哺乳類脳神経幹細胞の特性の経時変化を制御するエピゲノム修飾と細胞間シグナルの研究

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In the last year, Wu continued to analyze the function of Fibrillarin in temporal fate change of neural stem cells (NSCs). As a result, Wu found that RNAi-mediated knockdown of Fibrillarin to ~50% at proliferative stage promoted premature neuronal differentiation of NSCs. Consistently, the activity of Notch signaling which is important for self-renewal of NSCs was strongly reduced after knockdown of Fibrillarin. In contrast, overexpression of Fibrillarin increased the population of NSCs. These results suggest that Fibrillarin is essential for proliferation of NSCs. Next, Wu tried to uncover the mechanism by which Fibrillarin affects the fate of NSCs. Because Fibrillarin is a methyltransferase of rRNA and methylation level of rRNA may affect translation, Wu asked that whether knockdown of Fibrillarin affects global protein translation or only impacts on specific targets. Using chemical probe to trace newly synthesized protein, Wu confirmed that RNAi-mediated knockdown of Fibrillarin to ~50% did not affect global protein translation. These results imply that Fibrillarin regulates cell fate through preferentially translating of target mRNAs. Then, to search the targets of Fibrillarin, Wu, cooperating with Dr. Iwasaki Shitano, performed ribosome profiling, a novel method to detect translating mRNAs based on deep-sequencing. Even this experiment is still ongoing, I think that results of this experiment will help us to better understand how NSC fate is precisely controlled. After finish of JSPS fellowship, Wu will continue to complete this project in my lab.