The Research On Role And Mechanism Of H3K9me3 In The Maturation Of Mouse Oocytes

Oocyte maturation includes cytoplasmic maturation and nuclear maturation.Cytoplasmic maturation includes the redistribution of mitochondria,endoplasmic reticulum and other important organelles.Nuclear maturation mainly refers to the change of chromatin structure and state in oocytes.The development of cytoplasm and nucleus are interrelated and dependent on each other,and their maturation synchronization is vital to the growth of gametes,subsequent fertilization,genome reprogramming and zygote activation.Both cytoplasmic maturation and nuclear maturation are regulated by sophisticated and strict spatiotemporal modification mechanisms.Asynchrony of maturation leads to oocyte maturation disorders.At present,the mechanism of oocyte maturation disorder is not perfect,and epigenetic modification may be involved in regulating the development and maturation of oocytes.The development of oocytes is accompanied by a variety of epigenetic modifications,especially histone methylation modifications.Histone H3K9 methylation modification refers to the modification of lysine N-terminal at position 9 of histone 3 on the surface of nucleosome by set domain containing methyltransferase or demethyltransferase,real-time regulation of methylation occurs.And H3K9me3 is generally considered to be closely related to heterochromatin formation and gene silencing.SUV39H1(suppressor of variegation3-9 homolog 1)is an H3K9 methyltransferase that can specifically catalyze the formation of H3K9me3.As oocytes enter meiosis,the chromatin changes from loose to condensed and the genome stops transcription with higher developmental potential.The level of H3K9me3 modification in cells has increased significantly,which is essential for switching oocytes from NSN type to SN type.This study analyzed the effect of SUV39H1 overexpression on GV oocyte maturation,and explored the possible mechanism of H3K9me3 regulating maturation of mouse oocytes.ObjectiveThis study focused on the possible mechanism by which H3K9me3 regulates mouse oocyte maturation,laying a theoretical foundation for the later detection of the epigenetic modification of human immature oocytes and analyzing other important epigenetic modification sites that affect human oocyte maturation.MethodsIn this study,we supplemented with IBMX to maintain oocytes at the GV stage and constructed SUV39H1 mRNA that could be used for micro-injection of mouse GV oocytes and mouse zygotes.We detected whether SUV39H1 mRNA was effectively translated in oocytes by Western blotting.The level of H3K9me3 modification and the maturation rate of the oocytes were compared and analyzed in the GV oocytes and SUV39H1 overexpressed oocytes by immunofluorescence staining and the morphology of oocytes.Then,we analyzed the H3K9me3 modification changes,the effect of SUV39H1 overexpression on early embryo development and transplantation offspring between control mouse zygotes and SUV39H1 overexpression zygotes by immunofluorescence staining and early embryo development.Results1.In untreated controls,the level of H3K9me3 modification in SN oocytes was significantly higher than that of NSN oocytes;H3K9me3 modification was significantly increased in SUV39H1 overexpression mouse oocytes compared with control oocytes.2.SUV39H1 overexpression significantly promoted GVBD in immature GV oocytes by increasing the level of H3K9me3 modification and broke through IBMX block after being cultured in vitro;however,these oocytes showed a higher rate of aberrant chromosome arrangement in the metaphase of the first meiosis.3.The overexpression of SUV39H1 increased the level of H3K9me3 modification,and both of them synergistically promoted the recruitment of HP1.4.SUV39H1 overexpression significantly altered H3K9me3 of the male pronucleus in the zygote and changed the asymmetrical phenotype of the male and female pronuclei;however,this had no significant effect on the early embryo development and transplanted offspring.Conclusions1.SUV39H1 overexpression increased H3K9me3 levels and promoted the rates of GVBD.2.H3K9me3 modification could recruit HP1 to participate in heterochromatin formation,and SUV39H1 overexpression might also directly promote HP1 recruitment and chromatin condensation.3.In this study,a single epigenetic modification in the zygote stage of mouse had a relatively weak influence on early embryo development.