A subtype of the latter – basal radial glia – is thought to drive neocortex growth in human development. But there are two types of neural progenitors in mammalian neocortex: apical and basal. It does this by increasing the number of neural progenitors, the cells that give rise to neurons. Introducing ARHGAP11B into the neocortex of mouse embryos increases its size and can induce folding. The answer may lie in genes that are unique to humans, such as ARHGAP11B. But how did the human neocortex become so big? The human neocortex is roughly three times bigger than that of our closest relatives, the chimpanzees, and helps support advanced cognitive skills such as reasoning and language. As the brain evolved, the neocortex, the evolutionarily youngest part of the cerebral cortex, expanded dramatically and so had to fold into wrinkles to fit inside the skull. All mammals have a cerebral cortex, but its size varies greatly between species. The human brain owes its characteristic wrinkled appearance to its outer layer, the cerebral cortex. Thus, human-specific ARHGAP11B can elicit hallmarks of neocortical expansion in the developing ferret neocortex. Consequently, the postnatal ferret neocortex exhibits increased neuron density in the upper cortical layers and expands in both the radial and tangential dimensions. In contrast to its effects in mouse, ARHGAP11B markedly increases proliferative basal radial glia, a progenitor cell type thought to be instrumental for neocortical expansion, and results in extension of the neurogenic period and an increase in upper-layer neurons. Here, we study the effects of ARHGAP11B expression in the developing neocortex of the gyrencephalic ferret. ARHGAP11B is a human-specific gene that, based on its expression pattern in fetal human neocortex and progenitor effects in embryonic mouse neocortex, has been proposed to have a key function in the evolutionary expansion of the neocortex. The evolutionary increase in size and complexity of the primate neocortex is thought to underlie the higher cognitive abilities of humans.

Ferret duplicate detector