Dataset Information

Imprinted genes and satellite loci are differentially methylated in bovine somatic cell nuclear transfer clones.

ABSTRACT: In mammals, genome-wide epigenetic reprogramming systems exist in primordial germ cells and zygotes. These reprogramming systems play crucial roles in regulating genome functions during critical stages of embryonic development, and they confer the stability of gene expression during mammalian development. The frequent unexpected loss of progeny from somatic cell nuclear transfer (SCNT) is an ongoing problem. In this study, we used six cloned bovines (named NT-1 to NT-6), which were created by ear fibroblast nuclear transfer and displayed short life spans with multiple organ defects, as an experimental model. We focus here on three imprinted genes (IGF2, H19, and XIST) and four satellite loci (Satellite I, Satellite II, Art2, and VNTR) to investigate their methylation changes. The results revealed that aberrant methylation frequently occurred in the analyzed imprinted genes, but not in the satellite loci, of the cloned bovines. After the bovine fibroblast cells were treated with the 5-aza-2(')-deoxycytidine (5-Aza-dc) demethylation agent, the methylation percentages of the XIST and H19 putative differentially methylated region (DMR) were significantly decreased (XIST, p<0.01; H19, p<0.05) followed by an increase in their mRNA expression levels (p<0.01). Furthermore, we found that five short-lived cloned bovines (NT-1 to NT-5) exhibited more severe aberrant methylation changes in the three imprinted genes examined than the little longer-lived clone (NT-6) compared with wild-type (WT) cows. Our data suggest that the reprogramming of the methylation-controlled regions between the imprinted genes and satellite loci are differences and may be involved with additional mechanisms that need further elucidation.

SUBMITTER: Shen CJ

PROVIDER: S-EPMC3787327 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature

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Imprinted genes and satellite loci are differentially methylated in bovine somatic cell nuclear transfer clones.

Shen Chih-Jie CJ Lin Chiao-Chieh CC Shen Perng-Chih PC Cheng Winston T K WT Chen Hsiao-Ling HL Chang Tsung-Chou TC Liu Shyh-Shyan SS Chen Chuan-Mu CM

Cellular reprogramming 20130820 5

In mammals, genome-wide epigenetic reprogramming systems exist in primordial germ cells and zygotes. These reprogramming systems play crucial roles in regulating genome functions during critical stages of embryonic development, and they confer the stability of gene expression during mammalian development. The frequent unexpected loss of progeny from somatic cell nuclear transfer (SCNT) is an ongoing problem. In this study, we used six cloned bovines (named NT-1 to NT-6), which were created by ea ...[more]

PMID: 23961768

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Project description:Incomplete epigenetic reprogramming is postulated to contribute to the low developmental success following somatic cell nuclear transfer (SCNT). Here, we describe the epigenetic reprogramming of DNA methylation at an alpha satellite I CpG site (αsatI-5) during development of cattle generated either by artificial insemination (AI) or in vitro fertilization (IVF) and SCNT. Quantitative methylation analysis identified that SCNT donor cells were highly methylated at αsatI-5 and resulting SCNT blastocysts showed significantly more methylation than IVF blastocysts. At implantation, no difference in methylation was observed between SCNT and AI in trophoblast tissue at αsatI-5, however, SCNT embryos were significantly hyper-methylated compared to AI controls at this time point. Following implantation, DNA methylation at αsatI-5 decreased in AI but not SCNT placental tissues. In contrast to placenta, the proportion of methylation at αsatI-5 remained high in adrenal, kidney and muscle tissues during development. Differences in the average proportion of methylation were smaller in somatic tissues than placental tissues but, on average, SCNT somatic tissues were hyper-methylated at αsatI-5. Although sperm from all bulls was less methylated than somatic tissues at αsatI-5, on average this site remained hyper-methylated in sperm from cloned bulls compared with control bulls. This developmental time course confirms that epigenetic reprogramming does occur, at least to some extent, following SCNT. However, the elevated methylation levels observed in SCNT blastocysts and cellular derivatives implies that there is either insufficient time or abundance of appropriate reprogramming factors in oocytes to ensure complete reprogramming. Incomplete reprogramming at this CpG site may be a contributing factor to low SCNT success rates, but more likely represents the tip of the iceberg in terms of incompletely reprogramming. Until protocols ensure the epigenetic signature of a differentiated somatic cell is reset to a state resembling totipotency, the efficiency of SCNT is likely to remain low.

Project description:Since the first cloned animal Dolly Sheep was successfully created by using somatic cell nuclear transfer(SCNT) technique. It has become an irreplaceable tool to understand nuclear reprogramming and totipotency and holds huge potentials for regenerative medicine. However, extremely poor development rate of SCNT embryos indicates it is still questionable. The nature of reprogramming oocyte factors and their mechanism of action remain largely unknown.It is evident that the major barrier that hinders the developing iSCNT embryo mainly appears at the time of embryonic genome activation (EGA), which primarily occurs at the eight-cell stage in mammalian. The interspecies somatic cell nuclear transfer (iSCNT) is desired model for nuclear reprogramming research and a powerful tool for discovering the master genome activation genes. In this study, a valuable transcriptome recourse of iSCNT embryos was established, which derived from more than 2000 clone embryos of four different inter-family donor cells. Based on weighted gene co-expression network (WGCNA) approach, we provide an extensive transcriptome analysis of differentially expressed genes(DEG) for iSCNT embryos. The total gene expression patterns of different iSCNT embryos were discussed. 26 cell-specific modules with were identified, and those module significance and GO enriched categories were analyzed. The regulatory pathways of reprogramming barriers were further enriched. As master genome trigger genes, the transcripts related to TFIID subunit, RNA polymerase and Mediator were incomplete activated in iSCNT embryos. This indicated that pioneer factors, present in the cytoplasm of the oocyte, were failed to bind the sequence target on the heterology nuclear genome. This genomic incompatibility between the nuclear donor cell and the cytoplast may be as a major contributing factor causes the developmental failure of iSCNT cloned embryos. This study demonstrates that the iSCNT embryos undergoes only partial or incomplete reprogramming at eight-cell stage in mammalian. Our results offered convincing evidence that the abnormal expression of key master pathways may be caused the embryo developmental block of cloning embryo. This work will contribute to a better understanding of the molecular interaction between nuclear–cytoplasmic interaction and provides insight into the molecular determinants of nuclear reprogramming, human embryonic stem cell (hESC)-based therapies and rescuing highly endangered species.

Dataset Information

Imprinted genes and satellite loci are differentially methylated in bovine somatic cell nuclear transfer clones.

Publications

Imprinted genes and satellite loci are differentially methylated in bovine somatic cell nuclear transfer clones.

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