Effects of MG132 on the in vitro development and epigenetic modification of Debao porcine somatic cell nuclear transfer embryos

- The development of porcine nuclear transfer embryos can be improved by treating recipient oocytes or embryos with MG132.
- Treating SCNT embryos with MG132 can result in less apoptotic cells, higher Oct4 expression and cell number of blastocysts.
- Treating SCNT embryos with MG132 can increase the expression of RNA pol, eIF3A and TFIIA at 2-cell and 4-cell stages.
- MG132 treatment can increase the methylation of H3K4me3 and decrease the methylation of H3K9me3 at 1 to 4-cell stages.

The present study was undertaken to examine the effect of MG132, a proteasome inhibitor, on the in vitro development, zygotic genome activation (ZGA) and epigenetic modification of Debao porcine somatic cell nuclear transfer (SCNT) embryos. Treatment of oocytes with 1 μM MG132 from 30 h to 42 h of maturation and SCNT embryos with 5 μM MG132 for 2 h after fusion resulted in higher blastocyst yield (36.5%) of SCNT embryos compared with the control group (11.0%). The ZGA of SCNT embryos at 2- and 4-cell stages was also enhanced by MG132 treatment through altering the RNA pol II status and increasing the expression of eIF3A and TFIIA. Meanwhile, MG132 treatment also resulted in increase of inner cell mass (ICM) and trophectoderm (TE) and total cell numbers and decrease of apoptotic cell numbers of SCNT blastocysts. Expression of BCL-2, OCT4, NANOG and CDX2 in SCNT blastocysts developed from SCNT embryos and oocytes treated with MG132 was increased significantly (P < 0.01), while the expression of pro-apoptotic BAX gene was suppressed significantly (P < 0.01). In addition, MG132 treatment not only affected the expression patterns of H3K9 acetylation, H3K4 and H3K9 trimethylation, but also regulated the relative expression of SMYD3, ASH2L, KDM5B, HAT1, HDAC1 and HDAC2 of Debao porcine SCNT embryos. These results demonstrate that MG132 treatment can improve the developmental potential of Debao porcine SCNT embryos through regulating the expression of genes related to histone acetylation and the processes of ZGA.