|Budget Amount *help
¥6,300,000 (Direct Cost : ¥6,300,000)
Fiscal Year 1997 : ¥2,500,000 (Direct Cost : ¥2,500,000)
Fiscal Year 1996 : ¥3,800,000 (Direct Cost : ¥3,800,000)
Mouse primordial germ cells appear at the base of allantois in the posterior extraembryonic region, migrate to the genital ridges, and differentiate into oocytes or prospermatogonia in the fetal ovary or testis. We carried out the following experiments to study mechanisms in the development and differentiation of fetal germ cells.
There have been no culture system of fetal germ cells after arrival at gonads, because they go into apoptosis and disappear in usual culture conditions. We developed novel methods of sexing embryos, isolation of germ cells with magnetic beads, and detection of meiotic cells with specific antibodies. As a result, we detected many germ cells entering into meiotic prophase in our culture system.
Mammalian sex-determination and differentiation is controlled by several genes, such as Sry, Sox-9, Dax-1 and Ad4BP/SF-1, but their upstream and downstream genes are largely unknown. In order to identify these genes involved in the sex-differentiation, we carried out the differential hybridization of the mouse embryonic gonad cDNA library using presumably male-specific probes. We identified nephgonadin, which encodes a basic helix-loop-helix motif. The earliest expression of nephgonadin was observed at 8.5 days post coitum (dpc) in the intermediate mesodermal tissues of anterior and posterior parts of the mouse embryo. The posterior expression continued until this region forms the urogenital ridge. From 13.5 dpc to 2 weeks postnatal, nephgonadin was expressed at higher levels in the male than female gonad. In adults, however, expression of nephgonadin was drastically decreased in the testis, while it was increased in the ovary. These sex- and stage-dependent expression patterns are similar to that of Ad4BP/SF-1, which is important for the development and sex-differentiation of the gonad.