title: Apoptosis in mouse fetal and neonatal oocytes during meiotic prophase one.
abstract: BACKGROUND
  The vast majority of oocytes formed in the fetal ovary do not survive beyond birth. Possible reasons for their loss include the elimination of non-viable genetic constitutions arising through meiosis, however, the precise relationship between meiotic stages and prenatal apoptosis of oocytes remains elusive. We studied oocytes in mouse fetal and neonatal ovaries, 14.5-21 days post coitum, to examine the relationship between oocyte development and programmed cell death during meiotic prophase I.
  
  
  RESULTS
  Microspreads of fetal and neonatal ovarian cells underwent immunocytochemistry for meiosis- and apoptosis-related markers. COR-1 (meiosis-specific) highlighted axial elements of the synaptonemal complex and allowed definitive identification of the stages of meiotic prophase I. Labelling for cleaved poly-(ADP-ribose) polymerase (PARP-1), an inactivated DNA repair protein, indicated apoptosis. The same oocytes were then labelled for DNA double strand breaks (DSBs) using TUNEL. 1960 oocytes produced analysable results. Oocytes at all stages of meiotic prophase I stained for cleaved PARP-1 and/or TUNEL, or neither. Oocytes with fragmented (19.8%) or compressed (21.2%) axial elements showed slight but significant differences in staining for cleaved PARP-1 and TUNEL to those with intact elements. However, fragmentation of axial elements alone was not a good indicator of cell demise. Cleaved PARP-1 and TUNEL staining were not necessarily coincident, showing that TUNEL is not a reliable marker of apoptosis in oocytes.
  
  
  CONCLUSIONS
  Our data indicate that apoptosis can occur throughout meiotic prophase I in mouse fetal and early postnatal oocytes, with greatest incidence at the diplotene stage. Careful selection of appropriate markers for oocyte apoptosis is essential.
authors.affiliation: Department of Biological Sciences, University of Warwick, Coventry, UK. ghafarif@yahoo.co.uk <ghafarif@yahoo.co.uk>
authors.forename: Fataneh
authors.initials: F
authors.lastname: Ghafari
authors.forename: Carlos G
authors.initials: CG
authors.lastname: Gutierrez
authors.forename: Geraldine M
authors.initials: GM
authors.lastname: Hartshorne
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics*; D002470:Cell Survival; D004622:Embryo, Mammalian; D005260:Female; D020287:In Situ Nick-End Labeling; D008297:Male; D049469:Meiotic Prophase I / Q000235:genetics*; D051379:Mice; D008815:Mice, Inbred Strains; D009865:Oocytes / Q000166:cytology*; D010053:Ovary / Q000196:embryology; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics; D011247:Pregnancy; D013573:Synaptonemal Complex / Q000235:genetics
chemical_list: C499321:Parp1 protein, mouse; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases