Single Cell Sequencing Identifies Key Epigenetic Regulators in Nuclear Transfer Mediated Reprogramming [ChIP-seq]

Differentiated cell can be reprogrammed into totipotent embryo through somatic cell nuclear transfer (SCNT). However, this process is highly inefficient and most cloned embryos arrest at certain developmental stages. Through single cell sequencing combined with embryo biopsy, here we generate a global map of DNA methylome and RNA transcriptome for SCNT embryos with distinct developmental fates. We subsequently demonstrate that the unfaithful reactivation of two histone demethylases, Kdm4b and Kdm5b, accounts for the arrest of cloned embryos at 2-cell and 4-cell stage, respectively. Ectopic expression of Kdm4b and Kdm5b in SCNT can remove H3K9me3 barrier, restore the transcription profile and facilitate the blastocyst developmental efficiency over 95%. Moreover, these cloned embryos can further support full-term development and the derivation of SCNT-embryonic stem cells with greater efficiency. Our study reveals that histone methylation reset is crucial for the development of SCNT embryos, which provides a clue to further improve therapeutic cloning. Overall design: Examination of histone H3K9me3 modifications in 2-cell embryos and cumulus cells.