Building a resilient ovarian reserve: Early soma-oocyte interactions.

Soma-oocyte interactions are a key component in female fertility. First the ovary must adopt a female fate and become populated with supporting somatic cells. We discuss the origins of each somatic cell type with a particular focus on pre-granulosa cell origins and differentiation. Upon germ cell arrival into the ovary, the oogonia develop into cysts and begin their interactions with neighboring pre-granulosa cells. Cell to cell contacts change over time as the germline cysts form and then break down to facilitate primordial follicle formation. These changes do not happen in isolation, rather, they are mediated by signaling cascades and changes in the physical structures. The processes and developmental changes explored in this chapter are crucial for the longevity and success of the primordial follicle and thus, an essential part of female fertility.