Oocyte Maturation and Fertilization: A Long History for a Short Event

Indexed in: Chemical Abstracts, EBSCO.

Events of reproduction occurring from meiotic resumption of the immature oocyte up to its exit from the second meiotic block following activation will be revealed. Morphological modifications of the ...
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The Enhancers of Oocyte Competence

Pp. 64-70 (7)

Yves JR. Menezo and Kay Elder

Abstract

During oocyte maturation, nuclear maturation i.e. the condensation of chromosomes and formation of the meiotic apparatus is generally considered as the most significant physiological process. However, disruption of the contact between granulosa cells and the oocyte leads to spontaneous nuclear maturation of oocytes which, however, have poor or nil developmental competence after fertilisation. Acquisition of cytoplasmic competence, i.e., the ability to sustain early development of embryos with high developmental potential, is the result of concomitant synergic actions of gonadotrophins and growth factors. The transforming growth factor beta superfamiliy, the epidermal growth factor network, insulin growth factors and growth hormone together with Leukaemia inhibiting factor are partners in the mechanism of acquisition of developmental competence in oocytes. These interactions allow the (quantitatively and qualitatively) correct storage of mRNAs and proteins necessary for the early embryonic divisions prior to genomic activation. However, the quality of the endogenous pool of metabolic intermediates such as (sulphur) amino acids is a mandatory prerequisite for oocyte activation, sperm decondensation and further on early embryo divisions. A correct timing of translation of the mRNAs stored during oocyte maturation is mandatory for the successful passage of the maternal to zygotic transition, usually considered as the critical step in early embryonic developmental arrest.

Affiliation:

UNILABS France, Laboratoire d’Eylau, 55 Rue St Didier 75116 Paris, France and Laboratoires Nurilia, Rue Boileau, 6900 Lyon, France and 1Bourn Hall Clinic, Cambridge, UK.