Abstract: 【Objective】The variation of Dnmts expression during follicular theca cells maturation in mouse was studied, and its possible mechanisms were discussed. 【Method】 Ovary sections that made from mice on days post parturition 3, 5 and 8 (dpp3, dpp5, dpp8) were treated with H.E staining, then, the theca cells of primordial follicles, primary follicles, secondary follicles were observed and the proportions of each developmental stage follicles as well as the number of theca cells around primary and secondary follicle were counted. The transcriptional variation of theca cells maker gene CYP17A1 and Dnmts in dpp3, 5, and 8 ovaries were tested by semi-quantitative PCR. The protein Dnmt1 distribution in dpp3, 5, and 8 ovaries were observed through immunohistochemistry.【Result】“Shuttling cells” were found around primary follicles in dpp3 mice ovaries. With the lapse of time after birth, the proportion of primordial follicles in mice ovaries maintained reducing during post-neonatal dpp3, 5 and 8 (P＜0.01), while the proportion of secondary follicles maintained increasing (P＜0.01), the proportion of primary follicles had no statistical difference between dpp3 and dpp5, but it reduced at dpp8 (P＜0.05). Mean number of “Shuttling cell” around primary follicles was found no statistical difference between dpp3 and dpp5 (P＞0.05), and it increased at dpp8 (P＜0.05). Mean number of “Shuttling cell” around secondary follicles was found no statistical difference between dpp3 and dpp5 (P＞0.05)，and it increased at dpp8 (P＜0.01).The transcription level of CYP17A1 was extremely low at dpp3 and dpp5, and there was no statistical difference between the two stages (P＞0.05), but it up-regulated at dpp8 (P＜0.01). The transcriptional level of Dnmt1s continually up-regulated during dpp3, 5 and 8 (P＜0.01). The transcriptional level of Dnmt1o up-regulated at dpp5 (P＜0.05), and down-regulated at dpp8 (P＜0.01). Dnmt3a reached the highest transcription level at dpp5 (P＜0.01), and there was no statistical difference between dpp3 and dpp8 (P＞0.05). Immunohistochemistry staining of Dnmt1 showed that the granulosa cells stained positive in dpp5 and dpp8 ovaries, but it was negative at dpp3. Meanwhile, the “Shuttling cells” at dpp3 and dpp5 ovaries stained negative, but it was positive at dpp8.【Conclusion】The down-regulated transcription level of Dnmt3a may caused by theca cells maturation. The transcription and expression level of Dnmt1s maintained low before theca cells maturation and up-regulated after the maturation, which contribute to maintain the re-established methylation pattern during theca cells proliferation.

Key words: DNA methyltransferases, follicular theca cells, maturation, mouse