title: Strain-specific spontaneous activation during mouse oocyte maturation.
abstract: OBJECTIVE
  To examine whether spontaneous oocyte activation is determined by genetic differences and interacts with culture environment.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  Temple University School of Medicine.
  
  
  METHODS
  C57BL/6, DBA/2, C3H/HeJ, and A/J strains, along with reciprocal F1 hybrid female mice (5-6 weeks).
  
  
  METHODS
  Immature oocytes from different mouse strains collected and cultured in different maturation conditions, including different serum, serum replacement, bovine serum albumin (BSA), and follicle-stimulation hormone (FSH).
  
  
  METHODS
  The emission of first polar body, pronucleus formation, meiotic arrest, spontaneous activation, and expression of maturation regulators.
  
  
  RESULTS
  Oocytes from C57BL/6 mice display a high rate of delayed first meiotic division and spontaneous activation after the first meiotic division with in vitro maturation (IVM), and the second meiotic division with in vivo maturation (VVM) after superovulation. Spontaneous activation with IVM is sensitive to culture environment. Oocytes that spontaneously activated during the first meiotic division with IVM have unusual replicated sister chromatid pairs with slight connections at centromeres at first mitosis, whereas oocytes that activated in vivo display haploidization from the second meiotic division. Spontaneous activation is also seen in F1 hybrid oocytes, indicating a dominant trait from C57BL/6. Delayed meiosis was associated with reduced cyclin B and securin expression.
  
  
  CONCLUSIONS
  Both mouse strain and culture environment have a statistically significant effect on the incidence of meiotic defects and spontaneous activation. Reduced expression of meiotic regulators may underlie this effect.
authors.affiliation: The Fels Institute for Cancer Research and Molecular Biology, Temple University Medical School, Philadelphia, Pennsylvania, USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Cheng
authors.forename: Zhisheng
authors.initials: Z
authors.lastname: Zhong
authors.forename: Keith E
authors.initials: KE
authors.lastname: Latham
mesh_terms: D000818:Animals; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D060833:Cellular Microenvironment / Q000502:physiology; D005260:Female; D008540:Meiosis / Q000502:physiology; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D009866:Oogenesis / Q000502:physiology*; D010312:Parthenogenesis / Q000502:physiology; D013045:Species Specificity