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 fertilization.
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, published today in Cell Stem Cell, was co-led by Professor Tony Perry at the University of Bath, Dr. Giles Yeo at the University of Cambridge and Dr. Matthew VerMilyea at Ovation Fertility, US. 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 Professor Perry, from the Department of Biology and Biochemistry at Bath. "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. Read more...
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