ABSTRACT
Another means by which neuronal numbers are regulated in the developing nervous system is through programmed cell death (PCD), a process by which subsets of neurons produced during neurogenesis are later eliminated. Programmed cell death is now understood to be a developmentally necessary event that further helps establish the final, correct number of neurons in the nervous system. This chapter focuses on the discovery and role of target-derived proteins, their receptors, and the intracellular signaling pathways that intersect to regulate neuronal survival and programmed cell death during the course of neural development.
From the late nineteenth through to the mid-twentieth century, neuroembryologists debated what role, if any, target tissues served in regulating aspects of neural development. The importance of target tissues was gradually accepted after a number of detailed studies documented that neuronal survival was altered by the presence or absence of target tissues. By the 1950s, the view that target-derived growth factor proteins were important in promoting neuronal survival and preventing neuronal death during embryonic development was firmly established.
