RT Journal Article SR Electronic T1 Origin and segregation of the human germline JF Life Science Alliance JO Life Sci. Alliance FD Life Science Alliance LLC SP e202201706 DO 10.26508/lsa.202201706 VO 6 IS 8 A1 Castillo-Venzor, Aracely A1 Penfold, Christopher A A1 Morgan, Michael D A1 Tang, Walfred WC A1 Kobayashi, Toshihiro A1 Wong, Frederick CK A1 Bergmann, Sophie A1 Slatery, Erin A1 Boroviak, Thorsten E A1 Marioni, John C A1 Surani, M Azim YR 2023 UL http://www.life-science-alliance.org/content/6/8/e202201706.abstract AB Human germline–soma segregation occurs during weeks 2–3 in gastrulating embryos. Although direct studies are hindered, here, we investigate the dynamics of human primordial germ cell (PGCs) specification using in vitro models with temporally resolved single-cell transcriptomics and in-depth characterisation using in vivo datasets from human and nonhuman primates, including a 3D marmoset reference atlas. We elucidate the molecular signature for the transient gain of competence for germ cell fate during peri-implantation epiblast development. Furthermore, we show that both the PGCs and amnion arise from transcriptionally similar TFAP2A-positive progenitors at the posterior end of the embryo. Notably, genetic loss of function experiments shows that TFAP2A is crucial for initiating the PGC fate without detectably affecting the amnion and is subsequently replaced by TFAP2C as an essential component of the genetic network for PGC fate. Accordingly, amniotic cells continue to emerge from the progenitors in the posterior epiblast, but importantly, this is also a source of nascent PGCs.