Disruption of the non-canonical Wnt gene PRICKLE2 leads to autism-like behaviors with evidence for hippocampal synaptic dysfunction

Unraveling the Role of Wnt Signaling Pathway in the Pathogenesis of Autism Spectrum Disorder (ASD): A Systematic Review

Autism spectrum disorder (ASD), or simply autism, is a neurodevelopmental disorder characterized by social communication deficit, restricted interests, and repetitive behavior. Several studies suggested a link between autism and the dysregulation of the Wnt signaling pathway which is mainly involved in cell fate determination, cell migration, cell polarity, neural patterning, and organogenesis. Despite the absence of effective therapy, significant progress has been made in understanding the pathogenesis of ASD. Neuropharmacological studies showed that drugs acting on the Wnt pathway like Canagliflozin can alleviate autistic-like behavior in animal models. Hence, this pathway could potentially be a futuristic therapeutic target to mitigate autism's symptoms. This systematic review aims to collect and analyze evidence that elucidates how alterations in the Wnt pathway may contribute to the pathogenesis of autism in animal models at the molecular, cellular, and physiological levels. Comprehensive searches were conducted across multiple databases, including PubMed, Web of Science, Embase, and Scopus to identify relevant studies up to March 2024. The inclusion criteria encompassed experimental studies that focused on the link between autism and this pathway, and the quality assessment was ensured by SYRCLE's risk of bias tools. Collectively, the included articles highlighted the possible implication of this pathway in the abnormalities found in autism, which impacted processes such as energy metabolism, oxidative stress, and neurogenesis. These alterations could underlie autistic behavior by affecting synaptic transmission and mitochondrial function.

Evolving Insights into Prickle2 in Neurodevelopment and Neurological Disorders

The development of neural circuits is a complex, highly coordinated process crucial for the proper functioning of the nervous system. This process involves the intricate interplay of numerous genes and signaling pathways. Prickle2, a protein encoded by the planar cell polarity (PCP) genes, is a key component of the noncanonical Wnt/PCP signaling pathway and plays a critical role in neural circuit development. Recent studies have highlighted the essential functions of Prickle2 in various stages of neural circuit formation, including the development of the initial segment of neuronal axons, axon elongation and regeneration, dendrite formation, synapse formation, and vesicle transport. The normal expression and spatial distribution of Prickle2 are vital for these processes, and its dysregulation has been associated with several neurological disorders, including congenital neural tube defects, Alzheimer's disease, epilepsy, and autism spectrum disorders. This review aims to systematically summarize the upstream and downstream signaling pathways and regulatory interactions involving Prickle2 in neurodevelopment and neural circuit formation. By discussing the expression patterns of Prickle2 in neurodevelopment and its associations with neurological diseases, we provide insights into the mechanisms through which Prickle2 influences neurodevelopment and its potential implications in neurological disorders.

Decoding Epilepsy: Prickle2 and Multifaceted Molecular Pathway Connections

BACKGROUND

The Prickle2 (Pk2) gene shows promising potential in uncovering the underlying causes of epilepsy, a neurological disorder that is currently not well understood. This paper utilizes the online tool PubMed to gather and condense information on the involvement of PCP channels and the associated roles of PCP pathway molecules in the onset of epilepsy. These findings are significant for advancing epilepsy treatment. Additionally, the paper discusses future directions for clinical trials and outlines potential therapeutic targets.

METHODS

This review systematically analyzes the biological functions and mechanisms of the Prickle2 gene in epilepsy. Studies were retrieved from PubMed using keywords such as "Prickle2", "epilepsy", and "PCP pathway", focusing on research published between 2000 and 2023 in English. Inclusion criteria included original studies and reviews on Prickle2's role in epilepsy. Studies unrelated to these topics or lacking sufficient data were excluded. Key data on Prickle2's functions and its link to epilepsy were extracted, and findings were summarized after a quality assessment of the literature.

RESULTS

Although there are currently conflicting results regarding the possibility that Prickle2 may cause epilepsy in different organisms, we believe that as more cases involving Prickle2 mutations are reported and more related animal experiments are conducted, the findings will become clearer.

CONCLUSION

Due to the biological functions and mechanisms associated with the Prickle2 protein, it may serve as a useful biomarker or potential therapeutic target for epilepsy treatment.

Epigenetic toxicity of heavy metals - implications for embryonic stem cells

Exposure to heavy metals, such as cadmium, nickel, mercury, arsenic, lead, and hexavalent chromium has been linked to dysregulated developmental processes, such as impaired stem cell differentiation. Heavy metals are well-known modifiers of the epigenome. Stem and progenitor cells are particularly vulnerable to exposure to potentially toxic metals since these cells rely on epigenetic reprogramming for their proper functioning. Therefore, exposure to metals can impair stem and progenitor cell proliferation, pluripotency, stemness, and differentiation. In this review, we provide a comprehensive summary of current evidence on the epigenetic effects of heavy metals on stem cells, focusing particularly on DNA methylation and histone modifications. Moreover, we explore the underlying mechanisms responsible for these epigenetic changes. By providing an overview of heavy metal exposure-induced alterations to the epigenome, the underlying mechanisms, and the consequences of those alterations on stem cell function, this review provides a foundation for further research in this critical area of overlap between toxicology and developmental biology.

Knockdown of the Non-canonical Wnt Gene Prickle2 Leads to Cerebellar Purkinje Cell Abnormalities While Cerebellar-Mediated Behaviors Remain Intact

Autism spectrum disorders (ASD) involve brain wide abnormalities that contribute to a constellation of symptoms including behavioral inflexibility, cognitive dysfunction, learning impairments, altered social interactions, and perceptive time difficulties. Although a single genetic variation does not cause ASD, genetic variations such as one involving a non-canonical Wnt signaling gene, Prickle2, has been found in individuals with ASD. Previous work looking into phenotypes of Prickle2 knock-out (Prickle2-/-) and heterozygous mice (Prickle2-/+) suggest patterns of behavior similar to individuals with ASD including altered social interaction and behavioral inflexibility. Growing evidence implicates the cerebellum in ASD. As Prickle2 is expressed in the cerebellum, this animal model presents a unique opportunity to investigate the cerebellar contribution to autism-like phenotypes. Here, we explore cerebellar structural and physiological abnormalities in animals with Prickle2 knockdown using immunohistochemistry, whole-cell patch clamp electrophysiology, and several cerebellar-associated motor and timing tasks, including interval timing and eyeblink conditioning. Histologically, Prickle2-/- mice have significantly more empty spaces or gaps between Purkinje cells in the posterior lobules and a decreased propensity for Purkinje cells to fire action potentials. These structural cerebellar abnormalities did not impair cerebellar-associated behaviors as eyeblink conditioning and interval timing remained intact. Therefore, although Prickle-/- mice show classic phenotypes of ASD, they do not recapitulate the involvement of the adult cerebellum and may not represent the pathophysiological heterogeneity of the disorder.

Tet1-mediated 5hmC regulates hippocampal neuroinflammation via wnt signaling as a novel mechanism in obstructive sleep apnoea leads to cognitive deficit

BACKGROUND

Obstructive sleep apnoea (OSA) is a sleep-disordered breathing characterized by intermittent hypoxia (IH) that may cause cognitive dysfunction. However, the impact of IH on molecular processes involved in cognitive function remains unclear.

METHODS

C57BL / 6 J mice were exposed to either normoxia (control) or IH for 6 weeks. DNA hydroxymethylation was quantified by hydroxymethylated DNA immunoprecipitation (hMeDIP) sequencing. ten-eleven translocation 1 (Tet1) was knocked down by lentivirus. Specifically, cognitive function was assessed by behavioral experiments, pathological features were assessed by HE staining, the hippocampal DNA hydroxymethylation was examined by DNA dot blot and immunohistochemical staining, while the Wnt signaling pathway and its downstream effects were studied using qRT-PCR, immunofluorescence staining, and Luminex liquid suspension chip analysis.

RESULTS

IH mice showed pathological changes and cognitive dysfunction in the hippocampus. Compared with the control group, IH mice exhibited global DNA hydroxylmethylation in the hippocampus, and the expression of three hydroxylmethylases increased significantly. The Wnt signaling pathway was activated, and the mRNA and 5hmC levels of Wnt3a, Ccnd2, and Prickle2 were significantly up-regulated. Further caused downstream neurogenesis abnormalities and neuroinflammatory activation, manifested as increased expression of IBA1 (a marker of microglia), GFAP (a marker of astrocytes), and DCX (a marker of immature neurons), as well as a range of inflammatory cytokines (e.g. TNFa, IL3, IL9, and IL17A). After Tet1 knocked down, the above indicators return to normal.

CONCLUSION

Activation of Wnt signaling pathway by hippocampal Tet1 is associated with cognitive dysfunction induced by IH.

Expression profile of circulating miRNAs in patients with atrial fibrillation-dominated cardioembolic stroke: A systematic review and bioinformatics analysis

Background

Cardioembolic stroke is a type of ischemic stroke with high disability and mortality, a high recurrence rate and poor prognosis. miRNAs have been explored as potential noninvasive biomarkers in atrial fibrillation and ischemic stroke, but their expression profile in cardioembolic stroke still needs to be explored. This study will explore the differences in miRNA expression between cardioembolic stroke patients and healthy people through meta-analysis and attempt to analyze the target genes by bioinformatics analysis.

Methods

Literature databases and gene expression databases were searched from the inception date to June 2022. The study reported the circulating miRNA expression profiles in cardioembolic stroke patients and healthy controls. miRNAs with significantly differential expression and their target genes were analyzed.

Results

Three articles and one gene expression dataset were included in the analysis. The results showed that miR-21-5p (SMD: 2.16; 95 % CI: 1.57, 2.75; p < 0.001), miR-943, miR-145-3p, and miR-3148 were upregulated in cardioembolic stroke patients compared with controls. The downregulated miRNAs included miR-3136-5p, miR-2277-5p, and miR-2277-3p. The area under the receiver operating characteristic curve of miR-21-5p for cardioembolic stroke was 0.975 (0.933-0.989). For the enrichment results, the target genes of upregulated miRNAs were enriched in the MAPK signaling pathway, Ras signaling pathway, etc. The target genes of downregulated miRNAs were also enriched in the Ras signaling pathway.

Conclusions

This study suggested that circulating miR-21-5p is upregulated in cardioembolic stroke patients compared to healthy controls. The Ras signaling pathway plays an important role in pathogenesis according to enrichment analysis.

Celsr2 regulates NMDA receptors and dendritic homeostasis in dorsal CA1 to enable social memory

Social recognition and memory are critical for survival. The hippocampus serves as a central neural substrate underlying the dynamic coding and transmission of social information. Yet the molecular mechanisms regulating social memory integrity in hippocampus remain unelucidated. Here we report unexpected roles of Celsr2, an atypical cadherin, in regulating hippocampal synaptic plasticity and social memory in mice. Celsr2-deficient mice exhibited defective social memory, with rather intact levels of sociability. In vivo fiber photometry recordings disclosed decreased neural activity of dorsal CA1 pyramidal neuron in Celsr2 mutants performing social memory task. Celsr2 deficiency led to selective impairment in NMDAR but not AMPAR-mediated synaptic transmission, and to neuronal hypoactivity in dorsal CA1. Those activity changes were accompanied with exuberant apical dendrites and immaturity of spines of CA1 pyramidal neurons. Strikingly, knockdown of Celsr2 in adult hippocampus recapitulated the behavioral and cellular changes observed in knockout mice. Restoring NMDAR transmission or CA1 neuronal activities rescued social memory deficits. Collectively, these results show a critical role of Celsr2 in orchestrating dorsal hippocampal NMDAR function, dendritic and spine homeostasis, and social memory in adulthood.

Biomarker potential of competing endogenous RNA networks in Polycystic Ovary Syndrome (PCOS)

Polycystic ovary syndrome (PCOS) is the most common condition affecting women of reproductive age globally. PCOS continues to be the largest contributing factor to female infertility despite significant progress in our knowledge of the molecular underpinnings and treatment of the condition. The fact that PCOS is a very diverse condition makes it one of the key reasons why we haven't been able to overcome it. Non-coding RNAs (ncRNAs) are implicated in the development of PCOS, according to growing evidence. However, it is unclear how the complex regulatory relationships between the many ncRNA types contribute to the growth of this malignancy. Competing endogenous RNA (ceRNA), a recently identified mechanism in the RNA world, suggests regulatory interactions between various RNAs, including long non-coding RNAs (lncRNAs), microRNAs (miRNAs), transcribed pseudogenes, and circular RNAs (circRNAs). Recent studies on PCOS have shown that dysregulation of multiple ceRNA networks (ceRNETs) between these ncRNAs plays crucial roles in developing the defining characteristics of PCOS development. And it is believed that such a finding may open a new door for a deeper comprehension of PCOS's unexplored facets. In addition, it may be able to provide fresh biomarkers and effective therapy targets for PCOS. This review will go over the body of information that exists about the primary roles of ceRNETs before highlighting the developing involvement of several newly found ceRNETs in a number of PCOS characteristics.

Risk and Resilience Variants in the Retinoic Acid Metabolic and Developmental Pathways Associated with Risk of FASD Outcomes

Fetal Alcohol Spectrum Disorder (FASD) is a common neurodevelopmental disorder that affects an estimated 2-5% of North Americans. FASD is induced by prenatal alcohol exposure (PAE) during pregnancy and while there is a clear genetic contribution, few genetic factors are currently identified or understood. In this study, using a candidate gene approach, we performed a genetic variant analysis of retinoic acid (RA) metabolic and developmental signaling pathway genes on whole exome sequencing data of 23 FASD-diagnosed individuals. We found risk and resilience alleles in ADH and ALDH genes known to normally be involved in alcohol detoxification at the expense of RA production, causing RA deficiency, following PAE. Risk and resilience variants were also identified in RA-regulated developmental pathway genes, especially in SHH and WNT pathways. Notably, we also identified significant variants in the causative genes of rare neurodevelopmental disorders sharing comorbidities with FASD, including STRA6 (Matthew-Wood), SOX9 (Campomelic Dysplasia), FDG1 (Aarskog), and 22q11.2 deletion syndrome (TBX1). Although this is a small exploratory study, the findings support PAE-induced RA deficiency as a major etiology underlying FASD and suggest risk and resilience variants may be suitable biomarkers to determine the risk of FASD outcomes following PAE.

The role of prickle proteins in vertebrate development and pathology

Prickle is an evolutionarily conserved family of proteins exclusively associated with planar cell polarity (PCP) signalling. This signalling pathway provides directional and positional cues to eukaryotic cells along the plane of an epithelial sheet, orthogonal to both apicobasal and left-right axes. Through studies in the fruit fly Drosophila, we have learned that PCP signalling is manifested by the spatial segregation of two protein complexes, namely Prickle/Vangl and Frizzled/Dishevelled. While Vangl, Frizzled, and Dishevelled proteins have been extensively studied, Prickle has been largely neglected. This is likely because its role in vertebrate development and pathologies is still being explored and is not yet fully understood. The current review aims to address this gap by summarizing our current knowledge on vertebrate Prickle proteins and to cover their broad versatility. Accumulating evidence suggests that Prickle is involved in many developmental events, contributes to homeostasis, and can cause diseases when its expression and signalling properties are deregulated. This review highlights the importance of Prickle in vertebrate development, discusses the implications of Prickle-dependent signalling in pathology, and points out the blind spots or potential links regarding Prickle, which could be studied further.

Novel α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor (AMPAR) potentiator LT-102: A promising therapeutic agent for treating cognitive impairment associated with schizophrenia

AIMS

We aimed to evaluate the potential of a novel selective α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor (AMPAR) potentiator, LT-102, in treating cognitive impairments associated with schizophrenia (CIAS) and elucidating its mechanism of action.

METHODS

The activity of LT-102 was examined by Ca2+ influx assays and patch-clamp in rat primary hippocampal neurons. The structure of the complex was determined by X-ray crystallography. The selectivity of LT-102 was evaluated by hERG tail current recording and kinase-inhibition assays. The electrophysiological characterization of LT-102 was characterized by patch-clamp recording in mouse hippocampal slices. The expression and phosphorylation levels of proteins were examined by Western blotting. Cognitive function was assessed using the Morris water maze and novel object recognition tests.

RESULTS

LT-102 is a novel and selective AMPAR potentiator with little agonistic effect, which binds to the allosteric site formed by the intradimer interface of AMPAR's GluA2 subunit. Treatment with LT-102 facilitated long-term potentiation in mouse hippocampal slices and reversed cognitive deficits in a phencyclidine-induced mouse model. Additionally, LT-102 treatment increased the protein level of brain-derived neurotrophic factor and the phosphorylation of GluA1 in primary neurons and hippocampal tissues.

CONCLUSION

We conclude that LT-102 ameliorates cognitive impairments in a phencyclidine-induced model of schizophrenia by enhancing synaptic function, which could make it a potential therapeutic candidate for CIAS.

Epilepsy-associated genes: an update

PURPOSE

To provide an updated list of epilepsy-associated genes based on clinical-genetic evidence.

METHODS

Epilepsy-associated genes were systematically searched and cross-checked from the OMIM, HGMD, and PubMed databases up to July 2023. To facilitate the reference for the epilepsy-associated genes that are potentially common in clinical practice, the epilepsy-associated genes were ranked by the mutation number in the HGMD database and by case number in the China Epilepsy Gene 1.0 project, which targeted common epilepsy.

RESULTS

Based on the OMIM database, 1506 genes were identified to be associated with epilepsy and were classified into three categories according to their potential association with epilepsy or other abnormal phenotypes, including 168 epilepsy genes that were associated with epilepsies as pure or core symptoms, 364 genes that were associated with neurodevelopmental disorders as the main symptom and epilepsy, and 974 epilepsy-related genes that were associated with gross physical/systemic abnormalities accompanied by epilepsy/seizures. Among the epilepsy genes, 115 genes (68.5%) were associated with epileptic encephalopathy. After cross-checking with the HGMD and PubMed databases, an additional 1440 genes were listed as potential epilepsy-associated genes, of which 278 genes have been repeatedly identified variants in patients with epilepsy. The top 100 frequently reported/identified epilepsy-associated genes from the HGMD database and the China Epilepsy Gene 1.0 project were listed, among which 40 genes were identical in both sources.

SIGNIFICANCE

Recognition of epilepsy-associated genes will facilitate genetic screening strategies and be helpful for precise molecular diagnosis and treatment of epilepsy in clinical practice.

Distinct overlapping functions for Prickle1 and Prickle2 in the polarization of the airway epithelium

Planar cell polarity (PCP) signaling polarizes cells within the plane of an epithelium. In the airways, planar cell polarity signaling orients the directional beating of motile cilia required for effective mucociliary clearance. The planar cell polarity signaling mechanism is best understood from work in Drosophila, where it has been shown to both coordinate the axis of polarity between cells and to direct the morphological manifestations of polarization within cells. The ‘core’ planar cell polarity signaling mechanism comprises two protein complexes that segregate to opposite sides of each cell and interact with the opposite complex in neighboring cells. Proper subcellular localization of core planar cell polarity proteins correlates with, and is almost certainly responsible for, their ability to direct polarization. This mechanism is highly conserved from Drosophila to vertebrates, though for most of the core genes, mammals have multiple paralogs whereas Drosophila has only one. In the mouse airway epithelium, the core protein Prickle2 segregates asymmetrically, as is characteristic for core proteins, but is only present in multiciliated cells and is absent from other cell types. Furthermore, Prickle2 mutant mice show only modest ciliary polarity defects. These observations suggest that other Prickle paralogs might contribute to polarization. Here, we show that Prickle1 segregates asymmetrically in multiciliated and nonciliated airway epithelial cell types, that compared to Prickle2, Prickle1 has different spatial and temporal expression dynamics and a stronger ciliary polarity phenotype, and that Prickle1 and Prickle2 mutants genetically interact. We propose distinct and partially overlapping functions for the Prickle paralogs in polarization of the airway epithelium.

The core PCP protein Prickle2 regulates axon number and AIS maturation by binding to AnkG and modulating microtubule bundling

Core planar cell polarity (PCP) genes, which are involved in various neurodevelopmental disorders such as neural tube closure, epilepsy, and autism spectrum disorder, have poorly defined molecular signatures in neurons, mostly synapse-centric. Here, we show that the core PCP protein Prickle-like protein 2 (Prickle2) controls neuronal polarity and is a previously unidentified member of the axonal initial segment (AIS) proteome. We found that Prickle2 is present and colocalizes with AnkG480, the AIS master organizer, in the earliest stages of axonal specification and AIS formation. Furthermore, by binding to and regulating AnkG480, Prickle2 modulates its ability to bundle microtubules, a crucial mechanism for establishing neuronal polarity and AIS formation. Prickle2 depletion alters cytoskeleton organization, and Prickle2 levels determine both axon number and AIS maturation. Last, early Prickle2 depletion produces impaired action potential firing.

Central FGF21 production regulates memory but not peripheral metabolism

Fibroblast growth factor 21 (FGF21) is a liver-derived endocrine hormone that functions to regulate energy homeostasis and macronutrient intake. Recently, FGF21 was reported to be produced and secreted from hypothalamic tanycytes, to regulate peripheral lipid metabolism; however, rigorous investigation of FGF21 expression in the brain has yet to be accomplished. Using a mouse model that drives CRE recombinase in FGF21-expressing cells, we demonstrate that FGF21 is not expressed in the hypothalamus, but instead is produced from the retrosplenial cortex (RSC), an essential brain region for spatial learning and memory. Furthermore, we find that central FGF21 produced in the RSC enhances spatial memory but does not regulate energy homeostasis or sugar intake. Finally, our data demonstrate that administration of FGF21 prolongs the duration of long-term potentiation in the hippocampus and enhances activation of hippocampal neurons. Thus, endogenous and pharmacological FGF21 appear to function in the hippocampus to enhance spatial memory.

Zhou et al. reveal that the endocrine hormone FGF21 is expressed in the brain. Central FGF21 expression occurs in distinct areas, including the retrosplenial cortex, but not the hypothalamus. Interestingly, brain-derived FGF21 regulates spatial memory formation, but not metabolism, and the converse is true for liver-derived FGF21.

Polarity proteins: Shaping dendritic spines and memory

The morphogenesis and plasticity of dendritic spines are associated with synaptic strength, learning, and memory. Dendritic spines are highly compartmentalized structures, which makes proteins involved in cellular polarization and membrane compartmentalization likely candidates regulating their formation and maintenance. Indeed, recent studies suggest polarity proteins help form and maintain dendritic spines by compartmentalizing the spine neck and head. Here, we review emerging evidence that polarity proteins regulate dendritic spine plasticity and stability through the cytoskeleton, scaffolding molecules, and signaling molecules. We specifically analyze various polarity complexes known to contribute to different forms of cell polarization processes and examine the essential conceptual context linking these groups of polarity proteins to dendritic spine morphogenesis, plasticity, and cognitive functions.

Abnormal larval neuromuscular junction morphology and physiology in Drosophila prickle isoform mutants with known axonal transport defects and adult seizure behavior

Previous studies have demonstrated the striking mutational effects of the Drosophila planar cell polarity gene prickle (pk) on larval motor axon microtubule-mediated vesicular transport and on adult epileptic behavior associated with neuronal circuit hyperexcitability. Mutant alleles of the prickle-prickle (pk^pk) and prickle-spiny-legs (pk^sple) isoforms (hereafter referred to as pk and sple alleles, respectively) exhibit differential phenotypes. While both pk and sple affect larval motor axon transport, only sple confers motor circuit and behavior hyperexcitability. However, mutations in the two isoforms apparently counteract to ameliorate adult motor circuit and behavioral hyperexcitability in heteroallelic pk^pk/pk^sple flies. We have further investigated the consequences of altered axonal transport in the development and function of the larval neuromuscular junction (NMJ). We uncovered robust dominant phenotypes in both pk and sple alleles, including synaptic terminal overgrowth (as revealed by anti-HRP and -Dlg immunostaining) and poor vesicle release synchronicity (as indicated by synaptic bouton focal recording). However, we observed recessive alteration of synaptic transmission only in pk/pk larvae, i.e. increased excitatory junctional potential (EJP) amplitude in pk/pk but not in pk/+ or sple/sple. Interestingly, for motor terminal excitability sustained by presynaptic Ca²⁺ channels, both pk and sple exerted strong effects to produce prolonged depolarization. Notably, only sple acted dominantly whereas pk/+ appeared normal, but was able to suppress the sple phenotypes, i.e. pk/sple appeared normal. Our observations contrast the differential roles of the pk and sple isoforms and highlight their distinct, variable phenotypic expression in the various structural and functional aspects of the larval NMJ.

Genetics of glutamate and its receptors in autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental impairment characterized by deficits in social interaction skills, impaired communication, and repetitive and restricted behaviors that are thought to be due to altered neurotransmission processes. The amino acid glutamate is an essential excitatory neurotransmitter in the human brain that regulates cognitive functions such as learning and memory, which are usually impaired in ASD. Over the last several years, increasing evidence from genetics, neuroimaging, protein expression, and animal model studies supporting the notion of altered glutamate metabolism has heightened the interest in evaluating glutamatergic dysfunction in ASD. Numerous pharmacological, behavioral, and imaging studies have demonstrated the imbalance in excitatory and inhibitory neurotransmitters, thus revealing the involvement of the glutamatergic system in ASD pathology. Here, we review the effects of genetic alterations on glutamate and its receptors in ASD and the role of non-invasive imaging modalities in detecting these changes. We also highlight the potential therapeutic targets associated with impaired glutamatergic pathways.

A multi-environments-gene interaction study of anxiety, depression and self-harm in the UK Biobank cohort

The effects of gene-by-environment (G×E) interactions on complex diseases are significant, especially the superimposed effects of multiple environmental factors. However, research on the multi-environments-gene interactions of anxiety, depression, and self-harm is still limited. This study included white individuals (N = 66,041-74,482) from the UK Biobank. We fitted all environmental factors to a single environmental score (ES), and the estimated ES was used to calculate the multiplicative interaction effects between ES and genome-wide SNPs. Heritability was stratified by minor allele frequency (MAF) and linkage disequilibrium (LD). Our research found 10 loci with significant interaction effects, such as rs114830993 (PRICKLE2, P = 2.30 × 10^-8), rs151323364 (ASTN2, P = 2.71 × 10^-10) and rs536631793 (SYN3, P = 4.09 × 10^-8). In addition, we found that G×E heritability has a significant contribution to the depression of Patient Health Questionnaire-9 (PHQ-9) scores (h²_{G×E (female)} = 6.1%, h²_{G×E (male)} = 8.7%). Our research supported the important influence of multi-environments-gene interactions on anxiety, depression, and self-harm and provided clues for the prevention and etiological research of them.

Mutation of the murine Prickle1 (R104Q) causes phenotypes analogous to human symptoms of epilepsy and autism

Epilepsy and autism spectrum disorders (ASD) frequently show comorbidity, suggesting shared or overlapping neurobiological basis underlying these conditions. R104Q is the first mutation in the PRICKLE 1(PK1) gene that was discovered in human patients with progressive myoclonus epilepsy (PME). Subsequently, a number of mutations in the PK1 gene were shown to be associated with either epilepsy, autism, or both, as well as other developmental disorders. Using CRISPR-Cas9-mediated gene editing, we generated a PK1R104Q mouse line. The mutant mice showed reduced density of excitatory synapses in hippocampus and impaired interaction between PK1 and the repressor element 1(RE-1) silencing transcription factor (REST). They also displayed reduced seizure threshold, impaired social interaction, and cognitive functions. Taken together, the PK1R104Q mice display characteristic behavioral features similar to the key symptoms of epilepsy and ASD, providing a useful model for studying the molecular and neural circuit mechanisms underlying the comorbidity of epilepsy and ASD.

Post-synaptic scaffold protein TANC2 in psychiatric and somatic disease risk

Understanding the shared genetic aetiology of psychiatric and medical comorbidity in neurodevelopmental disorders (NDDs) could improve patient diagnosis, stratification and treatment options. Rare tetratricopeptide repeat, ankyrin repeat and coiled-coil containing 2 (TANC2)-disrupting variants were disease causing in NDD patients. The post-synaptic scaffold protein TANC2 is essential for dendrite formation in synaptic plasticity and plays an unclarified but critical role in development. We here report a novel homozygous-viable Tanc2-disrupted function model in which mutant mice were hyperactive and had impaired sensorimotor gating consistent with NDD patient psychiatric endophenotypes. Yet, a multi-systemic analysis revealed the pleiotropic effects of Tanc2 outside the brain, such as growth failure and hepatocellular damage. This was associated with aberrant liver function including altered hepatocellular metabolism. Integrative analysis indicates that these disrupted Tanc2 systemic effects relate to interaction with Hippo developmental signalling pathway proteins and will increase the risk for comorbid somatic disease. This highlights how NDD gene pleiotropy can augment medical comorbidity susceptibility, underscoring the benefit of holistic NDD patient diagnosis and treatment for which large-scale preclinical functional genomics can provide complementary pleiotropic gene function information.

Summary: Disruption of mouse Tanc2 causes brain and liver abnormality, increasing psychiatric and somatic disease risk long term, highlighting the benefit of holistic diagnosis and treatment approaches for human neurodevelopmental disorder.

Prickle promotes the formation and maintenance of glutamatergic synapses by stabilizing the intercellular planar cell polarity complex

Whether there exists a common signaling mechanism that assembles all glutamatergic synapses is unknown. We show here that knocking out Prickle1 and Prickle2 reduced the formation of the PSD-95–positive glutamatergic synapses in the hippocampus and medial prefrontal cortex in postnatal development by 70–80%. Prickle1 and Prickle2 double knockout in adulthood lead to the disassembly of 70 to 80% of the postsynaptic-density(PSD)-95–positive glutamatergic synapses. PSD-95–positive glutamatergic synapses in the hippocampus of Prickle2E8Q/E8Q mice were reduced by 50% at postnatal day 14. Prickle2 promotes synapse formation by antagonizing Vangl2 and stabilizing the intercellular complex of the planar cell polarity (PCP) components, whereas Prickle2 E8Q fails to do so. Coculture experiments show that the asymmetric PCP complexes can determine the presynaptic and postsynaptic polarity. In summary, the PCP components regulate the assembly and maintenance of a large number of glutamatergic synapses and specify the direction of synaptic transmission.

PRICKLE2 revisited-further evidence implicating PRICKLE2 in neurodevelopmental disorders

PRICKLE2 encodes a member of a highly conserved family of proteins that are involved in the non-canonical Wnt and planar cell polarity signaling pathway. Prickle2 localizes to the post-synaptic density, and interacts with post-synaptic density protein 95 and the NMDA receptor. Loss-of-function variants in prickle2 orthologs cause seizures in flies and mice but evidence for the role of PRICKLE2 in human disease is conflicting. Our goal is to provide further evidence for the role of this gene in humans and define the phenotypic spectrum of PRICKLE2-related disorders. We report a cohort of six subjects from four unrelated families with heterozygous rare PRICKLE2 variants (NM_198859.4). Subjects were identified through an international collaboration. Detailed phenotypic and genetic assessment of the subjects were carried out and in addition, we assessed the variant pathogenicity using bioinformatic approaches. We identified two missense variants (c.122 C > T; p.(Pro41Leu), c.680 C > G; p.(Thr227Arg)), one nonsense variant (c.214 C > T; p.(Arg72*) and one frameshift variant (c.1286_1287delGT; p.(Ser429Thrfs*56)). While the p.(Ser429Thrfs*56) variant segregated with disease in a family with three affected females, the three remaining variants occurred de novo. Subjects shared a mild phenotype characterized by global developmental delay, behavioral difficulties ± epilepsy, autistic features, and attention deficit hyperactive disorder. Computational analysis of the missense variants suggest that the altered amino acid residues are likely to be located in protein regions important for function. This paper demonstrates that PRICKLE2 is involved in human neuronal development and that pathogenic variants in PRICKLE2 cause neurodevelopmental delay, behavioral difficulties and epilepsy in humans.

[Genetic risk factors and their influence on neural development in autism spectrum disorders]

Genetic risk factors and their influence on neural development in autism spectrum disorders Abstract. Abstract. Autism spectrum disorders are etiologically based on genetic and specific gene x biologically relevant environmental risk factors. They are diagnosed based on behavioral characteristics, such as impaired social communication and stereotyped, repetitive behavior and sensory as well as special interests. The genetic background is heterogeneous, i. e., it comprises diverse genetic risk factors across the disorder and high interindividual differences of specific genetic risk factors. Nevertheless, risk factors converge regarding underlying biological mechanisms and shared pathways, which likely cause the autism-specific behavioral characteristics. The current selective literature review summarizes differential genetic risk factors and focuses particularly on mechanisms and pathways currently being discussed by international research. In conclusion, clinically relevant aspects and open translational research questions are presented.

Histone Deacetylase Inhibitors Ameliorate Morphological Defects and Hypoexcitability of iPSC-Neurons from Rubinstein-Taybi Patients

Rubinstein-Taybi syndrome (RSTS) is a rare neurodevelopmental disorder caused by mutations in CREBBP or EP300 genes encoding CBP/p300 lysine acetyltransferases. We investigated the efficacy of the histone deacetylase inhibitor (HDACi) Trichostatin A (TSA) in ameliorating morphological abnormalities of iPSC-derived young neurons from P149 and P34 CREBBP-mutated patients and hypoexcitability of mature neurons from P149. Neural progenitors from both patients’ iPSC lines were cultured one week with TSA 20 nM and, only P149, for 6 weeks with TSA 0.2 nM, in parallel to neural progenitors from controls. Immunofluorescence of MAP2/TUJ1 positive cells using the Skeletonize Image J plugin evidenced that TSA partially rescued reduced nuclear area, and decreased branch length and abnormal end points number of both 45 days patients’ neurons, but did not influence the diminished percentage of their neurons with respect to controls. Patch clamp recordings of TSA-treated post-mitotic P149 neurons showed complete/partial rescue of sodium/potassium currents and significant enhancement of neuron excitability compared to untreated replicas. Correction of abnormalities of P149 young neurons was also affected by valproic acid 1 mM for 72 h, with some variation, with respect to TSA, on the morphological parameter. These findings hold promise for development of an epigenetic therapy to attenuate RSTS patients cognitive impairment.

MRCKβ links Dasm1 to actin rearrangements to promote dendrite development

Proper dendrite morphogenesis and synapse formation are essential for neuronal development and function. Dasm1, a member of the immunoglobulin superfamily, is known to promote dendrite outgrowth and excitatory synapse maturation in vitro. However, the in vivo function of Dasm1 in neuronal development and the underlying mechanisms are not well understood. To learn more, Dasm1 knockout mice were constructed and employed to confirm that Dasm1 regulates dendrite arborization and spine formation in vivo. We performed a yeast two-hybrid screen using Dasm1, revealing MRCKβ as a putative partner; additional lines of evidence confirmed this interaction and identified cytoplasmic proline-rich region (823–947 aa) of Dasm1 and MRCKβ self-activated kinase domain (CC1, 410–744 aa) as necessary and sufficient for binding. Using co-immunoprecipitation assay, autophosphorylation assay, and BS3 cross-linking assay, we show that Dasm1 binding triggers a change in MRCKβ’s conformation and subsequent dimerization, resulting in autophosphorylation and activation. Activated MRCKβ in turn phosphorylates a class 2 regulatory myosin light chain, which leads to enhanced actin rearrangement, causing the dendrite outgrowth and spine formation observed before. Removal of Dasm1 in mice leads to behavioral abnormalities. Together, these results reveal a crucial molecular pathway mediating cell surface and intracellular signaling communication to regulate actin dynamics and neuronal development in the mammalian brain.

Fyn depletion ameliorates tauP301L-induced neuropathology

The Src family non-receptor tyrosine kinase Fyn has been implicated in neurodegeneration of Alzheimer's disease through interaction with amyloid β (Aβ). However, the role of Fyn in the pathogenesis of primary tauopathies such as FTDP-17, where Aβ plaques are absent, is poorly understood. In the current study, we used AAV2/8 vectors to deliver tauP301L to the brains of WT and Fyn KO mice, generating somatic transgenic tauopathy models with the presence or absence of Fyn. Although both genotypes developed tau pathology, Fyn KO developed fewer neurofibrillary tangles on Bielschowsky and Thioflavin S stained sections and showed lower levels of phosphorylated tau. In addition, tauP301L-induced behavior abnormalities and depletion of synaptic proteins were not observed in the Fyn KO model. Our work provides evidence for Fyn being a critical protein in the disease pathogenesis of FTDP-17.

A truncating Aspm allele leads to a complex cognitive phenotype and region-specific reductions in parvalbuminergic neurons

Neurodevelopmental disorders are heterogeneous and identifying shared genetic aetiologies and converging signalling pathways affected could improve disease diagnosis and treatment. Truncating mutations of the abnormal spindle-like microcephaly associated (ASPM) gene cause autosomal recessive primary microcephaly (MCPH) in humans. ASPM is a positive regulator of Wnt/β-Catenin signalling and controls symmetric to asymmetric cell division. This process balances neural progenitor proliferation with differentiation during embryogenesis, the malfunction of which could interfere with normal brain development. ASPM mutations may play a role also in other neurodevelopmental disorders, nevertheless, we lack the details of how or to what extent. We therefore assessed neurodevelopmental disease and circuit endophenotypes in mice with a truncating Aspm^1-7 mutation. Aspm^1-7 mice exhibited impaired short- and long-term object recognition memory and markedly enhanced place learning in the IntelliCage®. This behaviour pattern is reminiscent of a cognitive phenotype seen in mouse models and patients with a rare form of autism spectrum disorder (ASD) as well as in mouse models of altered Wnt signalling. These alterations were accompanied by ventriculomegaly, corpus callosum dysgenesis and decreased parvalbumin (PV)+ interneuron numbers in the hippocampal Cornu Ammonis (CA) region and thalamic reticular nucleus (TRN). PV+ cell number correlated to object recognition (CA and TRN) and place learning (TRN). This opens the possibility that, as well as causing MCPH, mutant ASPM potentially contributes to other neurodevelopmental disorders such as ASD through altered parvalbuminergic interneuron development affecting cognitive behaviour. These findings provide important information for understanding the genetic overlap and improved treatment of neurodevelopmental disorders associated with ASPM.

Targeted next-generation sequencing identifies novel variants in candidate genes for Parkinson's disease in Black South African and Nigerian patients

BACKGROUND

The prevalence of Parkinson's disease (PD) is increasing in sub-Saharan Africa, but little is known about the genetics of PD in these populations. Due to their unique ancestry and diversity, sub-Saharan African populations have the potential to reveal novel insights into the pathobiology of PD. In this study, we aimed to characterise the genetic variation in known and novel PD genes in a group of Black South African and Nigerian patients.

METHODS

We recruited 33 Black South African and 14 Nigerian PD patients, and screened them for sequence variants in 751 genes using an Ion AmpliSeq™ Neurological Research panel. We used bcftools to filter variants and annovar software for the annotation. Rare variants were prioritised using MetaLR and MetaSVM prediction scores. The effect of a variant on ATP13A2's protein structure was investigated by molecular modelling.

RESULTS

We identified 14,655 rare variants with a minor allele frequency ≤ 0.01, which included 2448 missense variants. Notably, no common pathogenic mutations were identified in these patients. Also, none of the known PD-associated mutations were found highlighting the need for more studies in African populations. Altogether, 54 rare variants in 42 genes were considered deleterious and were prioritized, based on MetaLR and MetaSVM scores, for follow-up studies. Protein modelling showed that the S1004R variant in ATP13A2 possibly alters the conformation of the protein.

CONCLUSIONS

We identified several rare variants predicted to be deleterious in sub-Saharan Africa PD patients; however, further studies are required to determine the biological effects of these variants and their possible role in PD. Studies such as these are important to elucidate the genetic aetiology of this disorder in patients of African ancestry.

Association of genes with phenotype in autism spectrum disorder

Autism spectrum disorder (ASD) is a genetic heterogeneous neurodevelopmental disorder that is characterized by impairments in social interaction and speech development and is accompanied by stereotypical behaviors such as body rocking, hand flapping, spinning objects, sniffing and restricted behaviors. The considerable significance of the genetics associated with autism has led to the identification of many risk genes for ASD used for the probing of ASD specificity and shared cognitive features over the past few decades. Identification of ASD risk genes helps to unravel various genetic variants and signaling pathways which are involved in ASD. This review highlights the role of ASD risk genes in gene transcription and translation regulation processes, as well as neuronal activity modulation, synaptic plasticity, disrupted key biological signaling pathways, and the novel candidate genes that play a significant role in the pathophysiology of ASD. The current emphasis on autism spectrum disorders has generated new opportunities in the field of neuroscience, and further advancements in the identification of different biomarkers, risk genes, and genetic pathways can help in the early diagnosis and development of new clinical and pharmacological treatments for ASD.

Bisphenol A inhibits autophagosome-lysosome fusion and lipid droplet degradation

Bisphenol A (BPA) is an artificial xenoestrogen widely used in consumer products containing polycarbonate plastics and epoxy resins. Exposure to BPA occurs through various channels, including ingestion of contaminated food and water. Autophagy is an important catabolic pathway that plays an important role in liver lipid metabolism. Evidence suggests that BPA exposure causes abnormal lipid droplet accumulation in liver, but the mechanism remains unknown. Here, we investigate the function of BPA in lipid metabolism and autophagy. BPA exposure increases lipid droplet and ROS accumulation which is accompanied by a defect in the fusion of the autophagosome to the lysosome. BPA exposure decreases the translocation of Stx17 to lysosome resulting in the autophagogome-lysosome fusion defect. There is no defect in the formation of the autophagosome indicated by increased LC3-II, p62 level, GFP/mRFP-LC3 ratios and decreased colocalization between LAMP2 with LC3. Mechanistically, BPA exposure reduces autophagy SNARE complex formation. Promoting autophagy by autophagy inducer (Torin2) partially reverses lipid droplet accumulation caused by BPA exposure. In summary, our results demonstrate BPA exposure inhibits autophagy resulting in decreased lipid droplet degradation and increased ROS levels. These results also provide a novel implication between autophagosome-lysosome fusion.

Loss of tau and Fyn reduces compensatory effects of MAP2 for tau and reveals a Fyn-independent effect of tau on calcium

Microtubule-associated protein tau associates with Src family tyrosine kinase Fyn and is tyrosine phosphorylated by Fyn. The presence of tyrosine phosphorylated tau in AD and the involvement of Fyn in AD has drawn attention to the tau-Fyn complex. In this study, a tau-Fyn double knockout (DKO) mouse was generated to investigate the role of the complex. DKO mice resembled Fyn KO in novel object recognition and contextual fear conditioning tasks and resembled tau KO mice in the pole test and protection from pentylenetetrazole-induced seizures. In glutamate-induced Ca2+ response, Fyn KO was decreased relative to WT and DKO had a greater reduction relative to Fyn KO, suggesting that tau may have a Fyn-independent role. Since tau KO resembled WT in its Ca2+ response, we investigated whether microtubule-associated protein 2 (MAP2) served to compensate for tau, since the MAP2 level was increased in tau KO but decreased in DKO mice. We found that like tau, MAP2 increased Fyn activity. Moreover, tau KO neurons had increased density of dendritic MAP2-Fyn complexes relative to WT neurons. Therefore, we hypothesize that in the tau KO, the absence of tau would be compensated by MAP2, especially in the dendrites, where tau-Fyn complexes are of critical importance. In the DKO, decreased levels of MAP2 made compensation more difficult, thus revealing the effect of tau in the Ca2+ response.

Impaired neurodevelopmental pathways in autism spectrum disorder: a review of signaling mechanisms and crosstalk

Background

The development of an autistic brain is a highly complex process as evident from the involvement of various genetic and non-genetic factors in the etiology of the autism spectrum disorder (ASD). Despite being a multifactorial neurodevelopmental disorder, autistic patients display a few key characteristics, such as the impaired social interactions and elevated repetitive behaviors, suggesting the perturbation of specific neuronal circuits resulted from abnormal signaling pathways during brain development in ASD. A comprehensive review for autistic signaling mechanisms and interactions may provide a better understanding of ASD etiology and treatment.

Main body

Recent studies on genetic models and ASD patients with several different mutated genes revealed the dysregulation of several key signaling pathways, such as WNT, BMP, SHH, and retinoic acid (RA) signaling. Although no direct evidence of dysfunctional FGF or TGF-β signaling in ASD has been reported so far, a few examples of indirect evidence can be found. This review article summarizes how various genetic and non-genetic factors which have been reported contributing to ASD interact with WNT, BMP/TGF-β, SHH, FGF, and RA signaling pathways. The autism-associated gene ubiquitin-protein ligase E3A (UBE3A) has been reported to influence WNT, BMP, and RA signaling pathways, suggesting crosstalk between various signaling pathways during autistic brain development. Finally, the article comments on what further studies could be performed to gain deeper insights into the understanding of perturbed signaling pathways in the etiology of ASD.

Conclusion

The understanding of mechanisms behind various signaling pathways in the etiology of ASD may help to facilitate the identification of potential therapeutic targets and design of new treatment methods.

Linking Cell Polarity to Cortical Development and Malformations

Cell polarity refers to the asymmetric distribution of signaling molecules, cellular organelles, and cytoskeleton in a cell. Neural progenitors and neurons are highly polarized cells in which the cell membrane and cytoplasmic components are compartmentalized into distinct functional domains in response to internal and external cues that coordinate polarity and behavior during development and disease. In neural progenitor cells, polarity has a prominent impact on cell shape and coordinate several processes such as adhesion, division, and fate determination. Polarity also accompanies a neuron from the beginning until the end of its life. It is essential for development and later functionality of neuronal circuitries. During development, polarity governs transitions between multipolar and bipolar during migration of postmitotic neurons, and directs the specification and directional growth of axons. Once reaching final positions in cortical layers, neurons form dendrites which become compartmentalized to ensure proper establishment of neuronal connections and signaling. Changes in neuronal polarity induce signaling cascades that regulate cytoskeletal changes, as well as mRNA, protein, and vesicle trafficking, required for synapses to form and function. Hence, defects in establishing and maintaining cell polarity are associated with several neural disorders such as microcephaly, lissencephaly, schizophrenia, autism, and epilepsy. In this review we summarize the role of polarity genes in cortical development and emphasize the relationship between polarity dysfunctions and cortical malformations.

Vangl2 interaction plays a role in the proteasomal degradation of Prickle2

The PET and LIM domain-containing protein, Prickle, plays a key role in planar cell polarity (PCP) in Drosophila. It has been reported that mutations in the PRICKLE2 gene, which encodes one of the human orthologues of Prickle, are associated with human diseases such as epilepsy and autism spectrum disorder. To develop preventive and therapeutic strategies for these intractable diseases, we studied the regulation of Prickle2 protein levels in transfected HEK293T cells. Prickle2 levels were negatively regulated by a physical interaction with another PCP protein, Van Gogh-like 2 (Vangl2). The Vangl2-mediated reduction in Prickle2 levels was, at least in part, relieved by proteasome inhibitors or by functional inhibition of the Cullin-1 E3 ubiquitin ligase. Furthermore, the expression of Vangl2 enhanced the polyubiquitination of Prickle2. This ubiquitination was partially blocked by co-expression of a ubiquitin mutant, which cannot be polymerised through their Lys48 residue to induce target proteins toward proteasomal degradation. Together, these results suggest that Prickle2 is polyubiquitinated by the Vangl2 interaction in a Cullin-1-dependent manner to limit its expression levels. This regulation may play a role in the local and temporal fine-tuning of Prickle protein levels during PCP signal-dependent cellular behaviours.

Prenatal diagnosis of a 3.2-Mb 2p16.1-p15 duplication associated with familial intellectual disability

OBJECTIVE

We present prenatal diagnosis of a 2p16.1-p15 duplication associated with familial intellectual disability, and we discuss the genotype-phenotype correlation.

CASE REPORT

A 22-year-old, primigravid woman underwent amniocentesis at 22 weeks of gestation because of a family history of intellectual disability. The woman and her two sisters had intellectual disability but no behavioral disorders. The intellectual disability was noted in at least one paternal aunt and six paternal cousins of the woman. Cytogenetic analysis revealed the karyotype of 46,XX in the fetus and the two women. Array comparative genomic hybridization (aCGH) analysis on the DNAs extracted from cultured amniocytes and the bloods of the woman and the her sister revealed a 3.244-Mb duplication of 2p16.1-p15 or arr 2p16.1p15 (58,288,588-61,532,538) × 3.0 [GRCh37 (hg19)] encompassing eight Online Mendelian Inheritance in Man (OMIM) genes of VRK2, FANCL, BCL11A, PAPOLG, REL, PUS10, PEX13 and USP34 in the fetus and the two women. Prenatal ultrasound findings were unremarkable. The woman elected to continue the pregnancy. A 3244-g female baby was delivered at term with neither craniofacial dysmorphism nor structural abnormalities.

CONCLUSION

aCGH is useful in prenatal diagnosis of inherited subtle chromosome imbalance in pregnancy with familial intellectual disability. Chromosome 2p16.1-p15 duplication can be associated with intellectual disability.

Activity-Dependent Neuroplasticity Induced by an Enriched Environment Reverses Cognitive Deficits in Scribble Deficient Mouse

Planar cell polarity (PCP) signaling is well known to play a critical role during prenatal brain development; whether it plays specific roles at postnatal stages remains rather unknown. Here, we investigated the role of a key PCP-associated gene scrib in CA1 hippocampal structure and function at postnatal stages. We found that Scrib is required for learning and memory consolidation in the Morris water maze as well as synaptic maturation and NMDAR-dependent bidirectional plasticity. Furthermore, we unveiled a direct molecular interaction between Scrib and PP1/PP2A phosphatases whose levels were decreased in postsynaptic density of conditional knock-out mice. Remarkably, exposure to enriched environment (EE) preserved memory formation in CaMK-Scrib-/- mice by recovering synaptic plasticity and maturation. Thus, Scrib is required for synaptic function involved in memory formation and EE has beneficiary therapeutic effects. Our results demonstrate a distinct new role for a PCP-associated protein, beyond embryonic development, in cognitive functions during adulthood.

The Wnt Signaling Pathway and Related Therapeutic Drugs in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a series of neurodevelopmental disorder with a large genetic component. However, the pathogenic genes and molecular mechanisms of ASD have not been clearly defined. Recent technological advancements, such as next-generation sequencing, have led to the identification of certain loci that is responsible for the pathophysiology of ASD. Three functional pathways, such as chromatin remodeling, Wnt signaling and mitochondrial dysfunction are potentially involved in ASD. In this review, we will focus on recent studies of the involvement of Wnt signaling pathway components in ASD pathophysiology and related drugs used in ASD treatment.

Hub connectivity, neuronal diversity, and gene expression in the Caenorhabditis elegans connectome

Studies of nervous system connectivity, in a wide variety of species and at different scales of resolution, have identified several highly conserved motifs of network organization. One such motif is a heterogeneous distribution of connectivity across neural elements, such that some elements act as highly connected and functionally important network hubs. These brain network hubs are also densely interconnected, forming a so-called rich club. Recent work in mouse has identified a distinctive transcriptional signature of neural hubs, characterized by tightly coupled expression of oxidative metabolism genes, with similar genes characterizing macroscale inter-modular hub regions of the human cortex. Here, we sought to determine whether hubs of the neuronal C. elegans connectome also show tightly coupled gene expression. Using open data on the chemical and electrical connectivity of 279 C. elegans neurons, and binary gene expression data for each neuron across 948 genes, we computed a correlated gene expression score for each pair of neurons, providing a measure of their gene expression similarity. We demonstrate that connections between hub neurons are the most similar in their gene expression while connections between nonhubs are the least similar. Genes with the greatest contribution to this effect are involved in glutamatergic and cholinergic signaling, and other communication processes. We further show that coupled expression between hub neurons cannot be explained by their neuronal subtype (i.e., sensory, motor, or interneuron), separation distance, chemically secreted neurotransmitter, birth time, pairwise lineage distance, or their topological module affiliation. Instead, this coupling is intrinsically linked to the identity of most hubs as command interneurons, a specific class of interneurons that regulates locomotion. Our results suggest that neural hubs may possess a distinctive transcriptional signature, preserved across scales and species, that is related to the involvement of hubs in regulating the higher-order behaviors of a given organism.

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.

Molecular genetics and targeted therapy of WNT-related human diseases (Review)

Canonical WNT signaling through Frizzled and LRP5/6 receptors is transduced to the WNT/β-catenin and WNT/stabilization of proteins (STOP) signaling cascades to regulate cell fate and proliferation, whereas non-canonical WNT signaling through Frizzled or ROR receptors is transduced to the WNT/planar cell polarity (PCP), WNT/G protein-coupled receptor (GPCR) and WNT/receptor tyrosine kinase (RTK) signaling cascades to regulate cytoskeletal dynamics and directional cell movement. WNT/β-catenin signaling cascade crosstalks with RTK/SRK and GPCR-cAMP-PKA signaling cascades to regulate β-catenin phosphorylation and β-catenin-dependent transcription. Germline mutations in WNT signaling molecules cause hereditary colorectal cancer, bone diseases, exudative vitreoretinopathy, intellectual disability syndrome and PCP-related diseases. APC or CTNNB1 mutations in colorectal, endometrial and prostate cancers activate the WNT/β-catenin signaling cascade. RNF43, ZNRF3, RSPO2 or RSPO3 alterations in breast, colorectal, gastric, pancreatic and other cancers activate the WNT/β-catenin, WNT/STOP and other WNT signaling cascades. ROR1 upregulation in B-cell leukemia and solid tumors and ROR2 upregulation in melanoma induce invasion, metastasis and therapeutic resistance through Rho-ROCK, Rac-JNK, PI3K-AKT and YAP signaling activation. WNT signaling in cancer, stromal and immune cells dynamically orchestrate immune evasion and antitumor immunity in a cell context-dependent manner. Porcupine (PORCN), RSPO3, WNT2B, FZD5, FZD10, ROR1, tankyrase and β-catenin are targets of anti-WNT signaling therapy, and ETC-159, LGK974, OMP-18R5 (vantictumab), OMP-54F28 (ipafricept), OMP-131R10 (rosmantuzumab), PRI-724 and UC-961 (cirmtuzumab) are in clinical trials for cancer patients. Different classes of anti-WNT signaling therapeutics are necessary for the treatment of APC/CTNNB1-, RNF43/ZNRF3/RSPO2/RSPO3- and ROR1-types of human cancers. By contrast, Dickkopf-related protein 1 (DKK1), SOST and glycogen synthase kinase 3β (GSK3β) are targets of pro-WNT signaling therapy, and anti-DKK1 (BHQ880 and DKN-01) and anti-SOST (blosozumab, BPS804 and romosozumab) monoclonal antibodies are being tested in clinical trials for cancer patients and osteoporotic post-menopausal women. WNT-targeting therapeutics have also been applied as reagents for in vitro stem-cell processing in the field of regenerative medicine.

Targeted sequencing and functional analysis reveal brain-size-related genes and their networks in autism spectrum disorders

Autism spectrum disorder (ASD) represents a set of complex neurodevelopmental disorders with large degrees of heritability and heterogeneity. We sequenced 136 microcephaly or macrocephaly (Mic-Mac)-related genes and 158 possible ASD-risk genes in 536 Chinese ASD probands and detected 22 damaging de novo mutations (DNMs) in 20 genes, including CHD8 and SCN2A, with recurrent events. Nine of the 20 genes were previously reported to harbor DNMs in ASD patients from other populations, while 11 of them were first identified in present study. We combined genetic variations of the 294 sequenced genes from publicly available whole-exome or whole-genome sequencing studies (4167 probands plus 1786 controls) with our Chinese population (536 cases plus 1457 controls) to optimize the power of candidate-gene prioritization. As a result, we prioritized 67 ASD-candidate genes that exhibited significantly higher probabilities of haploinsufficiency and genic intolerance, and significantly interacted and co-expressed with each another, as well as other known ASD-risk genes. Probands with DNMs or rare inherited mutations in the 67 candidate genes exhibited significantly lower intelligence quotients, supporting their strong functional impact. In addition, we prioritized 39 ASD-related Mic-Mac-risk genes, and showed their interaction and co-expression in a functional network that converged on chromatin remodeling, synapse transmission and cell cycle progression. Genes within the three functional subnetworks exhibited distinct and recognizable spatiotemporal-expression patterns in human brains and laminar-expression profiles in the developing neocortex, highlighting their important roles in brain development. Our results indicate some of Mic-Mac-risk genes are involved in ASD.

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.

Evidence for opposing roles of Celsr3 and Vangl2 in glutamatergic synapse formation

The signaling mechanisms that choreograph the assembly of the highly asymmetric pre- and postsynaptic structures are still poorly defined. Using synaptosome fractionation, immunostaining, and coimmunoprecipitation, we found that Celsr3 and Vangl2, core components of the planar cell polarity (PCP) pathway, are localized at developing glutamatergic synapses and interact with key synaptic proteins. Pyramidal neurons from the hippocampus of Celsr3 knockout mice exhibit loss of ∼50% of glutamatergic synapses, but not inhibitory synapses, in culture. Wnts are known regulators of synapse formation, and our data reveal that Wnt5a inhibits glutamatergic synapses formed via Celsr3. To avoid affecting earlier developmental processes, such as axon guidance, we conditionally knocked out Celsr3 in the hippocampus 1 week after birth. The CA1 neurons that lost Celsr3 also showed a loss of ∼50% of glutamatergic synapses in vivo without affecting the inhibitory synapses assessed by miniature excitatory postsynaptic current (mEPSC) and electron microscopy. These animals displayed deficits in hippocampus-dependent behaviors in adulthood, including spatial learning and memory and fear conditioning. In contrast to Celsr3 conditional knockouts, we found that the conditional knockout of Vangl2 in the hippocampus 1 week after birth led to a large increase in synaptic density, as evaluated by mEPSC frequency and spine density. PCP signaling is mediated by multiple core components with antagonizing functions. Our results document the opposing roles of Celsr3 and Vangl2 in glutamatergic synapse formation.

Neurodevelopmental Perspectives on Wnt Signaling in Psychiatry

Mounting evidence indicates that Wnt signaling is relevant to pathophysiology of diverse mental illnesses including schizophrenia, bipolar disorder, and autism spectrum disorder. In the 35 years since Wnt ligands were first described, animal studies have richly explored how downstream Wnt signaling pathways affect an array of neurodevelopmental processes and how their disruption can lead to both neurological and behavioral phenotypes. Recently, human induced pluripotent stem cell (hiPSC) models have begun to contribute to this literature while pushing it in increasingly translational directions. Simultaneously, large-scale human genomic studies are providing evidence that sequence variation in Wnt signal pathway genes contributes to pathogenesis in several psychiatric disorders. This article reviews neurodevelopmental and postneurodevelopmental functions of Wnt signaling, highlighting mechanisms, whereby its disruption might contribute to psychiatric illness, and then reviews the most reliable recent genetic evidence supporting that mutations in Wnt pathway genes contribute to psychiatric illness. We are proponents of the notion that studies in animal and hiPSC models informed by the human genetic data combined with the deep knowledge base and tool kits generated over the last several decades of basic neurodevelopmental research will yield near-term tangible advances in neuropsychiatry.

Wnt signaling networks in autism spectrum disorder and intellectual disability

Background

Genetic factors play a major role in the risk for neurodevelopmental disorders such as autism spectrum disorders (ASDs) and intellectual disability (ID). The underlying genetic factors have become better understood in recent years due to advancements in next generation sequencing. These studies have uncovered a vast number of genes that are impacted by different types of mutations (e.g., de novo, missense, truncation, copy number variations).

Abstract

Given the large volume of genetic data, analyzing each gene on its own is not a feasible approach and will take years to complete, let alone attempt to use the information to develop novel therapeutics. To make sense of independent genomic data, one approach is to determine whether multiple risk genes function in common signaling pathways that identify signaling “hubs” where risk genes converge. This approach has led to multiple pathways being implicated, such as synaptic signaling, chromatin remodeling, alternative splicing, and protein translation, among many others. In this review, we analyze recent and historical evidence indicating that multiple risk genes, including genes denoted as high-confidence and likely causal, are part of the Wingless (Wnt signaling) pathway. In the brain, Wnt signaling is an evolutionarily conserved pathway that plays an instrumental role in developing neural circuits and adult brain function.

Conclusions

We will also review evidence that pharmacological therapies and genetic mouse models further identify abnormal Wnt signaling, particularly at the synapse, as being disrupted in ASDs and contributing to disease pathology.