Genes physically held in silencing 'lock-down' in embryonic stem cells

August 31, 2015, Babraham Institute
Left-hand figure: the wild type mouse ESC genome, right-hand figure: reduced interactions in a mouse ESC genome from mouse ESCs lacking PRC1. The thickness of the lines relates to strength of interactions. Loss of the yellow lines demonstrates loss of biologically significant interactions. Credit: Schoenfelder et al. Nature Genetics, 2015

Researchers at the Babraham Institute have discovered a strong physical gene interaction network that is responsible for holding genes in a silencing grip during early development. In the same way that people can interact with others in close proximity, say within the same room, or others millions of miles apart, there are also short- and long-range interactions within the genome forming a three-dimensional configuration where different parts of the genome come into contact with each other. The research, reported online in Nature Genetics, presents how key decision-making genes which specify the embryo's blueprint for subsequent development are physically clustered in the nucleus of embryonic stem cells and maintained in a silent state.

The different cell types forming an embryo are derived from (ESCs). These cells are self-renewing and are maintained in an undifferentiated state meaning that they have the potential to become any cell type in the body. To become a specific cell type, embryonic progress along a developmental pathway, losing their stem cell characteristics and gaining new features. At a genomic level, assuming a specialised cellular identity reflects the switching on of appropriate . Conversely, maintaining a stem cell identity requires the repression of developmental genes.

Using a novel technique developed at the Babraham Institute (Promoter Capture Hi-C), the researchers identified an unusually strong 3D network of developmental genes in ESCs. These genes encode proteins that establish the embryo's body plan and direct organ development. As an ESC, you don't want these instructions being read at this stage and so to prevent this, the genes are clustered together and silenced. The research showed that at the heart of this repression is a protein complex called Polycomb repressive complex (PRC1), a master regulator of ESC genome architecture. The research therefore establishes a mechanism, acting by physical interaction between specific genes and PRC1, which effectively holds genes in a silenced state. This prevents their expression in ESCs and so ensures maintenance of the undifferentiated state.

The researchers propose that the selective release of genes from this network leads to their expression and thus controls early development decisions that start the stem cell along the road to becoming a defined cell type. Lastly, de-regulation of Polycomb complexes has been shown to be the cause of several cancers and developmental disorders emphasising the importance of understanding Polycomb-mediated gene repression in development and disease.

Interactions of all 22,000 genes throughout the genome. The cluster at the centre of this model contains key developmental genes that are silenced in embryonic stem cells by PRC1. Credit: Schoenfelder et al. Nature Genetics, 2015

Dr Sarah Elderkin, Group Leader in the Institute's Nuclear Dynamics research programme and lead author on the Nature Genetics paper said: "Analysing the genome-wide connections of 22,225 promoters in the genome of mouse embryonic stem cells allowed us to identify a sub-set of nearly 100 promoters which form the strongest interaction network seen in the entire genome. This is exciting because the members of this sub-set encode early developmental regulators which define what the embryonic stem cell will become. This research uncovers a mechanism for how inappropriate expression of developmental genes is prevented and also suggests how are freed from this silencing in order for normal embryonic development to proceed."

Explore further: Viral elements originating from human ancestors are systematically activated in the early development of embryos

More information: Polycomb repressive complex PRC1 spatially constrains the mouse embryonic stem cell genome, DOI: 10.1038/ng.3393

Related Stories

Viral elements originating from human ancestors are systematically activated in the early development of embryos

June 24, 2015
Viruses incorporated into the human genome millions of years ago may now play a role in the early stages of human embryo development, according to researchers at A*STAR.

A master gene determines whether cells become pancreatic or liver cells

July 15, 2015
A gene in human embryonic stem cells not only steers them to form a pancreas but simultaneously prevents them from becoming liver cells, A*STAR researchers have shown. This discovery is an important step toward growing functioning ...

Recommended for you

Gene mutation found to cause macrocephaly and intellectual deficits

November 13, 2018
The absence of one copy of a single gene in the brain causes a rare, as-yet-unnamed neurological disorder, according to new research that builds on decades of work by a University at Buffalo biochemist and his colleagues.

Mutations, CRISPR, and the biology behind movement disorders

November 12, 2018
Scientists at the RIKEN Center for Brain Science (CBS) in Japan have discovered how mutations related to a group of movement disorders produce their effects. Published in Proceedings of the National Academy of Sciences, the ...

Decrease in specific gene 'silencing' molecules linked with pediatric brain tumors

November 12, 2018
Experimenting with lab-grown brain cancer cells, Johns Hopkins Medicine researchers have added to evidence that a shortage of specific tiny molecules that silence certain genes is linked to the development and growth of pediatric ...

Recessive genes explain only small fraction of undiagnosed developmental disorders

November 8, 2018
The Deciphering Developmental Disorders study has discovered that only a small fraction of rare, undiagnosed developmental disorders in the British Isles are caused by recessive genes. The study by researchers from the Wellcome ...

A look at how colds and chronic disease affect DNA expression

November 8, 2018
We're all born with a DNA sequence that encodes (in the form of genes) the very traits that make us, us—eye color, height, and even personality. We think of those genes as unchanging, but in reality, the way they are expressed, ...

Mutant protein tackles DNA guardian to promote cancer development

November 7, 2018
Melbourne scientists have discovered how tumour development is driven by mutations in the most important gene in preventing cancer, p53.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.