How are the vast number of cells within the central nervous system generated during the development of an organism? Experiments described in this proposal focus on special cells within the central nervous system to learn how gene regulation controls the way cells develop and make specific connections. The cells are called midline cells because they are centrally located within the central nervous system and split it in half.
The central nervous system is an extensive communication system consisting of two cell types: neurons and glia. For cells to function within this system, they must express the appropriate battery of genes. Dissecting how genes are regulated within the various cell types provide information on how this complicated communication network is established. This research focuses on the Drosophila nervous system that is an excellent experimental model for the study of nervous system development and function and shares similarities with mammalian systems.
Regulatory regions are parts of the genome responsible for gene activity in particular cell types. Regulatory regions can be identified and studied by comparing similar genes in related species of flies. Small changes within these regulatory sequences can cause a gene to switch from being active only in midline glia to being active in both glia and neurons. Even smaller changes can abolish gene activity in the central nervous system altogether. By comparing regulatory regions of a number of genes expressed in various cell types, sequence signatures, or tags, are identified that are shared by a particular cell type. These regions can also be used to identify the proteins that regulate gene activity.
Much of the research is conducted by graduate and undergraduate students. It provides students scientific training in genetics and molecular, cellular, and developmental biology that enhances their education and prepares them for careers in the life sciences.
Experiments conducted during this project investigated how particular cell types arise during development and how they function coordinately within the central nervous system. The cells investigated were midline cells which split the central nervous system into two symmetrical parts. For these studies, the fruit fly was used as a model organism because of its simplicity, the tools available to study the central nervous system as well as the similarity of the fly midline to that of vertebrates. To understand how the central nervous system develops, genes expressed in neural cell types and mechanisms that regulate gene activity were identified. Regions of the genome that control gene expression within the central nervous system, as well as the factors that turn genes on and off were identified. In addition, tools that label specific midline neurons with fluorescent tags were generated, allowing the cells to be followed during development in living flies. Moreover, neural circuits generated from midline cells within the adult brain of the fly were identified. Additional experiments indicated that silencing midline neurons caused adult flies to die at a young age, demonstrating the importance of these neurons. In addition to basic knowledge in developmental neuroscience, these experiments were conducted by and provided training for twenty-two undergraduate and two graduate students who are now attending graduate school, medical school or working in industry or as post-doctoral research fellows. To impact a broader audience during the project, the PI and students visited grade schools and middle schools in the Raleigh, North Carolina area to discuss this research as well as careers in genetics and neuroscience and to engage students in activities that reinforce their classroom efforts. Results of the experiments were also incorporated into a course in "Genes and Development" taught by the PI each spring. During the course of the project, the PI led a team that received funding for a state of the art confocal microscope that greatly enhanced imaging capabilities at North Carolina State University.
