Nakagawa Haruka, Ishizu Hirotsugu, Chinone Ayako, Kobayashi Kazuya, Matsumoto Midori
Department of Biological Sciences and Informatics, Keio University, Hiyoshi, Kouhoku-ku, Yokohama, Japan.
Int J Dev Biol. 2012;56(1-3):165-71. doi: 10.1387/ijdb.113433hn.
Homologs of nanos are required for the formation and maintenance of germline stem cell (GSC) systems and for gametogenesis in many metazoans. Planarians can change their reproductive mode seasonally, alternating between asexual and sexual reproduction; they develop and maintain their somatic stem cells (SSCs) and GCSs from pluripotent stem cells known as neoblasts. We isolated a nanos homolog, Dr-nanos, from the expressed sequence tags (ESTs) of the sexualized form of Dugesia ryukyuensis. We examined the expression of Dr-nanos in asexual and sexualized planarians by in situ hybridization and analyzed its function using RNA interference (RNAi) together with a planarian sexualization assay. A nanos homolog, Dr-nanos, was identified in the planarian D. ryukyuensis. Dr-nanos expression was observed in the ovarian primordial cells of the asexual worms. This expression increased in proportion to sexualization and was localized in the early germline cells of the ovaries and testes. In X-ray-irradiated worms, the expression of Dr-nanos decreased to a large extent, indicating that Dr-nanos is expressed in some subpopulations of stem cells, especially in GSCs. During the sexualization process, worms in which Dr-nanos was knocked down by RNAi exhibited decreased numbers of oogonia in the ovaries and failed to develop testes, whereas the somatic sexual organs were not affected. We conclude that Dr-nanos is essential for the development of germ cells in the ovaries and testes and may have a function in the early stages of germ cell specification, but not in the development of somatic sexual organs.
在许多后生动物中，nanos同源物对于生殖系干细胞（GSC）系统的形成和维持以及配子发生是必需的。涡虫可以季节性地改变其生殖模式，在无性生殖和有性生殖之间交替；它们从被称为新生细胞的多能干细胞发育并维持其体细胞干细胞（SSC）和生殖系干细胞（GCS）。我们从琉球枝肠涡虫有性化形式的表达序列标签（EST）中分离出一个nanos同源物，即Dr-nanos。我们通过原位杂交检测了Dr-nanos在无性和有性化涡虫中的表达，并使用RNA干扰（RNAi）结合涡虫有性化试验分析了其功能。在涡虫琉球枝肠涡虫中鉴定出一个nanos同源物Dr-nanos。在无性涡虫的卵巢原始细胞中观察到Dr-nanos的表达。这种表达随着有性化程度的增加而增加，并定位于卵巢和睾丸的早期生殖系细胞中。在X射线照射的涡虫中，Dr-nanos的表达大幅下降，表明Dr-nanos在某些干细胞亚群中表达，尤其是在生殖系干细胞中。在有性化过程中，通过RNAi敲低Dr-nanos的涡虫卵巢中的卵原细胞数量减少，并且无法发育出睾丸，而体性器官未受影响。我们得出结论，Dr-nanos对于卵巢和睾丸中生殖细胞的发育至关重要，并且可能在生殖细胞特化的早期阶段发挥作用，但对体性器官的发育没有作用。
