Involvement of SIRT3-GSK3ß deacetylation pathway in the effects of maternal diabetes on oocyte meiosis.

OBJECTIVES: It has been widely reported that maternal diabetes impairs oocyte quality. However, the responsible mechanisms remain to be explored. In the present study, we focused on whether SIRT3-GSK3ß pathway mediates the meiotic defects in oocytes from diabetic mice. MATERIALS AND METHODS: GSK3ß functions in mouse oocyte meiosis were first detected by targeted siRNA knockdown. Spindle assembly and chromosome alignment were visualized by immunostaining and analysed under the confocal microscope. PCR-based site mutation of specific GSK3ß lysine residues was used to confirm which lysine residues function in oocyte meiosis. siRNA knockdown coupled with cRNA overexpression was performed to detect SIRT3-GSK3ß pathway functions in oocyte meiosis. Immunofluorescence was performed to detect ROS levels. T1DM mouse models were induced by a single intraperitoneal injection of streptozotocin. RESULTS: In the present study, we found that specific depletion of GSK3ß disrupts maturational progression and meiotic apparatus in mouse oocytes. By constructing site-specific mutants, we further revealed that acetylation state of lysine (K) 15 on GSK3ß is essential for spindle assembly and chromosome alignment during oocyte meiosis. Moreover, non-acetylation-mimetic mutant GSK3ß-K15R is capable of partly preventing the spindle/chromosome anomalies in oocytes with SIRT3 knockdown. A significant reduction in SIRT3 protein was detected in oocytes from diabetic mice. Of note, forced expression of GSK3ß-K15R ameliorates maternal diabetes-associated meiotic defects in mouse oocytes, with no evident effects on oxidative stress. CONCLUSION: Our data identify GSK3ß as a cytoskeletal regulator that is required for the assembly of meiotic apparatus, and discover a beneficial effect of SIRT3-dependent GSK3ß deacetylation on oocyte quality from diabetic mice.