Neurogenesis in the Developing Mammalian Neocortex

Abstract

Abstract The neocortex is the evolutionarily newest and most complex part of the mammalian brain. The neurons of the neocortex are born from different neural stem and progenitor cells (for simplicity collectively referred to as progenitors) that reside in proliferative zones during embryonic development. During the neurogenic period, distinct populations of neural progenitors appear, each having specific molecular and cell biological characteristics. These characteristics and the environment of the neural progenitor are responsible for the self‐renewing or neurogenic potential of each neural progenitor type. The fate of daughter cells after neural progenitor division is determined by the mode of division, intrinsic factors such as transcription factors or regulatory ribonucleic acids (RNAs), and by extrinsic signals coming from the surrounding cells. This tight regulation controls the rate of production of neural progenitor types and neurons. The ratios of different progenitor types have a huge impact on the final number of neurons in the adult neocortex, and are partly responsible for vast differences in the brains of different mammals. Key Concepts: Neocortex is a part of the brain characteristic of mammals. Neocortex is a six‐layered structure comprised of post‐mitotic neurons and glial cells. Neocortical neurons are born from neural progenitor cells, mostly during embryonic development. Neural progenitor cells can be classified into different populations based on molecular and cell‐biological features. The molecular and cell‐biological features of neural progenitor cells influence their propensity to self‐renew or produce neurons. Neural progenitor cells are under tight intrinsic and extrinsic control, in order to maintain the equilibrium between proliferative and neurogenic divisions. The relative abundance of different progenitor populations influences the final number of neurons in the adult neocortex.