Recommendable! What differentiates the human brain from other animal brains? We are learning more about it!
"... A new study that explores genetic changes unique to the human branch of evolution has found another paradox: Sifting through our uniquely quickly evolving DNA, which scientists have dubbed “human accelerated regions” of the genome, a team of researchers found a human-specific effect on one gene that slows down the pace of our brain cells’ growth early in development. ...
Scientists define these “accelerated regions” of the genome as those that are the same, or conserved, among other mammals but different in humans. This human-specific rapid evolution in certain pieces of DNA implies that those genetic changes led to the physical and mental features that set humans apart from other animals. ...
It turned out that of the known 3,171 human accelerated regions, 99 percent of these human-specific mutations fall into “non-coding” regions of DNA, or regions of DNA that don’t contain instructions for making a protein. Many of them are in stretches of our genome known as enhancers, regions which regulate nearby genes, and about half of those are nestled in enhancers that are active in the developing human brain. ...
When they added extra amounts of the gene product to mouse brain cells, the cells’ growth and division slowed. It’s known that primates, and humans specifically, have a slower cell cycle than other animals, especially in development. This slower cell growth is likely tied to humans’ longer pregnancies, which are thought to be important to support the growth of our large and complex brains. ..."
Scientists define these “accelerated regions” of the genome as those that are the same, or conserved, among other mammals but different in humans. This human-specific rapid evolution in certain pieces of DNA implies that those genetic changes led to the physical and mental features that set humans apart from other animals. ...
It turned out that of the known 3,171 human accelerated regions, 99 percent of these human-specific mutations fall into “non-coding” regions of DNA, or regions of DNA that don’t contain instructions for making a protein. Many of them are in stretches of our genome known as enhancers, regions which regulate nearby genes, and about half of those are nestled in enhancers that are active in the developing human brain. ...
The scientists looked at a single human gene, PPP1R17, that sits next to two of these human accelerated regions and is active in the stem cells that give rise to neurons as the brain develops during pregnancy. The team looked at developing human, macaque, ferret and mouse brains and found that PPP1R17 is switched on in different regions of the brain and in different types of brain cells in humans as compared to the other animals.
From the abstract:
"Human accelerated regions (HARs) are the fastest-evolving regions of the human genome, and many are hypothesized to function as regulatory elements that drive human-specific gene regulatory programs. We interrogate the in vitro enhancer activity and in vivo epigenetic landscape of more than 3,100 HARs during human neurodevelopment, demonstrating that many HARs appear to act as neurodevelopmental enhancers and that sequence divergence at HARs has largely augmented their neuronal enhancer activity. Furthermore, we demonstrate PPP1R17 to be a putative HAR-regulated gene that has undergone remarkable rewiring of its cell type and developmental expression patterns between non-primates and primates and between non-human primates and humans. Finally, we show that PPP1R17 slows neural progenitor cell cycle progression, paralleling the cell cycle length increase seen predominantly in primate and especially human neurodevelopment. ..."
No comments:
Post a Comment