APOE loci using the large CSF-PET meta-GWAS, identifying multiple AD-associated genes including the novel GADL1 locus. Additionally, we found 1,387 FDR-significant SOMAscan proteins associated with CSF Aβ42 levels. The overlap among GWAS loci and proteins associated with amyloid burden was minimal (n = 35). The enrichment analysis revealed mechanisms connecting amyloidosis with the plasma membrane's anchored component, synapse physiology and mental disorders that were replicated in the large CSF-PET meta-analysis. Combining CSF and PET amyloid GWAS with CSF proteome analyses may effectively elucidate causative molecular mechanisms behind amyloid mobilization and AD physiopathology.

Association Analysis of Rare CNTN5 Variants With Autism Spectrum Disorder in a Japanese Population

BACKGROUND

Contactin-5 (CNTN5), a neural adhesion molecule involved in synaptogenesis and synaptic maturation in the auditory pathway, has been associated with the pathophysiology of autism spectrum disorder (ASD), particularly hyperacusis. To investigate the role of rare CNTN5 variants in ASD susceptibility, we performed resequencing and association analysis in a Japanese population.

METHODS

We resequenced the CNTN5 coding regions in 302 patients with ASD and prioritized rare putatively damaging variants. The prioritized variants were then genotyped in 313 patients with ASD and 1065 controls. Subsequently, we conducted an association study of selected variants with ASD in 614 patients with ASD and 61 057 controls. Clinical data were reviewed for patients carrying prioritized variants.

RESULTS

Through resequencing, we prioritized three rare putatively damaging missense variants (W69G, I227L, and L1000S) in patients with ASD. Although we found a nominally significant association between the I227L variant and ASD, it did not remain significant after post hoc correction. Hyperacusis was found in three out of nine patients carrying prioritized variants.

CONCLUSION

This study does not provide evidence for the contribution of rare CNTN5 variants to the genetic etiology of ASD in the Japanese population.

Animal Models of Autistic-like Behavior in Rodents: A Scoping Review and Call for a Comprehensive Scoring System

Appropriate animal models of human diseases are a cornerstone in the advancement of science and medicine. To create animal models of neuropsychiatric and neurobehavioral diseases such as autism spectrum disorder (ASD) necessitates the development of sufficient neurobehavioral measuring tools to translate human behavior to expected measurable behavioral features in animals. If possible, the severity of the symptoms should also be assessed. Indeed, at least in rodents, adequate neurobehavioral and neurological tests have been developed. Since ASD is characterized by a number of specific behavioral trends with significant severity, animal models of autistic-like behavior have to demonstrate the specific characteristic features, namely impaired social interactions, communication deficits, and restricted, repetitive behavioral patterns, with association to several additional impairments such as somatosensory, motor, and memory impairments. Thus, an appropriate model must show behavioral impairment of a minimal number of neurobehavioral characteristics using an adequate number of behavioral tests. The proper animal models enable the study of ASD-like-behavior from the etiologic, pathogenetic, and therapeutic aspects. From the etiologic aspects, models have been developed by the use of immunogenic substances like polyinosinic-polycytidylic acid (PolyIC), lipopolysaccharide (LPS), and propionic acid, or other well-documented immunogens or pathogens, like Mycobacterium tuberculosis. Another approach is the use of chemicals like valproic acid, polychlorinated biphenyls (PCBs), organophosphate pesticides like chlorpyrifos (CPF), and others. These substances were administered either prenatally, generally after the period of major organogenesis, or, especially in rodents, during early postnatal life. In addition, using modern genetic manipulation methods, genetic models have been created of almost all human genetic diseases that are manifested by autistic-like behavior (i.e., fragile X, Rett syndrome, SHANK gene mutation, neuroligin genes, and others). Ideally, we should not only evaluate the different behavioral modes affected by the ASD-like behavior, but also assess the severity of the behavioral deviations by an appropriate scoring system, as applied to humans. We therefore propose a scoring system for improved assessment of ASD-like behavior in animal models.

Connecting genomic and proteomic signatures of amyloid burden in the brain

Background

Alzheimer's disease (AD) has a high heritable component characteristic of complex diseases, yet many of the genetic risk factors remain unknown. We combined genome-wide association studies (GWAS) on amyloid endophenotypes measured in cerebrospinal fluid (CSF) and positron emission tomography (PET) as surrogates of amyloid pathology, which may be helpful to understand the underlying biology of the disease.

Methods

We performed a meta-analysis of GWAS of CSF Aβ42 and PET measures combining six independent cohorts (n=2,076). Due to the opposite effect direction of Aβ phenotypes in CSF and PET measures, only genetic signals in the opposite direction were considered for analysis (n=376,599). Polygenic risk scores (PRS) were calculated and evaluated for AD status and amyloid endophenotypes. We then searched the CSF proteome signature of brain amyloidosis using SOMAscan proteomic data (Ace cohort, n=1,008) and connected it with GWAS results of loci modulating amyloidosis. Finally, we compared our results with a large meta-analysis using publicly available datasets in CSF (n=13,409) and PET (n=13,116). This combined approach enabled the identification of overlapping genes and proteins associated with amyloid burden and the assessment of their biological significance using enrichment analyses.

Results

After filtering the meta-GWAS, we observed genome-wide significance in the rs429358-APOE locus and nine suggestive hits were annotated. We replicated the APOE loci using the large CSF-PET meta-GWAS and identified multiple AD-associated genes as well as the novel GADL1 locus. Additionally, we found a significant association between the AD PRS and amyloid levels, whereas no significant association was found between any Aβ PRS with AD risk. CSF SOMAscan analysis identified 1,387 FDR-significant proteins associated with CSF Aβ42 levels. The overlap among GWAS loci and proteins associated with amyloid burden was very poor (n=35). The enrichment analysis of overlapping hits strongly suggested several signalling pathways connecting amyloidosis with the anchored component of the plasma membrane, synapse physiology and mental disorders that were replicated in the large CSF-PET meta-analysis.

Conclusions

The strategy of combining CSF and PET amyloid endophenotypes GWAS with CSF proteome analyses might be effective for identifying signals associated with the AD pathological process and elucidate causative molecular mechanisms behind the amyloid mobilization in AD.

CNTN4 modulates neural elongation through interplay with APP

The neuronal cell adhesion molecule contactin-4 (CNTN4) is genetically associated with autism spectrum disorder (ASD) and other psychiatric disorders. Cntn4-deficient mouse models have previously shown that CNTN4 plays important roles in axon guidance and synaptic plasticity in the hippocampus. However, the pathogenesis and functional role of CNTN4 in the cortex has not yet been investigated. Our study found a reduction in cortical thickness in the motor cortex of Cntn4 -/- mice, but cortical cell migration and differentiation were unaffected. Significant morphological changes were observed in neurons in the M1 region of the motor cortex, indicating that CNTN4 is also involved in the morphology and spine density of neurons in the motor cortex. Furthermore, mass spectrometry analysis identified an interaction partner for CNTN4, confirming an interaction between CNTN4 and amyloid-precursor protein (APP). Knockout human cells for CNTN4 and/or APP revealed a relationship between CNTN4 and APP. This study demonstrates that CNTN4 contributes to cortical development and that binding and interplay with APP controls neural elongation. This is an important finding for understanding the physiological function of APP, a key protein for Alzheimer's disease. The binding between CNTN4 and APP, which is involved in neurodevelopment, is essential for healthy nerve outgrowth.

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.

Characterization of cell-cell communication in autistic brains with single-cell transcriptomes

BACKGROUND

Autism spectrum disorder is a neurodevelopmental disorder, affecting 1-2% of children. Studies have revealed genetic and cellular abnormalities in the brains of affected individuals, leading to both regional and distal cell communication deficits.

METHODS

Recent application of single-cell technologies, especially single-cell transcriptomics, has significantly expanded our understanding of brain cell heterogeneity and further demonstrated that multiple cell types and brain layers or regions are perturbed in autism. The underlying high-dimensional single-cell data provides opportunities for multilevel computational analysis that collectively can better deconvolute the molecular and cellular events altered in autism. Here, we apply advanced computation and pattern recognition approaches on single-cell RNA-seq data to infer and compare inter-cell-type signaling communications in autism brains and controls.

RESULTS

Our results indicate that at a global level, there are cell-cell communication differences in autism in comparison with controls, largely involving neurons as both signaling senders and receivers, but glia also contribute to the communication disruption. Although the magnitude of changes is moderate, we find that excitatory and inhibitor neurons are involved in multiple intercellular signaling that exhibits increased strengths in autism, such as NRXN and CNTN signaling. Not all genes in the intercellular signaling pathways show differential expression, but genes in the affected pathways are enriched for axon guidance, synapse organization, neuron migration, and other critical cellular functions. Furthermore, those genes are highly connected to and enriched for genes previously associated with autism risks.

CONCLUSIONS

Overall, our proof-of-principle computational study using single-cell data uncovers key intercellular signaling pathways that are potentially disrupted in the autism brains, suggesting that more studies examining cross-cell type effects can be valuable for understanding autism pathogenesis.

Down-regulation of the brain-specific cell-adhesion molecule contactin-3 in tuberous sclerosis complex during the early postnatal period

Background

The genetic disorder tuberous sclerosis complex (TSC) is frequently accompanied by the development of neuropsychiatric disorders, including autism spectrum disorder and intellectual disability, with varying degrees of impairment. These co-morbidities in TSC have been linked to the structural brain abnormalities, such as cortical tubers, and recurrent epileptic seizures (in 70–80% cases). Previous transcriptomic analysis of cortical tubers revealed dysregulation of genes involved in cell adhesion in the brain, which may be associated with the neurodevelopmental deficits in TSC. In this study we aimed to investigate the expression of one of these genes – cell-adhesion molecule contactin-3.

Methods

Reverse transcription quantitative polymerase chain reaction for the contactin-3 gene (CNTN3) was performed in resected cortical tubers from TSC patients with drug-resistant epilepsy (n = 35, age range: 1–48 years) and compared to autopsy-derived cortical control tissue (n = 27, age range: 0–44 years), as well as by western blot analysis of contactin-3 (n = 7 vs n = 7, age range: 0–3 years for both TSC and controls) and immunohistochemistry (n = 5 TSC vs n = 4 controls). The expression of contactin-3 was further analyzed in fetal and postnatal control tissue by western blotting and in-situ hybridization, as well as in the SH-SY5Y neuroblastoma cell line differentiation model in vitro.

Results

CNTN3 gene expression was lower in cortical tubers from patients across a wide range of ages (fold change = − 0.5, p < 0.001) as compared to controls. Contactin-3 protein expression was lower in the age range of 0–3 years old (fold change = − 3.8, p < 0.001) as compared to the age-matched controls. In control brain tissue, contactin-3 gene and protein expression could be detected during fetal development, peaked around birth and during infancy and declined in the adult brain. CNTN3 expression was induced in the differentiated SH-SY5Y neuroblastoma cells in vitro (fold change = 6.2, p < 0.01).

Conclusions

Our data show a lower expression of contactin-3 in cortical tubers of TSC patients during early postnatal period as compared to controls, which may affect normal brain development and might contribute to neuropsychiatric co-morbidities observed in patients with TSC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11689-022-09416-2.

A Comprehensive Review of Receptor-Type Tyrosine-Protein Phosphatase Gamma (PTPRG) Role in Health and Non-Neoplastic Disease

Protein tyrosine phosphatase receptor gamma (PTPRG) is known to interact with and regulate several tyrosine kinases, exerting a tumor suppressor role in several type of cancers. Its wide expression in human tissues compared to the other component of group 5 of receptor phosphatases, PTPRZ expressed as a chondroitin sulfate proteoglycan in the central nervous system, has raised interest in its role as a possible regulatory switch of cell signaling processes. Indeed, a carbonic anhydrase-like domain (CAH) and a fibronectin type III domain are present in the N-terminal portion and were found to be associated with its role as [HCO3-] sensor in vascular and renal tissues and a possible interaction domain for cell adhesion, respectively. Studies on PTPRG ligands revealed the contactins family (CNTN) as possible interactors. Furthermore, the correlation of PTPRG phosphatase with inflammatory processes in different normal tissues, including cancer, and the increasing amount of its soluble form (sPTPRG) in plasma, suggest a possible role as inflammatory marker. PTPRG has important roles in human diseases; for example, neuropsychiatric and behavioral disorders and various types of cancer such as colon, ovary, lung, breast, central nervous system, and inflammatory disorders. In this review, we sum up our knowledge regarding the latest discoveries in order to appreciate PTPRG function in the various tissues and diseases, along with an interactome map of its relationship with a group of validated molecular interactors.

Neuronal Cell Adhesion Molecules May Mediate Neuroinflammation in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition characterized by restrictive and repetitive behaviors, alongside deficits in social interaction and communication. The etiology of ASD is largely unknown but is strongly linked to genetic variants in neuronal cell adhesion molecules (CAMs), cell-surface proteins that have important roles in neurodevelopment. A combination of environmental and genetic factors are believed to contribute to ASD pathogenesis. Inflammation in ASD has been identified as one of these factors, demonstrated through the presence of proinflammatory cytokines, maternal immune activation, and activation of glial cells in ASD brains. Glial cells are the main source of cytokines within the brain and, therefore, their activity is vital in mediating inflammation in the central nervous system. However, it is unclear whether the aforementioned neuronal CAMs are involved in modulating neuroimmune signaling or glial behavior. This review aims to address the largely unexplored role that neuronal CAMs may play in mediating inflammatory cascades that underpin neuroinflammation in ASD, primarily focusing on the Notch, nuclear factor-κB (NF-κB), and mitogen-activated protein kinase (MAPK) cascades. We will also evaluate the available evidence on how neuronal CAMs may influence glial activity associated with inflammation. This is important when considering the impact of environmental factors and inflammatory responses on ASD development. In particular, neural CAM1 (NCAM1) can regulate NF-κB transcription in neurons, directly altering proinflammatory signaling. Additionally, NCAM1 and contactin-1 appear to mediate astrocyte and oligodendrocyte precursor proliferation which can alter the neuroimmune response. Importantly, although this review highlights the limited information available, there is evidence of a neuronal CAM regulatory role in inflammatory signaling. This warrants further investigation into the role other neuronal CAM family members may have in mediating inflammatory cascades and would advance our understanding of how neuroinflammation can contribute to ASD pathology.

Pleiotropy between language impairment and broader behavioral disorders-an investigation of both common and rare genetic variants

BACKGROUND

Language plays a major role in human behavior. For this reason, neurodevelopmental and psychiatric disorders in which linguistic ability is impaired could have a big impact on the individual's social interaction and general wellbeing. Such disorders tend to have a strong genetic component, but most past studies examined mostly the linguistic overlaps across these disorders; investigations into their genetic overlaps are limited. The aim of this study was to assess the potential genetic overlap between language impairment and broader behavioral disorders employing methods capturing both common and rare genetic variants.

METHODS

We employ polygenic risk scores (PRS) trained on specific language impairment (SLI) to evaluate genetic overlap across several disorders in a large case-cohort sample comprising ~13,000 autism spectrum disorder (ASD) cases, including cases of childhood autism and Asperger's syndrome, ~15,000 attention deficit/hyperactivity disorder (ADHD) cases, ~3000 schizophrenia cases, and ~21,000 population controls. We also examine rare variants in SLI/language-related genes in a subset of the sample that was exome-sequenced using the SKAT-O method.

RESULTS

We find that there is little evidence for genetic overlap between SLI and ADHD, schizophrenia, and ASD, the latter being in line with results of linguistic analyses in past studies. However, we observe a small, significant genetic overlap between SLI and childhood autism specifically, which we do not observe for SLI and Asperger's syndrome. Moreover, we observe that childhood autism cases have significantly higher SLI-trained PRS compared to Asperger's syndrome cases; these results correspond well to the linguistic profiles of both disorders. Our rare variant analyses provide suggestive evidence of association for specific genes with ASD, childhood autism, and schizophrenia.

CONCLUSIONS

Our study provides, for the first time, to our knowledge, genetic evidence for ASD subtypes based on risk variants for language impairment.

Cntn4, a risk gene for neuropsychiatric disorders, modulates hippocampal synaptic plasticity and behavior

Neurodevelopmental and neuropsychiatric disorders, such as autism spectrum disorders (ASD), anorexia nervosa (AN), Alzheimer's disease (AD), and schizophrenia (SZ), are heterogeneous brain disorders with unknown etiology. Genome wide studies have revealed a wide variety of risk genes for these disorders, indicating a biological link between genetic signaling pathways and brain pathology. A unique risk gene is Contactin 4 (Cntn4), an Ig cell adhesion molecule (IgCAM) gene, which has been associated with several neuropsychiatric disorders including ASD, AN, AD, and SZ. Here, we investigated the Cntn4 gene knockout (KO) mouse model to determine whether memory dysfunction and altered brain plasticity, common neuropsychiatric symptoms, are affected by Cntn4 genetic disruption. For that purpose, we tested if Cntn4 genetic disruption affects CA1 synaptic transmission and the ability to induce LTP in hippocampal slices. Stimulation in CA1 striatum radiatum significantly decreased synaptic potentiation in slices of Cntn4 KO mice. Neuroanatomical analyses showed abnormal dendritic arborization and spines of hippocampal CA1 neurons. Short- and long-term recognition memory, spatial memory, and fear conditioning responses were also assessed. These behavioral studies showed increased contextual fear conditioning in heterozygous and homozygous KO mice, quantified by a gene-dose dependent increase in freezing response. In comparison to wild-type mice, Cntn4-deficient animals froze significantly longer and groomed more, indicative of increased stress responsiveness under these test conditions. Our electrophysiological, neuro-anatomical, and behavioral results in Cntn4 KO mice suggest that Cntn4 has important functions related to fear memory possibly in association with the neuronal morphological and synaptic plasticity changes in hippocampus CA1 neurons.

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.

Genome-wide association study of word reading: Overlap with risk genes for neurodevelopmental disorders

Reading disabilities (RD) are the most common neurocognitive disorder, affecting 5% to 17% of children in North America. These children often have comorbid neurodevelopmental/psychiatric disorders, such as attention deficit/hyperactivity disorder (ADHD). The genetics of RD and their overlap with other disorders is incompletely understood. To contribute to this, we performed a genome-wide association study (GWAS) for word reading. Then, using summary statistics from neurodevelopmental/psychiatric disorders, we computed polygenic risk scores (PRS) and used them to predict reading ability in our samples. This enabled us to test the shared aetiology between RD and other disorders. The GWAS consisted of 5.3 million single nucleotide polymorphisms (SNPs) and two samples; a family-based sample recruited for reading difficulties in Toronto (n = 624) and a population-based sample recruited in Philadelphia [Philadelphia Neurodevelopmental Cohort (PNC)] (n = 4430). The Toronto sample SNP-based analysis identified suggestive SNPs (P ~ 5 × 10^-7 ) in the ARHGAP23 gene, which is implicated in neuronal migration/axon pathfinding. The PNC gene-based analysis identified significant associations (P < 2.72 × 10^-6 ) for LINC00935 and CCNT1, located in the region of the KANSL2/CCNT1/LINC00935/SNORA2B/SNORA34/MIR4701/ADCY6 genes on chromosome 12q, with near significant SNP-based analysis. PRS identified significant overlap between word reading and intelligence (R²  = 0.18, P = 7.25  × 10^-181 ), word reading and educational attainment (R²  = 0.07, P = 4.91 × 10^-48 ) and word reading and ADHD (R²  = 0.02, P = 8.70 × 10^-6 ; threshold for significance = 7.14 × 10^-3 ). Overlap was also found between RD and autism spectrum disorder (ASD) as top-ranked genes were previously implicated in autism by rare and copy number variant analyses. These findings support shared risk between word reading, cognitive measures, educational outcomes and neurodevelopmental disorders, including ASD.

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.

Contribution of de novo and inherited rare CNVs to very preterm birth

BACKGROUND

The genomic contribution to adverse health sequelae in babies born very preterm (<32 weeks' gestation) is unknown. We conducted an investigation of rare CNVs in infants born very preterm as part of a study to determine the feasibility and acceptability of a larger, well-powered genome-wide investigation in the UK, with follow-up using linked National Health Service records and DNA storage for additional research.

METHODS

We studied 488 parent-offspring trios. We performed genotyping using Illumina Infinium OmniExpress Arrays. CNV calling and quality control (QC) were undertaken using published protocols. We examined de novo CNVs in infants and the rate of known pathogenic variants in infants, mothers and fathers and compared these with published comparator data. We defined rare pathogenic CNVs as those consistently reported to be associated with clinical phenotypes.

RESULTS

We identified 14 de novo CNVs, representing a mutation rate of 2.9%, compared with 2.1% reported in control populations. The median size of these CNV was much higher than in comparator data (717 kb vs 255 kb). The rate of pathogenic CNVs was 4.3% in infants, 2.7% in mothers and 2% in fathers, compared with 2.3% in UK Biobank participants.

CONCLUSION

Our findings suggest that the rate of de novo CNVs, especially rare pathogenic CNVs, could be elevated in those born very preterm. However, we will need to conduct a much larger study to corroborate this conclusion.

Neuronal migration genes and a familial translocation t (3;17): candidate genes implicated in the phenotype

BACKGROUND

While Miller-Dieker syndrome critical region deletions are well known delineated anomalies, submicroscopic duplications in this region have recently emerged as a new distinctive syndrome. So far, only few cases have been described overlapping 17p13.3 duplications.

METHODS

In this study, we report on clinical and cytogenetic characterization of two new cases involving 17p13.3 and 3p26 chromosomal regions in two sisters with familial history of lissencephaly. Fluorescent In Situ Hybridization and array Comparative Genomic Hybridization were performed.

RESULTS

A deletion including the critical region of the Miller-Dieker syndrome of at least 2,9 Mb and a duplication of at least 3,6 Mb on the short arm of chromosome 3 were highlighted in one case. The opposite rearrangements, 17p13.3 duplication and 3p deletion, were observed in the second case. This double chromosomal aberration is the result of an adjacent 1:1 meiotic segregation of a maternal reciprocal translocation t(3,17)(p26.2;p13.3).

CONCLUSIONS

17p13.3 and 3p26 deletions have a clear range of phenotypic features while duplications still have an uncertain clinical significance. However, we could suggest that regardless of the type of the rearrangement, the gene dosage and interactions of CNTN4, CNTN6 and CHL1 in the 3p26 and PAFAH1B1, YWHAE in 17p13.3 could result in different clinical spectrums.

Neuropsychopathology of Autism Spectrum Disorder: Complex Interplay of Genetic, Epigenetic, and Environmental Factors

Autism spectrum disorder (ASD) is a complex heterogeneous consortium of pervasive development disorders (PDD) which ranges from atypical autism, autism, and Asperger syndrome affecting brain in the developmental stage. This debilitating neurodevelopmental disorder results in both core as well as associated symptoms. Core symptoms observed in autistic patients are lack of social interaction, pervasive, stereotyped, and restricted behavior while the associated symptoms include irritability, anxiety, aggression, and several comorbid disorders.ASD is a polygenic disorder and is multifactorial in origin. Copy number variations (CNVs) of several genes that regulate the synaptogenesis and signaling pathways are one of the major factors responsible for the pathogenesis of autism. The complex integration of various CNVs cause mutations in the genes which code for molecules involved in cell adhesion, voltage-gated ion-channels, scaffolding proteins as well as signaling pathways (PTEN and mTOR pathways). These mutated genes are responsible for affecting synaptic transmission by causing plasticity dysfunction responsible, in turn, for the expression of ASD.Epigenetic modifications affecting DNA transcription and various pre-natal and post-natal exposure to a variety of environmental factors are also precipitating factors for the occurrence of ASD. All of these together cause dysregulation of glutamatergic signaling as well as imbalance in excitatory: inhibitory pathways resulting in glial cell activation and release of inflammatory mediators responsible for the aberrant social behavior which is observed in autistic patients.In this chapter we review and provide insight into the intricate integration of various genetic, epigenetic, and environmental factors which play a major role in the pathogenesis of this disorder and the mechanistic approach behind this integration.

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.

Language deficits in specific language impairment, attention deficit/hyperactivity disorder, and autism spectrum disorder: An analysis of polygenic risk

Language is one of the cognitive domains often impaired across many neurodevelopmental disorders. While for some disorders the linguistic deficit is the primary impairment (e.g., specific language impairment, SLI), for others it may accompany broader behavioral problems (e.g., autism). The precise nature of this phenotypic overlap has been the subject of debate. Moreover, several studies have found genetic overlaps across neurodevelopmental disorders. This raises the question of whether these genetic overlaps may correlate with phenotypic overlaps and, if so, in what manner. Here, we apply a genome‐wide approach to the study of the linguistic deficit in SLI, autism spectrum disorder (ASD), and attention deficit/hyperactivity disorder (ADHD). Using a discovery genome‐wide association study of SLI, we generate polygenic risk scores (PRS) in an independent sample which includes children with language impairment, SLI, ASD or ADHD and age‐matched controls and perform regression analyses across groups. The SLI‐trained PRS significantly predicted risk in the SLI case–control group (adjusted R² = 6.24%; P = 0.024) but not in the ASD or ADHD case‐control groups (adjusted R² = 0.0004%, 0.01%; P = 0.984, 0.889, respectively) nor for height, used as a negative control (R² = 0.2%; P = 0.452). Additionally, there was a significant difference in the normalized PRS between children with SLI and children with ASD (common language effect size = 0.66; P = 0.044). Our study suggests no additive common‐variant genetic overlap between SLI and ASD and ADHD. This is discussed in the context of phenotypic studies of SLI and related disorders. Autism Res 2020, 13: 369–381. © 2019 The Authors. Autism Research published by International Society for Autism Research published by Wiley Periodicals, Inc.

Lay Summary

Language deficits are characteristic of specific language impairment (SLI), but may also be found in other neurodevelopmental disorders, such as autism spectrum disorder (ASD) and attention deficit/hyperactivity disorder (ADHD). Many studies examined the overlaps and differences across the language deficits in these disorders, but few studies have examined the genetic aspect thereof. In this study, we use a genome‐wide approach to evaluate whether common genetic variants increasing risk of SLI may also be associated with ASD and ADHD in the same manner. Our results suggest that this is not the case, and we discuss this finding in the context of theories concerning the etiologies of these disorders.

Intragenic CNTN4 copy number variants associated with a spectrum of neurobehavioral phenotypes

Deletions and duplications involving the CNTN4 gene, which encodes for the contactin 4 protein, have been reported in children with autism spectrum disorder (ASD) and other neurodevelopmental phenotypes. In this study, we performed clinical and genetic characterization of three individuals from unrelated families with copy number variants (CNV) (one deletion and two duplications) within CNTN4. The patients exhibited cognitive delay (3/3), growth restriction (3/3), motor delay (2/3), and febrile seizure/epilepsy (2/3). In contrast to previous reports, all probands presented with speech apraxia or delay with no diagnosis of ASD. Parental studies for the proband with the deletion and one of the 2 probands with the duplication revealed paternal origin of the CNTN4 CNV. Interestingly, previously documented CNV involving this gene were mostly inherited from unaffected fathers, raising questions regarding reduced penetrance and potential parent-of-origin effect. Our findings are compared with previously reported patients and patients in the DECIPHER database. The speech impairment in the three probands suggests a role for CNTN4 in language development. We discuss potential factors contributing to phenotypic heterogeneity and reduced penetrance and attempt to find possible genotype-phenotype correlation. Larger cohorts are needed for comprehensive and unbiased phenotyping and molecular characterization that may lead to better understanding of the underlying mechanisms of reduced penetrance, variable expressivity, and potential parent-of-origin effect of copy number variants encompassing CNTN4.

Modulation of Nerve Cell Differentiation: Role of Polyphenols and of Contactin Family Components

In this study the mechanisms are explored, which modulate expression and function of cell surface adhesive glycoproteins of the Immunoglobulin Supergene Family (IgSF), and in particular of its Contactin subset, during neuronal precursor developmental events. In this context, a specific topic concerns the significance of the expression profile of such molecules and their ability to modulate signaling pathways activated through nutraceuticals, in particular polyphenols, administration. Both in vitro and in vivo approaches are chosen. As for the former, by using as a model the human SH-SY5Y neuroblastoma line, the effects of grape seed polyphenols are evaluated on proliferation and commitment/differentiation events along the neuronal lineage. In SH-SY5Y cell cultures, polyphenols were found to counteract precursor proliferation while promoting their differentiation, as deduced by studying their developmental parameters through the expression of cell cycle and neuronal commitment/differentiation markers as well as by measuring neurite growth. In such cultures, Cyclin E expression and BrdU incorporation were downregulated, indicating reduced precursor proliferation while increased neuronal differentiation was inferred from upregulation of cell cycle exit (p27^–Kip) and neuronal commitment (NeuN) markers as well as by measuring neurite length through morphometric analysis. The polyphenol effects on developmental parameters were also explored in vivo, in cerebellar cortex, by using as a model the TAG/F3 transgenic line, which undergoes delayed neural development as a consequence of Contactin1 adhesive glycoprotein upregulation and premature expression under control of the Contactin2 gene (Cntn-2) promoter. In this transgenic line, a Notch pathway activation is known to occur and polyphenol treatment was found to counteract such an effect, demonstrated through downregulation of the Hes-1 transcription factor. Polyphenols also downregulated the expression of adhesive glycoproteins of the Contactin family themselves, demonstrated for both Contactin1 and Contactin2, indicating the involvement of changes in the expression of the underlying genes in the observed phenotype. These data support the hypothesis that the complex control exerted by polyphenols on neural development involves modulation of expression and function of the genes encoding cell adhesion molecules of the Contactin family and of the associated signaling pathways, indicating potential mechanisms whereby such compounds may control neurogenesis.

Novel Contribution of Secreted Amyloid-β Precursor Protein to White Matter Brain Enlargement in Autism Spectrum Disorder

The most replicated neuroanatomical finding in autism is the tendency toward brain overgrowth, especially in younger children. Research shows that both gray and white matter are enlarged. Proposed mechanisms underlying brain enlargement include abnormal inflammatory and neurotrophic signals that lead to excessive, aberrant dendritic connectivity via disrupted pruning and cell adhesion, and enlargement of white matter due to excessive gliogenesis and increased myelination. Amyloid-β protein precursor (βAPP) and its metabolites, more commonly associated with Alzheimer's disease (AD), are also dysregulated in autism plasma and brain tissue samples. This review highlights findings that demonstrate how one βAPP metabolite, secreted APPα, and the ADAM family α-secretases, may lead to increased brain matter, with emphasis on increased white matter as seen in autism. sAPPα and the ADAM family α-secretases contribute to the anabolic, non-amyloidogenic pathway, which is in contrast to the amyloid (catabolic) pathway known to contribute to Alzheimer disease. The non-amyloidogenic pathway could produce brain enlargement via genetic mechanisms affecting mRNA translation and polygenic factors that converge on molecular pathways (mitogen-activated protein kinase/MAPK and mechanistic target of rapamycin/mTOR), promoting neuroinflammation. A novel mechanism linking the non-amyloidogenic pathway to white matter enlargement is proposed: α-secretase and/or sAPPα, activated by ERK receptor signaling activates P13K/AKt/mTOR and then Rho GTPases favoring myelination via oligodendrocyte progenitor cell (OPC) activation of cofilin. Applying known pathways in AD to autism should allow further understanding and provide options for new drug targets.

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.

Immunoglobulin-Like Receptors and Their Impact on Wiring of Brain Synapses

Synapse formation is mediated by a surprisingly large number and wide variety of genes encoding many different protein classes. One of the families increasingly implicated in synapse wiring is the immunoglobulin superfamily (IgSF). IgSF molecules are by definition any protein containing at least one Ig-like domain, making this family one of the most common protein classes encoded by the genome. Here, we review the emerging roles for IgSF molecules in synapse formation specifically in the vertebrate brain, focusing on examples from three classes of IgSF members: ( a) cell adhesion molecules, ( b) signaling molecules, and ( c) immune molecules expressed in the brain. The critical roles for IgSF members in regulating synapse formation may explain their extensive involvement in neuropsychiatric and neurodevelopmental disorders. Solving the IgSF code for synapse formation may reveal multiple new targets for rescuing IgSF-mediated deficits in synapse formation and, eventually, new treatments for psychiatric disorders caused by altered IgSF-induced synapse wiring.

Pathophysiology of Trans-Synaptic Adhesion Molecules: Implications for Epilepsy

Chemical synapses are specialized interfaces between neurons in the brain that transmit and modulate information, thereby integrating cells into multiplicity of interacting neural circuits. Cell adhesion molecules (CAMs) might form trans-synaptic complexes that are crucial for the appropriate identification of synaptic partners and further for the establishment, properties, and dynamics of synapses. When affected, trans-synaptic adhesion mechanisms play a role in synaptopathies in a variety of neuropsychiatric disorders including epilepsy. This review recapitulates current understanding of trans-synaptic interactions in pathophysiology of interneuronal connections. In particular, we discuss here the possible implications of trans-synaptic adhesion dysfunction for epilepsy.

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.

Neurodevelopmental risk copy number variants in adults with intellectual disabilities and comorbid psychiatric disorders

BACKGROUND

Copy number variants (CNVs) are established risk factors for neurodevelopmental disorders. To date the study of CNVs in psychiatric illness has focused on single disorder populations. The role of CNVs in individuals with intellectual disabilities and psychiatric comorbidities are less well characterised.AimsTo determine the type and frequency of CNVs in adults with intellectual disabilities and comorbid psychiatric disorders.

METHOD

A chromosomal microarray analysis of 599 adults recruited from intellectual disabilities psychiatry services at three European sites.

RESULTS

The yield of pathogenic CNVs was high - 13%. Focusing on established neurodevelopmental disorder risk loci we find a significantly higher frequency in individuals with intellectual disabilities and comorbid psychiatric disorder (10%) compared with healthy controls (1.2%, P<0.0001), schizophrenia (3.1%, P<0.0001) and intellectual disability/autism spectrum disorder (6.5%, P < 0.00084) populations.

CONCLUSIONS

In the largest sample of adults with intellectual disabilities and comorbid psychiatric disorders to date, we find a high rate of pathogenic CNVs. This has clinical implications for the use of genetic investigations in intellectual disability psychiatry.Declaration of interestNone.

Common Ribs of Inhibitory Synaptic Dysfunction in the Umbrella of Neurodevelopmental Disorders

The term neurodevelopmental disorder (NDD) is an umbrella term used to group together a heterogeneous class of disorders characterized by disruption in cognition, emotion, and behavior, early in the developmental timescale. These disorders are heterogeneous, yet they share common behavioral symptomatology as well as overlapping genetic contributors, including proteins involved in the formation, specialization, and function of synaptic connections. Advances may arise from bridging the current knowledge on synapse related factors indicated from both human studies in NDD populations, and in animal models. Mounting evidence has shown a link to inhibitory synapse formation, specialization, and function among Autism, Angelman, Rett and Dravet syndromes. Inhibitory signaling is diverse, with numerous subtypes of inhibitory interneurons, phasic and tonic modes of inhibition, and the molecular and subcellular diversity of GABA_A receptors. We discuss common ribs of inhibitory synapse dysfunction in the umbrella of NDD, highlighting alterations in the developmental switch to inhibitory GABA, dysregulation of neuronal activity patterns by parvalbumin-positive interneurons, and impaired tonic inhibition. Increasing our basic understanding of inhibitory synapses, and their role in NDDs is likely to produce significant therapeutic advances in behavioral symptom alleviation for interrelated NDDs.

Cell adhesion and matricellular support by astrocytes of the tripartite synapse

Astrocytes contribute to the formation, function, and plasticity of synapses. Their processes enwrap the neuronal components of the tripartite synapse, and due to this close interaction they are perfectly positioned to modulate neuronal communication. The interaction between astrocytes and synapses is facilitated by cell adhesion molecules and matricellular proteins, which have been implicated in the formation and functioning of tripartite synapses. The importance of such neuron-astrocyte integration at the synapse is underscored by the emerging role of astrocyte dysfunction in synaptic pathologies such as autism and schizophrenia. Here we review astrocyte-expressed cell adhesion molecules and matricellular molecules that play a role in integration of neurons and astrocytes within the tripartite synapse.

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.

Unexpected phenotypic effects of a transgene integration causing a knockout of the endogenous Contactin-5 gene in mice

Contactins (Cntn1-6) are a family of neuronal membrane proteins expressed in the brain. They are required for establishing cell-to-cell contacts between neurons and for the growth and maturation of the axons. In humans, structural genomic variations in the Contactin genes are implicated in neurodevelopmental disorders. In addition, population genetic studies associate Contactins loci with obesity and hypertension. Cntn5 knockout mice were first described in 2003, but showed no gross physiological or behavioral abnormalities (just minor auditory defects). We report a novel Cntn5 knockout mouse line generated by a random transgene integration as an outcome of pronuclear microinjection. Investigation of the transgene integration site revealed that the 6Kbp transgene construct coding for the human granulocyte-macrophage colony-stimulating factor (hGMCSF) replaced 170 Kbp of the Cntn5 gene, including four exons. Reverse transcription PCR analysis of the Cntn5 transcripts in the wild-type and transgenic mouse lines showed that splicing of the transgene leads to a set of chimeric hGMCSF-Cntn5 transcript variants, none of which encode functional Cntn5 protein due to introduction of stop codons. Although Cntn5 knockout animals displayed no abnormalities in behavior, we noted that they were leaner, with less body mass and fat percentage than wild-type animals. Their cardiovascular parameters (heart rate, blood pressure and blood flow speed) were elevated compared to controls. These findings link Cntn5 deficiency to obesity and hypertension.

A novel relationship for schizophrenia, bipolar and major depressive disorder Part 3: Evidence from chromosome 3 high density association screen

Familial clustering of schizophrenia (SCZ), bipolar disorder (BPD), and major depressive disorder (MDD) was systematically reported (Aukes et al, Genet Med 2012, 14, 338-341) and convergent evidence from genetics, symptomatology, and psychopharmacology imply that there are intrinsic connections between these three major psychiatric disorders, for example, any two or even three of these disorders could co-exist in some families. A total of 60, 838 single-nucleotide polymorphisms (SNPs) on chromosome 3 were genotyped by Affymetrix Genome-Wide Human SNP array 6.0 on 119 SCZ, 253 BPD (type-I), 177 MDD patients and 1,000 controls. The population of Shandong province was formed in 14 century and believed that it belongs to homogenous population. Associated SNPs were systematically revealed and outstanding susceptibility genes (CADPS, GRM7,KALRN, LSAMP, NLGN1, PRICKLE2, ROBO2) were identified. Unexpectedly, flanking genes for the associated SNPs distinctive for BPD and/or MDD were replicated in an enlarged cohort of 986 SCZ patients. The evidence from this chromosome 3 analysis supports the notion that both of bipolar and MDD might be subtypes of schizophrenia rather than independent disease entity. Also, a similar finding was detected on chromosome 5, 6, 7, and 8 (Chen et al. Am J Transl Res 2017;9 (5):2473-2491; Curr Mol Med 2016;16(9):840-854; Behav Brain Res 2015;293:241-251; Mol Neurobiol 2016. doi: 10.1007/s12035-016-0102-1). Furthermore, PRICKLE2 play an important role in the pathogenesis of three major psychoses in this population.

Nanomechanics of multidomain neuronal cell adhesion protein contactin revealed by single molecule AFM and SMD

Contactin-4 (CNTN4) is a complex cell adhesion molecule (CAM) localized at neuronal membranes, playing a key role in maintaining the mechanical integrity and signaling properties of the synapse. CNTN4 consists of six immunoglobulin C2 type (IgC2) domains and four fibronectin type III (FnIII) domains that are shared with many other CAMs. Mutations in CNTN4 gene have been linked to various psychiatric disorders. Toward elucidating the response of this modular protein to mechanical stress, we studied its force-induced unfolding using single molecule atomic force microscopy (smAFM) and steered molecular dynamics (SMD) simulations. Extensive smAFM and SMD data both indicate the distinctive mechanical behavior of the two types of modules distinguished by unique force-extension signatures. The data also reveal the heterogeneity of the response of the individual FNIII and IgC2 modules, which presumably plays a role in the adaptability of CNTN4 to maintaining cell-cell communication and adhesion properties under different conditions. Results show that extensive sampling of force spectra, facilitated by robot-enhanced AFM, can help reveal the existence of weak stabilizing interactions between the domains of multidomain proteins, and provide insights into the nanomechanics of such multidomain or heteromeric proteins.

Satb1 Regulates Contactin 5 to Pattern Dendrites of a Mammalian Retinal Ganglion Cell

The size and shape of dendritic arbors are prime determinants of neuronal connectivity and function. We asked how ON-OFF direction-selective ganglion cells (ooDSGCs) in mouse retina acquire their bistratified dendrites, in which responses to light onset and light offset are segregated to distinct strata. We found that the transcriptional regulator Satb1 is selectively expressed by ooDSGCs. In Satb1 mutant mice, ooDSGC dendrites lack ON arbors, and the cells selectively lose ON responses. Satb1 regulates expression of a homophilic adhesion molecule, Contactin 5 (Cntn5). Both Cntn5 and its co-receptor Caspr4 are expressed not only by ooDSGCs, but also by interneurons that form a scaffold on which ooDSGC ON dendrites fasciculate. Removing Cntn5 from either ooDSGCs or interneurons partially phenocopies Satb1 mutants, demonstrating that Satb1-dependent Cntn5 expression in ooDSGCs leads to branch-specific homophilic interactions with interneurons. Thus, Satb1 directs formation of a morphologically and functionally specialized compartment within a complex dendritic arbor.

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.

Manduca Contactin Regulates Amyloid Precursor Protein-Dependent Neuronal Migration

Amyloid precursor protein (APP) was originally identified as the source of β-amyloid peptides that accumulate in Alzheimer's disease (AD), but it also has been implicated in the control of multiple aspects of neuronal motility. APP belongs to an evolutionarily conserved family of transmembrane proteins that can interact with a variety of adapter and signaling molecules. Recently, we showed that both APP and its insect ortholog [APPL (APP-Like)] directly bind the heterotrimeric G-protein Goα, supporting the model that APP can function as an unconventional Goα-coupled receptor. We also adapted a well characterized assay of neuronal migration in the hawkmoth, Manduca sexta, to show that APPL-Goα signaling restricts ectopic growth within the developing nervous system, analogous to the role postulated for APP family proteins in controlling migration within the mammalian cortex. Using this assay, we have now identified Manduca Contactin (MsContactin) as an endogenous ligand for APPL, consistent with previous work showing that Contactins interact with APP family proteins in other systems. Using antisense-based knockdown protocols and fusion proteins targeting both proteins, we have shown that MsContactin is selectively expressed by glial cells that ensheath the migratory neurons (expressing APPL), and that MsContactin-APPL interactions normally prevent inappropriate migration and outgrowth. These results provide new evidence that Contactins can function as authentic ligands for APP family proteins that regulate APP-dependent responses in the developing nervous system. They also support the model that misregulated Contactin-APP interactions might provoke aberrant activation of Goα and its effectors, thereby contributing to the neurodegenerative sequelae that typify AD.

SIGNIFICANCE STATEMENT

Members of the amyloid precursor protein (APP) family participate in many aspects of neuronal development, but the ligands that normally activate APP signaling have remained controversial. This research provides new evidence that members of the Contactin family function as authentic ligands for APP and its orthologs, and that this evolutionarily conserved class of membrane-attached proteins regulates key aspects of APP-dependent migration and outgrowth in the embryonic nervous system. By defining the normal role of Contactin-APP signaling during development, these studies also provide the framework for investigating how the misregulation of Contactin-APP interactions might contribute to neuronal dysfunction in the context of both normal aging and neurodegenerative conditions, including Alzheimer's disease.

Genetic Approaches to Understanding Psychiatric Disease

Human genetic studies have been the driving force in bringing to light the underlying biology of psychiatric conditions. As these studies fill in the gaps in our knowledge of the mechanisms at play, we will be better equipped to design therapies in rational and targeted ways, or repurpose existing therapies in previously unanticipated ways. This review is intended for those unfamiliar with psychiatric genetics as a field and provides a primer on different modes of genetic variation, the technologies currently used to probe them, and concepts that provide context for interpreting the gene-phenotype relationship. Like other subfields in human genetics, psychiatric genetics is moving from microarray technology to sequencing-based approaches as barriers of cost and expertise are removed, and the ramifications of this transition are discussed here. A summary is then given of recent genetic discoveries in a number of neuropsychiatric conditions, with particular emphasis on neurodevelopmental conditions. The general impact of genetics on drug development has been to underscore the extensive etiological heterogeneity in seemingly cohesive diagnostic categories. Consequently, the path forward is not in therapies hoping to reach large swaths of patients sharing a clinically defined diagnosis, but rather in targeting patients belonging to specific "biotypes" defined through a combination of objective, quantifiable data, including genotype.

The role of cell adhesion molecules in brain wiring and neuropsychiatric disorders

Cell adhesion molecules (CAMs) in the nervous system have long been a research focus, but many mice lacking CAMs show very subtle phenotypes, giving an impression that CAMs may not be major players in constructing the nervous system. However, recent human genetic studies suggest CAM involvement in many neuropsychiatric disorders, implicating that they must have significant functions in nervous system development, namely in circuitry formation. As CAMs can provide specificity through their molecular interactions, this review summarizes possible mechanisms on how alterations of CAMs can result in neuropsychiatric disorders through circuitry modification.

Body mass index change in gastrointestinal cancer and chronic obstructive pulmonary disease is associated with Dedicator of Cytokinesis 1

BACKGROUND

There have been a number of candidate gene association studies of cancer cachexia-related traits, but no genome-wide association study (GWAS) has been published to date. Cachexia presents in patients with a number of complex traits, including both cancer and COPD. The objective of the current investigation was to search for a shared genetic aetiology for change in body mass index (ΔBMI) among cancer and COPD by using GWAS data in the Framingham Heart Study.

METHODS

A linear mixed effects model accounting for age, sex, and change in smoking status was used to calculate ΔBMI in participants over 40 years of age with three consecutive BMI time points (n = 4162). Four GWAS of ΔBMI using generalized estimating equations were performed among 1085 participants with a cancer diagnosis, 204 with gastrointestinal (GI) cancer, 112 with lung cancer, and 237 with COPD to test for association with 418 365 single-nucleotide polymorphisms (SNPs).

RESULTS

Two SNPs reached a level of genome-wide significance (P < 5 × 10^-8 ) with ΔBMI: (i) rs41526344 within the CNTN4 gene, among COPD cases (β = 0.13, P = 4.3 × 10^-8 ); and (ii) rs4751240 in the gene Dedicator of Cytokinesis 1 (DOCK1) among GI cancer cases (β = 0.10, P = 1.9 × 10^-8 ). The DOCK1 SNP association replicated in the ΔBMI GWAS among COPD cases (β_meta-analyis  = 0.10, P_meta-analyis  = 9.3 × 10^-10 ). The DOCK1 gene codes for the dedicator of cytokinesis 1 protein, which has a role in myoblast fusion.

CONCLUSIONS

In sum, one statistically significant common variant in the DOCK1 gene was associated with ΔBMI in GI cancer and COPD cases providing support for at least partially shared aetiology of ΔBMI in complex diseases.

Dendrite and spine modifications in autism and related neurodevelopmental disorders in patients and animal models

Dendrites and spines are the main neuronal structures receiving input from other neurons and glial cells. Dendritic and spine number, size, and morphology are some of the crucial factors determining how signals coming from individual synapses are integrated. Much remains to be understood about the characteristics of neuronal dendrites and dendritic spines in autism and related disorders. Although there have been many studies conducted using autism mouse models, few have been carried out using postmortem human tissue from patients. Available animal models of autism include those generated through genetic modifications and those non-genetic models of the disease. Here, we review how dendrite and spine morphology and number is affected in autism and related neurodevelopmental diseases, both in human, and genetic and non-genetic animal models of autism. Overall, data obtained from human and animal models point to a generalized reduction in the size and number, as well as an alteration of the morphology of dendrites; and an increase in spine densities with immature morphology, indicating a general spine immaturity state in autism. Additional human studies on dendrite and spine number and morphology in postmortem tissue are needed to understand the properties of these structures in the cerebral cortex of patients with autism. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 419-437, 2017.

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

Contactin genes CNTN5 and CNTN6 code for neuronal cell adhesion molecules that promote neurite outgrowth in sensory-motor neuronal pathways. Mutations of CNTN5 and CNTN6 have previously been reported in individuals with autism spectrum disorders (ASDs), but very little is known on their prevalence and clinical impact. In this study, we identified CNTN5 and CNTN6 deleterious variants in individuals with ASD. Among the carriers, a girl with ASD and attention-deficit/hyperactivity disorder was carrying five copies of CNTN5. For CNTN6, both deletions (6/1534 ASD vs 1/8936 controls; P=0.00006) and private coding sequence variants (18/501 ASD vs 535/33480 controls; P=0.0005) were enriched in individuals with ASD. Among the rare CNTN6 variants, two deletions were transmitted by fathers diagnosed with ASD, one stop mutation CNTN6W923X was transmitted by a mother to her two sons with ASD and one variant CNTN6P770L was found de novo in a boy with ASD. Clinical investigations of the patients carrying CNTN5 or CNTN6 variants showed that they were hypersensitive to sounds (a condition called hyperacusis) and displayed changes in wave latency within the auditory pathway. These results reinforce the hypothesis of abnormal neuronal connectivity in the pathophysiology of ASD and shed new light on the genes that increase risk for abnormal sensory perception in ASD.

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.

Loss-of-function of PTPR γ and ζ, observed in sporadic schizophrenia, causes brain region-specific deregulation of monoamine levels and altered behavior in mice

RATIONALE

The receptor protein tyrosine phosphatase PTPRG has been genetically associated with psychiatric disorders and is a ligand for members of the contactin family, which are themselves linked to autism spectrum disorders.

OBJECTIVE

Based on our finding of a phosphatase-null de novo mutation in PTPRG associated with a case of sporadic schizophrenia, we used PTPRG knockout (KO) mice to model the effect of a loss-of-function mutation. We compared the results with loss-of-function in its close paralogue PTPRZ, previously associated with schizophrenia. We tested PTPRG ^-/- , PTPRZ ^-/- , and wild-type male mice for effects on social behavior, forced swim test, and anxiety, as well as on regional brain neurochemistry.

RESULTS

The most notable behavioral consequences of PTPRG gene inactivation were reduced immobilization in the forced swim test, suggestive of some negative symptoms of schizophrenia. By contrast, PTPRZ ^-/- mice demonstrated marked social alteration with increased aggressivity, reminiscent of some positive symptoms of schizophrenia. Both knockouts showed elevated dopamine levels in prefrontal cortex, hippocampus, and most particularly amygdala, but not striatum, accompanied by reduced dopamine beta hydroxylase activity only in amygdala. In addition, PTPRG KO elicited a distinct increase in hippocampal serotonin level not observed in PTPRZ KO.

CONCLUSION

PTPRG and PTPRZ gene loss therefore induces distinct patterns of behavioral change and region-specific alterations in neurotransmitters, highlighting their usefulness as models for neuropsychiatric disorder mechanisms and making these receptors attractive targets for therapy.

Dynamic Control of Synaptic Adhesion and Organizing Molecules in Synaptic Plasticity

Synapses play a critical role in establishing and maintaining neural circuits, permitting targeted information transfer throughout the brain. A large portfolio of synaptic adhesion/organizing molecules (SAMs) exists in the mammalian brain involved in synapse development and maintenance. SAMs bind protein partners, forming trans-complexes spanning the synaptic cleft or cis-complexes attached to the same synaptic membrane. SAMs play key roles in cell adhesion and in organizing protein interaction networks; they can also provide mechanisms of recognition, generate scaffolds onto which partners can dock, and likely take part in signaling processes as well. SAMs are regulated through a portfolio of different mechanisms that affect their protein levels, precise localization, stability, and the availability of their partners at synapses. Interaction of SAMs with their partners can further be strengthened or weakened through alternative splicing, competing protein partners, ectodomain shedding, or astrocytically secreted factors. Given that numerous SAMs appear altered by synaptic activity, in vivo, these molecules may be used to dynamically scale up or scale down synaptic communication. Many SAMs, including neurexins, neuroligins, cadherins, and contactins, are now implicated in neuropsychiatric and neurodevelopmental diseases, such as autism spectrum disorder, schizophrenia, and bipolar disorder and studying their molecular mechanisms holds promise for developing novel therapeutics.

Molecular dissection of germline chromothripsis in a developmental context using patient-derived iPS cells

Background

Germline chromothripsis causes complex genomic rearrangements that are likely to affect multiple genes and their regulatory contexts. The contribution of individual rearrangements and affected genes to the phenotypes of patients with complex germline genomic rearrangements is generally unknown.

Methods

To dissect the impact of germline chromothripsis in a relevant developmental context, we performed trio-based RNA expression analysis on blood cells, induced pluripotent stem cells (iPSCs), and iPSC-derived neuronal cells from a patient with de novo germline chromothripsis and both healthy parents. In addition, Hi-C and 4C-seq experiments were performed to determine the effects of the genomic rearrangements on transcription regulation of genes in the proximity of the breakpoint junctions.

Results

Sixty-seven genes are located within 1 Mb of the complex chromothripsis rearrangements involving 17 breakpoints on four chromosomes. We find that three of these genes (FOXP1, DPYD, and TWIST1) are both associated with developmental disorders and differentially expressed in the patient. Interestingly, the effect on TWIST1 expression was exclusively detectable in the patient’s iPSC-derived neuronal cells, stressing the need for studying developmental disorders in the biologically relevant context. Chromosome conformation capture analyses show that TWIST1 lost genomic interactions with several enhancers due to the chromothripsis event, which likely led to deregulation of TWIST1 expression and contributed to the patient’s craniosynostosis phenotype.

Conclusions

We demonstrate that a combination of patient-derived iPSC differentiation and trio-based molecular profiling is a powerful approach to improve the interpretation of pathogenic complex genomic rearrangements. Here we have applied this approach to identify misexpression of TWIST1, FOXP1, and DPYD as key contributors to the complex congenital phenotype resulting from germline chromothripsis rearrangements.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-017-0399-z) contains supplementary material, which is available to authorized users.

A current view on contactin-4, -5, and -6: Implications in neurodevelopmental disorders

Contactins (Cntns) are a six-member subgroup of the immunoglobulin cell adhesion molecule superfamily (IgCAMs) with pronounced brain expression and function. Recent genetic studies of neuropsychiatric disorders have pinpointed contactin-4 (CNTN4), contactin-5 (CNTN5) and contactin-6 (CNTN6) as candidate genes in neurodevelopmental disorders, particularly in autism spectrum disorders (ASDs), but also in intellectual disability, schizophrenia (SCZ), attention-deficit hyperactivity disorder (ADHD), bipolar disorder (BD), alcohol use disorder (AUD) and anorexia nervosa (AN). This suggests that they have important functions during neurodevelopment. This suggestion is supported by data showing that neurite outgrowth, cell survival and neural circuit formation can be affected by disruption of these genes. Here, we review the current genetic data about their involvement in neuropsychiatric disorders and explore studies on how null mutations affect mouse behavior. Finally, we highlight to role of protein-protein interactions in the potential mechanism of action of Cntn4, -5 and -6 and emphasize that complexes with other membrane proteins may play a role in neuronal developmental functions.

Anatomy and Cell Biology of Autism Spectrum Disorder: Lessons from Human Genetics

Until recently autism spectrum disorder (ASD) was regarded as a neurodevelopmental condition with unknown causes and pathogenesis. In the footsteps of the revolution of genome technologies and genetics, and with its high degree of heritability, ASD became the first neuropsychiatric disorder for which clues towards molecular and cellular pathogenesis were uncovered by genetic identification of susceptibility genes. Currently several hundreds of risk genes have been assigned, with a recurrence below 1% in the ASD population. The multitude and diversity of known ASD genes has extended the clinical notion that ASD comprises very heterogeneous conditions ranging from severe intellectual disabilities to mild high-functioning forms. The results of genetics have allowed to pinpoint a limited number of cellular and molecular processes likely involved in ASD including protein synthesis, signal transduction, transcription/chromatin remodelling and synaptic function all playing an essential role in the regulation of synaptic homeostasis during brain development. In this context, we highlight the role of protein synthesis as a key process in ASD pathogenesis as it might be central in synaptic deregulation and a potential target for intervention. These current insights should lead to a rational design of interventions in molecular and cellular pathways of ASD pathogenesis that may be applied to affected individuals in the future.

Association of Cell Adhesion Molecules Contactin-6 and Latrophilin-1 Regulates Neuronal Apoptosis

In view of important neurobiological functions of the cell adhesion molecule contactin-6 (Cntn6) that have emerged from studies on null-mutant mice and autism spectrum disorders patients, we set out to examine pathways underlying functions of Cntn6 using a proteomics approach. We identified the cell adhesion GPCR latrophilin-1 (Lphn1, a.k.a. CIRL1/CL, ADGRL1) as a binding partner for Cntn6 forming together a heteromeric cis-complex. Lphn1 expression in cultured neurons caused reduction in neurite outgrowth and increase in apoptosis, which was rescued by coexpression of Cntn6. In cultured neurons derived from Cntn6^-/- mice, Lphn1 knockdown reduced apoptosis, suggesting that the observed apoptosis was Lphn1-dependent. In line with these data, the number of apoptotic cells was increased in the cortex of Cntn6^-/- mice compared to wild-type littermate controls. These results show that Cntn6 can modulate the activity of Lphn1 by direct binding and suggests that Cntn6 may prevent apoptosis thereby impinging on neurodevelopment.