H3K4 Methylation-Dependent Memory of Somatic Cell Identity Inhibits Reprogramming and Development of Nuclear Transfer Embryos

Eva Hörmanseder,Angela Simeone,George E Allen,Charles R Bradshaw,Magdalena Figlmüller,John Gurdon,Jerome Jullien

doi:10.1016/j.stem.2017.03.003

Eva Hörmanseder, Angela Simeone + Show 5 more

Open Access

https://doi.org/10.1016/j.stem.2017.03.003

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Abstract

SummaryVertebrate eggs can induce the nuclear reprogramming of somatic cells to enable production of cloned animals. Nuclear reprogramming is relatively inefficient, and the development of the resultant embryos is frequently compromised, in part due to the inappropriate expression of genes previously active in the donor nucleus. Here, we identify H3K4 methylation as a major epigenetic roadblock that limits transcriptional reprogramming and efficient nuclear transfer (NT). Widespread expression of donor-cell-specific genes was observed in inappropriate cell types in NT embryos, limiting their developmental capacity. The expression of these genes in reprogrammed embryos arises from epigenetic memories of a previously active transcriptional state in donor cells that is characterized by high H3K4 methylation. Reducing H3K4 methylation had little effect on gene expression in donor cells, but it substantially improved transcriptional reprogramming and development of NT embryos. These results show that H3K4 methylation imposes a barrier to efficient nuclear reprogramming and suggest approaches for improving reprogramming strategies.

Highlights

During development, cells lose their pluripotent status and acquire a stable cell identity, which only rarely, if ever, changes to another kind
Identification of Reprogramming Resistant ON-Memory Genes Expressed in the Wrong Cell Type of nuclear transfer (NT) Embryos The low success rate of current cloning strategies was suggested to be partly due to the persistence of a donor-cell-typespecific gene expression pattern in NT embryos, which could hinder the generation of new cell types (Firas et al, 2014; Liu et al, 2016; Matoba et al, 2014)
As a first step to test this hypothesis, we evaluated the extent of memory gene expression in Xenopus NT embryos on a transcriptome-wide level

Summary

Introduction

Cells lose their pluripotent status and acquire a stable cell identity, which only rarely, if ever, changes to another kind. Somatic cells can be reprogrammed to another cell fate by nuclear transfer (NT) to eggs (Gurdon, 1960), by the expression of a combination of transcription factors (Takahashi and Yamanaka, 2006) or by cell-cell fusion (Blau et al, 1983) In these reprogramming procedures, the geneexpression pattern and epigenetic state characteristic of one differentiated cell identity is erased and the gene expression pattern specific to another cell type is established. The efficiency of complete reprogramming via NT is low, as less than 10% of NT embryos generated from differentiated cells reach adulthood (Gurdon, 1960; Meissner and Jaenisch, 2006) This led to the hypothesis that differentiated cells acquire a resistance to reprogramming procedures, which during normal development, helps to stabilize their cell fate. The epigenetic mechanisms that confer memory of an active state of gene expression and that maintain the differentiated state of cells during nuclear reprogramming and embryonic development remain elusive

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