Scientists have discovered the genes responsible for the human brain

For ethical reasons, animal studies
of apes have long been banned in Europe.
Another option for using animals in research is to use so-called organoids, a three-dimensional cellular structure that can be generated in the lab and is only a few millimeters in size
.

These organoids can be created from pluripotent stem cells, which then develop into specific cell types, such as nerve cells
.
In this way, the team created brain organs
from chimpanzees and humans.

Wieland Huttner of the Max Planck Institute for Molecular Cell Biology and Genetics, one of the study's three lead authors, said: "These brain organoids allow us to study a central question
about ARHGAP11B.
In a previous study, we were able to show that ARHGAP11B can amplify primate brains
.
However, it was not previously clear whether ARHGAP11B played a major or secondary role in the evolutionary expansion of the human neocortex.
"

To clarify this, the ARGHAP11B gene was first inserted into the organoid ventricle-like structure of chimpanzees
.
Does the ARGHAP11B gene cause the proliferation of brain stem cells in the chimpanzee brain, which is required for the enlargement of the neocortex?

"Our study shows that genes in chimpanzee organoids lead to an increase in associated brain stem cells and neurons that play a vital role in extraordinary human intelligence," said
Michael Heide, lead author of the study.
He is the head of the Junior Research Group on Brain Development and Evolution at the German Primate Center and an employee of
MPI-CBG.

When the ARGHAP11B gene is knocked out in human brain organoids or the function of the ARHGAP11B protein is inhibited, the number of these brain stem cells decreases to the number of
chimpanzees.

"Thus, we were able to demonstrate that ARHGAP11B plays a crucial role in the development of the neocortex during human evolution," said
Michael Heide.
Julia Ladewig of HITBR, third lead author, added: "Given the important role of ARHGAP11B, it is further conceivable that some of the poor development of the neocortex may be caused
by mutations in this gene.
"

Reference: Human-specific ARHGAP11B ensures human-like basal progenitor levels in hominid cerebral organoids