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Lookup NU author(s): Professor Keith Jones
Mammalian oocytes begin meiosis in the fetal ovary, but only complete it when fertilized in the adult reproductive tract. This review examines the cell biology of this protracted process: from entry of primordial germ cells into meiosis to conception. The defining feature of meiosis is two consecutive cell divisions (meiosis I and II) and two cell cycle arrests: at the germinal vesicle (GV), dictyate stage of prophase I and at metaphase II. These arrests are spanned by three key events, the focus of this review: (i) passage from mitosis to GV arrest during fetal life, regulated by retinoic acid; (ii) passage through meiosis I and (iii) completion of meiosis II following fertilization, both meiotic divisions being regulated by cyclin-dependent kinase (CDK1) activity. Meiosis I in human oocytes is associated with an age-related high rate of chromosomal mis-segregation, such as trisomy 21 (Down's syndrome), resulting in aneuploid conceptuses. Although aneuploidy is likely to be multifactorial, oocytes from older women may be predisposed to be becoming aneuploid as a consequence of an age-long decline in the cohesive ties holding chromosomes together. Such loss goes undetected by the oocyte during meiosis I either because its ability to respond and block division also deteriorates with age, or as a consequence of being inherently unable to respond to the types of segregation defects induced by cohesion loss. © The Author 2007. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved.
Author(s): Jones KT
Publication type: Review
Publication status: Published
Journal: Human Reproduction Update
Year: 2008
Volume: 14
Issue: 2
Pages: 143-158
Print publication date: 01/03/2008
ISSN (print): 1355-4786
ISSN (electronic): 1460-2369
URL: http://dx.doi.org/10.1093/humupd/dmm043
DOI: 10.1093/humupd/dmm043
PubMed id: 18084010
