The Role of Zic1 in Neural Patterning and in Mid-/hindbrain Boundary Formation

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Christa MerzdorfMontana State UniversityProject summary 1) Intellectual merit: The correct formation of the nervous system is critical to the development of any viable multicelular organism. The initial formation of the neural tube, followed by its differentiation into the various compartments of the central nervous system, is a highly orchestrated process. This process is directed at the molecular level by complex and dynamic patterns of gene expression. These genes are expressed very early in development, when the cells that will form the nervous system are just being set aside. The resulting gene expression patterns specify the different parts of the brain, such as forebrain, midbrain, and hindbrain. The junction between the midbrain and the hindbrain, the midbrain/hindbrain boundary (MHB), is critical for providing the signals that allow correct development of the midbrain (optic tectum) and the anterior hindbrain (cerebellum). When these MHB signals are misexpressed in a different region of the embryo (for example the spinal cord region), they direct their new surroundings change fate to midbrain/hindbrain character. The MHB begins to form during gastrula stages and an increasingly complex gene regulatory network is found to regulate its formation. One gene that is active very early in the development of the nervous system is the transcription factor zic1. zic1 contributes to early molecular patterning of the neural plate and preliminary data indicate that it participates in formation of the MHB. Thus, the goals of this proposal are twofold: first, to determine whether zic1 expression is required for early neural development, and, second, to determine whether zic1 functions as an upstream regulator of midbrain/hindbrain boundary formation. These studies will be conducted in Xenopus, since its early development is highly accessible to experimentation. Various dominant interfering constructs will be expressed in Xenopus embryos to ablate normal zic1 function. These experiments will determine wether zic1 is required for neural patterning, whether it functions as an activator and/or repressor of transcription, and what role it plays in MHB formation. In order to dissect further the molecular interactions that give rise to the MHB and the involvement of zic1 in these interactions, gene expression in ectodermal explants (animal cap assays) will be used. These explants will mimic aspects of MHB formation in a more easily controlled tissue away from the various signals during normal development. Together, the data from these experiments will significantly enhance our understanding of the molecular mechanisms that drive establishment of the different parts of the developing nervous system.2) Broader impact: The proposed research activities will increase our understanding of how the brain develops and how zic1 contributes to MHB formation. zic1 performs other functions in development as well and is highly conserved among organisms. Thus, knowledge of how zic1 fits into the molecular interactions that give rise to the MHB in Xenopus will allow comparison of shared and divergent regulatory pathways with respect to other developmental functions of zic1 and with respect to evolutionary conservation in other organisms. In addition, the proposed research activities will be integral part of the P.I.'s educational activities. The work will be performed by two Ph.D. students. Multiple smaller projects will allow the involvement of several undergraduate students with independent projects. The P.I. is committed to the education of Native American students and has two Native American students involved in research in her laboratory. One of these Native American students will be participating in this project and her work in the P.I.'s laboratory was recognized for outstanding poster at the national SACNES conference last summer. It is likely that other Native American undergraduate students will be involved in the proposed research. Further, discussion of this research will be part of undergraduate and graduate lecture and laboratory courses taught by the P.I. Finally, this research will be performed at Montana State Universiry, which is an EPSCoR institution, and will provide critical research experience to a number of excellent undergraduate students who might otherwise not have the opportunity to be involved in discovery-based research.