A gene unique to humans determined the large size of the cerebral cortex

(ORDO NEWS) —  Chinese biologists have identified a gene that does not code for proteins even in our closest relatives. It performs such a task only in humans, stimulating the growth of the cerebral cortex.

The vast majority of genes encode messenger RNA molecules on which proteins are synthesized. However, some genes serve as the basis for the production of RNA, which does not turn into proteins.

Such molecules can perform a variety of functions. For example, long non-coding RNA (lncRNA) remain in the cell nucleus and are involved in the regulation of other genes.

New work by scientists from Peking University has shown that such molecules played an important role in the emergence of our species, determining the development of the large brain.

As one or another species evolves, ordinary genes encoding proteins are able to change their specialization and switch to lncRNA and vice versa.

Such transitions can affect the fine tuning of the genome, changing the degree and timing of the activity of various genes.

A person’s DNA differs very little from that of their immediate family, and it is these settings that are thought to determine what makes a person human.

A group of Chinese biologists led by Chuan-Yun Li used open genome databases to compare the DNA of humans, chimpanzees, bonobos, and a few more evolutionarily distant macaques.

The scientists found 29 cases of transitions from lncRNA genes to protein-coding genes that have occurred since our evolutionary branch (greater primates) split from macaques.

But even more – as many as 45 – such transitions occurred later and became a unique feature of the human genome.

One of these areas attracted particular attention of researchers. ENSG00000205704 is active in brain neurons and encodes a short (only 107 amino acid bases) peptide that is found both in the cell nucleus and in the cytoplasm.

To find out its function, scientists set up experiments with stem cells, in which the work of ENSG00000205704 was either suppressed or, conversely, enhanced beyond the norm.

By growing such cells in vitro , “in vitro”, they were then stimulated to develop into mature neurons.

It was found that high activity of ENSG00000205704 delays the maturation of neurons. Thanks to this, they have time to go through more division cycles, and as a result, more adult nerve cells are formed.

Conversely, deletion (loss of a chromosome region) ENSG00000205704 leads to rapid maturation and the appearance of only a small number of neurons.

These conclusions were also confirmed by in vivo experiments on laboratory mice.

By introducing ENSG00000205704 into the genome of animals, scientists have shown that their neocortex grows larger than usual.

Thus, the transition of ENSG00000205704 from regulatory to coding functions can be called one of the factors that determined the development of our species.

Its activity stimulates the growth of a large brain, and above all, the neocortex, which is barely developed in lower mammals, and only in humans makes up the bulk of the cerebral cortex.

Recall that other genes were previously found that are also unique to our species and stimulate the growth of the brain in its entirety.


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