Retrotransposon expression as a defining event of genome reprograming in fertilized and cloned bovine embryos

Abstract

Genome reprograming is the ability of a nucleus to modify its epigenetic characteristics and gene expression pattern when placed in a new environment. Low efficiency of mammalian cloning is attributed to the incomplete and aberrant nature of genome reprograming after somatic cell nuclear transfer (SCNT) in oocytes. To date, the aspects of genome reprograming critical for full-term development after SCNT remain poorly understood. To identify the key elements of this process, changes in gene expression during maternalto-embryonic transition in normal bovine embryos and changes in gene expression between donor cells and SCNT embryos were compared using a new cDNA array dedicated to embryonic genome transcriptional activation in the bovine. Three groups of transcripts were mostly affected during somatic reprograming: endogenous terminal repeat (LTR) retrotransposons and mitochondrial transcripts were up-regulated, while genes encoding ribosomal proteins were downregulated. These unexpected data demonstrate specific categories of transcripts most sensitive to somatic reprograming and likely affecting viability of SCNT embryos. Importantly, massive transcriptional activation of LTR retrotransposons resulted in similar levels of their transcripts in SCNT and fertilized embryos. Taken together, these results open a new avenue in the quest to understand nuclear reprograming driven by oocyte cytoplasm.

Comprehensive cross production system assessment of the impact of in vitro microenvironment on the expression of messengers and long non-coding RNAs in the bovine blastocyst

“…Genomic assembly of these ESTs and functional analyses through their knock down is underway. Our results showing that, in addition to protein encoding RNAs, mitochondrial RNAs and also lncRNAs are important component of the embryonic transcriptome corroborates results from Bui et al (2009). However, in this report, quantification of one of the retrotransposons at the morulae stage showed similar levels between in vitro fertilized and Figure 7 Pathway influenced by the presence of serum during either IVM or IVC (treatments 3 and 4).…”

“…cloned from somatic cell nuclear transfer (SCNT) counterparts, which is indicative of normal reprogramming (Bui et al 2009). In contrast, we report in this study that the in vitro culture environment is influencing the level of expression of lncRNAs.…”

Diversity and functional convergence of small noncoding RNAs in male germ cell differentiation and fertilization

“…6A). The reason for this replacement is not fully understood, but it has been reported that differential expression of transposable elements triggers sequential reprogramming on the embryonic genome (Peaston et al 2004;Bui et al 2009). First, by NGS and later confirmed by RT-qPCR, we detected high expression levels of mmur001272954 small RNA, which was classified as endosiRNA.…”

An integrated platform for bovine DNA methylome analysis suitable for small samples

“…In this regard, robust LTR retrotransposon up-regulation has been shown during activation of the bovine embryo genome [63] and found to be a general requirement for progression through to the cleavage stage in mouse embryos [64, 65]. However, the nature of its role in mammalian early development remains elusive.…”