The relationship between Evi-1 expression and mouse ovarian follicular development

The ecotropic viral integration site-1 (Evi-1) is a transcription factor with two sets of zinc finger domains. It is an important regulator of the transforming growth factor beta superfamily. In the present study, we investigated the spatiotemporal expression patterns of Evi-1 using immunohistochemistry in ovaries from neonatal mice, gonadotropin-induced immature mice and mice in estrous cycle. Positive staining for Evi-1 was detected in the cytoplasm of oocytes. In postnatal mice, a high level of Evi-1 immunostaining was found from day 1 to 6, an intermediate level from day 10 to 16 and a low level on day 23. After gonadotropin treatment, Evi-1 was mainly expressed in small follicles and exhibited a very low level in large antral follicles. During the estrous cycle, the expression of Evi-1 was higher in diestrus and estrus than in proestrus and metestrus. Real-time PCR was performed to examine the relationship between Evi-1 mRNA and ovulation related genes (Ptgs2, Tnfaip6, Has2, Cd44, C1qbp). At 4 h after hCG treatment, Evi-1 mRNA was down-regulated whereas ovulation related genes were up-regulated. Overall, the results indicate that Evi-1 is expressed in a stage-specific manner during ovarian follicular development and may be involved in early follicle development.