In common marmosets with the human genome ARHGAP11B the cerebral cortex of the brain has grown more long and thick than the wild monkeys. In addition, in the brain of transgenic animals had more neurons in the upper layers of the cortex and radial glial. A study published in the journal Science, confirms the role ARHGAP11B in the growth of the cortex in humans compared to other primates.
The growth of the cortex of the brain has allowed man to develop unique cognitive abilities. The increase in size of the cortex, in turn, is associated with expression of specific human gene ARHGAP11B in stem cells that give rise to neurons of the neocortex. Indirect evidence of the role of ARHGAP11B the size of the crust man got on evolutionarily distant mammals, mice and ferrets. When the gene expression was launched in the embryos of these animals, the final part of the brain they grew disproportionately large. But the influence ARHGAP11B on brain development in primates is still not studied.
Scientists from Germany and Japan under the leadership of Huttner Wieland (Wieland Huttner) from Institute of molecular cell biology and genetics max Planck introduced the viral vector with a human ARHGAP11B and its promoter into a fertilized egg of an ordinary marmosets (Callithrix jacchus). Then the embryos were transferred to females, and on day 101 of pregnancy (approximately 16 week human foetus development) underwent a caesarean section, estimated the size of the brain of embryos and the expression of ARHGAP11B in it.
In five out of seven embryos was expressed ARHGAP11B brains of these animals were larger, and the neocortex is thicker and longer than usual, and they appeared folds (normal brain of marmosets smooth). Scientists have painted different types of neurons and found that grown mainly, cells of the upper layers of the cortex (which is 40-50 percent more). Especially the increased thickness of the outer subventricular areas of the brain (the area where the migrating embryonic nerve cells) — it is the number of cells-predecessors of neurons was three times more than the wild-type marmosets. At least half of the stem cells subventricular outer zone was expressed markers of basal radial glia, these cells play a key role in the development of the neocortex in mammals.