Mechanisms and function of germ line-somatic communication during mammalian follicular growth

ABSTRACT Throughout the reproductive life of female mammals, ovarian primordial follicles housing small oocytes regularly enter the growth phase. The production and ovulation of a healthy egg at the end of this process depends on precise co-ordination of the developmental programs of the germ and somatic cells within the follicle. This co-ordination is achieved through continuing and dynamic interactions between the two cell types. Here we describe the structures that link the follicular granulosa cells to the enclosed oocyte, thereby facilitating their interaction. We then describe the role of signals from the granulosa cells in initiating and sustaining oocyte growth. We close by describing classical and newly identified oocyte factors that regulate granulosa cell differentiation. The ovarian follicle presents an elegant example of mechanisms and functions of cellular interactions during the life of multicellular organisms.