2020/06/25
Keio University School of Medicine
Central Institute for Experimental Animals
RIKEN
A group of researchers, including Professor Wieland Huttner and Researcher Michael Heide of the Max Planck Institute of Molecular Cell Biology and Genetics; Professor Hideyuki Okano of the Department of Physiology, Keio University School of Medicine (also Team Leader of the Laboratory for Marmoset Neural Architecture at the RIKEN Center for Brain Science (CBS)); Project Assistant Professor Ayako Murayama (also a visiting researcher at CBS and a concurrent researcher at the Central Institute for Experimental Animals); and Department Head Erika Sasaki, Section Chief Yoko Kurotaki, and Researcher Haruka Shinohara of the Central Institute for Experimental Animals, conducted the following research and elucidated the mechanism behind the human-specific expansion of the brain.
First, the team created a non-human primate, the common marmoset, that expresses the human-only gene ARHGAP11B at a physiologically relevant level similar to that found in healthy humans (hereafter referred to as ARHGAP11B-transgenic marmosets). Anatomical analysis of the brain and quantitative analysis of neural cells in the late fetal stage revealed that in the ARHGAP11B-transgenic marmosets, brain folds (gyri and sulci) formed in areas where they are not normally present, and the Gyrification Index (GI), an index of brain surface folding, increased to approximately 1.1 times that of the wild type. This was found to be caused by an increase in basal radial glia (bRG) cells, a type of neural progenitor cell, which led to a roughly 20% increase in neurons in the upper cortical layers that contribute to the expansion of the brain's surface area. From these results, the research group has demonstrated that ARHGAP11B is a key gene responsible for the expansion of the neocortex and the increase in gyri and sulci during human evolution after the split from the chimpanzee lineage. In other words, the expansion of the neocortex brought about by ARHGAP11B is thought to be related to the acquisition of characteristically human brain functions.
This research was published in the academic scientific journal "Science" on June 18, 2020 (Central European Summer Time, CEST).
Please see below for the full press release.