Epigenetic changes of histone deacetylation in murine oocytes matured in vitro versus in vivo.

OBJECTIVE: In this study, we studied changes in histone acetylation during mouse oocytes meiosis. The aim was to investigate HDAC1 expression patterns in the mouse oocytes and effects of in-vitro maturation on epigenetic modifications during meiosis. MATERIALS AND METHODS: Immature and mature oocytes were collected from female Kunming white mice of 4-6 weeks in age. Dynamic changes of histone H3K9, H4K12 acetylation were explored. HDAC1 spatial and temporal expression patterns during meiosis and their expression changes in in-vitro maturation were determined. RESULTS: It was found that histone H3K9 and H4K12 acetylations were gradually disappeared during the meiotic maturation of mouse oocytes. HDAC1 proteins were localized mainly throughout the nucleoplasm in GV-intact oocyte, and colocalized with chromosomes at metaphase II (MII). The acetylated H3K9 and H4K12 were absent in oocytes matured in vivo, while the elevated acetylation of H3K9 and H4K12 was detected in oocytes matured in vitro. When cultured in vitro, the decrease of HDAC1 protein level and mRNA level were observed compared with oocytes matured in vivo. CONCLUSIONS: the acetylation of H3K9, H4K12 decreased gradually to undetectable during oocyte meiosis. The histone deacetylation in oocytes was inadequate during in vitro maturation, and the in vitro maturation might lead to reduced HDAC1 expression in oocytes.