Antral follicles confer developmental competence on oocytes

Abstract

This paper addresses the proposition, first advanced by Wilson (1925), that successful embryogenesis depends on an ordered series of events in oogenesis. It is at the completion of this varied set of intracellular changes that the oocyte finally acquires its full capacity to support fertilisation and development. Amongst the earliest nuclear events are those associated with chromosome pairing and meiotic recombination. During the growth phase cell volume increases 300-fold and the cytoplasm becomes the storage site for RNA and protein which will be mobilised during early development. Finally, a short phase of intracellular reprogramming, or maturation, completes the series of events during oogenesis that confer developmental competence upon the oocyte. Follicle cell support is an indispensable requirement for ordered oocyte development and provides the early germline cell with many of the essential nutrients and growth regulators required to ensure progression through the protracted growth phase (see contributions by Cecconi & Rosella and De Feliciet al.this issue). Although different, the interactions between the full-grown oocyte and the antral follicle are no less crucial to the acquisition of competence than those involved in the earlier stages of oogenesis.