Expression profiling reveals differential expressed genes between bovine IVF and SCNT embryos

Global hypermethylations of histone H3 lysine 9 (H3K9) tri- and di-methylation (H3K9me3/2) have been identified in bovine cloned embryos at the embryonic genome activation (EGA) stage (eight-cell stage), but the intrinsic reason for these anomalies remains elusive. To ascertain key factors responsible for aberrant H3K9 methylation, we performed RNA sequencing of transcripts in eight-cell bovine in vitro fertilized (IVF) and SCNT embryo. From the differentially expressed genes (DEGs) between IVF and SCNT embryos, we identified that the unsuccessful reactivation of two histone demethylases, KDM4D and KDM4E, is responsible for the incomplete H3K9me3/2 demethylation in SCNT embryos at the EGA stage. By mRNA injection, ectopic expression of either KDM4D or KDM4E could erase H3K9me3/2 barriers, improve blastocyst formation, and elevate cloning efficiency of bovine SCNT. To examine the detailed genes responsive to KDM4E overexpression, we also performed RNA sequencing of bovine eight-cell SCNT embryos with KDM4E compensation and found an obvious restoration of global transcriptional patterns in SCNT embryos. Our study first provides the transcriptome data set of bovine IVF and SCNT embryos during EGA with or without KDM4E overexpression, which advance the understanding of incomplete nuclear reprogramming, and contribute to the practical implications for genetically modified livestock breeding using SCNT. RNA-Seq profiles from pools of 8 eight-embryos from bovine IVF (3 replicates) and SCNT with (2 replicates) or without (3 replicates) KDM4E overexpression were generated using Illumina HiSeq 4000. SCNT without KDM4E overexpression are defined as the control compared with the other two samples, respectively.