Molecular analysis of germ cell specification

The first step to ensure successful sexual reproduction and species survival is the correct differentiation of primordial germ cells (PGCs). PGCs are the first cells in the germline, and their correct specification is essential for the eventual production of gametes (eggs and sperm). Murine PGCs arise as a small population in the post-implantation epiblast in response to external signals, including BMP4 and WNT. However, what governs the first steps in the decision of cells to enter the germline remains unknown. Here we use single cell omics (scRNA-seq and scATAC-seq) to characterise the progressive alterations in gene expression and chromatin readout at short time intervals during in vitro germline specification. Our results establish distinct trajectories for the specification of early somatic and germline cells during pluripotent cell differentiation. Epiblast-like cells (EpiLCs) do not contain cells predisposed for germline differentiation. Rather, two populations emerge after 48h of exposure to external signals: cells expressing early PGC markers (i.e Prdm1, Ap2y, Esrrb) and cells expressing mesoderm markers (i.e T, Mixl1, Wnt3a). These populations are mutually exclusive, as germline markers are expressed in different cells than mesoderm markers. Moreover, commitment of cells to these fates is asynchronous, as cells expressing PGC markers appear before cells expressing somatic markers. We propose novel regulators of both WNT and Epithelial-to-Mesenchymal transition (EMT) which might play a key role in the earliest steps of the decision between germline and the somatic fate. Moreover, we assess the germline differentiation potential of cells lacking all three TET enzymes and we show that TET triple knockout cells are unable to commit to the somatic fate but instead enter the germline and at an enhanced and accelerated rate. These data establish the order with which cells commit to the germline and to the soma and suggest that germline entry might be enhanced in cells unable to commit to the somatic fate.

Grantor dc:publisher

The University of Edinburgh

Year dc:date.issued

2025

Author dc:creator

• Gonzalez Brito, Sara

Advisors dc:contributor.advisor

• Chambers, Ian
• Chandra, Tamir

• germline specification
• single cell RNA-sequencing
• embryonic stem cells
• embryonic development

Language dc:language.iso

en

Identifier URI

http://dx.doi.org/10.7488/era/6368

OAI identifier oai:identifier

oai:era.ed.ac.uk:1842/43837