1. Preformation and induction models of PGC specification.
Preformation and induction models of PGC specification. Schematic representation of the two modes of germ cell specification. (A) Preformation, as occurs in Drosophila. The nurse cells synthesise RNAs and proteins (pink) that are localised to the posterior pole of the oocyte. This germ plasm will be segregated into PGCs. (B) Induction, as occurs in the mouse. Signals from the extra-embryonic ectoderm (grey) induce the formation of PGCs (dark pink) from within pluripotent epiblast (red). Non-induced cells (green) go on to form the soma. ExE, extra-embryonic ectoderm; VE, visceral endoderm (brown). Adapted from Extavour and Akam (Extavour and Akam, 2003).
Harry G. Leitch, and Austin Smith Development 2013;140:
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