Cellular proliferation in the vertebrate brain: Comparative features in embryonic and adult turtle
Several long-standing conceptions regarding cellular proliferation in the mammalian brain have been revised in recent years. Two served as the impetus for this comparative study of proliferation in the brain of the embryonic and adult turtle, Trachemys scripta elegans. The first of these revisions is the acceptance of adult neurogenesis in mammals. A central dogma of neuroscience has been that the mammalian brain is incapable of generating neurons after early developmental periods. Recently however, it has been discovered that two restricted areas of the brain continue producing neurons in adults: the adult subventricular zone, and the dentate gyrus of the hippocampus. Thus, new hope has emerged that we will find ways to replace neurons lost during illnesses such as Parkinson's disease, stroke, and traumatic brain injury.
A second conceptual revision fully emerged when recent work from our laboratory and others demonstrated that mammalian radial glial cells generate neurons in the embryonic forebrain. Previously, neural precursors were thought to be in a class of their own, distinct from the glial lineage. The identification of radial glial cells as key neural progenitor cells contributed to the burgeoning theme that neural precursors share features with glial cells in both embryos and adults.
Unlike adult mammals, the turtle brain maintains a ubiquitous population of radial glia-like cells that persists throughout adult life. Additionally, adult neurogenesis has been reported in most areas of the turtle telencephalon, in contrast to the spatially restricted neurogenesis observed in mammals. Thus, we suspected that the persistence of radial glial cells in the adult turtle may contribute directly to more widespread adult neurogenesis. This dissertation first discusses the role of radial glial cells in mammalian brain development. Secondly, it focuses on comparative features of cellular proliferation in the brain of both embryonic and adult turtles.
Anatomy & physiology;
0433: Anatomy & physiology