Dot1L mediated histone H3 lysine79 methylation is essential to meiosis progression in mouse oocytes

OBJECTIVES: Post-translational modifications of lysine residues of histones can result in a series of functional changes. Lysine 79 of histone H3 (H3K79) can be methylated specifically by the Dot1 family of histone lysine methyltransferases. Although multiple developmental abnormalities in Dot1L-deficient mouse embryos have been studied, the biological function of H3K79 methylation in mammal oocytes remains unclear. Here, the distribution of Dot1L, methyltransferase of residue lys79 of histone H3 (H3K79) in mouse, and its effect on mouse oocytes meiosis were investigated to examine whether there are changes in the pattern of distribution and effect of Dot1L on mouse oocytes meiosis. METHODS: The mRNA level of Dot1l in mouse oocytes was examined using real-time qPCR (RT-qPCR) technique. The distribution and level of Dot1L protein and H3K79 methylation were examined using immunofluorescence and western-blot techniques, respectively. The down regulation of Dot1l in mouse oocytes was conducted using siRNA injection technique. RESULTS: Dot1L was detected diffuse staining in the nuclear of mouse GV (Germinal Vesicle) stage oocytes. The Dot1l expression and H3K79 methylation level were suppressed effectively with anti-Dot1l siRNA injection. In Dot1L deficient, accompanying with BubR1 (MAD3/Bub1b) remains on the chromosome, the mouse oocytes was blocked in metaphase of meiosis I. The histone deacetylation was also incomplete in Dot1L-deficient mouse oocytes. CONCLUSION: Dot1L protein is well distributed in mouse GV stage oocytes. Dot1L and H3K79 methylation play important roles in meiosis progression and are supposed to be associated with chromosome deacetylation of mouse oocytes.