BÁO CÁO KHOA HỌC VỀ NGHIÊN CỨU VÀ GIẢNG DẠY SINH HỌC Ở VIỆT NAM - HỘI NGHỊ KHOA HỌC QUỐC GIA LẦN THỨ 5 DOI: 10.15625/vap.2022.0095 THE EFFECT OF HISTONE DEACETYLATION INHIBITORS (HDACI) TREATMENT DURING ZYGOTIC GENE ACTIVATION ON PRE- IMPLANTATION DEVELOPMENT OF CLONED BOVINE EMBRYOS Do Minh Tan 1,# , Nguyen Mai Phuong 1,# , Cao Hoang Nam 1 , Nguyen Tuan Anh 1 , Nguyen Huu Hoang Minh 1 , Pham Minh Chien 1 , Pham Quoc Dinh 1 , Nguyen Van Thuan 1,* Abstract: The born of Dolly sheep marked the success of cloned animals by SCNT technique. Until now, many healthy cloned animals were born such as mouse, cow, and monkey. Moreover, cloning technique also carried potential future applications such as animal preservation and human therapy. Therefore, a lot of research focus into improve the success of producing cloned animals. This study aimed to examine the effect of HDACi treatment during the ZGA period. In this study, the effect of HDACi treatment with different concentrations on preimplantation development of cloned bovine embryos is done. SCNT bovine oocytes treated with TSA 5 nM + SCR 125 nM reached the highest rate at morula stage (35.0 %) while untreated group and TSA 10nM + SCR 250 nM groups was only 21.7 % and 21.1 %, respectively. Continually, the rate of cloned bovine blastocyst was 20.0 % for TSA 5 nM + SCR 125 nM. The second experiment was optimizing timing treatment during ZGA for the second step of cloned bovine embryos. According to the result, HDACi treatment at the first step after activation and the second step at 52–62 h after activation had 28.6 % of cloned embryos developed to the blastocyst stage. In conclusion, 2-steps treatment of TSA 5 nM + SCR 125 nM in which the first step occurs during embryo activation timing prolonged to 10 hours and the second step at 52 hours post activation prolonged to 62 hours post activation improved the preimplantation development of cloned bovine embryos and cloned blastocyst formation rates. Keywords: Bovine cloning, HDACi, SCNT, zygotic gene activation. 1. INTRODUCTION The first success of somatic cell nuclear transfer (SCNT) technique on mammalian was labeled by the born of Dolly sheep (Wilmut et al., 1997). However, for more than twenty-years so far, the success rate of producing cloned offspring remained extremely low, only about 2-10 % (Keefer, 2015). Many pieces of evidence demonstrated that abnormal epigenetic modification involves in DNA methylation and histone modification such as acetylation, methylation, phosphorylation and ubiquitylation are likely associated 1 International University, Vietnam National University, Ho Chi Minh City # Equally contributed to this work * Email: nvthuan@hcmiu.edu.vn