Submitted to: Nature
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/2015
Publication Date: 12/7/2015
Citation: Jiang, Z., Hong, D., Zheng, X., Donovan, D.M., Chen, J., Tian, X. 2015. mRNA levels of imprinted genes in bovine in vivo oocytes, embryos and cross species comparisons in humans, mice and pigs. Nature. 5:17898. doi: 10.1038/srep17898. Interpretive Summary: There is a need to develop technologies for improving livestock species and to verify and test the role of genes believed to contribute to economically important traits. Stem cells are part of a technology that is believed important to achieving this goal. Understanding these cells and the cellular processes involved in early embryonic gene expression might help make the process for creating livestock stem cells more readily accessible to interested scientists for further experimentation. In this work, bovine embryos and oocytes were subjected to a technology that quantifies gene expression of genes that are known to show imprinting (maternal or paternal factors affect their expression). The results identified patterns of imprinted gene expression and thus implied differences in imprinting status that were maintained across four species. The data presented here will serve as a reference base for scientists interested in expression profiles of imprinted genes by embryos produced from assisted reproductive technologies.
Technical Abstract: Twenty-six confirmed imprinted genes in the bovine were quantified in in vivo produced oocytes and embryos. Eighteen were detectable and their transcriptional abundance were categorized into five patterns: largely decreased (MEST and PLAGL1); first decreased and then increased (CDKN1C and IGF2R); peaked at a specific stage (PHLDA2, SGCE, PEG10 and PEG3); low until peaked in blastocysts (GNAS, MEG3, DGAT1, ASCL2, NNAT, and NAP1L5); and finally constant low (DIRAS3, IGF2, H19 and RTL1). A number of genes were expressed at surprisingly high levels. For instance, the mRNAs for the paternally expressed MEST, and to a lesser extent PLAGL1, were highly abundant in oocytes and could only be expressed from the maternal allele. On the contrary, GNAS and MEG3, both maternally expressed, were barely detectable in bovine oocytes but highly expressed in blastocysts, suggesting that their genomic imprints were not established/recognized until much later in development. Furthermore, we compared these genes to their counterparts in mice, humans and pigs. We found differences in the imprinting status, levels and dynamics of gene expression among these four species. The data presented here will serve as a reference base for expression profiles of imprinted genes by embryos produced from assisted reproductive biotechnologies.