The Pace of Neurogenesis Is Regulated by the Transient Retention of the Apical Endfeet of Differentiating Cells.

The development of the mammalian cerebral cortex involves a variety of temporally organized events such as successive waves of neuronal production and the transition of progenitor competence for each neuronal subtype generated. The number of neurons generated in a certain time period, that is, the rate of neuron production, varies across the regions of the brain and the specific developmental stage; however, the underlying mechanism of this process is poorly understood. We have recently found that nascent neurons communicate with undifferentiated progenitors and thereby regulate neurogenesis, through a transiently retained apical endfoot that signals via the Notch pathway. Here, we report that the retention time length of the neuronal apical endfoot correlates with the rate of neuronal production in the developing mouse cerebral cortex. We further demonstrate that a forced reduction or extension of the retention period through the disruption or stabilization of adherens junction, respectively, resulted in the acceleration or deceleration of neurogenesis, respectively. Our results suggest that the apical endfeet of differentiating cells serve as a pace controller for neurogenesis, thereby assuring the well-proportioned laminar organization of the neocortex.