Germline and somatic stem cells are distinct types of stem cells that
are dedicated to reproduction and somatic tissue regeneration,
respectively. Germline stem cells (GSCs), which can self-renew and
generate gametes, are unique stem cells in that they are solely
dedicated to transmit genetic information from generation to
generation. We developed a 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 vitro and are
functional, as shown by fertilization after intra-cytoplasmic injection
into mouse oocytes. In other approach, we show that bone marrow stem
(BMS) cells are able to trans-differentiate into male germ cells. BMS
cell-derived germ cells expressed the known molecular markers of
primordial germ cells. The ability to derive male germ cells from ES
and BMS cells reveals novel aspects of germ cell development and opens
the possibilities for use of these cells in reproductive medicine.
Conversely, we showed that adult male germline stem cells,
spermatogonial stem cells (SSCs), can be converted into embryonic stem
cell like cells which can differentiate into the somatic stem cells of
three germ layers. Understanding how SSC can give rise to pluripotent
stem cells and how somatic stem cells differentiate into germ cells
could give significant insights into the regulation of developmental
totipotency as well as having important implications for male fertility
and regenerative medicine