3 Detection and Phenotypic Characterization of Adult Neurogenesis

Abstract

Advances in our understanding of the extent and regulation of adult neurogenesis have been dependent on continued improvements in the detection and quantification of critical events in neurogenesis. To date, no specific and exclusive stem cell marker has been described that would allow for prospective studies of neurogenesis. As a result, detection of neurogenic events has depended on a combination of labeling approaches that document the two critical events in neurogenesis: the generation of new cells and their subsequent progression through lineage commitment to a mature neuron. Detection of neurogenesis in vivo requires the ability to image at a cellular resolution. Although advances in noninvasive imaging approaches, such as magnetic resonance imaging (MRI), show promise for longitudinal studies of neurogenesis, the lack of suitable resolution to characterize individual cells limits the information that can be obtained. In vivo microscopy, using deeply penetrating UV illumination with mulitphoton microscopy or by the recently available endoscopic confocal microscopy, may provide new opportunities for longitudinal studies of neurogenesis in the living animal with single-cell resolution. These latter microscopy approaches are particularly compelling when coupled with transgenic mice expressing phenotype-specific fluorescent reporter genes. However, at present, the predominant approach for studies of neurogenesis relies on traditional histological methods of fixation, production of tissue sections, staining, and microscopic analysis. This chapter discusses methodological considerations for in vivo detection of neurogenesis in the adult brain according to our current state of knowledge. First, detection of newly generated cells is evaluated and the strengths of using exogenous or...