The developmental competence of mammalian oocytes: A convenient but biologically fuzzy concept

Oocyte developmental competence is often used to qualify in vitro procedure s for embryo production. It supposedly accounts for the oocyte's ability to develop into a normal, viable and fertile offspring after fertilization, b ut for practical reasons it often characterizes the ability of such oocytes to develop to the blastocyst stage in vitro. Molecular tools compatible wi th the analysis of very small amounts of material have resulted in research aimed at designing molecular criteria to define this competence. However w e feel that such research strategies easily lead to misunderstanding of the regulative processes that drive embryo development. Artificially induced b lastocyst stage is a poor predictor of oocyte developmental competence. How ever preimplantation stages also appear to be sensitive to environmental co nditions that can induce long-lasting detrimental effects. Larger scale ana lysis now made available by a functional genomics approach provides a more accurate understanding of the complex regulative networks that sustain the molecular mechanisms responsible for normal development. We propose that th e concept of developmental competence should be used more cautiously and al so should refer more explicitly to the experimental context it intends to e nlighten. (C) 2001 by Elsevier Science Inc.