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Alterations of Spindle and Microfilament Assembly in Aged Cat Oocytes
Author(s) -
Jin YX,
Cui XS,
Yu XF,
Han YJ,
Kong IK,
Kim NH
Publication year - 2010
Publication title -
reproduction in domestic animals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.546
H-Index - 66
eISSN - 1439-0531
pISSN - 0936-6768
DOI - 10.1111/j.1439-0531.2009.01400.x
Subject(s) - germinal vesicle , microfilament , pronucleus , microbiology and biotechnology , metaphase , biology , microtubule , polar body , meiosis , oocyte , andrology , embryo , cytoskeleton , embryogenesis , genetics , cell , chromosome , zygote , medicine , gene
Contents To obtain insights into the cytoplasmic maturation status of cat oocytes recovered from cat ovaries following hormone treatment, we first examined microtubule and microfilament assembly in cat oocytes recovered from hormone‐treated ovaries at various stages of maturation. Additionally, we determined the alteration of spindle and microfilament assembly, as well as mitogen‐acitvated protein kinase (MAPK) activity, in cat oocytes at 0, 6, 12 and 18 h of further maturation in vitro . We then looked at pronuclear formation and cleavage of these oocytes following parthenogenetic activation. Similar to other species, microtubules are present in germinal vesicle (GV) stage cat oocytes, and following GV breakdown, microtubules encompassed condensed chromatin particles to form the meiotic metaphase spindle. Microfilaments were located in the cortex and around the GV. A microfilament‐rich area, in which the chromatin is located, was observed in the oocytes during meiotic maturation. Maturation rates in aged oocytes (cultured for 18 h) were increased when compared with that in relatively fresh oocytes (<12 h culture), and the number of oocytes with abnormal spindle shapes was also increased in aged oocytes. Furthermore, in aged oocytes, the incidence of the metaphase plate observed outside the thick microfilament domain was higher compared with that of young oocytes, and this seemed to result in an increase in the number of oocytes with two pronuclei and one polar body following activation. Western blot analysis revealed a decrease in MAPK activity in aged cat oocytes. Taken collectively, these results suggest that the optimum time for improved cytoplasmic maturation is <12 h in cat oocytes recovered from hormone‐treated ovaries.