Stem cells play a central role in generating and maintaining most adult tissues in higher organisms. They are defined by their ability to self-renew and to produce numerous differentiated daughter cells. The stem-cell properties are maintained in the adult tissues by a special microenvironment called “niche”. However, how stem cell fate and niche are initially established during tissue development is currently unknown. The Drosophila ovary provides an excellent opportunity to study the establishment of the stem cell fate and the niche cell fate in individual tissues. This is because the germline in Drosophila ovary is well characterized as a tissue lineage and stem cells in the germline (GSCs) and its niche are well characterized at a cellular level in the adult ovary. Using these advantages and our cell-transplantation technique, we have done a lineage tracing of individual primordial germ cells (PGCs) and found that PGCs destined to become stem cells locate in the sub region of the embryonic gonads. This suggests the existence of a niche for GSC fate establishment in the embryonic gonads. We identified and are currently studying some genes which function in sub region of somatic embryonic gonads to regulate GSC and niche cell fate establishment.

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Somatic cells in the embryonic gonad provide a “niche” for the formation of germline stem cells in Drosophia. A: normal ovary. B-C: Genetic knock down of niche function results in the absence of germline stem cell in the adult ovary. magenta: germ cells. green: somatic cells.
生殖幹細胞の形成には，胚期の生殖巣の体細胞によって作られる微小環境（ニッチ）が必要である．A：正常な卵巣．B-C：ニッチ機能を阻害すると，生殖細胞（マゼンタ）をほとんど持たない卵巣が形成される．