|dc.description.abstracteng||Primordial germ cells (PGCs) are the precursors of sperm and egg cells. They arise early in mammalian embryonic development and have to translocate from their extraembryonic tissue of specification over a significant distance to reach the prospective gonads. The development of mammalian PGCs has been investigated mostly in rodents due to the broad availability of mouse embryos and the genetic tools established in this species. However, results obtained in mice cannot be directly transferred onto the human and other species, and many questions remain concerning PGC specification and migration mechanisms. Therefore, this project aimed at investigating germ cell development in a non-human primate animal model, the common marmoset monkey (Callithrix jacchus). One goal was the in situ characterisation of PGCs in marmoset embryo tissue sections and identification of new PGC specific marker proteins. This led to the discovery of Aminopeptidase N (ANPEP) expression on the cell surface of marmoset PGCs.
A study on human embryos demonstrated a close spatial relationship between migrating PGCs and peripheral nerves, suggesting a guiding function of the neurons. Therefore, I tested the hypothesis that this might be a conserved strategy in mammalian PGC development by analysing sections of mouse and common marmoset monkey embryos via immunohistochemical double staining. In both investigated species, no spatial association between neurons and migrating PGCs could be detected, and the PGCs had reached the gonads before neurons could be detected in the gonads’ vicinity.
Pluripotent stem cells (PSCs) form the basis of emerging therapies to degenerative diseases since they can develop into all tissues of the adult body. PGCs can be considered as potentially pluripotent cells, and the culture of mouse and human PGCs was reported to result in the derivation of PSC lines, so called embryonic germ cells (EGCs). Therefore, it was the second aim of this study to establish EGC lines of the marmoset monkey, and compare them with already available marmoset embryonic stem cells and induced pluripotent stem cells. For this purpose, PGCs were isolated from marmoset embryos of defined developmental stages and cultured according to published protocols. Even after testing several culture approaches, no EGCs could be derived from marmoset PGCs.
This work provides new insights into PGC translocation in mammals and identifies ANPEP as a novel PGC surface protein in the marmoset monkey. However, for the conversions of PGCs to EGCs additional cell culture conditions need to be tested.||de