title: Primordial germ cell development in the marmoset monkey as revealed by pluripotency factor expression: suggestion of a novel model of embryonic germ cell translocation.
abstract: Primordial germ cells (PGCs) are the embryonic progenitors of sperm and egg cells. Mammalian PGCs are thought to actively migrate from the yolk sac endoderm over long distances across the embryo to reach the somatic genital ridges. The general principles of mammalian PGC development were discovered in mice. In contrast, little is known about PGC development in primates due to extremely limited access to primate embryos. Here, we analyzed 12 well preserved marmoset monkey (Callithrix jacchus) embryos covering the phase from PGC emergence in the endoderm to the formation of the sexually differentiated gonad (embryonic day (E) 50 to E95). We show using immunohistochemistry that the pluripotency factors OCT4A and NANOG specifically mark PGCs throughout the period studied. In contrast, SALL4 and LIN28 were first expressed ubiquitously and only later down-regulated in somatic tissues. We further show, for the first time, that PGCs are located in the endoderm in E50 embryos in close spatial proximity to the prospective genital ridge, making a long-range migration of PGCs dispensable. At E65, PGCs are already present in the primitive gonad, while significantly later embryonic stages still exhibit PGCs at their original endodermal site, revealing a wide spatio-temporal window of PGC distribution. Our findings challenge the 'dogma' of active long-range PGC migration from the endoderm to the gonads. We therefore favor an alternative model based primarily on passive translocation of PGCs from the mesenchyme that surrounds the gut to the prospective gonad through the intercalar expansion of mesenchymal tissue which contains the PGCs. In summary, we (i) show differential pluripotency factor expression during primate embryo development and (ii) provide a schematic model for embryonic PGC translocation.
authors.affiliation: Stem Cell Biology Unit, German Primate Center - Leibniz Institute for Primate Research, Kellnerweg 4, 37077 Göttingen, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Aeckerle
authors.affiliation: Stem Cell Biology Unit, German Primate Center - Leibniz Institute for Primate Research, Kellnerweg 4, 37077 Göttingen, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Drummer
authors.affiliation: Stem Cell Biology Unit, German Primate Center - Leibniz Institute for Primate Research, Kellnerweg 4, 37077 Göttingen, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Debowski
authors.affiliation: Department of Anatomy and Embryology, Center of Anatomy, University of Göttingen, Kreuzbergring 36, 37075 Göttingen, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Viebahn
authors.affiliation: Stem Cell Biology Unit, German Primate Center - Leibniz Institute for Primate Research, Kellnerweg 4, 37077 Göttingen, Germany rbehr@dpz.eu.
authors.forename: R
authors.initials: R
authors.lastname: Behr
mesh_terms: D000818:Animals; D002144:Callithrix; D002465:Cell Movement / Q000502:physiology*; D005260:Female; D005854:Germ Cells / Q000166:cytology* / Q000378:metabolism; D006066:Gonads / Q000166:cytology* / Q000196:embryology; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D018398:Homeodomain Proteins; D016601:RNA-Binding Proteins; D014157:Transcription Factors
keywords: embryo; marmoset monkey; pluripotency factor; primordial germ cell