FIG. 5.

Schematics of developmental events in the ventral and dorsal ovarian regions during the embryonic period and first wave of follicle activation. Early onset of meiosis in the ventral region is represented in the insert (OCT4 and STRA8). First primordial follicles were observed at 18.5 dpc at the interface between cortex and medulla in the anterior-dorsal region of the ovary, the area where the first cohort of growing follicles appear during the first week of postnatal development. In contrast, during this same period, germ cells in the ventral region of the ovary are still breaking the nest and forming individual follicles. The area containing growing follicles expands gradually during the postnatal period, occupying the whole medullar area of the dorsal region of the ovary. Altogether, our data indicated that the first wave of follicle activation follows a predictable anatomic pattern resulting from regional differences in timing of follicle formation. *Color resulting from the overlay of the three fluorescent proteins is represented. A, anterior; P, posterior.