公募シンポジウム

公募シンポジウム脳神経系の発生と病理、そして性差

7月6日（木）　9:00-11:00　Room G 1SY③-1 マウス胎仔脳における分子プログラムの性差 Sex differences of molecular program in the murine embryonic brain 吉川　貴子, 眞鍋　柊, Sara Ebrahimiazar, 越智　翔平, 大隅　典子東北大学　院医　発生発達神経科学 Takako Kikkawa, Shyu Manabe, Sara Ebrahimiazar, Shohei Ochi, Noriko Osumi Dept. of Dev. Neurosci., Tohoku Univ. Grad. Sch. of Med., Sendai, Japan Brain structure exhibits sex dimorphisms, proposed that perinatal exposure to the sex hormone is a primary trigger for the sexual differentiation of the brain, while gene expression patterns in the rodent embryonic brain are different between male and female, implying that the difference may have already begun prior to the critical period. However, it is unknown how and when the sex difference is generated through brain development. To identify molecular mechanisms leading to the sexual differentiation of the brain, we performed RNA-seq using the male and female mouse telencephalons at embryonic days (E) 11.5 and E14.5. The RNA-seq data show a large number of differentially expressed genes (DEGs) between males and females, although the number of DEGs between sexes were fewer at E11.5. These results suggest that sex differences in molecular profiles of the embryonic brain emerge between E11.5 to E14.5 when the neurogenesis of mice actively occurs. A recent study revealed that genes associated with neurodevelopmental disorder (NDD) regulate neurogenesis in the embryonic brain (Willsey et al., 2021). Since the pathogenesis of the NDD, e.g., autism spectrum disorder (ASD), exhibits sex differences, we will discuss how differences in molecular mechanisms influence the sexual dimorphism of NDD during brain development based on our analyses on the RNA-seq data.		7月6日（木）　9:00-11:00　Room G 1SY③-2 常染色体のDNAメチル化性差と精神疾患の関連について Sex differences in autosomal DNA methylation and its implications for psychiatric disorders 岩本　和也熊本大学大学院生命科学研究部分子脳科学講座 Kazuya Iwamoto Department of Molecular Brain Science, Graduate School of Medical Sciences, Kumamoto university Accumulating evidence suggests that robust sex differences in DNA methylation exist not only sex chromosomes but also autosomes. Although these may contribute to the sex-associated traits in psychiatric disorders, few studies have conducted a systematic approach to explore this relationship. In site-specific DNA methylation analysis, we have often experienced that some CpG sites showed large DNA methylation differences between males and females, and such sites showed sex-specific DNA methylation changes in case-control study of psychiatric disorders. Motivated by this observation, we have systematically surveyed sex-associated autosomal DNA methylation differences using the whole genome single-nucleotide resolution data, and characterized its pathophysiological significance in psychiatric disorders. In this symposium. I will present the current understanding of sex differences in DNA methylation and their possible roles in psychiatric disorders with our recent results.

7月6日（木）　9:00-11:00　Room G 1SY③-3 ヒト・非ヒト脳を分けるノンコーディングRNAの機能 non-coding RNA functions that differentiate human and mouse brain 今村　拓也広島大学　統合生命　生命医科 Takuya Imamura Prog of Biomed Sci, Grad Sch of Integr Sci for Life, Hiroshima Univ, Higashi-Hiroshima, Japan In this study, we induced neural stem cells (NSCs) from female human and chimpanzee iPSCs in vitro by direct neurosphere formation and analyzed time-series transcriptome data. We reconstructed early neurogenesis of humans and chimpanzees in similar inductive conditions. We found that the progression of neurogenesis was indeed delayed in humans. In human NSCs, dorsal markers of the cerebrum tended to have high expression in chimpanzees while ventral markers of the cerebrum tended to have high expression, indicating that human NSCs are easier committed to ventral fate compared with chimpanzees. Notably, biased expression of ribosomal proteins reflects species-specific metabolic states during neurodevelopment, that may have affected brain expansion in mammals. We profiled the expressions of hundreds of species-specific promoter-associated non-coding RNA (pancRNA) that potentially differentiated gene-specific epigenetic regulation. pancRNAs positively correlated their partnered genes in terms of their expressions in line with our previous finding that pancRNA activates the partner gene expression. We also found several differences between the transcriptomes of female and male stem cells. In this symposium, I will discuss prevailing effects of the sex- and species-dependent timescale of neurodevelopment and differentiation of metabolic states.		7月6日（木）　9:00-11:00　Room G 1SY③-4 内在性DNAを介した広汎性発達障害レット症候群発症のメカニズム Involvement of endogenous DNA-mediated microglial activation in the pathogenesis of Rett syndrome 中島　欽一九州大学大学院　医学研究院 Kinichi Nakashima Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan Rett syndrome (RTT) is a severe neurological disorder with impaired brain development caused by mutations in methyl-CpG binding protein 2 (MECP2). We observed an increased number of activated microglia in the perinatal hippocampus of MeCP2 knockout (KO) RTT model mice, yet the mechanism underlying the activation has yet to be elucidated. Previously, we reported an increase in expression and transposition of a retrotransposon, long interspersed nuclear element 1 (L1) in the MeCP2KO brain. In addition, we have found that endogenous DNAs activate microglia in the brain through DNA-recognizing Toll like receptor 9 (TLR9). Taking these findings into account, we hypothesized that L1cDNA-TLR9-microglial activation pathway could be involved in the onset of RTT. Here we show that crossing MeCP2 KO and TLR9 KO mice leads to extension life span and amelioration of RTT symptoms in MeCP2 KO mice. We further demonstrate that treatment with reverse transcriptase inhibitors to prevent L1 cDNA synthesis prolonged the longevity and alleviated RTT symptoms in MeCP2 KO mice. Altogether, these findings suggest the involvement of endogenous DNA-TLR9-microglial activation axis in the RTT pathogenesis and potentially uncovers an additional layer of this complex and devastating developmental disease.

7月6日（木）　9:00-11:00　Room G 1SY③-5 Ptf1a遺伝子が脳の発生と性分化に果たす役割 Function of Ptf1a in the brain development and sex differentiation 星野　幹雄国立精神神経医療研究センター神経研究所 Mikio Hoshino National Center of Neurology and Psychiatry, National Institute of Neuroscience We previously investigated mouse mutants lacking the cerebellum and identified Ptf1a (Pancreas transcription factor 1a), as the causative gene. Our extensive analysis revealed that the PTF1a protein acts as a fate determinant of cerebellar inhibitory neurons. Furthermore, we found that PTF1a is involved in the development of climbing fiber neurons in the inferior olivary nucleus and inhibitory neurons in the cochlear nucleus. The mammalian brain is known to undergo gonadal hormone-induced sex differentiation during the perinatal critical period. However, the machinery before the critical period has not been well studied. PTF1a was found to be expressed in specific neuroepithelial cells within the third ventricle, which give rise to various neurons in the several nuclei of the hypothalamus. We found that conditionally Ptf1a deficient mice (Ptf1a cKO) exhibit sex-specific behavioral and reproductive organ abnormalities. By administration of gonadal hormones to gonadectomized animals, abnormal behavior was found to be due to disrupted sexual development in the mutant brain (not reproductive organ malfunction). These findings suggest that hippothalamic Ptf1a is one of the earliest regulators for brain sex differentiation.