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THE ROLE OF Y81 (A SECRETED FRIZZLED RELATED PROTEIN) IN OVULATION.
Dharmarajan, Arun1, Drake, Jeremy1, Lareu, Ricky1, 1
ABSTRACT- Ovulation is a key event in reproduction and a complex, multi-factorial process. Apoptosis has been shown to play an important role in this process. Y81 (frizzled related protein), a recently discovered gene has been shown to be upregulated during apoptotic death in reproductive tissues. The objective of this study was to investigate whether Y81 is involved in follicle rupture. Sexually immature Wistar rats were treated subcutaneously with 25 IU of PMSG and 8 IU of CG 56 hours later to induce ovulation. Ovariectomy was performed at 0, 3, 6, 9, 12, 18 and 24 hours after CG administration. Blood samples were collected at these time points for progesterone determination. The ovaries were processed for 3′-end labeling of DNA, TUNEL, and in situ hybridization. Nine hours following CG administration, the plasma progesterone levels were significantly higher (p<0.001) than controls (saline treated). 3′-end labelling of nuclear fragmentation (indication of apoptosis) also demonstrated a 2.5 fold increase 12 hours after treatment (p<0.01). Similarly, in situ DNA analysis revealed an increase in nuclear labelling of thecal cells. Interestingly, in situ hybridisation revealed an increase in Y81 mRNA expression in the preovulatory follicle. These data together with our previous findings of the role of Y81 in the corpus luteum apoptosis clearly suggest that this gene is closely associated with the process of follicle rupture. Supported by NH&MRC and ARC.
KEY WORDS: Ovulation, Apoptosis, Y81, Rat