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In Vitro Generation of Germ Cells: New Techniques to Solve Current Issues
aGraduate Program of Biological and Biomedical Sciences, Harvard Medical School, Boston, Massachusetts 02115, USA bHarvard Medical School, Center for Regenerative Medicine and Technology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
Address for correspondence: Niels Geijsen, Center for Regenerative Medicine and Technology, Massachusetts General Hospital, CPZN-4264, 185 Cambridge Street, Boston, MA 02114. Voice: 617-724-6013; fax: 617-724-2662. ngeijsen{at}partners.org
Primordial germ cells comprise a privileged cellular class within the embryo charged with the elite task of maintaining species longevity. While in lower organisms germ-cell fate is determined by the allocation of germ plasm, mammalian germ-line differentiation requires extracellular signals that converge upon the proximal epiblast. Studies using mutant mice or explanted embryos have identified some of the factors controlling primordial germ-cell specification, such as members of the BMP family, but considerable gaps still exist in our understanding of the complete signaling network. Comprehensive investigations of mammalian germ-line specification have been hampered by the inaccessibility of this cell population in the early embryo. Recently, however, several labs including our own have derived primordial germ cells from embryonic stem cells in vitro, thus providing a powerful new technique for the study of germ cells. In this review the different methods used for the in vitro generation of germ cells and how these techniques may be improved and applied to further advance our knowledge of germ-cell biology are discussed.
Key Words: primordial germ cells • embryonic stem cells • differentiation • bone morphogenic proteins • germ-line • mammals
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