Quite human: Scientists have identified a region of the genome that may be responsible for unique human adaptations. Sections of DNA called HAQERs (Human Ancestor Rapid Evolution Regions) control the reading of protein-coding genes and thus contribute to the development of the brain, digestive system and immune system. It evolved shortly after the separation of the human and chimpanzee lineages. HAQERS can bring not only benefits, but also diseases.
We humans differ from our closest primate relatives such as chimpanzees or gorillas. But the genetic causes of our “ordinary human” characteristics are only the beginning in pieces More clear, also because there are almost no differences in the protein-coding genes for the great apes. On the other hand, there is growing evidence that critical changes are taking place in the non-protein-coding parts of our genome, parts long thought to be passive.unwanted DNAapplied.
lightning change
A team led by Riley Mangan of Duke University in the United States also looked for traces of our evolution in this non-coding part of our genome. Until recently, DNA sequences that remained stable for a long time but then changed rapidly in our ancestors were considered very promising. ‘Such an acceleration of molecular evolution is assumed to reflect changes in selection,’ the researchers explain.
In contrast, Mangan and colleagues now also look at regions of the genome that have undergone dynamic changes. They explain that “many unique features of human anatomy, including brain size, limb proportions, or facial anatomy, are inconsistent even in non-human species.” Using high-throughput sequencing and genome matching, they looked for DNA fragments in regions of the genome that changed very rapidly after the chimpanzee and human lineages separated about 7.5 million years ago.
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In fact, researchers have been able to identify more than 1,500 such partitions. They are nicknamed HAQER (pronounced “Hackers”), which stands for Hominid Rapid Evolution Regions. As they reported, this section of DNA is among the fastest growing in the human genome. But when did this important development take place? In the context of earlier or early human evolution? Or was it separated from the chimpanzee?
To test this, Mangan and colleagues collected the 13 most significant sequences from their HAQER and compared them to the genome. NeanderthalsAnd Mr. DenisovChimpanzee and the reconstructed genome of the common ancestor of humans and chimpanzees.
The upshot: HAQER evolved after our family lineage split from chimpanzees, but before we, in turn, split from Denisovans and Neanderthals. This means that other pre and ancient human species also have this sequence.
Optimization of the brain and gut
But what is the function of the HAQER sequence? Scientists describe them as regulatory sections of DNA that act as a kind of switch. It seems that they activate the gene in a special way. They only do this to certain types of cells and only at certain times in their development. Or even if the environment changes in some way, explains Mangan’s colleague Craig Lowe. HAQER has added several genetic switches to the human operating system that weren’t there before.
As a detailed analysis reveals, this genetic switch is mainly used in the development of the human brain, digestive system and part of the immune system. Gene switches allow us to make a special fine-tuning by which we can specifically adapt to changing environmental influences.
HAQER as a trigger of typical human disease
But how was the despicable born? Typically, there are two general explanations for the rapid emergence of genomic regions: either they emerged as a result of local mutations, or they were of great benefit to species that survived natural selection. In the DNA sequences now described, the scientists found evidence for both explanations, “suggesting that the combination of these two forces forms the most distinct region of the human genome.”
By making us human, HAQER not only gives us positive characteristics such as a large brain, but also creates the foundation for uniquely human diseases, the researchers believe. These can include high blood pressure, unipolar and bipolar depression, and schizophrenia.
According to Mangan and colleagues, while all humans have very similar HAQER sequences, there are some differences, “and we’ve been able to show that these variants tend to be associated with certain diseases,” Lowe said. The exact appearance of these associations could be the subject of further research. (Mar 2022; doi: 10.1016/j.cell.2022.10.016)
Source: Duke University
