Transcriptional memory inherited from donor cells is a developmental defect of bovine cloned embryos

Abstract

Studies on the effects of transcriptional memory on clone reprogramming in mammals are limited. In the present study, we observed higher levels of active histone H3 lysine 4 trimethylation (H3K4me3 and 5‐hydroxymethylcytosine) and repressive (5‐methylcytosine) epigenetic modifications in bovine early cloned embryos than in in vitro fertilized embryos. We hypothesized that aberrant epigenetic modification may result in transcriptional disorders in bovine somatic cell nuclear transfer (SCNT) embryos. RNA sequencing results confirmed that both abnormal transcriptional silencing and transcriptional activation are involved in bovine SCNT reprogramming. The cloned embryos exhibited excessive transcription in RNA processing‐ and translation‐related genes as well as transcriptional defects in reproduction‐related genes whose transcriptional profiles were similar to those in donor cells. These results demonstrated the existence of active and silent memory genes inherited from donor cells in early bovine SCNT embryos. Further, H3K4me3‐specific demethylase 5B (KDM5B) mRNA was injected into the reconstructed embryos to reduce the increased H3K4me3 modification. KDM5B overexpression not only reduced the transcriptional level of active memory genes, but also promoted the expression of silent memory genes; in particular, it rescued the expression of multiple development‐related genes. These results showed that transcriptional memory acts as a reprogramming barrier and KDM5B improves SCNT reprogramming via bidirectional regulation effects on transcriptional memory genes in bovines.

Histone Demethylase KDM4D Could Improve the Developmental Competence of Buffalo (Bubalus Bubalis) Somatic Cell Nuclear Transfer (SCNT) Embryos

“…Many different determinants have been identified to be related to SCNT efficiency. They encompass (1) cytological and molecular quality of nuclear recipient oocytes characterized by meiotic, cytoplasmic, and epigenomic maturity parameters (Samiec & Skrzyszowska, 2012; Wang et al, 2018; Gupta et al, 2019); (2) the origin and phenotype of nuclear donor cells (Madheshiya et al, 2015; Em et al, 2016); (3) the capability of donor cell nuclear genome to be epigenetically reprogrammed in a cytoplasm of nuclear-transferred oocytes and descendant blastomeres of corresponding cloned embryos (Opiela et al, 2017; Monika & Selokar, 2018; Samiec & Skrzyszowska, 2018 a , 2018 b ; Zhou et al, 2020); (4) molecular and epigenetic communication between nuclear and mitochondrial genomes in nuclear-transferred oocytes and resultant cloned embryos (Hiendleder et al, 2003; Samiec, 2005 a , 2005 b ; Srirattana et al, 2011); (5) the strategies applied to artificially activate embryo-specific developmental programme of nuclear-transferred oocytes (Saikhun et al, 2004; Samiec & Skrzyszowska, 2010, 2014; George et al, 2011); and (6) the frequency of occurrence of apoptosis-dependent events in the in vitro -cultured nuclear donor cells and SCNT-derived embryos (Cui et al, 2011; Samiec et al, 2013; Agrawal et al, 2018; Mehta et al, 2019; Samiec et al, 2019).…”

Transcriptome Analyses Reveal Differential Transcriptional Profiles in Early- and Late-Dividing Porcine Somatic Cell Nuclear Transfer Embryos

“…Transcriptional memory has been confirmed during SCNT reprogramming [ 25 ], and the transcription profile of the donor cells is preserved in SCNT embryos, owing to incomplete reprogramming. Zhou et al (2020) reported that both abnormal transcriptional activation and transcriptional silencing are involved in the development of bovine SCNT embryos [ 25 ].…”

“…Transcriptional memory has been confirmed during SCNT reprogramming [ 25 ], and the transcription profile of the donor cells is preserved in SCNT embryos, owing to incomplete reprogramming. Zhou et al (2020) reported that both abnormal transcriptional activation and transcriptional silencing are involved in the development of bovine SCNT embryos [ 25 ]. They summarized 70 abnormally active memory genes and 45 abnormally silent memory genes inherited from donor cells, which were conserved between bovine and mouse reprogramming [ 25 , 26 ].…”

“…Zhou et al (2020) reported that both abnormal transcriptional activation and transcriptional silencing are involved in the development of bovine SCNT embryos [ 25 ]. They summarized 70 abnormally active memory genes and 45 abnormally silent memory genes inherited from donor cells, which were conserved between bovine and mouse reprogramming [ 25 , 26 ]. By analyzing the expression levels of these abnormally active or silent memory genes, we found 14 active memory genes and 13 silent memory genes that were differentially expressed in early- and late-dividing groups.…”

“…Combining the findings that the type of donor nucleus used for nuclear transfer affects the timing of the first cleavage [ 32 ] and that the donor cell gnome is likely to modify embryo metabolism and physiology as soon as gene transcription begins during the second half of the 1-cell stage [ 33 ], it is reasonable to infer that somatic cell nuclear reprogramming may be the main factor that affects the timing of the first cleavage of SCNT embryos. Donor cells from different tissues exhibited variable susceptibility to reprogramming, and donor-cell-specific genes showed abundant overexpression in SCNT embryos [ 25 , 27 ]. As many of the donor-cell-specific genes showed abundant overexpression in SCNT embryos, we hypothesized that there might be more abnormal transcriptional activation and transcriptional silencing in late-dividing SCNT embryos if the late-dividing SCNT embryos have a “worse” reprogramming status than the early-dividing embryos.…”