Confirmation study of PTEN mutations among individuals with autism or developmental delays/mental retardation and macrocephaly

Developmental trajectory and sex differences in auditory processing in a PTEN-deletion model of autism spectrum disorders

Autism Spectrum Disorders (ASD) encompass a wide array of debilitating symptoms, including severe sensory deficits and abnormal language development. Sensory deficits early in development may lead to broader symptomatology in adolescents and adults. The mechanistic links between ASD risk genes, sensory processing and language impairment are unclear. There is also a sex bias in ASD diagnosis and symptomatology. The current study aims to identify the developmental trajectory and genotype- and sex-dependent differences in auditory sensitivity and temporal processing in a Pten-deletion (phosphatase and tensin homolog missing on chromosome 10) mouse model of ASD. Auditory temporal processing is crucial for speech recognition and language development and deficits will cause language impairments. However, very little is known about the development of temporal processing in ASD animal models, and if there are sex differences. To address this major gap, we recorded epidural electroencephalography (EEG) signals from the frontal (FC) and auditory (AC) cortex in developing and adult Nse-cre PTEN mice, in which Pten is deleted in specific cortical layers (layers III-V) (PTEN conditional knock-out (cKO). We quantified resting EEG spectral power distribution, auditory event related potentials (ERP) and temporal processing from awake and freely moving male and female mice. Temporal processing is measured using a gap-in-noise-ASSR (auditory steady state response) stimulus paradigm. The experimental manipulation of gap duration and modulation depth allows us to measure cortical entrainment to rapid gaps in sounds. Temporal processing was quantified using inter-trial phase clustering (ITPC) values that account for phase consistency across trials. The results show genotype differences in resting power distribution in PTEN cKO mice throughout development. Male and female cKO mice have significantly increased beta power but decreased high frequency oscillations in the AC and FC. Both male and female PTEN cKO mice show diminished ITPC in their gap-ASSR responses in the AC and FC compared to control mice. Overall, deficits become more prominent in adult (p60) mice, with cKO mice having significantly increased sound evoked power and decreased ITPC compared to controls. While both male and female cKO mice demonstrated severe temporal processing deficits across development, female cKO mice showed increased hypersensitivity compared to males, reflected as increased N1 and P2 amplitudes. These data identify a number of novel sensory processing deficits in a PTEN-ASD mouse model that are present from an early age. Abnormal temporal processing and hypersensitive responses may contribute to abnormal development of language function in ASD.

Behavioural, developmental and psychological characteristics in children with germline PTEN mutations: a carer report study

BACKGROUND

PTEN is primarily known as a tumour suppressor gene. However, research describes higher rates of difficulties including intellectual disability and difficulties relating to autism spectrum conditions (ASCs) in people with germline PTEN mutations. Other psychological characteristics/experiences are less often reported and are explored in this study.

METHODS

The parents of 20 children with PTEN mutations completed an online survey exploring adaptive behaviour, ASC-associated behaviours, anxiety, mood, hypermobility, behaviours that challenge, sensory experiences, quality of life and parental wellbeing. Published normative data and data from groups of individuals with other genetic neurodevelopmental conditions were used to contextualise findings.

RESULTS

Overall levels of adaptive behaviour were below the 'typical' range, and no marked relative differences were noted between domains. Higher levels of ASC-related difficulties, including sensory experiences, were found in comparison with 'typically developing' children, with a possible peak in restrictive/repetitive behaviour; ASC and sensory processing atypicality also strongly correlated with reported joint hypermobility. A relative preservation of social motivation was noted. Anxiety levels were found to be elevated overall (and to relate to sensory processing and joint hypermobility), with the exception of social anxiety, which was comparable with normative data. Self-injurious behaviour was common.

CONCLUSIONS

Results suggest a wide range of possible difficulties in children with PTEN mutations, including elevated anxiety. Despite elevated ASC phenomenology, social motivation may remain relatively strong. Firm conclusions are restricted by a small sample size and potential recruitment bias, and future research is required to further explore the relationships between such characteristics.

Germline PTEN genotype-dependent phenotypic divergence during the early neural developmental process of forebrain organoids

PTEN germline mutations account for ~0.2-1% of all autism spectrum disorder (ASD) cases, as well as ~17% of ASD patients with macrocephaly, making it one of the top ASD-associated risk genes. Individuals with germline PTEN mutations receive the molecular diagnosis of PTEN Hamartoma Tumor Syndrome (PHTS), an inherited cancer predisposition syndrome, about 20-23% of whom are diagnosed with ASD. We generated forebrain organoid cultures from gene-edited isogenic human induced pluripotent stem cells (hiPSCs) harboring a PTENG132D (ASD) or PTENM134R (cancer) mutant allele to model how these mutations interrupt neurodevelopmental processes. Here, we show that the PTENG132D allele disrupts early neuroectoderm formation during the first several days of organoid generation, and results in deficient electrophysiology. While organoids generated from PTENM134R hiPSCs remained morphologically similar to wild-type organoids during this early stage in development, we observed disrupted neuronal differentiation, radial glia positioning, and cortical layering in both PTEN-mutant organoids at the later stage of 72+ days of development. Perifosine, an AKT inhibitor, reduced over-activated AKT and partially corrected the abnormalities in cellular organization observed in PTENG132D organoids. Single cell RNAseq analyses on early-stage organoids revealed that genes related to neural cell fate were decreased in PTENG132D mutant organoids, and AKT inhibition was capable of upregulating gene signatures related to neuronal cell fate and CNS maturation pathways. These findings demonstrate that different PTEN missense mutations can have a profound impact on neurodevelopment at diverse stages which in turn may predispose PHTS individuals to ASD. Further study will shed light on ways to mitigate pathological impact of PTEN mutants on neurodevelopment by stage-specific manipulation of downstream PTEN signaling components.

Female-specific dysfunction of sensory neocortical circuits in a mouse model of autism mediated by mGluR5 and estrogen receptor α

Little is known of the brain mechanisms that mediate sex-specific autism symptoms. Here, we demonstrate that deletion of the autism spectrum disorder (ASD)-risk gene, Pten, in neocortical pyramidal neurons (NSEPten knockout [KO]) results in robust cortical circuit hyperexcitability selectively in female mice observed as prolonged spontaneous persistent activity states. Circuit hyperexcitability in females is mediated by metabotropic glutamate receptor 5 (mGluR5) and estrogen receptor α (ERα) signaling to mitogen-activated protein kinases (Erk1/2) and de novo protein synthesis. Pten KO layer 5 neurons have a female-specific increase in mGluR5 and mGluR5-dependent protein synthesis. Furthermore, mGluR5-ERα complexes are generally elevated in female cortices, and genetic reduction of ERα rescues enhanced circuit excitability, protein synthesis, and neuron size selectively in NSEPten KO females. Female NSEPten KO mice display deficits in sensory processing and social behaviors as well as mGluR5-dependent seizures. These results reveal mechanisms by which sex and a high-confidence ASD-risk gene interact to affect brain function and behavior.

Female specific dysfunction of sensory neocortical circuits in a mouse model of autism mediated by mGluR5 and Estrogen Receptor α

Autism manifests differently in males and females and the brain mechanisms that mediate these sex-dependent differences are unknown. Here, we demonstrate that deletion of the ASD-risk gene, Pten, in neocortical pyramidal neurons (NSE Pten KO) results in robust hyperexcitability of local neocortical circuits in female, but not male, mice, observed as prolonged, spontaneous persistent activity states (UP states). Circuit hyperexcitability in NSE Pten KO mice is mediated by enhanced and/or altered signaling of metabotropic glutamate receptor 5 (mGluR5) and estrogen receptor α (ERα) to ERK and protein synthesis selectively in Pten deleted female neurons. In support of this idea, Pten deleted Layer 5 cortical neurons have female-specific increases in mGluR5 and mGluR5-driven protein synthesis. In addition, mGluR5-ERα complexes are elevated in female cortex and genetic reduction of ERα in Pten KO cortical neurons rescues circuit excitability, protein synthesis and enlarged neurons selectively in females. Abnormal timing and hyperexcitability of neocortical circuits in female NSE Pten KO mice are associated with deficits in temporal processing of sensory stimuli and social behaviors as well as mGluR5-dependent seizures. Female-specific cortical hyperexcitability and mGluR5-dependent seizures are also observed in a human disease relevant mouse model, germline Pten +/- mice. Our results reveal molecular mechanisms by which sex and a high impact ASD-risk gene interact to affect brain function and behavior.

Three Decades of Valproate: A Current Model for Studying Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder with increased prevalence and incidence in recent decades. Its etiology remains largely unclear, but it seems to involve a strong genetic component and environmental factors that, in turn, induce epigenetic changes during embryonic and postnatal brain development. In recent decades, clinical studies have shown that inutero exposure to valproic acid (VPA), a commonly prescribed antiepileptic drug, is an environmental factor associated with an increased risk of ASD. Subsequently, prenatal VPA exposure in rodents has been established as a reliable translational model to study the pathophysiology of ASD, which has helped demonstrate neurobiological changes in rodents, non-human primates, and brain organoids from human pluripotent stem cells. This evidence supports the notion that prenatal VPA exposure is a valid and current model to replicate an idiopathic ASD-like disorder in experimental animals. This review summarizes and describes the current features reported with this animal model of autism and the main neurobiological findings and correlates that help elucidate the pathophysiology of ASD. Finally, we discuss the general framework of the VPA model in comparison to other environmental and genetic ASD models.

Genomic diversity in functionally relevant genes modifies neurodevelopmental versus neoplastic risks in individuals with germline PTEN variants

Individuals with germline PTEN variants (PHTS) have increased risks of the seemingly disparate phenotypes of cancer and neurodevelopmental disorders (NDD), including autism spectrum disorder (ASD). Etiology of the phenotypic variability remains elusive. Here, we hypothesized that decreased genomic diversity, manifested by increased homozygosity, may be one etiology. Comprehensive analyses of 376 PHTS patients of European ancestry revealed significant enrichment of homozygous common variants in genes involved in inflammatory processes in the PHTS-NDD group and in genes involved in differentiation and chromatin structure regulation in the PHTS-ASD group. Pathway analysis revealed pathways germane to NDD/ASD, including neuroinflammation and synaptogenesis. Collapsing analysis of the homozygous variants identified suggestive modifier NDD/ASD genes. In contrast, we found enrichment of homozygous ultra-rare variants in genes modulating cell death in the PHTS-cancer group. Finally, homozygosity burden as a predictor of ASD versus cancer outcomes in our validated prediction model for NDD/ASD performed favorably.

Endophenotype trait domains for advancing gene discovery in autism spectrum disorder

Autism spectrum disorder (ASD) is associated with a diverse range of etiological processes, including both genetic and non-genetic causes. For a plurality of individuals with ASD, it is likely that the primary causes involve multiple common inherited variants that individually account for only small levels of variation in phenotypic outcomes. This genetic landscape creates a major challenge for detecting small but important pathogenic effects associated with ASD. To address similar challenges, separate fields of medicine have identified endophenotypes, or discrete, quantitative traits that reflect genetic likelihood for a particular clinical condition and leveraged the study of these traits to map polygenic mechanisms and advance more personalized therapeutic strategies for complex diseases. Endophenotypes represent a distinct class of biomarkers useful for understanding genetic contributions to psychiatric and developmental disorders because they are embedded within the causal chain between genotype and clinical phenotype, and they are more proximal to the action of the gene(s) than behavioral traits. Despite their demonstrated power for guiding new understanding of complex genetic structures of clinical conditions, few endophenotypes associated with ASD have been identified and integrated into family genetic studies. In this review, we argue that advancing knowledge of the complex pathogenic processes that contribute to ASD can be accelerated by refocusing attention toward identifying endophenotypic traits reflective of inherited mechanisms. This pivot requires renewed emphasis on study designs with measurement of familial co-variation including infant sibling studies, family trio and quad designs, and analysis of monozygotic and dizygotic twin concordance for select trait dimensions. We also emphasize that clarification of endophenotypic traits necessarily will involve integration of transdiagnostic approaches as candidate traits likely reflect liability for multiple clinical conditions and often are agnostic to diagnostic boundaries. Multiple candidate endophenotypes associated with ASD likelihood are described, and we propose a new focus on the analysis of "endophenotype trait domains" (ETDs), or traits measured across multiple levels (e.g., molecular, cellular, neural system, neuropsychological) along the causal pathway from genes to behavior. To inform our central argument for research efforts toward ETD discovery, we first provide a brief review of the concept of endophenotypes and their application to psychiatry. Next, we highlight key criteria for determining the value of candidate endophenotypes, including unique considerations for the study of ASD. Descriptions of different study designs for assessing endophenotypes in ASD research then are offered, including analysis of how select patterns of results may help prioritize candidate traits in future research. We also present multiple candidate ETDs that collectively cover a breadth of clinical phenomena associated with ASD, including social, language/communication, cognitive control, and sensorimotor processes. These ETDs are described because they represent promising targets for gene discovery related to clinical autistic traits, and they serve as models for analysis of separate candidate domains that may inform understanding of inherited etiological processes associated with ASD as well as overlapping neurodevelopmental disorders.

The physical and psychiatric health conditions related to autism genetic scores, across genetic ancestries, sexes and age-groups in electronic health records

BACKGROUND

Although polygenic scores (PGS) for autism have been related to various psychiatric and medical conditions, most studies to date have been conducted in research ascertained populations. We aimed to identify the psychiatric and physical conditions associated with autism PGS in a health care setting.

METHODS

We computed PGS for 12,383 unrelated participants of African genetic ancestry (AF) and 65,363 unrelated participants of European genetic ancestry (EU) from Vanderbilt's de-identified biobank. Next, we performed phenome wide association studies of the autism PGS within these two genetic ancestries.

RESULTS

Seven associations surpassed the Bonferroni adjusted threshold for statistical significance (p = 0.05/1374 = 3.6 × 10-5) in the EU participants, including mood disorders (OR (95%CI) = 1.08(1.05 to 1.10), p = 1.0 × 10-10), autism (OR (95%CI) = 1.34(1.24 to 1.43), p = 1.2 × 10-9), and breast cancer (OR (95%CI) = 1.09(1.05 to 1.14), 2.6 × 10-5). There was no statistical evidence for PGS-phenotype associations in the AF participants. Conditioning on the diagnosis of autism or on median body mass index (BMI) did not impact the strength of the reported associations. Although we observed some sex differences in the pattern of associations, there was no significant interaction between sex and autism PGS. Finally, the associations between autism PGS and autism diagnosis were stronger in childhood and adolescence, while the associations with mood disorders and breast cancer were stronger in adulthood.

DISCUSSION

Our findings indicate that autism PGS is not only related to autism diagnosis but may also be related to adult-onset conditions, including mood disorders and some cancers.

CONCLUSIONS

Our study raises the hypothesis that genes associated with autism may also increase the risk for cancers later in life. Future studies are necessary to replicate and extend our findings.

Novel dermatological and skeletal features associated with PTEN variant in PTEN hamartoma tumor syndrome

PTEN hamartoma tumor syndromes (PHTS) comprise hamartomatous overgrowth syndromes associated with PTEN germline mutations. In this case report, we describe a variant identified by next generation sequencing causing peculiar dermatological and skeletal features not yet described in the literature. Being cognizant of such unique disease presentations in PHTS, that manifest at a very young age, could help facilitate a timely diagnosis by clinicians and thus the early education of families on active cancer surveillance. This specific case also strengthens the concept of variable presentation of PHTS and the need for genetic testing early on, even if not all criteria for PHTS are met for a formal clinical diagnosis.

Nuclear PTEN's Functions in Suppressing Tumorigenesis: Implications for Rare Cancers

Phosphatase and tensin homolog (PTEN) encodes a tumor-suppressive phosphatase with both lipid and protein phosphatase activity. The tumor-suppressive functions of PTEN are lost through a variety of mechanisms across a wide spectrum of human malignancies, including several rare cancers that affect pediatric and adult populations. Originally discovered and characterized as a negative regulator of the cytoplasmic, pro-oncogenic phosphoinositide-3-kinase (PI3K) pathway, PTEN is also localized to the nucleus where it can exert tumor-suppressive functions in a PI3K pathway-independent manner. Cancers can usurp the tumor-suppressive functions of PTEN to promote oncogenesis by disrupting homeostatic subcellular PTEN localization. The objective of this review is to describe the changes seen in PTEN subcellular localization during tumorigenesis, how PTEN enters the nucleus, and the spectrum of impacts and consequences arising from disrupted PTEN nuclear localization on tumor promotion. This review will highlight the immediate need in understanding not only the cytoplasmic but also the nuclear functions of PTEN to gain more complete insights into how important PTEN is in preventing human cancers.

Microglial Pten safeguards postnatal integrity of the cortex and sociability

Microglial abnormalities may contribute to neurodevelopmental disorders. PTEN is implicated as a susceptibility gene for autism spectrum disorders and its germline ablation in mice causes behavioral abnormalities. Here we find postnatal PTEN deletion in microglia causes deficits in sociability and novel object recognition test. Mutant mice harbor markedly more activated microglia that manifest enhanced phagocytosis. Interestingly, two-week postponement of microglia PTEN ablation leads to no social interaction defects, even though mutant microglia remain abnormal in adult animals. Disturbed neurodevelopment caused by early PTEN deletion in microglia is characterized by insufficient VGLUT1 protein in synaptosomes, likely a consequence of enhanced removal by microglia. In correlation, in vitro acute slice recordings demonstrate weakened synaptic inputs to layer 5 pyramidal neurons in the developing cortex. Therefore, microglial PTEN safeguards integrity of neural substrates underlying sociability in a developmentally determined manner.

Pten haploinsufficiency causes desynchronized growth of brain areas involved in sensory processing

How changes in brain scaling relate to altered behavior is an important question in neurodevelopmental disorder research. Mice with germline Pten haploinsufficiency (Pten ^+/-) closely mirror the abnormal brain scaling and behavioral deficits seen in humans with macrocephaly/autism syndrome, which is caused by PTEN mutations. We explored whether deviation from normal patterns of growth can predict behavioral abnormalities. Brain regions associated with sensory processing (e.g., pons and inferior colliculus) had the biggest deviations from expected volume. While Pten ^+/- mice showed little or no abnormal behavior on most assays, both sexes showed sensory deficits, including impaired sensorimotor gating and hyporeactivity to high-intensity stimuli. Developmental analysis of this phenotype showed sexual dimorphism for hyporeactivity. Mapping behavioral phenotypes of Pten ^+/- mice onto relevant brain regions suggested abnormal behavior is likely when associated with relatively enlarged brain regions, while unchanged or relatively decreased brain regions have little predictive value.

Behavioural and psychological features of PTEN mutations: a systematic review of the literature and meta-analysis of the prevalence of autism spectrum disorder characteristics

BACKGROUND

Phosphatase and tensin homologue (PTEN) is a cancer suppressor gene. Constitutional mutations affecting this gene are associated with several conditions, collectively termed PTEN hamartoma tumour syndromes (PHTS). In addition to hamartomas, PTEN aberrations have been associated with a range of non-tumoural phenotypes such as macrocephaly, and research indicates possibly increased rates of developmental delay and autism spectrum disorder (ASD) for people with germline mutations affecting PTEN.

METHOD

A systematic review of literature reporting behavioural and psychological variables for people with constitutional PTEN mutations/PHTS was conducted using four databases. Following in-depth screening, 25 articles met the inclusion criteria and were used in the review. Fourteen papers reported the proportion of people with PTEN mutations/PTHS meeting criteria for or having characteristics of ASD and were thus used in a pooled prevalence meta-analysis.

RESULTS

Meta-analysis using a random effects model estimated pooled prevalence of ASD characteristics at 25% (95% CI 16-33%), although this should be interpreted cautiously due to possible biases in existing literature. Intellectual disability and developmental delay (global, motor and speech and language) were also reported frequently. Emotional difficulties and impaired cognitive functioning in specific domains were noted but assessed/reported less frequently. Methods of assessment of psychological/behavioural factors varied widely (with retrospective examination of medical records common).

CONCLUSIONS

Existing research suggests approximately 25% of people with constitutional PTEN mutations may meet criteria for or have characteristics of ASD. Studies have also begun to establish a range of possible cognitive impairments in affected individuals, especially when ASD is also reported. However, further large-scale studies are needed to elucidate psychological/behavioural corollaries of this mutation, and how they may relate to physiological/physical characteristics.

A systematic review of brain MRI findings in monogenic disorders strongly associated with autism spectrum disorder

BACKGROUND

Research on monogenic forms of autism spectrum disorder (autism) can inform our understanding of genetic contributions to the autism phenotype; yet, there is much to be learned about the pathways from gene to brain structure to behavior. This systematic review summarizes and evaluates research on brain magnetic resonance imaging (MRI) findings in monogenic conditions that have strong association with autism. This will improve understanding of the impact of genetic variability on brain structure and related behavioral traits in autism.

METHODS

The search strategy for this systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Risk of bias (ROB) assessment was completed on included studies using the Newcastle-Ottawa Scales.

RESULTS

Of 4,287 studies screened, 69 were included pertaining to 13 of the top 20 genes with the strongest association with autism. The greatest number of studies related to individuals with PTEN variants and autism. Brain MRI abnormalities were reported for 12 of the 13 genes studied, and in 51.7% of participants across all 13 genes, including 100% of participants with ARID1B variants. Specific MRI findings were highly variable, with no clear patterns emerging within or between the 13 genes, although white matter abnormalities were the most common. Few studies reported specific details about methods for acquisition and processing of brain MRI, and descriptors for brain abnormalities were variable. ROB assessment indicated high ROB for all studies, largely due to small sample sizes and lack of comparison groups.

CONCLUSIONS

Brain abnormalities are common in this population of individuals, in particular, children; however, a range of different brain abnormalities were reported within and between genes. Directions for future neuroimaging research in monogenic autism are suggested.

PTEN mutations in autism spectrum disorder and congenital hydrocephalus: developmental pleiotropy and therapeutic targets

The lack of effective treatments for autism spectrum disorder (ASD) and congenital hydrocephalus (CH) reflects the limited understanding of the biology underlying these common neurodevelopmental disorders. Although ASD and CH have been extensively studied as independent entities, recent human genomic and preclinical animal studies have uncovered shared molecular pathophysiology. Here, we review and discuss phenotypic, genomic, and molecular similarities between ASD and CH, and identify the PTEN-PI3K-mTOR (phosphatase and tensin homolog-phosphoinositide 3-kinase-mammalian target of rapamycin) pathway as a common underlying mechanism that holds diagnostic, prognostic, and therapeutic promise for individuals with ASD and CH.

Genetic and Environmental Contributions to Autism Spectrum Disorder Through Mechanistic Target of Rapamycin

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that affects an individual’s reciprocal social interaction and communication ability. Numerous genetic and environmental conditions are associated with ASD, including tuberous sclerosis complex, phosphatase and tensin homolog hamartoma tumor syndrome, fragile X syndrome, and neurofibromatosis 1. The pathogenic molecular mechanisms of these diseases are integrated into the hyperactivation of mTORC1 (mechanistic target of rapamycin complex 1). Rodent models of these diseases have shown high mTORC1 activity in the brain and ASD-related behavioral deficits, which were reversed by the mTORC1 inhibitor rapamycin. Environmental stress can also affect this signaling pathway. In utero exposure to valproate caused ASD in offspring and enhanced mTORC1 activity in the brain, which was sensitive to mTORC1 inhibition. mTORC1 is a signaling hub for diverse cellular functions, including protein synthesis, through the phosphorylation of its targets, such as ribosomal protein S6 kinases. Metabotropic glutamate receptor 5–mediated synaptic function is also affected by the dysregulation of mTORC1 activity, such as in fragile X syndrome and tuberous sclerosis complex. Reversing these downstream changes that are associated with mTORC1 activation normalizes behavioral defects in rodents. Despite abundant preclinical evidence, few clinical studies have investigated the treatment of ASD and cognitive deficits. Therapeutics other than mTORC1 inhibitors failed to show efficacy in fragile X syndrome and neurofibromatosis 1. mTORC1 inhibitors have been tested mainly in tuberous sclerosis complex, and their effects on ASD and neuropsychological deficits are promising. mTORC1 is a promising target for the pharmacological treatment of ASD associated with mTORC1 activation.

PTEN hamartoma tumour syndrome: what happens when there is no PTEN germline mutation?

Hereditary cancer syndromes represent ~10% of all incident cancers. It is important to identify individuals having these disorders because, unlike patients with sporadic cancer, these patients require specialised life-long care, with implications for their families. Importantly, the identification of alterations in cancer-predisposing genes facilitates gene-informed molecular diagnosis, cancer risk assessment and gene-specific clinical management. Moreover, knowledge about gene function in the inherited cancers offers insights towards biological processes pertinent to the more common sporadic cancers. Conversely, without a known gene, clinical management is less precise, and it is impossible to offer predictive testing of family members. PTEN hamartoma tumour syndrome (PHTS) is an umbrella term encompassing four overgrowth and cancer predisposition disorders associated with germline PTEN mutations. With time, it became evident that only a finite subset of individuals with PHTS-associated phenotypes harbour germline PTEN mutations. Therefore, non-PTEN aetiologies exist in PTEN wildtype patients. Indeed, gene discovery efforts over the last decade elucidated multiple candidate cancer predisposition genes. While a subset of genes (e.g. AKT1, PIK3CA) are biologically plausible as being key effectors within the PTEN signalling cascade, other genes required meticulous functional interrogation to explain their contribution to PHTS-related phenotypes. Collectively, the extensive phenotypic heterogeneity of the clinical syndromes typically united by PTEN is reflected by the genetic heterogeneity revealed through gene discovery. Validating these gene discoveries is critical because, while PTEN wildtype patients can be diagnosed clinically, they do not have the benefit of specific gene-informed risk assessment and subsequent management.

Environmental Enrichment Rescues Social Behavioral Deficits and Synaptic Abnormalities in Pten Haploinsufficient Mice

Pten germline haploinsufficient (Pten+/-) mice, which model macrocephaly/autism syndrome, show social and repetitive behavior deficits, early brain overgrowth, and cortical-subcortical hyperconnectivity. Previous work indicated that altered neuronal connectivity may be a substrate for behavioral deficits. We hypothesized that exposing Pten+/- mice to environmental enrichment after brain overgrowth has occurred may facilitate adaptation to abnormal "hard-wired" connectivity through enhancing synaptic plasticity. Thus, we reared Pten+/- mice and their wild-type littermates from weaning under either standard (4-5 mice per standard-sized cage, containing only bedding and nestlet) or enriched (9-10 mice per large-sized cage, containing objects for exploration and a running wheel, plus bedding and nestlet) conditions. Adult mice were tested on social and non-social assays in which Pten+/- mice display deficits. Environmental enrichment rescued sex-specific deficits in social behavior in Pten+/- mice and partially rescued increased repetitive behavior in Pten+/- males. We found that Pten+/- mice show increased excitatory and decreased inhibitory pre-synaptic proteins; this phenotype was also rescued by environmental enrichment. Together, our results indicate that environmental enrichment can rescue social behavioral deficits in Pten+/- mice, possibly through normalizing the excitatory synaptic protein abundance.

Dopaminergic Dysregulation in Syndromic Autism Spectrum Disorders: Insights From Genetic Mouse Models

Autism spectrum disorder (ASD) is a neurodevelopmental disorder defined by altered social interaction and communication, and repetitive, restricted, inflexible behaviors. Approximately 1.5-2% of the general population meet the diagnostic criteria for ASD and several brain regions including the cortex, amygdala, cerebellum and basal ganglia have been implicated in ASD pathophysiology. The midbrain dopamine system is an important modulator of cellular and synaptic function in multiple ASD-implicated brain regions via anatomically and functionally distinct dopaminergic projections. The dopamine hypothesis of ASD postulates that dysregulation of dopaminergic projection pathways could contribute to the behavioral manifestations of ASD, including altered reward value of social stimuli, changes in sensorimotor processing, and motor stereotypies. In this review, we examine the support for the idea that cell-autonomous changes in dopaminergic function are a core component of ASD pathophysiology. We discuss the human literature supporting the involvement of altered dopamine signaling in ASD including genetic, brain imaging and pharmacologic studies. We then focus on genetic mouse models of syndromic neurodevelopmental disorders in which single gene mutations lead to increased risk for ASD. We highlight studies that have directly examined dopamine neuron number, morphology, physiology, or output in these models. Overall, we find considerable support for the idea that the dopamine system may be dysregulated in syndromic ASDs; however, there does not appear to be a consistent signature and some models show increased dopaminergic function, while others have deficient dopamine signaling. We conclude that dopamine dysregulation is common in syndromic forms of ASD but that the specific changes may be unique to each genetic disorder and may not account for the full spectrum of ASD-related manifestations.

Prevalence and clinical/molecular characteristics of PTEN mutations in Turkish children with autism spectrum disorders and macrocephaly

Background

Phosphatase and tensin homolog (PTEN) germline mutations are associated with cancer syndromes (PTEN hamartoma tumor syndrome; PHTS) and in pediatric patients with autism spectrum disorder (ASD) and macrocephaly. The exact prevalence of PTEN mutations in patients with ASD and macrocephaly is uncertain; with prevalence rates ranging from 1% to 17%. Most studies are retrospective and contain more adult than pediatric patients, there is a need for more prospective pediatric studies.

Methods

We recruited 131 patients (108 males, 23 females) with ASD and macrocephaly between the ages of 3 and 18 from five child and adolescent psychiatry clinics in Turkey from July 2018 to December 2019. We defined macrocephaly as occipito‐frontal HC size at or greater than 2 standard deviations (SD) above the mean for age and sex on standard growth charts. PTEN gene sequence analysis was performed using a MiSeq next generation sequencing (NGS) platform, (Illumina).

Conclusion

PTEN gene sequence analyses identified three pathogenic/likely pathogenic mutations [NM_000314.6; p.(Pro204Leu), (p.Arg233*) and novel (p.Tyr176Cys*8)] and two variants of uncertain significance (VUS) [NM_000314.6; p.(Ala79Thr) and c.*10del]. We also report that patient with (p.Tyr176Cys*8) mutation has Grade 1 hepatosteatosis, a phenotype not previously described. This is the first PTEN prevalence study of patients with ASD and macrocephaly in Turkey and South Eastern Europe region with a largest homogenous cohort. The prevalence of PTEN mutations was found 3.8% (VUS included) or 2.29% (VUS omitted). We recommend testing for PTEN mutations in all patients with ASD and macrocephaly.

[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.

Germline nuclear-predominant Pten murine model exhibits impaired social and perseverative behavior, microglial activation, and increased oxytocinergic activity

BACKGROUND

Autism spectrum disorder (ASD) has a strong genetic etiology. Germline mutation in the tumor suppressor gene PTEN is one of the best described monogenic risk cases for ASD. Animal modeling of cell-specific Pten loss or mutation has provided insight into how disruptions to the function of PTEN affect neurodevelopment, neurobiology, and social behavior. As such, there is a growing need to understand more about how various aspects of PTEN activity and cell-compartment-specific functions, contribute to certain neurological or behavior phenotypes.

METHODS

To understand more about the relationship between Pten localization and downstream effects on neurophenotypes, we generated the nuclear-predominant PtenY68H/+ mouse, which is identical to the genotype of some PTEN-ASD individuals. We subjected the PtenY68H/+ mouse to morphological and behavioral phenotyping, including the three-chamber sociability, open field, rotarod, and marble burying tests. We subsequently performed in vivo and in vitro cellular phenotyping and concluded the work with a transcriptomic survey of the PtenY68H/+ cortex, which profiled gene expression.

RESULTS

We observe a significant increase in P-Akt downstream of canonical Pten signaling, macrocephaly, decreased sociability, decreased preference for novel social stimuli, increased repetitive behavior, and increased thigmotaxis in PtenY68H/+ six-week-old (P40) mice. In addition, we found significant microglial activation with increased expression of complement and neuroinflammatory proteins in vivo and in vitro accompanied by enhanced phagocytosis. These observations were subsequently validated with RNA-seq and qRT-PCR, which revealed overexpression of many genes involved in neuroinflammation and neuronal function, including oxytocin. Oxytocin transcript was fivefold overexpressed (P = 0.0018), and oxytocin protein was strongly overexpressed in the PtenY68H/+ hypothalamus.

CONCLUSIONS

The nuclear-predominant PtenY68H/+ model has clarified that Pten dysfunction links to microglial pathology and this associates with increased Akt signaling. We also demonstrate that Pten dysfunction associates with changes in the oxytocin system, an important connection between a prominent ASD risk gene and a potent neuroendocrine regulator of social behavior. These cellular and molecular pathologies may related to the observed changes in social behavior. Ultimately, the findings from this work may reveal important biomarkers and/or novel therapeutic modalities that could be explored in individuals with germline mutations in PTEN with ASD.

HIF-1 α may play a role in late pregnancy hypoxia-induced autism-like behaviors in offspring rats

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that can be caused by various factors. The present study aimed to determine whether prenatal hypoxia can lead to ASD and the role of hypoxia-inducible factor-1α (HIF-1α) in this process. We constructed a prenatal hypoxia model of pregnant rats by piping nitrogen and oxygen mixed gas, with an oxygen concentration of 10 ± 0.5 %, into the self-made hypoxia chamber. Rats were subjected to different extents of hypoxia treatments at different points during pregnancy. The results showed that hypoxia for 6 h on the 17th gestation day is most likely to lead to autistic behavior in offspring rats, including social deficits, repetitive behaviors, and impaired learning and memory. The mRNA expression level of TNF-α also increased in hypoxia-induced autism group and valproic acid (VPA) group. Western blotting analysis showed increased levels of hypoxia inducible factor 1 alpha (HIF-1α) and decreased levels of phosphatase and tensin homolog (PTEN) in the hypoxic-induced autism group. Meanwhile, N-methyl d-aspartate receptor subtype 2 (NR2A) and glutamate ionotropic receptor AMPA type subunit 2 (GluR2) were upregulated in the hypoxic-induced autism group. HIF-1α might play a role in hypoxia-caused autism-like behavior and its regulatory effect is likely to be achieved by regulating synaptic plasticity.

Distinguishing between PTEN clinical phenotypes through mutation analysis

Phosphate and tensin homolog on chromosome ten (PTEN) germline mutations are associated with an overarching condition known as PTEN hamartoma tumor syndrome. Clinical phenotypes associated with this syndrome range from macrocephaly and autism spectrum disorder to Cowden syndrome, which manifests as multiple noncancerous tumor-like growths (hamartomas), and an increased predisposition to certain cancers. It is unclear, however, the basis by which mutations might lead to these very diverse phenotypic outcomes. Here we show that, by considering the molecular consequences of mutations in PTEN on protein structure and function, we can accurately distinguish PTEN mutations exhibiting different phenotypes. Changes in phosphatase activity, protein stability, and intramolecular interactions appeared to be major drivers of clinical phenotype, with cancer-associated variants leading to the most drastic changes, while ASD and non-pathogenic variants associated with more mild and neutral changes, respectively. Importantly, we show via saturation mutagenesis that more than half of variants of unknown significance could be associated with disease phenotypes, while over half of Cowden syndrome mutations likely lead to cancer. These insights can assist in exploring potentially important clinical outcomes delineated by PTEN variation.

PTEN Regulates Mitochondrial Biogenesis via the AKT/GSK-3β/PGC-1α Pathway in Autism

Autism spectrum disorder (ASD) is a widespread, complex and serious neurodevelopmental disorder. Complex genetic and environmental factors are thought to contribute to the development of ASD. Genome-wide association analysis has identified multiple autism-related genes. Mutation of the phosphatase and tensin homolog (Pten) is closely related to autism and accounts for 5-17% of cases of autism. However, the detailed mechanism is still unclear. Recently, mitochondrial dysfunction was tightly associated with ASD pathogenesis, such as developmental degeneration, learning and various behavioral disorders. The mitochondrial DNA (mtDNA) copy number in children with autism is also significantly increased. The correlation between Pten and mitochondrial dysfunction in autism is still unknown. In this study, we examined how Pten regulates mitochondrial biogenesis through the AKT/GSK-3β/PGC-1α signaling pathways. We found that PTEN could dephosphorylate AKT to inhibit its activity, leading to decreased GSK3β phosphorylation. This decrease in GSK3β phosphorylation, which could activate itself, increased PGC-1α phosphorylation to promote its degradation and then regulated mitochondrial biogenesis by NRF-1 and TFAM downstream of PGC-1α. In the Valproic acid (VPA) induced autism mouse model, the PTEN protein level was significantly decreased while PGC-1α and COX IV levels were increased in the hippocampus and cortex. Our data suggest that there is a correlation between PTEN and mitochondrial dysfunction and this correlation may be a potential mechanism of ASD.

Role of CNTNAP2 in autism manifestation outlines the regulation of signaling between neurons at the synapse

Background

Autism is characterized by high heritability and a complex genetic mutational landscape with restricted social behavior and impaired social communication. Whole-exome sequencing is a reliable tool to pinpoint variants for unraveling the disease pathophysiology. The present meta-analysis was performed using 222 whole-exome sequences deposited by Simons Simplex Collection (SSC) at the European Nucleotide Archive. This sample cohort was used to identify causal mutations in autism-specific genes to create a mutational landscape focusing on the CNTNAP2 gene.

Results

The authors account for the identification of 15 high confidence genes with 24 variants for autism with Simons Foundation Autism Research Initiative (SFARI) gene scoring. These genes encompass critical autism pathways such as neuron development, synapse complexity, cytoskeleton, and microtubule activation. Among these 15 genes, overlapping variants were present across multiple samples: KMT2C in 167 cases, CNTNAP2 in 192 samples, CACNA1C in 152 cases, and SHANK3 in 124 cases. Pathway analysis identifies clustering and interplay of autism genes—WDFY3, SHANK2, CNTNAP2, HOMER1, SYNGAP1, and ANK2 with CNTNAP2. These genes coincide across autism-relevant pathways, namely abnormal social behavior and intellectual and cognitive impairment. Based on multiple layers of selection criteria, CNTNAP2 was chosen as the master gene for the study. It is an essential gene for autism with speech-language delays, a typical phenotype in most cases under study. It showcases nine variants across multiple samples with one damaging variant, T589P, with a GERP rank score range of 0.065–0.95. This unique variant was present across 86.5% of the samples impairing the epithelial growth factor (EGF) domain. Established microRNA (miRNA) genes hsa-mir-548aq and hsa-mir-548f were mutated within the CNTNAP2 region, adding to the severity. The mutated protein showed reduced stability by 0.25, increased solvent accessibility by 9%, and reduced depth by 0.2, which rendered the protein non-functional. Secondary physical interactors of CNTNAP2 through CNTN2 proteins were mutated in the samples, further intensifying the severity.

Conclusion

CNTNAP2 has been identified as a master gene in autism manifestation responsible for speech-language delay by impairing the EGF protein domain and downstream cascade. The decrease in EGF is correlated with vital autism symptoms, especially language disabilities.

Perinatal Factors in Newborn Are Insidious Risk Factors for Childhood Autism Spectrum Disorders: A Population-based Study

We analyzed claims data from the Taiwan National Health Insurance database, which contains data of 23.5 million Taiwan residents. We included children born after January 1, 2000 who had received a diagnosis of autism spectrum disorders (ASD). Patients who were not diagnosed with ASD were included in the control group. The ASD prevalence was 517 in 62,051 (0.83%) children. Neonatal jaundice, hypoglycemia, intrauterine growth retardation (IUGR), and craniofacial anomalies (CFA) differed significantly between the ASD and control groups. After logistic regressive analysis, the adjusted odds ratios of IUGR, CFA, neonatal hypoglycemia, and neonatal jaundice were 8.58, 7.37, 3.83, and 1.32, respectively. Those insidiously perinatal risk factors, namely CFA, IUGR, neonatal hypoglycemia, and neonatal jaundice, could increase the risk of ASD.

Cross-level analysis of molecular and neurobehavioral function in a prospective series of patients with germline heterozygous PTEN mutations with and without autism

Background

PTEN is a well-established risk gene for autism spectrum disorder (ASD). Yet, little is known about how PTEN mutations and associated molecular processes influence neurobehavioral function in mutation carriers with (PTEN-ASD) and without ASD (PTEN no-ASD). The primary aim of the present study was to examine group differences in peripheral blood-derived PTEN pathway protein levels between PTEN-ASD, PTEN no-ASD, and idiopathic macrocephalic ASD patients (macro-ASD). Secondarily, associations between protein levels and neurobehavioral functions were examined in the full cohort.

Methods

Patients were recruited at four tertiary medical centers. Peripheral blood-derived protein levels from canonical PTEN pathways (PI3K/AKT and MAPK/ERK) were analyzed using Western blot analyses blinded to genotype and ASD status. Neurobehavioral measures included standardized assessments of global cognitive ability and multiple neurobehavioral domains. Analysis of variance models examined group differences in demographic, neurobehavioral, and protein measures. Bivariate correlations, structural models, and statistical learning procedures estimated associations between molecular and neurobehavioral variables. To complement patient data, Western blots for downstream proteins were generated to evaluate canonical PTEN pathways in the PTEN-m3m4 mouse model.

Results

Participants included 61 patients (25 PTEN-ASD, 16 PTEN no-ASD, and 20 macro-ASD). Decreased PTEN and S6 were observed in both PTEN mutation groups. Reductions in MnSOD and increases in P-S6 were observed in ASD groups. Elevated neural P-AKT/AKT and P-S6/S6 from PTEN murine models parallel our patient observations. Patient PTEN and AKT levels were independently associated with global cognitive ability, and p27 expression was associated with frontal sub-cortical functions. As a group, molecular measures added significant predictive value to several neurobehavioral domains over and above PTEN mutation status.

Limitations

Sample sizes were small, precluding within-group analyses. Protein and neurobehavioral data were limited to a single evaluation. A small number of patients were excluded with invalid protein data, and cognitively impaired patients had missing data on some assessments.

Conclusions

Several canonical PTEN pathway molecules appear to influence the presence of ASD and modify neurobehavioral function in PTEN mutation patients. Protein assays of the PTEN pathway may be useful for predicting neurobehavioral outcomes in PTEN patients. Future longitudinal analyses are needed to replicate these findings and evaluate within-group relationships between protein and neurobehavioral measures.

Trial registration

ClinicalTrials.gov Identifier NCT02461446

Conditional Pten knockout in parvalbumin- or somatostatin-positive neurons sufficiently leads to autism-related behavioral phenotypes

Disrupted GABAergic neurons have been extensively described in brain tissues from individuals with autism spectrum disorder (ASD) and animal models for ASD. However, the contribution of these aberrant inhibitory neurons to autism-related behavioral phenotypes is not well understood. We examined ASD-related behaviors in mice with conditional Pten knockout in parvalbumin (PV)-expressing or somatostatin (Sst)-expressing neurons, two common subtypes of GABAergic neurons. We found that mice with deletion of Pten in either PV-neurons or Sst-neurons displayed social deficits, repetitive behaviors and impaired motor coordination/learning. In addition, mice with one copy of Pten deletion in PV-neurons exhibited hyperlocomotion in novel open fields and home cages. We also examined anxiety behaviors and found that mice with Pten deletion in Sst-neurons displayed anxiety-like behaviors, while mice with Pten deletion in PV-neurons exhibited anxiolytic-like behaviors. These behavioral assessments demonstrate that Pten knockout in the subtype of inhibitory neurons sufficiently gives rise to ASD-core behaviors, providing evidence that both PV- and Sst-neurons may play a critical role in ASD symptoms.

Whole Exome Sequencing Identifies Novel De Novo Variants Interacting with Six Gene Networks in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a highly heritable condition caused by a combination of environmental and genetic factors such as de novo and inherited variants, as well as rare or common variants among hundreds of related genes. Previous genome-wide association studies have identified susceptibility genes; however, most ASD-associated genes remain undiscovered. This study aimed to examine rare de novo variants to identify genetic risk factors of ASD using whole exome sequencing (WES), functional characterization, and genetic network analyses of identified variants using Korean familial dataset. We recruited children with ASD and their biological parents. The clinical best estimate diagnosis of ASD was made according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5^TM), using comprehensive diagnostic instruments. The final analyses included a total of 151 individuals from 51 families. Variants were identified and filtered using the GATK Best Practices for bioinformatics analysis, followed by genome alignments and annotation to the reference genome assembly GRCh37 (liftover to GRCh38), and further annotated using dbSNP 154 build databases. To evaluate allele frequencies of de novo variants, we used the dbSNP, gnomAD exome v2.1.1, and genome v3.0. We used Ingenuity Pathway Analysis (IPA, Qiagen) software to construct networks using all identified de novo variants with known autism-related genes to find probable relationships. We identified 36 de novo variants with potential relations to ASD; 27 missense, two silent, one nonsense, one splice region, one splice site, one 5′ UTR, and one intronic SNV and two frameshift deletions. We identified six networks with functional relationships. Among the interactions between de novo variants, the IPA assay found that the NF-κB signaling pathway and its interacting genes were commonly observed at two networks. The relatively small cohort size may affect the results of novel ASD genes with de novo variants described in our findings. We did not conduct functional experiments in this study. Because of the diversity and heterogeneity of ASD, the primary purpose of this study was to investigate probable causative relationships between novel de novo variants and known autism genes. Additionally, we based functional relationships with known genes on network analysis rather than on statistical analysis. We identified new variants that may underlie genetic factors contributing to ASD in Korean families using WES and genetic network analyses. We observed novel de novo variants that might be functionally linked to ASD, of which the variants interact with six genetic networks.

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

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

PIK3R2/Pik3r2 Activating Mutations Result in Brain Overgrowth and EEG Changes

OBJECTIVE

Mutations in phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) complex have been associated with a broad spectrum of brain and organ overgrowth syndromes. For example, mutations in phosphatidylinositol-3-kinase regulatory subunit 2 (PIK3R2) have been identified in human patients with megalencephaly polymicrogyria polydactyly hydrocephalus (MPPH) syndrome, which includes brain overgrowth. To better understand the pathogenesis of PIK3R2-related mutations, we have developed and characterized a murine model.

METHODS

We generated a knock-in mouse model for the most common human PIK3R2 mutation, p.G373R (p.G367R in mice) using CRISPR/Cas9. The mouse phenotypes, including brain size, seizure activity, cortical lamination, cell proliferation/size/density, interneuron migration, and PI3K pathway activation, were analyzed using standard methodologies. For human patients with PIK3R2 mutations, clinical data (occipitofrontal circumference [OFC] and epilepsy) were retrospectively obtained from our clinical records (published / unpublished).

RESULTS

The PI3K-AKT pathway was hyperactivated in these mice, confirming the p.G367R mutation is an activating mutation in vivo. Similar to human patients with PIK3R2 mutations, these mice have enlarged brains. We found cell size to be increased but not cell numbers. The embryonic brain showed mild defects in cortical lamination, although not observed in the mature brain. Furthermore, electroencephalogram (EEG) recordings from mutant mice showed background slowing and rare seizures, again similar to our observations in human patients.

INTERPRETATION

We have generated a PIK3R2 mouse model that exhibits megalencephaly and EEG changes, both of which overlap with human patients. Our data provide novel insight into the pathogenesis of the human disease caused by PIK3R2 p.G373R mutation. We anticipate this model will be valuable in testing therapeutic options for human patients with MPPH. ANN NEUROL 2020;88:1077-1094.

Connecting Genotype with Behavioral Phenotype in Mouse Models of Autism Associated with PTEN Mutations

A subset of individuals with autism spectrum disorder (ASD) and macrocephaly carry mutations in the gene PTEN. Animal models, particularly mice, have been helpful in establishing a causal role for Pten mutations in autism-relevant behavioral deficits. These models are a useful tool for investigating neurobiological mechanisms of these behavioral phenotypes and developing potential therapeutic interventions. Here we provide an overview of various genetic mouse models that have been used to characterize behavioral phenotypes caused by perturbation of Pten We discuss convergent and divergent phenotypes across models with the aim of highlighting a set of behavioral domains that are sensitive to the effects of Pten mutation and that may provide useful readouts for translational and basic neuroscience research.

Clinical genetic testing and counselling in autism spectrum disorder

Autism spectrum disorders (ASDs) are phenotypically as well as genetically heterogeneous developmental disorders with a strong heritability. Clinical and basic science research has described many replicated genetic risk factors. Many findings can well be translated into clinical human genetic practice. The current article summarizes results of genetic studies in ASD, provides a diagnostic algorithm for the clinical human genetic work-up reflecting the German health care system options and gives information with regard to the obligatory genetic counselling after a clinical genetic assessment.

Studying Human Neurodevelopment and Diseases Using 3D Brain Organoids

In vitro differentiation of pluripotent stem cells provides a systematic platform to study development and disease. Recent advances in brain organoid technology have created new opportunities to investigate the formation and function of the human brain, under physiological and pathological conditions. Brain organoids can be generated to model the cellular and structural development of the human brain, and allow the investigation of the intricate interactions between resident neural and glial cell types. Combined with new advances in gene editing, imaging, and genomic analysis, brain organoid technology can be applied to address questions pertinent to human brain development, disease, and evolution. However, the current iterations of brain organoids also have limitations in faithfully recapitulating the in vivo processes. In this perspective, we evaluate the recent progress in brain organoid technology, and discuss the experimental considerations for its utilization.Dual Perspectives Companion Paper: Integrating CRISPR Engineering and hiPSC-Derived 2D Disease Modeling Systems, by Kristina Rehbach, Michael B. Fernando, and Kristen J. Brennand.

PI3K isoform-selective inhibition in neuron-specific PTEN-deficient mice rescues molecular defects and reduces epilepsy-associated phenotypes

Epilepsy affects all ages, races, genders, and socioeconomic groups. In about one third of patients, epilepsy is uncontrolled with current medications, leaving a vast need for improved therapies. The causes of epilepsy are diverse and not always known but one gene mutated in a small subpopulation of patients is phosphatase and tensin homolog (PTEN). Moreover, focal cortical dysplasia, which constitutes a large fraction of refractory epilepsies, has been associated with signaling defects downstream of PTEN. So far, most preclinical attempts to reverse PTEN deficiency-associated neurological deficits have focused on mTOR, a signaling hub several steps downstream of PTEN. Phosphoinositide 3-kinases (PI3Ks), by contrast, are the direct enzymatic counteractors of PTEN, and thus may be alternative treatment targets. PI3K activity is mediated by four different PI3K catalytic isoforms. Studies in cancer, where PTEN is commonly mutated, have demonstrated that inhibition of only one isoform, p110β, reduces progression of PTEN-deficient tumors. Importantly, inhibition of a single PI3K isoform leaves critical functions of general PI3K signaling throughout the body intact. Here, we show that this disease mechanism-targeted strategy borrowed from cancer research rescues or ameliorates neuronal phenotypes in male and female mice with neuron-specific PTEN deficiency. These phenotypes include cell signaling defects, protein synthesis aberrations, seizures, and cortical dysplasia. Of note, p110β is also dysregulated and a promising treatment target in the intellectual disability Fragile X syndrome, pointing towards a shared biological mechanism that is therapeutically targetable in neurodevelopmental disorders of different etiologies. Overall, this work advocates for further assessment of p110β inhibition not only in PTEN deficiency-associated neurodevelopmental diseases but also other brain disorders characterized by defects in the PI3K/mTOR pathway.

Decreased nuclear Pten in neural stem cells contributes to deficits in neuronal maturation

BACKGROUND

PTEN, a syndromic autism spectrum disorder (ASD) risk gene, is mutated in approximately 10% of macrocephalic ASD cases. Despite the described genetic association between PTEN and ASD and ensuing studies, we continue to have a limited understanding of how PTEN disruption drives ASD pathogenesis and maintenance.

METHODS

We derived neural stem cells (NSCs) from the dentate gyrus (DG) of Pten^m3m4 mice, a model that recapitulates PTEN-ASD phenotypes. We subsequently characterized the expression of stemness factors, proliferation, and differentiation of neurons and glia in Pten^m3m4 NSCs using immunofluorescent and immunoblotting approaches. We also measured Creb phosphorylation by Western blot analysis and expression of Creb-regulated genes with qRT-PCR.

RESULTS

The m3m4 mutation decreases Pten localization to the nucleus and its global expression over time. Pten^m3m4 NSCs exhibit persistent stemness characteristics associated with increased proliferation and a resistance to neuronal maturation during differentiation. Given the increased proliferation of Pten^m3m4 NSCs, a significant increase in the population of immature neurons relative to mature neurons occurs, an approximately tenfold decrease in the ratio between the homozygous mutant and wildtype. There is an opposite pattern of differentiation in some Pten^m3m4 glia, specifically an increase in astrocytes. These aberrant differentiation patterns associate with changes in Creb activation in Pten^m3m4/m3m4 NSCs. We specifically observed loss of Creb phosphorylation at S133 in Pten^m3m4/m3m4 NSCs and a subsequent decrease in expression of Creb-regulated genes important to neuronal function (i.e., Bdnf). Interestingly, Bdnf treatment is able to partially rescue the stunted neuronal maturation phenotype in Pten^m3m4/m3m4 NSCs.

CONCLUSIONS

Constitutional disruption of Pten nuclear localization with subsequent global decrease in Pten expression generates abnormal patterns of differentiation, a stunting of neuronal maturation. The propensity of Pten disruption to restrain neurons to a more progenitor-like state may be an important feature contributing to PTEN-ASD pathogenesis.

Cowden syndrome complicated by schizophrenia: A first clinical report

Patients with Cowden syndrome exhibit mucocutaneous lesions, hamartomatous polyposis of the gastrointestinal tract, and macrocephaly, often complicated by malignant tumors, such as breast, thyroid, and uterine cancers. Autism spectrum and epilepsy have been known as neuropsychiatric symptoms associated with Cowden syndrome; however, to the best of our knowledge, there is no report on cases complicated by schizophrenia. Here, we report a first case of Cowden syndrome complicated by schizophrenia. A 49-year-old Japanese woman started experiencing auditory hallucinations in her teens. She had left breast cancer at the age of 34 years, and right breast cancer at the age of 37 years, all of which were surgically treated. She was also being treated by oral medications for Hashimoto's disease. On consulting her previous doctor for abnormal uterine bleeding that lasted for a year, she was diagnosed with endometrial cancer. However, immediately before surgery, her auditory hallucinations and paranoid delusions became severe, and she was referred to our hospital for detailed examination and treatment. No abnormalities were found on head MRI, and she was diagnosed with schizophrenia on the basis of neuropsychiatric examination findings. After her psychiatric symptoms were controlled by 2 mg of risperidone, she underwent surgery for endometrial cancer. Although there was no apparent family history, physical findings including macrocephaly and papillomatous skin lesions together with her past medical history of multiple malignant tumors suggested Cowden syndrome. Postoperatively, genetic testing revealed a pathogenic variant c.655C > T; p. Gln219* (NM_000314.4) in PTEN, leading to the confirmation of the diagnosis of Cowden syndrome.

The Role of PTEN in Neurodevelopment

PTEN is a lipid and protein phosphatase that regulates cell growth and survival. Mutations to PTEN are highly penetrant for autism spectrum disorder (ASD). Here, we briefly review the evidence linking PTEN mutations to ASD and the mouse models that have been used to study the role of PTEN in neurodevelopment. We then focus on the cellular phenotypes associated with PTEN loss in neurons, highlighting the role PTEN plays in neuronal proliferation, migration, survival, morphology, and plasticity.

Autism-associated PTEN missense mutation leads to enhanced nuclear localization and neurite outgrowth in an induced pluripotent stem cell line

Germline mutation in the PTEN gene is the genetic basis of PTEN hamartoma tumor syndrome with the affected individuals harboring features of autism spectrum disorders. Characterizing a panel of 14 autism‐associated PTEN missense mutations revealed reduced protein stability, catalytic activity, and subcellular distribution. Nine out of 14 (64%) PTEN missense mutants had reduced protein expression with most mutations confined to the C2 domain. Selected mutants displayed enhanced polyubiquitination and shortened protein half‐life, but that did not appear to involve the polyubiquitination sites at lysine residues at codon 13 or 289. Analyzing their intrinsic lipid phosphatase activities revealed that 78% (11 out of 14) of these mutants had twofold to 10‐fold reduction in catalytic activity toward phosphatidylinositol phosphate substrates. Analyzing the subcellular localization of the PTEN missense mutants showed that 64% (nine out of 14) had altered nuclear‐to‐cytosol ratios with four mutants (G44D, H123Q, E157G, and D326N) showing greater nuclear localization. The E157G mutant was knocked‐in to an induced pluripotent stem cell line and recapitulated a similar nuclear targeting preference. Furthermore, iPSCs expressing the E157G mutant were more proliferative at the neural progenitor cell stage but exhibited more extensive dendritic outgrowth. In summary, the combination of biological changes in PTEN is expected to contribute to the behavioral and cellular features of this neurodevelopmental disorder.

NS-Pten adult knockout mice display both quantitative and qualitative changes in urine-induced ultrasonic vocalizations

The NS-Pten knockout (KO) mouse exhibits hyperactivity of the mammalian target of rapamycin (mTOR) and is a model of autism spectrum disorder (ASD). ASD presents with marked deficits in communication which can be elucidated by investigating their counterpart in mice, ultrasonic vocalizations (USVs). While USVs have been found to be altered in NS-Pten KO pups, no study has assessed whether this communication deficit persists into adulthood. In the present study, we investigate female urine-induced USVs, scent marking behavior, and open field activity in NS-Pten KO and wildtype (WT) adult male mice. Results showed that there was no difference in the quantity of vocalizations produced between groups, however, there were extensive alterations in the spectral properties of USVs. KO mice emitted vocalizations of a lower peak frequency, shorter duration, and higher peak amplitude compared to WT mice. KO animals also emitted a significantly different distribution of call-types relative to controls, displaying increased complex and short calls, but fewer upward, chevron, frequency steps, and composite calls. No significant differences between groups were observed for scent marking behavior and there was no difference between groups in the amount of time spent near the female urine. Overall, this study demonstrated that mTOR hyperactivity contributes to communication deficits in adult mice.

Identification, Evaluation, and Management of Children With Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a common neurodevelopmental disorder with reported prevalence in the United States of 1 in 59 children (approximately 1.7%). Core deficits are identified in 2 domains: social communication/interaction and restrictive, repetitive patterns of behavior. Children and youth with ASD have service needs in behavioral, educational, health, leisure, family support, and other areas. Standardized screening for ASD at 18 and 24 months of age with ongoing developmental surveillance continues to be recommended in primary care (although it may be performed in other settings), because ASD is common, can be diagnosed as young as 18 months of age, and has evidenced-based interventions that may improve function. More accurate and culturally sensitive screening approaches are needed. Primary care providers should be familiar with the diagnostic criteria for ASD, appropriate etiologic evaluation, and co-occurring medical and behavioral conditions (such as disorders of sleep and feeding, gastrointestinal tract symptoms, obesity, seizures, attention-deficit/hyperactivity disorder, anxiety, and wandering) that affect the child's function and quality of life. There is an increasing evidence base to support behavioral and other interventions to address specific skills and symptoms. Shared decision making calls for collaboration with families in evaluation and choice of interventions.  This single clinical report updates the 2007 American Academy of Pediatrics clinical reports on the evaluation and treatment of ASD in one publication with an online table of contents and section view available through the American Academy of Pediatrics Gateway to help the reader identify topic areas within the report.

Pten haploinsufficiency disrupts scaling across brain areas during development in mice

Haploinsufficiency for PTEN is a cause of autism spectrum disorder and brain overgrowth; however, it is not known if PTEN mutations disrupt scaling across brain areas during development. To address this question, we used magnetic resonance imaging to analyze brains of male Pten haploinsufficient (Pten^+/-) mice and wild-type littermates during early postnatal development and adulthood. Adult Pten^+/- mice display a consistent pattern of abnormal scaling across brain areas, with white matter (WM) areas being particularly affected. This regional and WM enlargement recapitulates structural abnormalities found in individuals with PTEN haploinsufficiency and autism. Early postnatal Pten^+/- mice do not display the same pattern, instead exhibiting greater variability across mice and brain regions than controls. This suggests that Pten haploinsufficiency may desynchronize growth across brain regions during early development before stabilizing by maturity. Pten^+/- cortical cultures display increased proliferation of glial cell populations, indicating a potential substrate of WM enlargement, and provide a platform for testing candidate therapeutics. Pten haploinsufficiency dysregulates coordinated growth across brain regions during development. This results in abnormally scaled brain areas and associated behavioral deficits, potentially explaining the relationship between PTEN mutations and neurodevelopmental disorders.

Therapeutic inhibition of mTORC2 rescues the behavioral and neurophysiological abnormalities associated with Pten-deficiency

Dysregulation of the mammalian target of rapamycin (mTOR) signaling, which is mediated by two structurally and functionally distinct complexes, mTORC1 and mTORC2, has been implicated in several neurological disorders1-3. Individuals carrying loss-of-function mutations in the phosphatase and tensin homolog (PTEN) gene, a negative regulator of mTOR signaling, are prone to developing macrocephaly, autism spectrum disorder (ASD), seizures and intellectual disability2,4,5. It is generally believed that the neurological symptoms associated with loss of PTEN and other mTORopathies (for example, mutations in the tuberous sclerosis genes TSC1 or TSC2) are due to hyperactivation of mTORC1-mediated protein synthesis1,2,4,6,7. Using molecular genetics, we unexpectedly found that genetic deletion of mTORC2 (but not mTORC1) activity prolonged lifespan, suppressed seizures, rescued ASD-like behaviors and long-term memory, and normalized metabolic changes in the brain of mice lacking Pten. In a more therapeutically oriented approach, we found that administration of an antisense oligonucleotide (ASO) targeting mTORC2's defining component Rictor specifically inhibits mTORC2 activity and reverses the behavioral and neurophysiological abnormalities in adolescent Pten-deficient mice. Collectively, our findings indicate that mTORC2 is the major driver underlying the neuropathophysiology associated with Pten-deficiency, and its therapeutic reduction could represent a promising and broadly effective translational therapy for neurological disorders where mTOR signaling is dysregulated.

PTEN Hamartoma tumor syndrome in childhood: A review of the clinical literature

PTEN hamartoma tumor syndrome (PHTS) is a highly variable autosomal dominant condition associated with intellectual disability, overgrowth, and tumor predisposition phenotypes, which often overlap. PHTS incorporates a number of historical clinical presentations including Bannayan-Riley-Ruvalcaba syndrome, Cowden syndrome, and a macrocephaly-autism/developmental delay syndrome. Many reviews in the literature focus on PHTS as an adult hamartoma and malignancy predisposition condition. Here, we review the current literature with a focus on pediatric presentations. The review starts with a summary of the main conditions encompassed within PHTS. We then discuss PHTS diagnostic criteria, and clinical features. We briefly address rarer PTEN associations, and the possible role of mTOR inhibitors in treatment. We acknowledge the limited understanding of the natural history of childhood-onset PHTS as a cancer predisposition syndrome and present a summary of important management considerations.

Genetic Suppression of mTOR Rescues Synaptic and Social Behavioral Abnormalities in a Mouse Model of Pten Haploinsufficiency

Heterozygous mutations in PTEN, which encodes a negative regulator of the mTOR and β-catenin signaling pathways, cause macrocephaly/autism syndrome. However, the neurobiological substrates of the core symptoms of this syndrome are poorly understood. Here, we investigate the relationship between cerebral cortical overgrowth and social behavior deficits in conditional Pten heterozygous female mice (Pten cHet) using Emx1-Cre, which is expressed in cortical pyramidal neurons and a subset of glia. We found that conditional heterozygous mutation of Ctnnb1 (encoding β-catenin) suppresses Pten cHet cortical overgrowth, but not social behavioral deficits, whereas conditional heterozygous mutation of Mtor suppresses social behavioral deficits, but not cortical overgrowth. Neuronal activity in response to social cues and excitatory synapse markers are elevated in the medial prefrontal cortex (mPFC) of Pten cHet mice, and heterozygous mutation in Mtor, but not Ctnnb1, rescues these phenotypes. These findings indicate that macroscale cerebral cortical overgrowth and social behavioral phenotypes caused by Pten haploinsufficiency can be dissociated based on responsiveness to genetic suppression of Ctnnb1 or Mtor. Furthermore, neuronal connectivity appears to be one potential substrate for mTOR-mediated suppression of social behavioral deficits in Pten haploinsufficient mice. Autism Res 2019, 12: 1463-1471. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: A subgroup of individuals with autism display overgrowth of the head and the brain during development. Using a mouse model of an autism risk gene, Pten, that displays both brain overgrowth and social behavioral deficits, we show here that that these two symptoms can be dissociated. Reversal of social behavioral deficits in this model is associated with rescue of abnormal synaptic markers and neuronal activity.

Autism Spectrum Disorder Associated with Germline Heterozygous PTEN Mutations

This review examines our current understanding of autism spectrum disorder (ASD), its prevalence, impact, behavioral treatment, and outcomes. Building on this knowledge, ASD associated with PTEN mutations is introduced and recent human studies of neurobehavioral and neuroimaging findings in patients with PTEN mutations with and without ASD are reviewed. In doing so, we present evidence supporting a model of PTEN loss leading to neurobehavioral deficits, including ASD and intellectual disability. Next, we describe the neurobehavioral spectrum observed across PTEN mutation cases, adding specificity where possible, based on data from recent studies of child and adult PTEN patients. Finally, we end with a discussion of potential clinical recommendations for improving interventions and supports for people with PTEN-ASD and future research avenues for understanding and treating the functional and cognitive deficits in PTEN-ASD.

Phosphoinositides: Regulators of Nervous System Function in Health and Disease

Phosphoinositides, the seven phosphorylated derivatives of phosphatidylinositol have emerged as regulators of key sub-cellular processes such as membrane transport, cytoskeletal function and plasma membrane signaling in eukaryotic cells. All of these processes are also present in the cells that constitute the nervous system of animals and in this setting too, these are likely to tune key aspects of cell biology in relation to the unique structure and function of neurons. Phosphoinositides metabolism and function are mediated by enzymes and proteins that are conserved in evolution, and analysis of knockouts of these in animal models implicate this signaling system in neural function. Most recently, with the advent of human genome analysis, mutations in genes encoding components of the phosphoinositide signaling pathway have been implicated in human diseases although the cell biological basis of disease phenotypes in many cases remains unclear. In this review we evaluate existing evidence for the involvement of phosphoinositide signaling in human nervous system diseases and discuss ways of enhancing our understanding of the role of this pathway in the human nervous system's function in health and disease.