THE ROLE OF TGF-? MODULATORS IN VERTEBRAL DEVELOPMENT

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Vertebral malformation associates with a large number of distressful human birth defects. Elucidation of the developmental and genetic mechanisms underlying normal vertebral formation will undoubtedly have great impacts on human health. The formation of vertebral system is a complex process involving the morphogenesis of neural tube, notochord, somites and cell  cell signaling events among these tissues. In particular, the formation and differentiation of somites play a critical role in vertebral development and vertebral disorders. Each somite has to establish an anterior-posterior (A-P) polarity and disruption of this A-P polarity during development often leads to the abnormal fusions between vertebrae bodies and ribs resulting in serious vertebral and spinal cord disorders. The development of vertebrate tail provides an excellent model system to study somite formation and differentiation due to its simple anatomic structure compared with the trunk vertebral system. The abnormal fusion between vertebrae bodies usually cause tail bending, kinky tail, that can be easily visualized. The A-P differentiation of somites can be examined by a set of well established molecular markers. In this study, we will focus on the regulation of TGF-b signaling pathway in somitogenesis by exploring the functions of two Smads interacting factors: Zfhx1a and TGIF. Zfhx1a, also called dEF1, encodes a zinc finger protein that contains multiple DNA and protein binding domains including homeodomain and Smad binding domain. In vitro studies showed that members of Zfhx protein family can bind to Smads proteins and recruit transcription activator p300 or repressor CtBP. Depending on the types of recruited co-factors, activators or repressors, Zfhx proteins can either up- or down- regulate TGF-b activity. Biochemical studies have revealed that TGIF antagonizes TGF-b signaling by binding to Smad2. Our recent studies with Zfhx1a and TGIF mutant mice uncovered that loss of Zfhx1a or TGIF function leads to a severe kinky tail phenotype, strongly indicating that these genes play important roles the A-P differentiation of somites. We therefore propose here to examine the functional requirements of Zfhx1a and TGIF during mouse somitogenesis and vertebral development. In addition, we will employ Zebrafish system to determine the specificity of Zfhx1a and TGIF mediated TGF-b suppression in vivo, namely which TGF-b member(s) activity is regulated by Zfhx1a and TGIF in vertebrate somitogenesis. Results from the proposed research will be significant as it address the regulation of an important pathway, TGF-b signaling, in a fundamental biological process, vertebrate body segmentation. In addition, the project features several advantages that fit the purpose of this COBRE application suitably: 1) It is a suitable project for the investigator to enter a new area of birth defect research, vertebral disorders; 2) An additional model system, Zebrafish, will allow the investigator to conduct more mechanistic studies as Zebrafish is more accessible to embryonic and genetic manuscript; 3) Since Zebrafish system is a popular and powerful model system in developmental biology, having a zebrafish model system in the laboratory will improve the research strength to a great extend.