p27Kip1 Negatively Regulates the Activation of Murine Primordial Oocytes

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Abstract

In mice, small oocytes (primordial oocytes) are enclosed within flattened granulosa cells to form primordial follicles around birth. A small number of primordial oocytes enter the growth phase, whereas others are quiescent. The mechanism regulating this selection of primordial oocytes is not well understood. The objective of the present study was to understand the role of p27<i><sup>Kip1</sup></i>, which regulates cell cycle progression in somatic cells, in the growth initiation of primordial oocytes in neonatal mice. We studied the localization of p27<i><sup>Kip1</sup></i> in 0-, 3-, 5-, 7- and 21-day-old mouse ovaries by immunohistochemistry. Ovaries from 3-day-old mice were treated with p27<i><sup>Kip1</sup></i> siRNAs (small interfering RNAs), and knockdown of p27<i><sup>Kip1</sup></i> was determined by immunohistochemistry and Western blotting. Ovaries treated with siRNAs were organ-cultured for 6 days, and oocyte growth was estimated histologically. Expression of p27<i><sup>Kip1</sup></i> was undetectable in the primordial oocytes of newborn mice. In the 3-day-old ovaries (n=3), p27<i><sup>Kip1</sup></i> was demonstrated in the nucleus of 36 ± 6% primordial oocytes. The percentage of p27<i><sup>Kip1</sup></i>-positive primordial oocytes increased to 72 ± 8 (n=3), 85 ± 7 (n=3) and 93 ± 5 (n=3) in the 5-, 7- and 21-day-old mouse ovaries, respectively. After knockdown of the p27<i><sup>Kip1</sup></i> protein by siRNAs, a higher proportion of oocytes entered the growth phase in cultured ovaries than those in the control. These results suggest that p27<i><sup>Kip1</sup></i> negatively regulates primordial oocyte growth and that knockdown of p27<i><sup>Kip1</sup></i> leads primordial oocytes to enter the growth phase <i>in vitro</i>.<br>

Journal

  • Journal of Reproduction and Development

    Journal of Reproduction and Development 57(2), 217-222, 2011

    THE SOCIETY FOR REPRODUCTION AND DEVELOPMENT

Cited by:  1

Codes

  • NII Article ID (NAID)
    130000436782
  • NII NACSIS-CAT ID (NCID)
    AA10936678
  • Text Lang
    ENG
  • Article Type
    Journal Article
  • ISSN
    0916-8818
  • NDL Article ID
    11058236
  • NDL Source Classification
    ZR22(科学技術--農林水産--畜産)
  • NDL Call No.
    Z54-H305
  • Data Source
    CJPref  NDL  J-STAGE 
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