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Discover the most talked about and latest scientific content & concepts.

Concept: Neural development

238

Synaesthesia is a neurodevelopmental condition in which a sensation in one modality triggers a perception in a second modality. Autism (shorthand for Autism Spectrum Conditions) is a neurodevelopmental condition involving social-communication disability alongside resistance to change and unusually narrow interests or activities. Whilst on the surface they appear distinct, they have been suggested to share common atypical neural connectivity.

Concepts: Nervous system, Autism, Pervasive developmental disorder, Asperger syndrome, Autism spectrum, PDD-NOS, Neural development, Neurodevelopmental disorder

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Bisphenol A (BPA), a ubiquitous endocrine disruptor that is present in many household products, has been linked to obesity, cancer, and, most relevant here, childhood neurological disorders such as anxiety and hyperactivity. However, how BPA exposure translates into these neurodevelopmental disorders remains poorly understood. Here, we used zebrafish to link BPA mechanistically to disease etiology. Strikingly, treatment of embryonic zebrafish with very low-dose BPA (0.0068 μM, 1,000-fold lower than the accepted human daily exposure) and bisphenol S (BPS), a common analog used in BPA-free products, resulted in 180% and 240% increases, respectively, in neuronal birth (neurogenesis) within the hypothalamus, a highly conserved brain region involved in hyperactivity. Furthermore, restricted BPA/BPS exposure specifically during the neurogenic window caused later hyperactive behaviors in zebrafish larvae. Unexpectedly, we show that BPA-mediated precocious neurogenesis and the concomitant behavioral phenotype were not dependent on predicted estrogen receptors but relied on androgen receptor-mediated up-regulation of aromatase. Although human epidemiological results are still emerging, an association between high maternal urinary BPA during gestation and hyperactivity and other behavioral disturbances in the child has been suggested. Our studies here provide mechanistic support that the neurogenic period indeed may be a window of vulnerability and uncovers previously unexplored avenues of research into how endocrine disruptors might perturb early brain development. Furthermore, our results show that BPA-free products are not necessarily safer and support the removal of all bisphenols from consumer merchandise.

Concepts: Central nervous system, Nervous system, Psychology, Estrogen, Bisphenol A, Endocrine system, Endocrine disruptor, Neural development

89

Advanced paternal age (APA) at conception has been linked with autism and schizophrenia in offspring, neurodevelopmental disorders that affect social functioning. The current study explored the effects of paternal age on social development in the general population.

Concepts: Sociology, Autism, Bipolar disorder, Neural development, Neurodevelopmental disorder

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The development of neural connectivity is essential for brain function, and disruption of this process is associated with autism spectrum disorders (ASDs). DIX domain containing 1 (DIXDC1) has previously been implicated in neurodevelopmental disorders, but its role in postnatal brain function remains unknown. Using a knockout mouse model, we determined that DIXDC1 is a regulator of excitatory neuron dendrite development and synapse function in the cortex. We discovered that MARK1, previously linked to ASDs, phosphorylates DIXDC1 to regulate dendrite and spine development through modulation of the cytoskeletal network in an isoform-specific manner. Finally, rare missense variants in DIXDC1 were identified in ASD patient cohorts via genetic sequencing. Interestingly, the variants inhibit DIXDC1 isoform 1 phosphorylation, causing impairment to dendrite and spine growth. These data reveal that DIXDC1 is a regulator of cortical dendrite and synaptic development and provide mechanistic insight into morphological defects associated with neurodevelopmental disorders.

Concepts: Nervous system, Neuron, Autism, Axon, Synapse, Dendrite, Neural development, Neurodevelopmental disorder

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Autism spectrum disorders (ASDs) are neurodevelopmental conditions characterized by social and behavioural impairments. In addition to neurological symptoms, ASD subjects frequently suffer from gastrointestinal abnormalities, thus implying a role of the gut microbiota in ASD gastrointestinal pathophysiology.

Concepts: Gut flora, Autism, Pervasive developmental disorder, Asperger syndrome, Autism spectrum, PDD-NOS, Neural development, Neurodevelopmental disorder

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Acetaminophen is extensively used during pregnancy. But there is a lack of population-representative cohort studies evaluating its effects on a range of neuropsychological and behavioural endpoints. We aimed to assess whether prenatal exposure to acetaminophen is adversely associated with neurodevelopmental outcomes at 1 and 5 years of age.

Concepts: Psychology, Cohort study, Pregnancy, Neuroscience, Autism, Neural development, Neurodevelopmental disorder

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The development of the nervous system involves a coordinated succession of events including the migration of GABAergic (γ-aminobutyric-acid-releasing) neurons from ventral to dorsal forebrain and their integration into cortical circuits. However, these interregional interactions have not yet been modelled with human cells. Here we generate three-dimensional spheroids from human pluripotent stem cells that resemble either the dorsal or ventral forebrain and contain cortical glutamatergic or GABAergic neurons. These subdomain-specific forebrain spheroids can be assembled in vitro to recapitulate the saltatory migration of interneurons observed in the fetal forebrain. Using this system, we find that in Timothy syndrome-a neurodevelopmental disorder that is caused by mutations in the CaV1.2 calcium channel-interneurons display abnormal migratory saltations. We also show that after migration, interneurons functionally integrate with glutamatergic neurons to form a microphysiological system. We anticipate that this approach will be useful for studying neural development and disease, and for deriving spheroids that resemble other brain regions to assemble circuits in vitro.

Concepts: Central nervous system, Nervous system, Neuron, Brain, Developmental biology, Stem cell, Neuroscience, Neural development

32

Schizophrenia is a debilitating familial neuropsychiatric disorder which affects 1% of people worldwide. Although the heritability for schizophrenia approaches 80% only a small proportion of the overall genetic risk has been accounted for, and to date only a limited number of genetic loci have been definitively implicated. We have identified recently through genetic and in vitro functional studies, a novel serine/threonine kinase gene, unc-51-like kinase 4 (ULK4), as a rare risk factor for major mental disorders including schizophrenia. Now using the approach of in utero gene transfer we have discovered that Ulk4 plays a key modulatory role in corticogenesis. Knockdown of Ulk4 leads to significantly decreased cell proliferation in germinal zones and profound deficits in radial migration and neurite ramification. These abnormalities can be reversed successfully by Ulk4 gene supplementation. Ulk4 also regulated acetylation of α-tubulin, an important post-translational modification of microtubules. We conclude that Ulk4 plays an essential role in normal brain development and when defective, the risk of neurodevelopmental disorders such as schizophrenia is increased.

Concepts: Gene, Genetics, Bacteria, Histone, Developmental biology, Autism, Mental disorder, Neural development

29

Abstract Children with listening difficulties, but normal audiometry, may be diagnosed with APD. The diagnosis is typically based on poor performance on tests of perception of both non-speech and speech stimuli. However, non-speech test results correlate only weakly with evaluations of speech-in-noise processing, cognitive skills, and caregiver evaluations of listening ability. The interpretation of speech test results is confounded by the involvement of language processing mechanisms. Overall, listening ability is associated more with higher-level, cognitive and analytic processing than with lower-level sensory processing. Current diagnosis of a child with APD, rather than another problem (e.g. language impairment, LI), is determined more by the referral route than by the symptoms. Co-occurrence with other learning problems suggests that APD may be a symptom of a more varied neurodevelopmental disorder. Alternately, APD has been proposed as a cause of language-based disorders, but there is no one-to-one mapping between listening and language among individuals. Screening for APD may be most appropriately based on a well-validated, caregiver questionnaire that captures the fundamental problem of listening difficulties and identifies areas for further assessment and management. This approach has proved successful for LI, and may in future serve as a metric to help assess other, objective testing methods. Foreword Auditory processing disorder (APD) has a long (> 30 years) and controversial history. The controversies concern absolutely fundamental issues: the definition of APD, its neural basis, test validity and standardization, differentiation from other disorders, and even whether it exists as an independent disorder ( Jerger, 2009 ). To evaluate and interpret the scientific evidence on APD, and to advise the audiology profession, the British Society of Audiology (BSA) established a Special Interest Group (BSA SIG) on APD in 2003. That group has recently published two key documents, a ‘Position Statement’ and a ‘Management Overview’ ( BSA, 2011, a , b . See www.thebsa.org.uk ‘Procedures and Publications’). In formulating the new position statement, it became clear to the group that several significant differences were developing between their interpretation of the evidence concerning APD and that of the American Academy of Audiology (AAA) , as stated in their recently published ‘Guidelines for the diagnosis, treatment and management of children and adults with central auditory processing disorder’ ( AAA, 2010 ). To address these differences, and borrowing from British Parliamentary procedure, the BSA SIG decided to develop a ‘white paper’, a discussion document that could then receive an international set of commentaries from other research groups working on APD. An approach was made to the editor of the International Journal of Audiology who agreed to this suggestion. This paper, and the associated commentaries that follow, are the result.

Concepts: Psychology, Cognition, Auditory system, Audiology, Evidence, Scientific evidence, Neural development, Auditory processing disorder

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Despite great advances in neuroscience and genetic studies, our understanding of neurodevelopmental disorders is still quite limited. An important reason is not having objective psychiatric clinical tests. Here we propose a quantitative neurodevelopment assessment by studying natural movement outputs. Movement is central to behaviors: It involves complex coordination, temporal alterations, and precise dynamic controls. We carefully analyzed the continuous movement output data, collected with high definition electromagnetic sensors at millisecond time scales. We unraveled new metrics containing striking physiological information that was unseen neither by using traditional motion assessments nor by naked eye observations. Our putative biomarker leads to precise individualized classifications. It illustrates clear differences between Autism Spectrum Disorder (ASD) subjects from mature typical developing (TD) individuals. It provides an ASD complementary quantitative classification, which closely agrees with the clinicaly assessed functioning levels in the spectrum. It also illustrates TD potential age-related neurodevelopmental trajectories. Applying our movement biomarker to the parents of the ASD individuals studied in the cohort also shows a novel potential familial signature ASD tie. This paper proposes a putative behavioral biomarker to characterize the level of neurodevelopment with high predicting power, as illustrated in ASD subjects as an example.

Concepts: Psychology, Neuroscience, Assessment, Autism, Autism spectrum, Output, Neural development, Neurodevelopmental disorder