Summary of Research Project Results Under the JSPS FY2000
"Research for the future Program"

1.Research Institution University of Tsukuba
2.Research Area Life Science
3.Research Field Organism Constructing Mechanisms
4.Term of Project FY1996〜FY2000
5.Project Number 96L00402
6.Title of Project Mechanisms underlying germ line development

7.Projetct Leader
Name Institution,Department Title of Position
Satoru Kobayashi Inst. of Biological Sciences, Univ. of Tsukuba Assistant Prof.

8.Core Members

Names Institution,Department Title of Position
Yumiko Saga Cellular & Molecular Toxicology Division National Institute of Health Sciences Project Leader

9.Cooperating Researchers

Names Institution,Department Title of Position
Takahiro Akiyama College of Environmental Health Azabu University Research Associate

10.Summary of Research Results

1. In Drosophila embryos, mitochondrial large and small ribosomal RNAs transported from mitochondria to polar granules form mitochondrial ribosomes on the granules. Since these ribosomes are integrated into polysomes on the surface of polar granules, we speculate that mitochondrial ribosomes are required for translation of mRNA(s), which encodes pole cell forming factors. Our preliminary result suggests that one of the candidates for the target mRNA is germ cell-less mRNA..
2. We show that Nanos protein inhibits the expression of somatically-transcribed gene (fushi tarazu) in pole cells by repressing Importin α2/Oho31-dependent nuclear import of its transcriptional activator.
3. We further shows that Nanos inhibits apoptosis of pole cells during their migration to the embryonic gonads.
4. We identify a novel serine/threonin kinase (STK) gene, which encodes two transcripts enriched in polar plasm and pole cells. While the shorter transcript is observed only in pole cells, the longer one is additionally detectable in somatic cells. The longer transcript encodes STK, but the shorter one encodes a truncated form of STK lacking kinase domain. Based on these results, we speculate that the truncated STK act as a dominant-negative repressor for STK function in pole cells.

11.Key Words

(1)Germ cells、(2)Mitochondria、(3)Drosophila
(4)mouse、(5)germ line determinant


[Reference Articles]
Author Title of Article
T. Mochizuki Expression and evolutionary conservation of Hydra nanos related genes
Journal Volume Year Pages Concerned
Develop. Genes and Evolution 210 2000 591-602

Author Title of Article
M. Kashikawa Mitochondrial small ribosomal RNA is a component of germinal granules in xeuopus embryos
Journal Volume Year Pages Concerned
Mech. Dev. (in press)      

Author Title of Article
A. Nakamura Translational silencing mediated by Me31B, a component of the cytoplasmic RNP complex・・・・
Journal Volume Year Pages Concerned
Development (in press)