Researchers increase the brain size of marmosets

A team of researchers from the Max Planck Institute has managed to increase the embryo brain size of marmosets, an idea that may make you smile given a certain Hollywood blockbuster recent, but which turns out to be a research tool interesting.

A team of scientists from the Max Planck Institute of Molecular Cell Biology and Genetics has managed to increase the brain size of marmosets, by expressing a human-specific gene in them. Michael Heide, reporter for the study, explains that “the size of the brain has increased and its surface has folded back.” He also said he had “noted an increase in progenitors of the radial basal glia”, a tissue essential for the establishment of the neocortex and increasingly dense as the primates evolve. The gene in question is called ARHGAP11. Behind this uninviting nickname hides a key function of human development since when activated, it will lead to the multiplication of brain stem cells and participate in growing the neocortex, that is, to popularize, the peripheral part of crumpled appearance of our brain. Over-developed among us other Homo sapiens, compared to our primate contemporaries, it is this which gives us certain advanced cognitive possibilities which range from language to our reasoning skills.

An illustration of the human brain. The green part represents the neocortex. © srossign – Pixabay

A window on human evolution

In genetics and evolutionary history, lines are traced by phylogenetic trees, the equivalent of genealogical trees for species. Except that a new branch of the tree does not separate at each birth, but when a character has changed enough for it to be considered that it is a new species, subspecies … L ‘One of the points that makes this gene so interesting is that it is precisely found at one of these crossings. Indeed, we have no record of this in Chimpanzees before the separation of our line from that of other humanoids.

A section of a hemisphere of marmoset brain. The different types of neurons are colored in different colors; in yellow, progenitors of the radial glia. © Heide et al. / MPI-CBG

In essence, the research team therefore activated one of the triggers that most certainly made the first monkeys move in our direction. It’s a key step. During the evolution of a species, the individuals that compose it will develop lots of mutations. Survivors are considered to be those whose mutations have most benefited them in their direct environment, and they will thus transmit them to their descendants who will replicate the process. The vast majority of mutations are thus lost, but a significantly more developed neocortex represents such an important advantage in terms of natural selection that, according to the researchers behind the study, it would have been immediately selected and “influenced the evolution human ”.

Two normal marmoset brains (left) and others with ARHGAP11B activated (right) – © Heide et al. / MPI-CBG

You might as well cut short the unbridled imagination of some: it is only a development experience. In accordance with current regulations and good practice in the field, these 101-day-old embryos (two-thirds of the term in the marmoset) were sacrificed and the team did not plan to bring them to fruition for a moment. So it’s an interesting step in the reconstruction of the vast puzzle of human evolution, but we should not fear a scenario that would resemble that described in the Planet of the Apes series … At least for now.

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