According to a paper published in the latest issue of the journal Science, German and Japanese scientists implanted a human gene in the brain of marmoset monkey embryos, causing the cerebral cortex of marmoset monkey fetuses to develop folds similar to those of the human brain. The experiment is reminiscent of the movie Planet of the Apes, in which genetically modified orangutans wage war against humans.
Stills from Planet of the Apes.
According to reports, German and Japanese scientists implanted a human gene called ARHGAP11B in 7 marmoset embryos, and image analysis during the 102 days of pregnancy found that the cerebral cortex of the marmoset fetus was induced to develop folds similar to the human brain, that is, the neocortex of the monkey brain expanded.
Normal marmoset fetal brain (left) versus AHRGAP11B marmoset fetal brain. The yellow line represents the boundary of the cerebral cortex; the white line indicates the developing cerebellum; and the arrow indicates the fold.
It is reported that the neocortex is the outer layer of the cerebral sulcus and involves important functions such as reasoning, language and conscious thinking. The ARHGAP11B gene is only found in humans, and is not found in other non-human primates or mammals. Experiments have shown that the genetically adjusted marmoset brain has developed natural bumps and depressions similar to human brains — known as "whirlwind" and "gully" respectively — characteristic of human evolution.
One of the paper's authors, Michael Heide of the Max Planck Institute for Molecular Cell Biology and Genetics (MPI-CBG) in Germany, said the neocortex of the average marmoset's brain expanded, the brain surface folded, and the number of neurons in the upper layers increased.
Human gene ARHGAP11B modified marmoset monkey fetal brain hemispheres, white nuclei visible. Scientists say the bulges in the brain resemble those of the human brain. The arrow on the left represents the gully (depression or groove in the cerebral cortex) and the arrow on the right represents the whirlwind (ridge-like bulge).
This is in stark contrast to the normal marmoset brain, which is much smoother and smaller than the human brain.
Another author, Marta Florio of MPI-CBG, said that "it's so cool" that a small gene is enough to affect the expression of stem cells, which contribute the most to the expansion of the neocortex.
It is reported that during evolution, the human brain folded into a unique wrinkle-like appearance to accommodate the spatial limitations of the skull, while allowing the surface area of the neocortex to increase greatly.
Scientists discovered a single gene in 2015 that could be responsible for the unique presence of a large number of neurons in the human brain. When this gene was implanted into the brains of mouse embryos (pictured), it led to the formation of more neurons (stained red).
Scientists from the Central Laboratory Animal Research Institute (CIEA) in Japan, Keio University in Tokyo, and the Wako Riken Brain Science Center Laboratory have also participated in the research, among which the Wakamitsu Riken Brain Science Center Laboratory has taken the lead in developing a technology for generating transgenic non-human primates.
It is reported that genetically modified marmoset fetuses are not allowed to be born. Wieland Huttner, one of the authors of the paper, MPI-CBG, said the scientific analysis was limited to marmoset fetuses because of "potential unforeseen consequences" in the brain function of marmosets after birth, so from an ethical point of view, it is also mandatory not to let genetically modified marmosets be born.
Text/Nandu reporter Chen Lin