Research seminars Mechanisms that Establish Neuronal Identity in the Cerebral Cortex

The functional integrity of the brain systems relies on the precisely coordinated production of diverse neurons and their placement along the three-dimensional axis. Specifically in the cerebral cortex, progenitor cells produce distinct neuronal subtypes in a stereotypical order and establish a six-layer structure, which are further modified into functional areas. A prevailing view concerning the neurogenesis of the neocortex was that, neural stem cells undergo successive rounds of asymmetric cell divisions to produce the principal layer subtypes: preplate neurons, deep-layer neurons and upper-layer neurons, through a progressive restriction in cell competence. Consistent with this view, we previously showed that Foxg1, a forkhead transcription factor expressed in the telencephalon, plays a central role in establishing early cortical gene network and switching neurogenesis from early preplate cells to deep-layer neurons. However, our recent studies have indicated that the specification and integration of neocortical neurons may also rely on communications between different cell types, in addition to intrinsic transcriptional network. Here, I would like to present our recent findings on the mechanisms by which neocortical subtype identities establish in the neocortex, by manipulating gene expression and number of cortical neurogenesis in vivo. Our results indicate that neocortical progenitors integrate both intrinsic and extrinsic cues to generate distinct layer subtypes, a system which ultimately balance the production of these neurons during neocortical development and possibly evolution.