| Congenital malformations are the most common cause of infant death in the United States. Skeletal and neural crest related structures, including cardiac outflow tract and craniofacial disorders, make up the majority of these malformations. Therefore, identifying molecular mechanisms that regulate skeletal and cardiac development is of great clinical importance. The Notch signaling pathway has been implicated in cell fate specification, migration, proliferation, and differentiation in a variety of cell types and organs and mis-expression of Notch signaling results in disease and associated malformations. Skeletogenesis encompasses several processes including somitogenesis, chondrogenesis, and osteogenesis that contribute to proper skeletal development. Notch signaling is necessary for proper somitogenesis and osteogenesis, but the role of Notch signaling in chondrogenesis in vivo was unknown. The studies detailed here demonstrate that Notch signaling is required for proper cartilage progenitor proliferation and hypertrophic chondrocyte differentiation in the axial and appendicular skeleton. During development, neural crest cells (NCCs) are formed in the dorsal neural tube and subsequently migrate, proliferate, and differentiate into a multitude of derivatives and structures including craniofacial and cardiac outflow tract derivatives. Notch signaling is also active in the neural crest and derivatives, but the mechanisms of Notch function at specific stages and developmental processes in NCC are unknown. Studies detailed in this dissertation demonstrate critical cell-autonomous roles for appropriate levels of Notch signaling during NCC migration, proliferation and differentiation with critical implications in craniofacial, cardiac, and neurogenic development and disease. |
