Analysis of neurogenesis in a mammalian neuroepithelium: Proliferation and differentiation of an olfactory neuron precursor in vitro

Anne L Calof,Dona M Chikaraishi

doi:10.1016/0896-6273(89)90120-7

Abstract

Development of a culture system for mammalian olfactory epithelium has permitted the process of neurogenesis to be examined in vitro. Antibody markers allowing the unambiguous identification of putative neuroepithelial stem cells (keratin + basal cells) and differentiated neurons (N-CAM + olfactory receptor neurons) are described. In combination with [ 3H]thymidine uptake analysis, these antibodies have been used to characterize the existence, proliferation, and differentiation of the immediate neuronal precursor in this system. This cell is distinct from basal cells and rapidly sorts out from them, dividing as it migrates. Data are presented which suggest that the precursor follows a simple lineage program, dividing to give rise to two N-CAM + daughter neurons. Although this precursor efficiently generates neurons in defined medium, neurogenesis subsequently ceases because new precursors are not produced, suggesting that epigenetic factors may regulate continual neurogenesis in this system.

Highlights

It is the number of neurons in a nervous system that determines its complexity.The fundamental process determining neuronal number is the proliferation of neuronal precursor cells and the terminal differentiation of their progeny into postmitotic neurons
Studies of regenerating olfactory receptor neurons in adult animals have already provided insights into cellular interactions that regulate neurogenesis in the olfactory epithelium (OE) (e.g., Graziadei, 1973; Monti Graziadei and Graziadei, 1979; Costanzo and Graziadei, 1983; Camara and Harding, 1984). This manuscript describes the development of in vitro methods of studying neurogenesis in the mammalian and the results obtained so far using this approach. These results suggest that neurogenesis is a multistage process, the final step of which involves a proliferating neuronal precursor not previously identified in this tissue
Studies of neuronal regeneration in the OE in vivo suggested that the basal cells, so named because they lie adjacent to the basement membrane, are self-renewing stem cells that give rise to the neurons in this system (Harding et al, 1977; Monti Graziadei and Graziadei, 1979)

Summary

Introduction

The fundamental process determining neuronal number is the proliferation of neuronal precursor cells and the terminal differentiation of their progeny into postmitotic neurons. The neurons and glia of the nervous system derive from the embryonic neural tube and neurogenic placodes, and for most of the nervous system, it is within these neuroepithelia that neurogenesis takes place (e.g., Sidman and Rakic, 1973; Jacobson, 1978). Studies of [3H]thymidine uptake by neuronal precursors in vivo show that neurogenesis is tightly regulated, both temporally and spatially, during development (e.g., Kauffman, 1968; Mares and Lodin, 1970; Shimada and tangman, 1970; Angevine, 1970). Because the structures in which neurogenesis takes place exist only transiently and for the most part very early in embryonic development, experimental manipulation of these tissues is difficult. Very little is known about the cellular regulation or the genetic control of neurogenesis

Results

Discussion

Conclusion