7月26日（金）9:30～9:50 第10会場（万代島ビル 6F 会議室）
2WD10bm2-1
Fat3は若齢期のミクログリア形態変化に重要である
Tomomi Okajima（岡島 智美），Ban Sato（佐藤 判），Tomoki Chiba（千葉 智樹），Fuminori Tsuruta（鶴田 文憲）
筑波大院 生命環境科学
Microglia, the resident immune cells in the central nervous systems (CNS), are vital for the normal development and function of the healthy brain. Recently works has revealed that microglia play a role in neuronal function during late stages of postnatal development. Remarkably, at a postnatal stage of development, microglia with different morphological and functional phenotypes are differentially located in different areas of the CNS. At early stages of development, microglia show an amoeboid shape with few processes, which is characteristic of immature microglia. Their morphology is incessantly evolving from amoeboid shapes to completely ramified surveilling microglia at juvenile stages. In developmental stage, microglia located at their destination gradually differentiate into ramified shapes. However, the mechanisms directing the conversion toward a mature phenotype are still poorly understood.
Here, we show that a protocadherin family Fat3 is a novel candidate that support for the microglial maturation. We found that microglia cell line BV-2 exhibit dynamically extending and retracting their thin protrusions under high nutrient medium (HNM) condition, DMEM/F12. In addition, we observed that BV-2 microglia cells increase the morphology with protrusions under HNM condition compared to standard condition, DMEM. Using DNA microarray analysis, we identified that expression of Fat3 is upregulated by culturing BV-2 under HNM condition. Knockdown of Fat3 decreased the microglial protrusions, demonstrating that Fat3 is necessary for inhibiting the retraction of these processes. Additionally, we have developed an in vitro screening system and identified that hypoxanthine induces Fat3 expression at the proximal region of microglial processes and hampers the retraction of their processes. Finally, we generated mice that lack Fat3 expression. We observed a significant decrease the P2Y12 expression in P17 microglia. As a result, Fat3 deficient mice delayed their microglial maturation. These results suggested that hypoxanthin-Fat3 axis is a novel pathway to regulate microglial morphogenesis. Our finding provide that Fat3 expression regulated by hypoxanthine turnover controls microglial morphogenesis during the developmental stages. | | 7月26日（金）9:50～10:10 第10会場（万代島ビル 6F 会議室）
2WD10bm2-2
発達過程における微小核を介した神経細胞―ミクログリア間の情報伝播
Sarasa Yano（矢野 更紗），Sato Ban（佐藤 伴），Tomoki Chiba（千葉 智樹），Fuminori Tsuruta（鶴田 文憲）
筑波大院 生命環境科学
The formation of the proper neuronal circuit during later developmental stages is crucial for the brain functions. Microglia critically contribute to the conditioning brain environment through phagocytosing cell debris or damaged neurons. In response to the secreting factor from the damaged neurons, microglia transform into active phagocytic forms, migrate, and accumulate around the target cells. When microglia sense exposed eat-me signals, they recognize and eliminate the target cells, contributing to the establishment of proper neuronal circuit. However, the mechanism by which microglia recognize and remove the damaged neurons during development has not been fully understood.
Here, we proposed that the micronuclei are secreted from neurons during the developmental stage, followed by regulating microglia activity. We found that micronuclei emerge in neurons during embryonic stages and are cleared by the autophagic pathway. Inhibition of autophagy induces to the accumulation of micronuclei in neurons, followed by the secreting them to extracellular region. Interestingly, treatment microglia with neuronal conditioned medium accumulates micronuclei. On the other hand, this effect was lost by the filtration of neuronal conditioned medium, implying that the large extracellular factors, such as micronuclei, are taken by microglia directly. Using the NexCre;SUN1-sGFP-Myc mice which is a neuron-specific nuclear membrane labeling mouse, we identified that some micronuclei in microglia could originate from the micronucleus exported from neuron. Taken together, these data provide evidence that micronucleus is a novel factor involved in the neuron-microglia communications to maintain the brain environment, and suggest a possibility that they act as a novel microglia-activating factor that underlies the development of the brain. |
