Dr. Toshie Kai （Temesek Lifesciences Laboratory, Singapore）

2009年10月09日(金) 12:00 より 13:00 まで

山手地区３号館９階セミナー室B

Division of Developmental Genetics Satoru Kobayashi 内線5875

The most important cell lineage for the survival of sexually reproducing metazoans is the germline, due to its unique role in gamete production and species continuity. The fidelity of genomic information in the germline has to be tightly regulated for accurate transmission to the next generation. In many animal germline cells, Piwi-interacting RNAs (piRNAs) are reported to silence the expression of one class of mobile genetic elements, retroelements, whose transposition may afflict the genome with mutational burden. We and others have proposed that nuage, a well-conserved perinuclear organelle found in germline cells, may be the sites where piRNAs are generated in a feed-forward loop, called ping-pong cycle. I will introduce our recent findings supporting this model. Proteins required for biogenesis of piRNAs, including Piwi-subfamily argonaute proteins such as Aubergine and Argonoute3, assemble at perinuclear region as a large complex to produce piRNAs. We also found that a large cytoplasmic RNP, which contain components of the perinuclear nuage as well as those of the mRNA processing body, appears to participate in post-transcriptional silencing of retrotransposons. Some nuage components have functions other than the repression of retroelements. Among those, I will talk about our recent finding on the nuclear function of Maelstrom; It regulates bam expression via miR-7 to ensure proper differentiation of the germline stem cell lineage. In the end, I also discuss our exciting findings unveiling an unknown function of a nuage component, Vasa, and piRNAs in cell cycle. References Lim AK, Tao L and Kai T: The Journal of Cell Biology (186): 333–342 (2009) Pek JW, Lim, AK and Kai T: Developmental Cell. In press