Dnmt3l-knockout donor cells improve somatic cell nuclear transfer reprogramming efficiency. 
Nuclear transfer (NT) is a technique used to investigate the development and reprogramming potential of a single cell.  DNA methyltransferase-3-like, which has been characterized as a repressive transcriptional regulator, is expressed in naturally fertilized egg and morula/blastocyst at pre-implantation stages.  In this study, we demonstrate that the use of Dnmt3l-knockout (Dnmt3l-KO) donor cells in combination with Trichostatin A treatment improved the developmental efficiency and quality of the cloned embryos.  Compared with the WT group, Dnmt3l-KO donor cell-derived cloned embryos exhibited increased cell numbers as well as restricted OCT4 expression in the inner cell mass (ICM) and silencing of transposable elements at the blastocyst stage.  In addition, our results indicate that zygotic Dnmt3l is dispensable for cloned embryo development at pre-implantation stages.  In Dnmt3l-KO mouse embryonic fibroblasts, we observed reduced nuclear localization of HDAC1, increased levels of the active histone mark H3K27ac and decreased accumulation of the repressive histone marks H3K27me3 and H3K9me3, suggesting that Dnmt3l-KO donor cells may offer a more permissive epigenetic state that is beneficial for NT reprogramming.