Jane Lee

4th Year Graduate Student

Department: Cold Spring Harbor Laboratory

Graduate Program: Neuroscience

Advisor: Holly Cline

Abstract:

Title:  Neurogenesis in the Xenopus laevis tectum: An in vivo study

Neural stem cells (NSCs) are present in the adult brain of many vertebrates including humans. Studies have shown these adult NSCs can generate neurons which can migrate long distances, project extensive axonal and dendritic processes, integrate into an established neural network, and contribute to the normal function of the adult brain. However, little is known about the stepwise details of these endogenous neurogenic events. Dissection and elucidation of the mechanisms that result in the functional integration of newly born neurons into a normal adult brain will provide an instructive blueprint for the enhanced integration of grafted neurons into a host brain. The albino Xenopus laevis retino-tectal model system is uniquely equipped to investigate functional neurogenesis. First, the skin of the albino X. laevis tadpole is transparent and the brain including the optic tectum is superficial; this allows us to time-lapse image neurons in vivo. Second, the optic-tectal cells are amenable to genetic manipulations such as plasmid or viral transfection. Third, the X. laevis brain, including the optic tectum, contains cells that are known to proliferate into adulthood and because the retino-tectal circuitry is established early in development, we can investigate how new neurons integrate into a pre-existing neural circuit even in tadpoles. Finally, the direct connection between the retina and the optic tectum permits us to explore how activity may play a role in the integration events of newly born neurons. In this study, the first aim is to establish a protocol to fluorescently label NSCs to observe their proliferation and integration into the retino-tectal circuit using known stem-cell markers. The second aim is to observe the proliferating pattern under normal conditions and then ask if visual stimulation changes the pattern. The last aim is to observe the survival and/or differentiation patterns of the newly born cells.