Project description:Mammalian oocytes can reprogram somatic cells into totipotent state, which allows animal cloning through somatic cell nuclear transfer (SCNT). However, the great majority of SCNT embryos fail to develop to term due to poorly defined reprogramming defects. Here we demonstrate that histone H3 lysine 9 trimethylation (H3K9me3) in donor nuclei is a major epigenetic barrier that prevents efficient nuclear reprogramming in mouse oocytes. Comparative transcriptome analysis of early embryos revealed reprogramming resistant regions (RRRs) where transcriptional activation at 2-cell embryos is inhibited by SCNT compared to in vitro fertilization (IVF). RRRs significantly overlap with H3K9me3 enrichment in donor somatic cells. Importantly, removal of the H3K9me3 by ectopic expression of an H3K9me3 demethylase Kdm4d in recipient oocytes not only reactivates most RRRs, but also greatly improves development of SCNT embryos. Furthermore, the use of Suv39h1/2-depleted somatic nuclei as donors also greatly improves the development of SCNT embryos. Our study thus reveals H3K9me3 as an epigenetic barrier in SCNT-mediated reprogramming and provides a feasible method for improving mammalian cloning efficiency.
Project description:KMT1A (also known as SUV39H1)was involved in improving reprogramming efficiency during inducing pluripotent stem cells (iPSC). However, the knowledge about KMT1A regulating somatic cell nuclear transfer (SCNT) mediated reprogramming was limited. To understand the role of KMT1A during SCNT embryos in vitro development; we performed based transcriptome profiling in SCNT embryos at 8-cell stages and KMT1A knockdown 8-cell SCNT embryos. The data show the mRNAs regulated after KMT1A was down-regulated.
Project description:As a histone hallmark for transcription repression, Histone H3 lysine 27 trimethylation (H3K27me3) plays important roles in mammalian embryo development and induced pluripotent stem cells (iPSCs) generation. However, the expression profile and roles of H3K27me3 in bovine somatic cell nuclear transfer (SCNT) reprogramming remain poorly understood. In this study, we find SCNT embryos exhibit global hypermethylation of H3K27me3 from two-cell to eight-cell stage and its removal by ectopically expressed H3K27me3 demethylase-KDM6A could greatly improves SCNT efficiency. To illuminate the mechanism of improving SCNT reprogramming efficiency of KDM6A overexpression, we performed RNA sequencing of transcripts in SCNT morula with or without KDM6A overexpression. RNA-seq reveal that KDM6A overexpression could enhance transcription of genes mainly involved cell adhesion and cellular metabolism process, as well as X-linked genes. We first provides the transcriptome data of bovine SCNT morula with or without KDM6A overexpression. Meanwhile, we compared the differences of transcriptome between SCNT eight-cell embryos and morula. Our study provide a more promising approach to improving the efficiency of SCNT reprogramming and contribute to understanding the mechanism of first cell fate determine during embryo development in bovine.
Project description:The extremely low efficiency of human embryonic stem cell (hESC) derivation using somatic cell nuclear transfer (SCNT) limits potential application. Blastocyst formation from human SCNT embryos occurs at a low rate and with only some oocyte donors. We previously showed in mice that reduction of histone H3 lysine 9 trimethylation (H3K9me3) through ectopic expression of the H3K9me3 demethylase Kdm4d greatly improves SCNT embryo development. Here we show that overexpression of a related H3K9me3 demethylase KDM4A improves human SCNT, and that, as in mice, H3K9me3 in the human somatic cell genome is an SCNT reprogramming barrier. Overexpression of KDM4A significantly improves the blastocyst formation rate in human SCNT embryos by facilitating transcriptional reprogramming, allowing derivation of NTESCs from all oocyte donors tested using adult AMD patient somatic nuclei donors. This conserved mechanistic insight has potential applications for improving SCNT in a variety of contexts, including regenerative medicine. Here we perform RNA-seq based transcriptome profiling in human Donor (fibroblast cells), in vitro fertilized embryos at 8-cell stages (IVF_8Cell), somatic cell nuclear transfer embryos at 8-cell stages (SCNT_8Cell), SCNT assisted by KDM4A 8-cell embryos (SCNT_KDM4A_8Cell). Besides, we also perform RNA-seq in Control human ES cells (CTR_hES) and SCNT assisted by KDM4A derived human ES cells (NTK) with duplicates.Â
Project description:Mammalian oocytes have the ability to reset the transcriptional program of differentiated somatic cells into that of totipotent embryos through somatic cell nuclear transfer (SCNT). However, the mechanisms underlying SCNT-mediated reprogramming are largely unknown. To understand the mechanisms governing chromatin reprogramming during SCNT, we profiled DNaseI hypersensitive sites (DHSs) in donor cumulus cells and 1-cell stage SCNT embryos. To our surprise, the chromatin accessibility landscape of the donor cells is drastically changed to recapitulate that of the in vitro fertilization (IVF)-derived zygotes within 12 hours. Interestingly, this DHS reprogramming takes place even in the presence of a DNA replication inhibitor, suggesting that SCNT-mediated DHS reprogramming is independent of DNA replication. Thus, the study not only reveals the rapid and drastic nature of the changes in chromatin accessibility through SCNT, but also provides a DNA replication-independent model for studying cellular reprogramming.
Project description:Placental gene expression in pregnancies established after the transfer of day 7 blastocysts derived from in vitro (IVP), somatic cell nuclear transfer (SCNT) and in vivo (AI) embryos
Project description:Animal cloning has been achieved in many species by transplanting differentiated cell nuclei to unfertilized oocytes. However, the low efficiencies of cloning have remained an unresolved issue. We find that the combination of two small molecules, trichostatin A (TSA) and vitamin C (VC), under culture condition with deionized bovine serum albumin (dBSA), dramatically improves the cloning efficiency in mice and 15% of cloned embryos develop to term by means of somatic cell nuclear transfer (SCNT). RNA-seq analyses of SCNT embryos at the 2-cell stage revealed that the treatment with TSA, followed by the VC treatment, resulted in the upregulated expression of the previously identified reprogramming-resistant genes. Moreover, the expression of 2-cell-specific retroelements was upregulated by the sequential treatment with TSA and VC. The best condition for reprogramming is to add TSA for 8 hours after nuclear transfer and then SCNT embryos are further cultured with VC for 7 hours.
Project description:We hypothesized aberrant transcriptional silence was existed in bovine clone reprogramming as well as abnormal transcriptional activation and the result of RNA-seq confirmed this hypothesis. On the one hand, SCNT (somatic cell nuclear transfer) embryos exhibited excessive RNA processing and translation while these two biological processes were deficient in human and mouse; on the other hand, SCNT embryos exhibited the transcriptional defects of reproduction-related genes. These results proved the existences of active- and silent-memory genes which inherited from donor cells in bovine early SCNT embryos. Then, H3K4me3-specific demethylase 5B (KDM5B) mRNAs were injected into cloned embryos to erase active or silent memory respectively. KDM5B overexpression not only reduced the transcription level of active-memory genes but also promoted the expression of silent-memory genes, especially rescued multiple development-related genes.