The emerging role of the oocyte cortical domain in maturation, fertilization, and development

The cell cortex, a cytoskeletal network with regulatory signalling pathways, is localized beneath the cell membrane: it is especially prominent in mammalian oocytes. As in other cells, the cortex ensures appropriate shape and robustness of oocytes. It is also involved in other key and more specific functions. The cortex is part of the interface between the germinal and somatic cell compartments; as such, it participates in the delicate bi-directional interaction by which oocytes regulate cumulus cell function and in return, oocytes receive nutrients and regulative factors from cumulus cells. During oocyte maturation, fertilization, and early development, the cortex undergoes major structural and functional modifications. Such changes are needed to support crucial processes, including meiotic spindle localization, polar body extrusion, chromosome segregation, and pronuclear formation. Cortex dysregulation may be also implicated in blastomere fragmentation during early embryo development. Mechanical properties of the cortex are associated with oocyte quality and developmental competence; with appropriate technology, such properties could be harnessed to develop new approaches to non-invasive oocyte assessment in human IVF.