Germ cell differentiation in culture
2003
Noce, T. (Mitsubishi Kasei Inst. of Life Sciences, Machida, Tokyo (Japan))
The generation of animals cloned by means of the nuclear transfer technique indicates that somatic cell nuclei can be reprogrammed when they are transplanted into the egg cytoplasm--in other words, the transplanted somatic nuclei can be induced to return to a pluripotent state similar to that of the nuclei of fertilized eggs. Therefore, the potential for both reprogramming and pluripotency is retained in germ cells throughout their development. For example, embryonic germ (EG) cells that are generated from primordial germ cells (PGCs) show similar pluripotency to the undifferentiated embryonic stem (ES) cells that originate in the inner cell mass of blastocyst embryos in mice [1]. And some teratomas that generate differentiated cells of various types--from all three primary germ layers--originate in PGCs in the embryonic gonads [2]. Therefore, germ cells must have the ability to be reprogrammed, as well as to differentiate to form gametes. So how do germ cells acquire these characteristics, and how are they maintained during development? The discovery of the molecular and cellular mechanisms that are involved in these processes will provide important insights not only for basic research into reproductive biology but also for the development of new techniques for regenerative medical treatments. There is an urgent need to develop in vitro systems that can model the entire developmental process--from pluripotent stem cells to functional sperm and eggs--to further our understanding of the mechanisms of germ-cell differentiation.
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