Changing a single amino acid in a protein can have significant effects. By this means, the production of neurons would be more important in the frontal lobe during the development of the brain in modern humans than in Neanderthals.
What makes modern humans unique? The answer lies partly in thefrom (an area of ), according to a appeared in Science. Admittedly, the endocranial structure of modern humans and Neanderthals was no different, suggesting a similar size of the brain and the . But it was unknown until now whether an identical size of the neocortex implied the same production of .
Few proteins show differences in the sequence of their amino acids betweenand our ancestors . However, this is the case with TKTL1, which differs from only one of the Neanderthal variant. Institute researchers of molecular and from Dresden (Germany) found that this increased a type of brain progenitor cells, called basal radials, which generate the majority of neurons in the developing neocortex.
More neurons formed with the modern human variant of TKTL1
Next, the study authors wanted to know the significance of this amino acid modification for the development of the neocortex. They introduced the modern human variant or the Neanderthal variant of TKTL1 into the neocortex ofof mouse. Result: basal radial glial cells increased with the modern human variant of TKTL1, but not with the variant of . Thus, the brains of mouse embryos with the modern human variant of TKTL1 contained more neurons.
In order to know if these same effects were found for the development ofhuman, the researchers used human brain organoids – miniature structures mimicking the main structure and functions of the brain and cultured in the laboratory from human. They thus replaced the of the TKTL1 of modern man by the of Neanderthal TKTL1 and they found that fewer basal radial glial cells were produced and therefore also fewer neurons.
In more detail, Homo sapiens TKTL1 acts through modifications of theby one of the pentose pathway followed by an increase in the synthesis of . In fact, the modern human TKTL1 increases the synthesis of certain membranes, which are necessary to generate the long process of basal radial glial cells, and therefore to increase the production of neurons.
An impact on the cognitive abilities associated with the frontal lobe?
If the study implies that neocortical neurogenesis in modern humans was greater than in Neanderthals (particularly in the frontal lobe), the authors speculate that this may have favored theof modern humans associated with the frontal lobe. Thus, the genetic evolution of our probably contributed to the development of language and voluntary motor coordination.