The early development of germ cells in chicken.

Primordial germ cells (PGCs) are the founder cells for mature gametes, the vehicles by which individuals transmit genetic and epigenetic information to later generations. Since the 19 century, avian species (chickens in particular) have been widely used for germ cell research. Previous studies have used chicken PGCs for a variety of research applications, including as a model for studies focusing on germline development. Other applications of chicken PGCs, including conservation efforts for avian species and methods of producing transgenic birds, have further reinforced the importance of these cells. However, much remains to be revealed about the origin and role of PGCs during their development in the chicken. Here, we provide a comprehensive review of chicken PGCs, focusing in particular upon their initial profiles and physiological changes during development as regulated by environmental factors and/or intrinsic mechanisms. We also emphasise sex-dependent differences in PGC development after settlement within the gonads, as well as future applications for avian PGCs.