Our central nervous system (CNS) carries out highly complex functions, which enable us to sense our environment, think and coordinate movements. Not surprisingly, even slight perturbations in the proper assembly of the CNS can have a dramatic impact on our lives. The goal of this research proposal is to analyze the role of two critical genes, N-cadherin (N-cad) and bumpy brain (bpb), in CNS development, using the zebrafish as a model system. While N-cad encodes a cell adhesion molecule, the molecular identity of bpb is currently unknown. Both N-cad and bpb are essential for the shaping of the neural tube, the precursor of the CNS, and genetic evidence indicates that the products of these genes interact. In addition, N-cad appears to be required for the maintenance of stem cell-like populations in the CNS. The specific aims of this research proposal are to investigate, at a cellular and molecular level, how N-cad and bpb function and interact to mediate these processes. Since zebrafish CNS development bears multiple similarities to that of other vertebrates, these studies should reveal fundamental mechanisms underlying CNS development. The broader educational goals of this research proposal are to 1) expose students at all levels to basic research and foster an interest in research-related careers, 2) increase the participation of underrepresented minorities in the sciences. The first goal will be accomplished by recruiting high school students from neighboring schools to carry out research projects in the laboratory, participation of the PI and her students in science-related lecture series at these high schools and the creation of innovative curricular offerings. Finally, by leveraging the institutional strengths of the University of Maryland Baltimore County, the PI will continue to provide a nurturing and stimulating learning environment for students from underrepresented groups.

The posterior region of the neural tube in amniotes undergoes "secondary neurulation", where a mesenchymal population of neural precursor cells first condenses into a solid medullary cord, undergoes a mesenchymal-to-epithelial transition and cavitates to form a lumen. Despite the high incidence of human posterior neural tube defects (1/1000 live births), the cellular and molecular mechanisms that mediate secondary neurulation remain for the most part unknown. The zebrafish is an ideal system in which to study neurulation, as it offers a combination of excellent imaging tools for investigating the cellular behaviors underlying morphogenesis and genetics to identify the essential molecules that regulate these behaviors. Moreover, evidence from our laboratory and others has demonstrated that the zebrafish embryo undergoes a form of secondary neurulation.

Formation of the neural tube in the zebrafish is dependent on the ability of cells to polarize properly. Polarity is first manifested by the extension of directional membrane protrusions that drive neural cell convergence towards the dorsal midline. Once these mesenchymal cells have coalesced into a neural rod, they become epithelial and establish a clearly defined apico-basal axis. The overall goal of this proposal is to understand how cell polarity is regulated during neurulation and how disruption of this polarity perturbs both the morphogenetic movements that shape the neural tube and neural cytoarchitecture.