Abstract
BackgroundInterspecies somatic cell nuclear transfer (iSCNT) has been regarded as a potential alternative for rescuing highly endangered species and can be used as a model for studying nuclear–cytoplasmic interactions. However, iSCNT embryos often fail to produce viable offspring. The alterations in normal molecular mechanisms contributing to extremely poor development are for the most part unknown.ResultsPrzewalski’s gazelle–bovine iSCNT embryos (PBNT) were produced by transferring Przewalski’s gazelle fibroblast nuclei into enucleated bovine oocytes. The percentages of PBNT embryos that developed to morula/blastocyst stages were extremely low even with the use of various treatments that included different SCNT protocols and treatment of embryos with small molecules. Transcriptional microarray analyses of the cloned embryos showed that the upregulation of reprogramming-associated genes in bovine–bovine SCNT (BBNT) embryos was significantly higher than those observed in PBNT embryos (1527:643). In all, 139 transcripts related to various transcription regulation factors (TFs) were unsuccessfully activated in the iSCNT embryos. Maternal degradation profiles showed that 1515 genes were uniquely downregulated in the BBNT embryos, while 343 genes were downregulated in the PBNT embryos. Incompatibilities between mitochondrial DNA (mtDNA) and nuclear DNA revealed that the TOMM (translocase of outer mitochondrial membrane)/TIMM (translocase of inner mitochondrial membrane) complex-associated genes in BBNT embryos had the highest expression levels, while the PBNT embryos exhibited much lower expression rates.ConclusionsImproper degradation of maternal transcripts, incomplete activation of TFs and abnormal expression of genes associated with mitochondrial function in PBNT embryos likely contributed to incomplete reprogramming of the donor cell nuclei and therefore led to the developmental failure of these cloned embryos.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-1113) contains supplementary material, which is available to authorized users.
Highlights
Interspecies somatic cell nuclear transfer has been regarded as a potential alternative for rescuing highly endangered species and can be used as a model for studying nuclear–cytoplasmic interactions
Treatment of Przewalski’s gazelle–bovine iSCNT embryos (PBNT) embryos with valproic acid (VPA) did not affect embryo development Fused PBNT embryos were treated with VPA at 0.5, 1.0, 2.0 and 4.0 mM for 24 h
1515 were uniquely downregulated in the bovine–bovine Somatic cell nuclear transfer (SCNT) (BBNT) embryos, whereas 343 genes were downregulated in PBNT embryos (Figure 6A). These results suggest that the BBNT embryos were capable of eliciting a more significant degradation of maternal RNA than the PBNT embryos
Summary
Interspecies somatic cell nuclear transfer (iSCNT) has been regarded as a potential alternative for rescuing highly endangered species and can be used as a model for studying nuclear–cytoplasmic interactions. Around 350–400 mature individuals are thought to remain [1] Their range exists today only in a small area surrounding Qinghai Lake [2,3]. Somatic cell nuclear transfer (SCNT) has been successfully utilized in the production of many mammal species including laboratory and domestic animals. Interspecies SCNT (iSCNT) where endangered animal somatic cell nuclei are transferred to domestic oocyte cytoplasts is an approach that might minimize the limitations of SCNT. The iSCNT cloned embryos generated in these studies had extremely poor development to the blastocyst stage. The best results of iSCNT in mammals occurred when using subspecies and sibling species that can hybridize naturally, such as among the cloned argali (Ovis ammon) [13] and the river buffalo (Bubalus bubalus arnee) [14]
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