title: Function of the pentose phosphate pathway and its key enzyme, transketolase, in the regulation of the meiotic cell cycle in oocytes.
abstract: OBJECTIVE
  Previously, we identified that transketolase (Tkt), an important enzyme in the pentose phosphate pathway, is highly expressed at 2 hours of spontaneous maturation in oocytes. Therefore, this study was performed to determine the function of Tkt in meiotic cell cycle regulation, especially at the point of germinal vesicle breakdown (GVBD).
  
  
  METHODS
  We evaluated the loss-of-function of Tkt by microinjecting Tkt double-stranded RNAs (dsRNAs) into germinal vesicle-stage oocytes, and the oocytes were cultured in vitro to evaluate phenotypic changes during oocyte maturation. In addition to maturation rates, meiotic spindle and chromosome rearrangements, and changes in expression of other enzymes in the pentose phosphate pathway were determined after Tkt RNA interference (RNAi).
  
  
  RESULTS
  Despite the complete and specific knockdown of Tkt expression, GVBD occurred and meiosis was arrested at the metaphase I (MI) stage. The arrested oocytes exhibited spindle loss, chromosomal aggregation, and declined maturation promoting factor and mitogen-activated protein kinase activities. The modified expression of two enzymes in the pentose phosphate pathway, Prps1 and Rbks, after Tkt RNAi and decreased maturation rates were amended when ribose-5-phosphate was supplemented in the culture medium, suggesting that the Tkt and pentose phosphate pathway are important for the maturation process.
  
  
  CONCLUSIONS
  We concluded that Tkt and its associated pentose phosphate pathway play an important role in the MI-MII transition of the oocytes' meiotic cell cycle, but not in the process of GVBD.
authors: Department of Biomedical Science, College of Life Science, CHA University, Seoul, Korea.
authors: Yunna
authors: Y
authors: Kim
authors: Eun-Young
authors: EY
authors: Kim
authors: You-Mi
authors: YM
authors: Seo
authors: Tae Ki
authors: TK
authors: Yoon
authors: Woo-Sik
authors: WS
authors: Lee
authors: Kyung-Ah
authors: KA
authors: Lee