Immunohistochemical studies of primordial follicles in mouse ovary. [(a)–(d)] Representative microscopic pictures of positively or negatively stained key proteins in the PI3K-PTEN-Akt-Foxo3 pathway (Foxo3, PTEN, pmTOR, p-Akt) in the nucleus of the primordial follicle in the mouse ovary. In primordial follicles, phosphorylation of Akt and mTOR initiates activation of dormant follicles, whereas the induction of PTEN and activation (nuclear expression) of Foxo3 maintains dormancy.