Graduate School of Frontier Biosciences, Osaka University

Japanese

Colloquium 199

Speaker Satomi Miyagawa (FBS Stem cell pathology / Associate professor)
Title Dnmt3L suppression by artificial piRNA production in male germ cells
Speaker Shinpei Yamaguchi (FBS Stem cell pathology / Assistant professor)
Title Molecular mechanism of the transition to 2 cell embryo-like state in ESC
Date Wed., November 14, 2018, 12:15~13:00
Place 2F Seminar room, BioSystems Building
Host Contact:Shinpei Yamaguchi(Assistant Professor, Laboratory of Stem Cell Pathology)
Tel :06-6879-3722
E-mail:yamaguchi@patho.med.osaka-u.ac.jp












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Title/Abstract

Dnmt3L suppression by artificial piRNA production in male germ cells

PIWI-interacting RNAs (piRNAs), germ cell-specific small RNAs, are synthesized from sense and anti-sense RNA containing Transposable Element (TE) sequences for retrotransposon silencing. piRNAs contribute to the methylation of TEs, which is important to spermatogenesis and fertile phenotype. In a previous study, we found that artificial sense and anti-sense RNA can induce a specific gene silencing by mimicking the natural piRNA system in the embryonic germ cells of transgenic mice. In the study, anti-sense Dnmt3L-expressing mice showed the DNMT3L-silencing phenotype with piRNA synthesis against Dnmt3L. Through whole genome sequencing, two transgene integration loci, were defined. With separated single-locus Tg-integrated mice, we investigated DNMT3L-silencing phenotypes in each Tg mouse. The suppressed DNMT3L phenotype was more severe in the Tg mice with a high copy number of the inserted transgene than those with a low one. Together, we concluded that artificial piRNA biosynthesis and piRNA-mediated silencing require a transgene copy number.

Molecular mechanism of the transition to 2 cell embryo-like state in ESC

Embryonic stem cell (ESC) sustains pluripotent state and genomic integrity through long-term culture. Recently, the minor population expressing 2-cell embryo-specific genes, including Zscan4 and MuERVL, was identified in ESC. Although the percentage of this 2-cell embryo-like (2CL) cell is only 0.5-2%, it is critical for the maintenance of telomere length, genomic integrity, and developmental competency. However, the molecular mechanism regulating the transition from non-2CL state to 2CL state was unclear. In this study, we found that ribosomal stress induced by the deletion of rRNA-processing gene Pum3 leads to significant increase in 2CL population. Furthermore, other type of stresses including UV irradiation and genotoxic drug administration also increased 2CL cell ratio. Importantly, increased 2CL population by these stresses was not observed in p53-KO ESC. Therefore, p53-dependent stress-induced transition to 2CL state is likely to play a role in the homeostasis of ESC.


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