Dynamics of Neurogenic Signals as Biological Switchers of Brain Plasticity

Abstract

AbstractThe discovery of adult neurogenesis in the middle of the past century is considered one of the most important breakthroughs in neuroscience. Despite its controversial nature, this discovery shaped our concept of neural plasticity, revolutionizing the way we look at our brains. In fact, after the discovery of adult neurogenesis, we started to consider the brain as something even more dynamic and highly adaptable. In neurogenic niches, adult neurogenesis is supported by neural stem cells (NSCs). These cells possess a unique set of characteristics such as being quiescent for long periods while actively sensing and reacting to their surroundings to influence a multitude of processes, including the generation of new neurons and glial cells. Therefore, NSCs can be viewed as sentinels to our brain’s homeostasis, being able to replace damaged cells and simultaneously secrete numerous factors that restore regular brain function. In addition, it is becoming increasingly evident that NSCs play a central role in memory formation and consolidation. In this review, we will dissect how NSCs influence their surroundings through paracrine and autocrine types of action. We will also depict the mechanism of action of each factor. Finally, we will describe how NSCs integrate different and often opposing signals to guide their fate. Graphical Abstract Different signaling pathways responsible for signal integration of NSCs-secreted autocrine/paracrine signals: Numerous superficial receptors are stimulated upon contact with NSCs-secreted factors. Interestingly, this schematic representation of the different pathways shows how different signals often converge into the same pathway. This allows the NSC to adopt the correct behavior in response to external stimuli.