Many strategies have been established to improve the efficiency of somatic cell nuclear transfer (SCNT), but relatively few focused on improving culture conditions. The effect of different culture media on preimplantation development of mouse nuclear transfer embryos was investigated. A modified sequential media method, named D media (M16/KSOM and CZB-EG/KSOM), was successfully established that significantly improves SCNT embryo development. Our result demonstrated that while lacking any adverse effect on in vivo fertilized embryos, the D media dramatically improves the blastocyst development of SCNT embryos compared with other commonly used media, including KSOM, M16, CZB, and αMEM. Specifically, the rate of blastocyst formation was 62.3% for D1 (M16/KSOM) versus 10–30% for the other media. An analysis of media components indicated that removing EDTA and glutamine from the media can be beneficial for early SCNT embryo development. Our results suggest that in vitro culture environment plays an important role in somatic cell reprogramming, and D media represent the most efficient culture method reported to date to support mouse SCNT early embryo development in vitro.
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Xiangpeng Dai, Jie Hao, and Qi Zhou
Cheng Peng, Zhuo Lv, Tang Hai, Xiangpeng Dai, and Qi Zhou
Trichostatin A (TSA), a histone deacetylase (HDAC) inhibitor, can significantly improve the reprogramming efficiency of somatic cells. However, whether TSA has a detrimental effect on other kinds of embryos is largely unknown because of the lack of integrated analysis of the TSA effect on natural fertilized embryos. To investigate the effect of TSA on mouse embryo development, we analyzed preimplantation and post-implantation development of in vivo, in vitro fertilized, and parthenogenetic embryos treated with TSA at different concentrations and durations. In vivo fertilized embryos appeared to be the most sensitive to TSA treatment among the three groups, and the blastocyst formation rate decreased sharply as TSA concentration and treatment time increased. TSA treatment also reduced the livebirth rate for in vivo fertilized embryos from 56.59 to 38.33% but did not significantly affect postnatal biological functions such as the pups’ reproductive performance and their ability for spatial learning and memory. Further analysis indicated that the acetylation level of H3K9 and H4K5 was enhanced by TSA treatment at low concentrations, while DNA methylation appeared to be also disturbed by TSA treatment only at high concentration. Thus, our data indicates that TSA has different effects on preimplantation embryonic development depending on the nature of the embryo’s reproductive origin, the TSA concentration and treatment time, whereas the effect of TSA at the indicated concentration on postnatal function was minor.
Yanhui Zhai, Meng Zhang, Xinglan An, Sheng Zhang, Xiangjie Kong, Qi Li, Hao Yu, Xiangpeng Dai, and Ziyi Li
Pre-implantation embryos undergo genome-wide DNA demethylation, however certain regions, like imprinted loci remain methylated. Further, the mechanisms ensuring demethylation resistance by TRIM28 in epigenetic reprogramming remain poorly understood. Here, TRIM28 was knocked down in oocytes, and its effects on porcine somatic cell nuclear transfer (SCNT) embryo development was examined. Our results showed that SCNT embryos constructed from TRIM28 knockdown oocytes had significantly lower cleavage (53.9 ± 3.4% vs 64.8 ± 2.7%) and blastocyst rates (12.1 ± 4.3% vs 19.8 ± 1.9%) than control-SCNT embryos. The DNA methylation levels at the promoter regions of the imprinting gene IGF2 and H19 were significantly decreased in the 4-cell stage, and the transcript abundance of other imprinting gene was substantially increased. We also identified an aberrant two-fold decrease in the expression of CXXC1and H3K4me3 methyltransferase (ASH2L and MLL2), and the signal intensity of H3K4me3 had a transient drop in SCNT 2-cell embryos. Our results indicated that maternal TRIM28 knockdown disrupted the genome imprints and caused epigenetic variability in H3K4me3 levels, which blocked the transcription activity of zygote genes and affected the normal developmental progression of porcine SCNT embryos.