Quiescence is a frequent phenotype of stem cells. We recently learned that the primordial germ cells (PGCs) of the sea urchin embryo have a broad set of quiescence phenotypes. In the sea urchin, the somatic cells divide rapidly and start to transcribe quickly after fertilization. In contrast, the PGCs of these embryos differ significantly relative to their sibling somatic cells by reducing their overall translational activity, decreasing their transcriptional activity, reducing their mitochondrial activity, and likely decreasing the pH of their cytoplasm reflective of a shift in metabolism from oxidative phosphorylation to glycolysis. In the sea urchin, we discovered that this quiescence is transient, the PGCs restart their activities after gastrulation, demonstrating a rapid and transient quiescent activity. My research is focused on the quiescence phenotypes of these stem cells. How do the PGCs enter, maintain and exit quiescence during the embryonic development?
