日本一个研究小组日前发现，在雌鳉鱼的卵巢内存在可发育成鳉鱼卵的干细胞。有关成果已经刊登在最新一期的美国《科学》杂志网络版上。

这一成果是日本自然科学研究机构基础生物学研究所的研究人员获得的。基础生物学研究所日前发表公告说，在脊椎动物中，已经发现雄性的精巢中存在发育成精子的干细胞，但是在卵巢中发现会发育成卵的干细胞则属世界首次。

研究小组对雌性鳉鱼进行基因操作，使其卵巢内的卵发出红光，结果发现了很多即将发育为卵的细胞。利用绿色荧光蛋白质给这些细胞做上标记以后，研究人员发现许多新形成的卵也会发出绿色荧光，这说明这些细胞的确发育成了卵，因此这些细胞就是干细。

鳉鱼等鱼类会大量产卵，但是详细机制一直没有弄清。研究小组成员田中实指出，他们的新发现可能为开发高效的养殖技术作出贡献。

Science DOI: 10.1126/science.1185473

Identification of Germline Stem Cells in the Ovary of the Teleost Medaka
Shuhei Nakamura,1 Kayo Kobayashi,1 Toshiya Nishimura,1,2 Shin-ichi Higashijima,3,4 Minoru Tanaka1,2,*

Germline stem cells continually produce sperm in vertebrate testes, whereas there is no direct evidence showing that germline stem cells are present in adult vertebrate ovaries. Using transgenic methods and clonal analysis, we identified germline stem cells that supported oogenesis and the production of offspring in the ovaries of adult medaka fish. Early-stage germ cells were localized in clusters along interwoven threadlike cords of sox9b-expressing somatic cells (termed "germinal cradles") where the germ cells developed. Germline stem cells gave rise to germ cells that divided to produce cysts, which then underwent cell death or separated to form follicles. Our results provide insight into germline stem cell biology of medaka and provide a model system for studying vertebrate stem cell niches.

1 Laboratory of Molecular Genetics for Reproduction, National Institute for Basic Biology, Okazaki 444-8787, Japan.
2 Department of Basic Biology, Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi 444-8585, Japan.
3 National Institutes of Natural Sciences, Okazaki Institute for Integrative Bioscience, National Institute for Physiological Sciences, Okazaki, Aichi 444-8787, Japan.
4 Department of Physiological Sciences, Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi 444-8585, Japan.