From stem cells to germ cells and from germ cells to stem cells

Germline and somatic stem cells are distinct types of stem cells that are dedicated toreproduction and somatic tissue regeneration, respectively. germline stem cells (gscs),which can self-renew and generate gametes, are unique stem cells in that they are solelydedicated to transmit genetic information from generation to generation. we developeda strategy for the establishment of germline stem cell lines from embryonic stem cells(es) . these cells are able to undergo meiosis, generate haploid male gametes in vitroand are functio nal, as shown by fertilization after intra-cytoplasmic injection into mouseoocytes. in other approach, we show that bone marrow stem (bms) cells are able totrans-differentiate into male germ cells. bms cell-derived germ cells expressed theknown molecular markers of primordial germ cells. the ability to derive male germcells from es and bms cells reveals novel aspects of germ cell development and opensthe possibilities for use of these cells in reproductive medicine. conversely, we showedthat adult male germline stem cells, spermatogonial stem cells (sscs), can be convertedinto embryonic stem cell like cells which can differentiate into the somatic stem cells ofthree germ layers. understanding how ssc can give rise to pluripotent stem cells andhow somatic stem cells differentiate into germ cells could give significant insights intothe regulation of developmental totipotency as well as having important implications formale fertility and regenerative medicine.