Neanderthal brain cells were dividing faster than modern humans

(ORDO NEWS) — German scientists investigated the differences between the proteins involved in cell division in modern humans and those that were in our closest relative, the Neanderthal.

It turned out that mitosis of the brain stem cells of extinct hominids occurred faster, but with a large number of errors in the divergence of chromosomes.

The evolutionary paths of the ancestors of modern man ( Homo sapiens ) and Neanderthals ( Homo neanderthalensis ) diverged about half a million years ago.

During this time, many changes have accumulated in our genome – according to estimates, H. sapiens differs from the extinct hominid (its closest relative) by about 100 amino acid residues in various proteins.

The biological significance of these changes is still poorly understood, but German researchers, authors of a new article in the journal Science Advances , figured out some of them.

They drew attention to six mutations – those that affect three proteins that control the work of the kinetochore (the part of the chromosome that attaches to the division spindle) and the divergence of chromosomes during mitosis.

These are the KIF18a, KNL1 and SPAG5 proteins, which are actively synthesized in stem cells during the formation of the cerebral cortex, or rather, the neocortex.

It is this part of the brain that is responsible for such complex functions as the perception of sensory signals, thinking, speech, and so on.

Anthropologists associate the emergence of the family of hominids precisely with a sharp complication of the brain, as well as upright posture and features of the hand – this is the so-called hominid triad.

Judging by the studied skulls, the Neanderthal had a brain comparable in size to that of a human, the only living hominid.

However, there were still important differences – to find out, the researchers had to “resurrect” some Neanderthal proteins.

In the first experiment, the mouse proteins were sequenced to match those of Homo sapiens exactly . In general, initially in mice they are identical to those that were in Neanderthals and still exist in great apes.

To obtain transgenic rodents, the CRISPR / Cas9 gene editing technology was used: it made it possible to obtain the so-called humanized mice, that is, those with human proteins.

“We found that all three amino acid residues in modern humans in two of these proteins are associated with a longer metaphase – the phase when chromosomes are preparing for cell division, which leads to fewer errors in their distribution to daughter cells, nerve stem cells – just like it does in modern humans,” explained Felipe Mora-Bermudez, head of the research team.

Next, the scientists found out whether the introduction of Neanderthal proteins into modern human cells has the opposite effect.

Of course, they did not raise a mutant child – instead, brain organelles, the so-called mini-brains in a test tube, were used.

This is a small semblance of a real organ, which is grown in a bioreactor using stem cells as a basis.

Recently, “mini-brains” have become a popular tool for biomedical research, because they reproduce the tissue organization of the brain, including the cerebral cortex.

This time the metaphase was shorter and the scientists noticed more errors in chromosome segregation. The authors suggest that three changes in the sequences of the KIF18a and KNL1 proteins in modern humans have reduced the number of disturbances in this process, which is critical for cell division and brain development.

Recall that violations of the divergence of chromosomes do not bode well – they can result in trisomy (for example, Down’s syndrome) or the development of cancer.

It looks like a new study has revealed an important new factor that helped Homo sapiens prevail over competitors, create a civilization and transform the face of the entire planet.


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