RNA sequencing and transcriptome analysis of buffalo (Bubalus bubalis) blastocysts produced by somatic cell nuclear transfer and in vitro fertilization

Abstract

Across farm animal species, the live birth rate obtained with somatic cell nuclear transfer (SCNT) embryos is only <2% compared with >40% obtained with in vitro fertilization (IVF) embryos, primarily due to incomplete nuclear reprogramming which results in aberrant embryonic gene expression. We used RNA sequencing to compare the global transcriptome profile of SCNT and IVF buffalo blastocysts. SCNT blastocysts expressed 17,061 transcripts, of which 941 were unique whereas, IVF blastocysts expressed 17,303 transcripts, of which 1,183 were unique. At ≥2-folds change (p < .05), 331 transcripts were differentially expressed in the two groups among which, 19 were unique, 188 were downregulated and 143 were upregulated in SCNT compared with IVF blastocysts. Many genes affecting pluripotency, trophectoderm development, developmental regulation, and epigenetic modifications were upregulated in SCNT compared with IVF blastocysts. Among the four functional categories analyzed, epigenetic regulators were the most affected. Most of the WNT signaling pathway genes were upregulated whereas, the inhibitors of this pathway, such as DKK1, were downregulated in SCNT blastocysts, suggesting that this pathway is overexpressed in SCNT embryos. Gene Ontology analysis revealed that 25 biological processes, 20 molecular functions, and 24 cellular compartment categories were enriched in SCNT blastocysts. This data can help identify reprogramming errors for improving cloning efficiency.

Keywords: IVF; RNA Seq; blastocyst; differential expression; nuclear transfer; transcriptome.