Neurons arise in the basal neuroepithelium of the early mammalian telencephalon: A major site of neurogenesis

TLDR

Neurons of the mammalian CNS are traditionally thought to arise from progenitors dividing at the apical surface of the neuroepithelium. The study aims to identify the specific cell divisions that generate CNS neurons. The authors used mouse embryos expressing GFP from the Tis21 locus, a marker of most neuron‑generating progenitors, to visualize these divisions. They found that basal progenitors in the neuroepithelium, particularly in the telencephalon, divide to produce two neurons, outnumber apical progenitors, and constitute the major source of neocortical neurons.

Abstract

Neurons of the mammalian CNS are thought to originate from progenitors dividing at the apical surface of the neuroepithelium. Here we use mouse embryos expressing GFP from the Tis21 locus, a gene expressed throughout the neural tube in most, if not all, neuron-generating progenitors, to specifically reveal the cell divisions that produce CNS neurons. In addition to the apical, asymmetric divisions of neuroepithelial (NE) cells that generate another NE cell and a neuron, we find, from the onset of neurogenesis, a second population of progenitors that divide in the basal region of the neuroepithelium and generate two neurons. Basal progenitors are most frequent in the telencephalon, where they outnumber the apically dividing neuron-generating NE cells. Our observations reconcile previous data on the origin and lineage of CNS neurons and show that basal, rather than apical, progenitors are the major source of the neurons of the mammalian neocortex.