Fig. 1.

Schematic representation of human and mouse primordial germ cell development (PGC) in vivo (upper half of figure) with selected embryo models and embryonic organoids (lower half of figure; human drawings partially adapted from [114]). The different in vitro models are positioned with respect to their resembling features along the in vivo developmental timeline. Note that this is a tentative placement according to particular features of the in vitro systems as they are currently, and may not reflect the potential of each model in the future. Embryo models have been categorized according to their potential to address questions in primordial germ cell specification (blue), migration and epigenetic reprogramming (green), and gametogenesis (orange). Mm, Mus musculus (Mouse); Mf, Macaca fascicularis (Macaque); Hs, Homo sapiens (Human).