The Involvement Of EZH2 In The Pathogenesis Of Human Recurrent Miscarriage

Recurrent miscarriage(RM)is defined as two or more losses of a clinicallyestablished intrauterine pregnancy before 24 weeks of gestation,which affects 2 to 5% of couples.Despite years of research,it continues to pose a clinically-frustrating and psychologically-charged challenge for both patients and physicians.To date,the etiology of RM remains poorly understood.Accumulating evidence has suggested that epigenetic modifications are involved in early embryogenesis and defects in epigenetic pattern may contribute to the development of RM.EZH2,the core catalytic subunit of Polycomb repressive complex 2(PRC2),mediates transcriptional silencing of target genes through di-and trimethylation of lysine 27 of histone H3(H3K27me2/3).EZH2 typically cooperates with other epigenetic modifications,such as DNA hypermethylation,lncRNA and microRNA,to affect chromatin condensation,and then controls target gene expression.Studies have shown that EZH2 plays an important role in the gametogenesis,embryo implantation and development,organ differentiation and metastasis of some types of malignant tumors in mammals.Here we studied the role of EZH2 in the pathogenesis of RM.We showed that EZH2 expression both at mRNA and protein level significantly decreased in villi from women with RM as compared with control villi.EZH2 knockdown or inactivation attenuated the invasiveness of trophoblast cells.Mechanistically,we found that EZH2 could directly downregulated the expression of E-cadherin and then promoted epithelial-to-mesenchymal transition(EMT)of trophoblast cells.In addition,we further found that EZH2 could indirectly promote EMT through epigenetically silencing tumor suppressor gene CDX1,which suppressed the process of EMT.EZH2 repressed CDX1 expression transcriptionally via direct binding to its promoter region and trimethylation of Histone3-Lysine27.The results were further confirmed by dual-luciferase report assay which showed that transient ectopic expression of EZH2 resulted in significant inhibition of CDX1 promoter activity.In conclusion,the occurrence of RM was related to the decrease of EZH2 expression and the attenuation of trophoblast invasion.EZH2 regulated the invasion of trophoblast cells via direct promotion of EMT,and also via indirect promotion of EMT mediating by transcriptional inhibition of CDX1 expression.Interstingly,we also found that ERK1/2 signal pathway,but not PI3K/AKT signal pathway,was responsible for the increase expression of EZH2 after incubation with progesterone.These findings revealed that molecular mechanisms of EZH2 in trophoblast invasiveness maybe an epigenetic factor reasonable for the administration of progesterone to prevent and cure pathological pregnancy,such as RM.These results suggested that EZH2 maybe a potential therapeutic target for RM.