Chen Huanhuan, Zhang Lei, Deng Tengfei, Zou Pengda, Wang Yongsheng, Quan Fusheng, Zhang Yong
Key Laboratory of Animal Biotechnology of the Ministry of Agriculture, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China.
Key Laboratory of Animal Biotechnology of the Ministry of Agriculture, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China.
Theriogenology. 2016 Aug;86(3):868-78. doi: 10.1016/j.theriogenology.2016.03.008. Epub 2016 Mar 12.
Oocyte cryopreservation has a great impact on subsequent embryonic development. Currently, several studies have primarily focused on the consequences of vitrification and the development potential of cellular structures. This study determined whether oocyte vitrification caused epigenetic instabilities of bovine embryos. The effects of oocyte vitrification on DNA methylation, histone modifications, and putative imprinted genes' expression in early embryos derived by intracytoplasmic sperm injection were examined. Results showed that oocyte vitrification did not affect zygote cleavage rates (67.0% vs. 73.8% control, P > 0.05) but reduced the blastocyst rate (9.6% vs. 23.0%, P < 0.05). The levels of DNA methylation and H3K9me3 in oocytes and early cleavage embryos were lower (P < 0.05) than those in control group, but the level of acH3K9 increased (P < 0.05) in the vitrification group during the early cleavage phases. No differences were observed for DNA methylation, H3K9me3, and acH3K9 in the inner cell mass of blastocysts, whereas decreased levels of DNA methylation and acH3K9 (P < 0.05) existed in TE cells after vitrification. The expression of putative-imprinted genes PEG10, XIST, and KCNQ1O1T was upregulated in blastocysts. These epigenetic abnormalities may be partially explained by altered expression of genes associated with epigenetic regulations. DNA methylation and H3K9 modification suggest that oocyte vitrification may excessively relax the chromosomes of oocytes and early cleavage embryos. In conclusion, these epigenetic indexes could be used as damage markers of oocyte vitrification during early embryonic development, which offers a new insight to assess oocyte vitrification.
卵母细胞冷冻保存对后续胚胎发育有很大影响。目前，多项研究主要集中在玻璃化的后果以及细胞结构的发育潜力上。本研究确定卵母细胞玻璃化是否会导致牛胚胎的表观遗传不稳定。研究了卵母细胞玻璃化对通过胞浆内单精子注射获得的早期胚胎中DNA甲基化、组蛋白修饰和假定印记基因表达的影响。结果显示，卵母细胞玻璃化不影响合子的分裂率（67.0%对73.8%，对照组，P>0.05），但降低了囊胚率（9.6%对23.0%，P<0.05）。卵母细胞和早期分裂胚胎中的DNA甲基化水平和H3K9me3水平低于对照组（P<0.05），但在玻璃化组早期分裂阶段，acH3K9水平升高（P<0.05）。在囊胚的内细胞团中，未观察到DNA甲基化、H3K9me3和acH3K9的差异，而玻璃化后滋养层细胞中的DNA甲基化和acH3K9水平降低（P<0.05）。假定印记基因PEG10、XIST和KCNQ1OT在囊胚中的表达上调。这些表观遗传异常可能部分由与表观遗传调控相关基因的表达改变来解释。DNA甲基化和H3K9修饰表明，卵母细胞玻璃化可能过度松弛了卵母细胞和早期分裂胚胎的染色体。总之，这些表观遗传指标可作为早期胚胎发育过程中卵母细胞玻璃化损伤的标志物，为评估卵母细胞玻璃化提供了新的视角。
