The finding that some genes are active from the get-go challenges the textbook view that genes don't become active in human embryos until they are made up of four-to-eight cells, two or three days after fertilisation.
The newly discovered activity begins at the one-cell stage – far sooner than previously thought – promising to change the way we think about our developmental origins. The research was published in Cell Stem Cell.
Using a method called RNA-sequencing, the team applied precision analysis to individual human eggs and one-cell embryos to make a detailed inventory of tell-tale products of gene activity, called RNA transcripts. It revealed that hundreds of genes awaken in human one-cell embryos. Because the gene activity starts small, previous techniques had not been sensitive enough to detect it. But state-of-the art RNA-sequencing used in this study was able to reveal even small changes.
"This is the first good look at the beginning of a biological process that we all go through – the transit through the one-cell embryo stage," said the senior author. "Without genome awakening, development fails, so it's a fundamental step."
The team found that many genes activated in one-cell embryos remain switched on until the four-to-eight cell stage, at which point they are switched off.
“It looks as if there is a sort of genetic shift-work in early embryos: the first shift starts soon after fertilisation, in one-cell embryos, and a second shift takes over at the eight-cell stage,” said the author.
At the moment of human fertilisation, sperm and egg genomes – the collection of all of their genes – are inactive: the sperm and egg rely on transcripts produced when they were being formed for instructions that regulate their characteristics.
Transcripts provide essential instructions in all cells, and embryo cells are no exception. This means that it is essential for parental (sperm and egg) genomes to awaken in the new embryo. But when and how does this happen?
Understanding the process of genome awakening is important: it is a key piece of the jigsaw of development that promises a better understanding of disease, inheritance and infertility. The scientists found some activated genes that might be expected to play roles in early embryos, but the roles of others were unknown and could point to embryonic events that we don't yet understand.
The team's findings also shine a light on how the genes are activated. "Although the trigger for activation is thought to come from the egg, it's not known how; now we know which genes are involved, we can locate their addresses and use molecular techniques to find out," said the author.
Remarkably, candidates that might trigger gene activation include factors usually associated with cancer, such as some well-known oncogenes. This led the researchers to speculate that the natural, healthy role of factors that are known to misbehave in cancer, is to awaken genes in one-cell embryos. If this proves to be correct, the team’s findings could illuminate events that initiate cancer, providing new diagnostic and preventive opportunities.
The findings also have clinical implications for the inheritance of acquired traits, such as obesity: parents who gain weight seem to pass the trait to their kids. It is not known how such acquired traits are transmitted, but altering gene activation after fertilisation is a possible mechanism.
The team also looked at unhealthy one-cell embryos that do not go on to develop, and found that many of their genes fail to activate. Abnormal embryos have been used to evaluate methods of human heritable genome editing, but the new findings suggest they may be inappropriate as a reliable test system.
https://www.cell.com/cell-stem-cell/fulltext/S1934-5909(21)00484-7
http://sciencemission.com/site/index.php?page=news&type=view&id=publications%2Fhuman-embryonic-genome&filter=22
Genes are switched on in the human embryo from the get-go
- 1,412 views
- Added
Latest News
Protein that helps COVID-19…
By newseditor
Posted 26 Jul
Spinal Muscular Atrophy (SM…
By newseditor
Posted 26 Jul
Link between bowel movement…
By newseditor
Posted 26 Jul
Inhibition of IL-11 signall…
By newseditor
Posted 25 Jul
Brain changes linked to obe…
By newseditor
Posted 25 Jul
Other Top Stories
Deep-sleep brain waves predict blood sugar control
Read more
Extracellular cytochrome nanowires appear to be ubiquitous in microbes
Read more
Distinct connectivity patterns for depression associated with traum…
Read more
Antisense therapy restores fragile X protein production in human cells
Read more
Biomarker for allergic reaction in kidneys identified!
Read more
Protocols
A systems biology approach…
By newseditor
Posted 24 Jul
quantms: a cloud-based pipe…
By newseditor
Posted 22 Jul
Emerging tools and best pra…
By newseditor
Posted 19 Jul
Directly selecting cell-typ…
By newseditor
Posted 17 Jul
PUFFFIN: an ultra-bright, c…
By newseditor
Posted 16 Jul
Publications
Hepatocyte-intrinsic SMN de…
By newseditor
Posted 26 Jul
Aberrant bowel movement fre…
By newseditor
Posted 26 Jul
A pseudoautosomal glycosyla…
By newseditor
Posted 26 Jul
Microglia protect against a…
By newseditor
Posted 26 Jul
Rigor and reproducibility i…
By newseditor
Posted 26 Jul
Presentations
Myelin plasticity in the ve…
By newseditor
Posted 10 Jun
Hydrogels in Drug Delivery
By newseditor
Posted 12 Apr
Lipids
By newseditor
Posted 31 Dec
Cell biology of carbohydrat…
By newseditor
Posted 29 Nov
RNA interference (RNAi)
By newseditor
Posted 23 Oct
Posters
A chemical biology/modular…
By newseditor
Posted 22 Aug
Single-molecule covalent ma…
By newseditor
Posted 04 Jul
ASCO-2020-HEALTH SERVICES R…
By newseditor
Posted 23 Mar
ASCO-2020-HEAD AND NECK CANCER
By newseditor
Posted 23 Mar
ASCO-2020-GENITOURINARY CAN…
By newseditor
Posted 23 Mar