Melatonin-Mediated Development of Ovine Cumulus Cells, Perhaps by Regulation of DNA Methylation

Cumulus cells of pre-pubertal domestic animals are dysfunctional, perhaps due to age-specific epigenetic events. This study was designed to determine effects of melatonin treatment of donors on methylation modification of pre-pubertal cumulus cells. Cumulus cells from germinal vesicle stage cumulus oocyte complexes (COCs) were collected from eighteen lambs which were randomly divided into control group (C) and melatonin group given an 18 mg melatonin implant subcutaneous (M). Compared to the C group, the M group had higher concentrations of melatonin in plasma and follicular fluid ( < 0.05), greater superovulation, a higher proportion of fully expanded COCs, and a lower proportion of apoptotic cumulus cells ( < 0.05). Real-time PCR results showed that melatonin up-regulated expression of genes , , , and , but down-regulated expression of genes , and ( < 0.05). Furthermore, melatonin increased FI of FITC (global methylation level) on cumulus cells ( < 0.05). To understand the regulation mechanism, the promoter methylation sequence were analyzed. Compared to the C group, although there was less methylation at two CpG sites of ( < 0.05) and higher methylation at two CpG sites of ( < 0.05), there were no significant differences in methylation of the detected and promoter regions. However, there were lower methylation levels at five CpG sites of , which decreased methylation of detected promoter region on M group ( < 0.05). In conclusion, alterations of methylation regulated by melatonin may mediate development of cumulus cells in lambs.