TOP ＞ Symposia

Symposia Multidemensional approach toward understanding of autism and neurodevelopmental disorders／自閉症・発達障害の病態解明への多面的アプローチ 2S7-1 Genetic and pathophysiological analysis for developmental disorder, mainly for autism spectrum disorder Takanori Yamagata Department of Pediatrics, Jichi Medical University Developmental disorder such as autism spectrum disorder (ASD) and attention deficit hyperactive disorder (ADHD) is a disease affecting developing brain. Genetic factors that disturb the synapse and neuronal network formation and function are one of the main pathophysiology for developmental disorders. As the genetic basis of ASD, copy number variations (CNV) were detected in 10-20% of the patients, and also, many pathogenic genes were identified by candidate gene analysis and exome sequence. Typical feature of ASD is the disorder of sociability and stereotypic behavior. Addition to that, associated problems including hyperactivity, panic, self-injury and sleep disturbance were observed. Among them, sleep disruption such as insomnia or short sleep cycles is one of the most common and distressed problems. In the previous study, we screened for mutations in the coding regions of circadian-relevant genes in ASD patients, and detected mutations in several genes including NR1D1. Therefore, circadian-relevant genes were likely to be impaired molecular clock mechanism potentially contributes to the etiology of ASD. And also, some of the circadian relevant genes were considered to have function in synapse. We detected several CNVs on ASD patients and several candidate genes in these regions focusing to the relation with synaptic function. Circadian relevant genes were also analyzed for mutations on ASD patients and contribution for synaptic function. Addition to the research for ASD, genetic analysis for intellectual disability and specific learning disorder, and brain functional analysis using fNIRS for ADHD will be discussed. 2S7-2 Analyses of causative genes for ASD with an analytical battery based on in utero electropolation Koh-ichi Nagata，Nanako Hamada Dept Mol Neurobiol. Inst Dev Res, Aichi Hum Serv Ctr While many different biological causes have been implicated in the etiologies of autism-spectrum disorder (ASD), genetic factors are considered to be the most important. It is thus essential to clarify the pathophysiological significance of respective disease-related genes. To this end, we have established a battery of in utero electroporation-based ex vivo and in vitro analyses. With this battery, we analyze functions of disease-related gene products in cortical neuron migration, axon elongation, dendrite development, spine morphogenesis. As a model case, we here focused on the pathophysiological significance of a neuron-specific splicing factor, RBFOX1 (aka A2BP1), since it has been identified as a “hub” gene in the ASD gene transcriptome network. Knockdown of Rbfox1 caused abnormal cortical neuron positioning during corticogenesis. Based on the live-imaging, migration defects occurred perhaps due to impaired nucleokinesis and Rbfox1-deficient neurons frequently showed abnormal polarity. Rbfox1 also regulated neuronal cell morphology in vivo as well as in vitro. In addition, electrophysiology analyses revealed significant abnormality in membrane and synaptic properties in the deficient neurons. Taken together, impaired cortical neuron migration, disturbed axon/dendrite growth, and defective synapse formation may induce structural and functional defects of the cerebral cortex, and consequently contribute to the clinical symptoms of neurodevelopmental disorders. 2S7-3 Neuro-functional analysis using disease-specific iPS cells Toshiyuki Yamamoto，Keiko Shimojima Institute of Medical Genetics, Tokyo Women's Medical University [Background] Neurodevelopmental disorders are a group of neurological disorders that cause intellectual impairments and autistic symptoms from infancy. Recent advances in genetic analysis technologies enabled us to disclose underlying genetic factors in patients with unknown etiologies. We have analyzed more than 100 patients with severe neurodevelopmental disorders. Approximately, half of the patients showed pathogenic genetic changes including copy number aberrations and single nucleotide alterations. Although identified abnormalities were variable and there was no common abnormality, most of the genes were related to synapse functions. On the other hand, there were some genes whose functional relevance not fully understood. Those genes were the target of the functional assays. However, it is difficult to use model animals for confirmation of the relationship between gene mutations and human neurodevelopmental disorders. Then, we tried to use disease-specific iPS cells established from patients whose genomic abnormality was clarified. [Results] Disease-specific iPS cells were established from patients with severe neurodevelopmental disorders whose genetic background was disclosed. The established cells were differentiated into neuronal cells and functionally analyzed. Some cells showed abnormal migration patterns. Numbers of the spines on the surface of the dendrites were analyzed and were reduced in patients. Action potentials were also analyzed by calcium imaging and also patch clamping. These analyses revealed abnormal neuronal activities in patients. [Conclusion] Disease-specific iPS cells were useful to use for patho-physiological assay. More convenient method for iPS differentiation will be desired for more spread usage of iPS cells. 2S7-4 Brain structural and behavioral abnormalities in a mouse model for 15q25.2-25.3 microdeletion syndrome Jun Nomura1，Akifumi Kanda2，Jacob Ellegood3，Jason P Lerch3，Yusuke Sotomaru2，Toru Takumi1,2 1Mental Biol., RIKEN　BSI，2Grad Sch Biomed & Health Sci, Hiroshima University，3Mouse Imaging Centre (MICe), The Hospital for Sick Children Toronto Human chromosome 15q25.2-25.3 microdeletion syndrome has recently been identified as one of the copy number variations (CNVs) associated with intellectual delay (ID) and mental retardation (MR) (Cooper et al., Nat. Genet., 2011). Patients with 15q25.2-25.3 microdeletion manifest variable clinical features, including mild motor delay, myopathy, mild cognitive deficits, and ASD (autism spectrum disorders). So far causal factors and mechanical evidences relevant to neuropsychiatric phenotypes have not been addressed. To analyze the consequence of 15q25.2-25.3 deletion, we developed an animal model of human 15q25.2-25.3 deletion by chromosome engineering. Although the mouse harboring 0.5 Mb deletion in chromosome 7 that corresponds to human 15q25.2-25.3 appeared normal and displayed no gross abnormalities so far, a series of behavioral analyses identified anxiety phenotypes in both open-field and elevated-plus maze tests. This model mouse, 15q25.2-25.3 del mouse, also showed behavioral inflexibility in reversal learning test of Barnes maze test although its hippocampal dependent spatial learning and memory tasks were normal. Furthermore, we performed brain imaging by 7-tesla Magnetic Resonance Imaging (MRI), and identified abnormalities in the cerebellar cortex in 15q25.2-25.3 del mice. Our analysis reveals that 15q25.2-25.3 deletion results in deficits in both behavioral and brain structure which may contributes to variable aspects of psychotic symptoms in patients with 15q25.2-25.3 deletion.