Figure 5

Model of OSC commitment for production of secondary germ cells. A) The uncommitted OSC (u-OSC) is present during sixth week of gestational age, prior to the arrival of primordial germ cells (pgc). B) Primordial germ cells invade OSC during seventh week and cause commitment of OSC (c-OSC) for production of secondary germ cells (sgc). C) The primordial germ cells degenerate and secondary germ cells are produced from OSC influenced by hormonal signaling and cellular signaling (MDC, Thy-1 pericytes, and T cells). The secondary germ cells enter ovarian cortex and differentiate into definitive oocytes (do). D) All OSC are influenced by systemic hormonal signals (HS), but only those influenced by CS undergo asymmetric division (ad) followed by symmetric division (sd) required for crossing over (co). Tadpole-like migrating secondary germ cells (m-sgc) leave OSC and enter the ovarian cortex. E) Origination of secondary germ cells from OSC by asymmetric division appears to require primitive (CD14+) MDC (P-MDC), activated pericytes (P) with a lack of suppressive neural signaling (NS-), activated (DR+) MDC (A-MDC) and activated (DR+) T cells (T). Adapted from [69] with permission, © Transworld Research Network.