TOP ＞ Symposium

Symposium 1 Lessons obtained from analyses of rare genomic variants and future perspective シンポジウム1 精神疾患のゲノム要因における稀な変異の意義と方向性について SY1-1 A rare schizophrenia-associated variant identified from mouse QTL analysis マウスQTL解析から同定した統合失調症関連の稀な遺伝子多型 Yoshikawa Takeo（吉川 武男） RIKEN Center for Brain Science Prepulse inhibition (PPI) is deemed to be an endophenotype of psychiatric illnesses, in particular schizophrenia. Previously we reported a QTL (quantitative trait loci) study of PPI using mice. Here, we re-performed the QTL analysis using exonic variants in mice to narrow down to single functional responsible variants. We identified the A753G of Chd23 gene. The polymorphism is a synonymous but is reported to affect alternative splicing of exon 9. A database search detected a syntenous SNP in human, and the SNP is associated with schizophrenia. Further we re-sequenced the CDH23 gene and its close partner PCDH15 gene using the molecular inversion probe method and schizophrenia samples. We identified multiple rare and possibly damaging variants of the two genes in schizophrenia. These results suggest that the rare variants of the CDH23 and PCDH15 genes could contribute to the risk of schizophrenia. SY1-2 Lessons from the comprehensive analysis of rare variants of a mitochondria-related gene in bipolar disorder 双極性障害におけるターゲットシーケンスで同定した稀な変異を生化学的解析やコンピューター予測などを組み合わせて評価してみた Kasahara Takaoki（笠原 和起） RIKEN Center for Brain Science Rare variants, low-frequency variants, and common variants, as well as de novo mutations, must jointly compose the genetic architecture of common complex disease. Advances in sequencing technology enable us to identify an enormous number of these variants; however, the impact of each variant on disease development is difficult to demonstrate. Even the impact of a variant on the gene function (for example, enzymatic activity of the encoded protein) is difficult and laborious to study. Currently, 'likely gene-disrupting' variants, which include nonsense, frame-shift and canonical splice-site mutations, and causative mutations for Mendelian diseases are solely considered in many studies. We aimed to examine the impacts of missense variants, as an example and proof of concept, of the POLG1 gene found in patients with bipolar disorder. POLG1 encodes mitochondrial DNA polymerase and is one of causative genes for a Mendelian-inheritance mitochondrial disease, which is occasionally accompanied by mood disorders. We searched for variants in POLG1 gene in 797 Japanese patients with bipolar disorder and 767 controls and comprehensively investigated all of 23 identified variants in three different modalities of assessment: in-silico predictions, in-vitro biochemical assays, and in-vivo clinical evaluation. Although the frequency of carriers of deleterious variants varied from one method to another, every assessment achieved the same conclusion that deleterious POLG1 variants were significantly enriched in the variants identified in patients with bipolar disorder compared to those in controls. In my talk in this symposium, I would like to discuss about the potency and limitation of the variant effect prediction programs. SY1-3 Rare variant analysis of neuropsychiatric disorders and its interpretation 精神神経疾患のrare variant解析とその解釈 Takata Atsushi（高田 篤） Department of Human Genetics, Yokohama City University Graduate School of Medicine 2000年代半ばから次世代シーケンサーが普及したことに伴い、例えば数千人に一人でしか認められないような稀な変異についても、網羅的な解析を行うことが可能となった。一方、遺伝子変異はゲノム中に無数に存在し、その中には、一見すると病的意義を有するように思える変異が多数含まれる。例えば、（重篤な疾患が明らかでない）一般集団においても、ヒト一人あたり、遺伝子機能を完全に喪失させるような変異（loss-of-function [LOF] 変異）が平均100個程度認められることが報告されている（MacArthur et al., Science 2012）。そのため、rare variantの解析から、真に疾患と関連する遺伝子・遺伝子変異を同定することや、正しく生物学的意義を引き出すことは、それほど簡単ではない。本演題では、rare variantのゲノムデータを適切に解釈し、有意義に活用するために構築された種々のフレームワーク、データソースについて概観する。さらに、精神神経疾患のrare variant研究によって得られた成果について、演者自身が携わった研究を含めて紹介したい。 SY1-4 CHD8 haploinsufficiency results in autistic-like phenotypes in mice クロマチンリモデリングタンパク質CHD8のハプロ不全は自閉症スペクトラムの原因となる Nishiyama Masaaki（西山 正章）1，中山 敬一2 1Dept. Hist. Cell Biol., Grad. Sch. Med. Sci., Kanazawa Univ. 2Dept. Mol. Cel. Biol., Med. Inst. Bioreg., Kyushu Univ. Autism spectrum disorder (ASD) comprises a range of neurodevelopmental disorders characterized by deficits in social interaction and communication as well as by restricted and repetitive behaviours. ASD has a strong genetic component with high heritability. Exome sequencing analysis has recently identified many de novo mutations in a variety of genes in individuals with ASD, with CHD8, a gene encoding a chromatin remodeller, being most frequently affected. Whether CHD8 mutations are causative for ASD and how they might establish ASD traits have remained unknown. We showed that mice heterozygous for Chd8 mutations manifest ASD-like behavioural characteristics including increased anxiety, repetitive behaviour, and altered social behaviour. CHD8 haploinsufficiency did not result in prominent changes in the expression of a few specific genes but instead gave rise to small but global changes in gene expression in the mouse brain, reminiscent of those in the brains of patients with ASD. Gene set enrichment analysis revealed that neurodevelopment was delayed in the mutant mouse embryos. Furthermore, reduced expression of CHD8 was associated with abnormal activation of RE-1 silencing transcription factor (REST), which suppresses the transcription of many neuronal genes. REST activation was also observed in the brains of humans with ASD, and CHD8 was found to interact physically with REST in the mouse brain. Our results are thus consistent with the notion that CHD8 haploinsufficiency is a highly penetrant risk factor for ASD, with disease pathogenesis probably resulting from a delay in neurodevelopment. SY1-5 Lessons from the sequencing study of genes for neurodevelopment in Schizophrenia 統合失調症における神経発達機能関連遺伝子のrare variant解析 Kimura Hiroki（木村 大樹），Branko Aleksic，尾崎 紀夫 Nagoya University, Graduate School of Medicine, Department of Psychiatry Recent large-scale whole genome sequencing and copy-number variant (CNV) analysis with Schizophrenia (SCZ) and Autism Spectrum disorder (ASD) samples have revealed that rare single-nucleotide variants (SNVs) and CNV exert significantly larger effects than common single-nucleotide polymorphisms (SNPs). Despite large effect size of the CNV, the pathological roles of CNV remains largely unknown, partially because it remains unclear how the functional change of the genes within the regions of the CNVs lead to the pathogenesis of neuropsychiatric disorders. On the other hand, there is growing evidence that rare SNVs, discovered from deep sequencing of SCZ candidate genes, may have large effect sizes, as well as contribute to understanding of the pathogenesis of neuropsychiatric disease through in vitro and in silico functional analysis. Therefore, in order to discover novel rare SNVs with large effect size and to evaluate the pathogenesis of the discovered mutations, we conducted the sequencing study of the genes involved in neurodevelopment from our CNV analysis using the Next Generation sequencing (Thermo Fisher Scientific Ion PGM) with the Japanese SCZ and ASD samples, performed genetic association analysis using a large number of unrelated individual, and performed in silico and in vitro functional assays of the variants that could have large effects. Through the sequencing study we performed , we found that rare SNV in genes related to neurodevelopment（NDE1, RTN4R） may have functional relevance for the pathophysiology of SCZ. In future research, a sequencing study that examines neurodevelopmental genes more comprehensively will be needed. In this symposium, I will discuss about the lessons from the sequencing study of genes for neurodevelopment in SCZ.