Function Of Malathion And Molecular Mechanism Of SURVIVIN In Meiotic Maturation Of Porcine Oocyte

The quality of mammalian oocytes is the basis for ensuring fertilization and embryonic development.The quality of oocytes caused by environmental pollution and abnormal regulation of meiotic progress during oocyte maturation will seriously affect the early embryonic development of mammals and the reproductive capacity of animals.malathion is a broad spectrum nonsystemic organophosphate acaricide/insecticide and it was proved to disturb both male and female mammalian reproduction.However,the mechanisms regarding how malathion affects the mammalian oocyte quality and how to prevent it have not been fully investigated.Pig oocyte maturation undergoes a complex and elaborate meiotic process,the chromosomal passenger complex(CPC)exhibits a highly dynamic distribution during meiosis and assumes corresponding functions during meiosis.SURVIVIN is an essential chromosomal passenger complex(CPC)subunit and participates in cell division,However,the interaction between SURVIVIN and CPC functional subunit AURORA B kinase has not been studied.In this study,we used porcine oocyte as a model to investigate the affect of malathion and the roles of SURVIVIN during porcine oocyte maturation.Our main results are showed as follows:1.Malathion exposure significantly impaired porcine oocyte maturation in a dose dependent manner.malathion decreased the first polar body extrusion by disrupting spindle assembly and chromosome alignment,impairing cortical granules distribution and increasing reactive oxygen species(ROS)level in oocytes.2.RNA-seq analyses showed that malathion altered the m RNA level of 2917 genes in the maturated oocytes and most of these genes were related to ROS,the lipid droplet process and the energy supplement.Nevertheless,these defects could be remarkably ameliorated by adding melatonin into the oocyte maturation medium with malathion.melatonin downregulated gene expression related to lipid droplet metabolism(PPAR? and PLIN2),increased ROS associated gene expression such as GPX4?TP53 and SOD2.3.Melatonin increased oocyte maturation and decreased the abnormities of spindle assembly,cortical granules distribution and ROS accumulation in malathion-exposed porcine oocytes.Melatonin increased the blastocysts formation and the cell numbers of blastocysts in malathion-exposed porcine oocytes after parthenogenetic activation,which was mediated by reduction of ROS levels and maintaining lipid droplet metabolism.4.SURVIVIN was highly expressed in germinal vesicle(GV)and germinal vesicle break down(GVBD)stages oocytes,mainly localized in the germinal vesicle at GV stage and on the chromosomes after GVBD.5.Using RNA interference to specifically deplete SURVIVIN in oocytes during in vitro maturation(IVM).Immunofluorescence assay showed that Survivin-depleted oocytes failed to produce polar body in meiosis I(failed to complete cytokinesis),and they were arrested in metaphase I with misaligned chromosomes.The homologous chromosomes in SURVIVIN-depleted oocytes could not be separated normally.Moreover,both the phosphorylation levels of AURORA B and the transcriptional level of MAD2L1 related to spindle assembly checkpoint(SAC)was decreased in SURVIVIN-depleted oocytes,which thus inhibited the degradation of Cyclin B1(CCNB1)to complete meiosis.