Dear Editor, Methyl-CpG-binding protein 2 (MeCP2) is a ubiquitously expressed nuclear protein originally identified as a methylated DNA binding protein, which is particularly abundant in mature neurons 1,2. Deficiency or excess of MeCP2 causes severe neurological problems. Mutations in MeCP2 account for 95% of the dominant X-linked neurological disorder Rett syndrome 3. MeCP2 have two key functional domains: the methyl-DNA binding domain (MBD) and the transcriptional repressor domain (TRD). Almost all of missense Rett mutations are clustered in these two domains, such as R133C, F155S, T158M in MBD, and R306H in TRD 4,5. The mechanism of the mutations leading to Rett syndrome is still not well understood. Here, we reveal that MeCP2 can drive the liquid-liquid phase separation (LLPS) in complex with DNA. Interestingly, this ability is compromised in the presence of mutations found in Rett syndrome patients, suggesting a potential common mechanism by disrupting LLPS of MeCP2 droplets underlying Rett syndrome. MeCP2 forms sharp condensed foci which highly overlap with DNA dense compartments in neuronal nuclei 6,7. Recently, LLPS has been recognized as an important mechanism to condensate molecules to form membraneless compartments within a cell 8. As both the MBD and TRD of MeCP2 bind to DNA 9 , we hypothesized that the sharp puncta of MeCP2 in the nuclei were phase separated liquid droplets mediated by multivalent interactions between MeCP2 and DNA. To test this hypothesis, we purified full-length recombinant His-MBP-MeCP2 (mouse MeCP2-e2 if not specified) and released

Resveratrol (Res) has been reported to be able to improve oocyte vitrification because of its antioxidative properties. The objective of this study was to further assess the positive effect of Res addition on the developmental potential of vitrified mouse oocytes from the perspective of epigenetic alterations. First, 2 μM Res was chosen as the optimal concentration on the basis of its effects on survival and its antioxidative properties. We found that Res addition significantly promoted fertilization (63.8% vs. 42.9%) and blastocyst formation (68.3% vs. 50.2%) after oocyte vitrification. The quality of the derived blastocysts was also higher after Res treatment. Regarding epigenetic aspects, the expression of the important deacetylase SIRT1 was found to decrease significantly upon vitrification, but it was rescued by Res. The abnormal levels of H3K9 acetylation and DNA methylation in vitrified oocytes were restored by Res addition. Moreover, the expression of several imprinted genes was affected by oocyte vitrification. Among them, abnormal Gtl2 and Peg3 expression levels were restored by Res addition. Therefore, the methylation of their imprinted control regions (ICRs) was examined. Surprisingly, the abnormal patterns of Gtl2 and Peg3 methylation in blastocysts developed from vitrified oocytes were both restored by Res addition. Finally, the full‐term embryonic development showed that the birth rate was improved significantly by Res addition (56.2% vs. 38.1%). Collectively, Res was beneficial for the pre‐ and postimplantation embryonic development. Except for the antioxidative activity, Res also played a role in the correction of some abnormal epigenetic modifications caused by oocyte vitrification.

Accumulating studies have suggested that microRNA play a part in regulating multiple cellular processes, such as cell proliferation, apoptosis, the cell cycle, and embryo development. This study explored the effects of miR-101-2 on donor cell physiological status and the development of Holstein cow somatic cell nuclear transfer (SCNT) embryos in vitro. Holstein cow bovine fetal fibroblasts (BFF) overexpressing miR-101-2 were used as donor cells to perform SCNT; then, cleavage rate, blastocyst rate, inner cell mass-to-trophectoderm ratio, and the expression of some development-and apoptosis-related genes in different groups were analyzed. The miR-101-2 suppressed the expression of inhibitor of growth protein 3 (ING3) at mRNA and protein levels, expedited cell proliferation, and decreased apoptosis in BFF, suggesting that ING3, a target gene of miR-101-2, is a potential player in this process. Moreover, by utilizing donor cells overexpressing miR-101-2, the development of bovine SCNT embryos in vitro was significantly enhanced; the apoptotic rate in SCNT blastocysts was reduced, and the inner cell mass-totrophectoderm ratio and SOX2, POU5F1, and BCL2L1 expression significantly increased, whereas BAX and ING3 expression decreased. Collectively, these findings suggest that miR-101-2 promotes BFF proliferation and vitality, reduces their apoptosis, and improves the early development of SCNT embryos.