Complex developmental processes that define organ morphology and cellular differentiation appear to be governed by only several signal transduction pathways, suggesting the likelihood of extensive interactions among those pathways. However, the mechanisms that coordinate the activity of different signaling cascades involved in this process remain ill defined. In this proposal, I wish to tackle this important issu by focusing on the interplay between two prominent signals that control development;the transcription coactivator Yes- associated protein (YAP), the prime target of the Hippo kinase cascade, and Sonic hedgehog (Shh) signaling. The main goals of this proposal are to 1) dissect the function of YAP in spinal cord development, and 2) define how the Shh and Hippo signaling pathways act in concert to control development in the vertebrate spinal cord. The overall hypothesis of this proposal is that YAP serves as a novel downstream effector of Shh during the control of NPC proliferation and specification of ventral cell fates in the CNS. Specifically, I postulate that the YAP-dependent signaling communicates with the Shh signaling pathway at multiple levels, providing an effective means of coordinating these two transduction cascades during neural development. I will test this hypothesis using an ensemble of molecular methods, chick embryos and mutant mice.
The specific aims of this proposal are as follows: 1) to determine the role of YAP in cell-type specification during neural tube development and 2) to define how the Shh and Hippo signaling pathways act in concert to control development in the vertebrate spinal cord. Besides defining the basic mechanisms by which YAP and Shh signaling coordinate key aspects of normal CNS development, this study should also uncover important principles applicable to other signaling networks that regulate organogenesis.
The goal of the proposed research is to understand how cellular signaling pathways operate to control cellular differentiation during spinal cord development. The dysregulation of these cellular signaling pathways leads to a variety of neurodevelopmental disorders, such as holoprosencephaly. The studies outlined in this proposal should augment our understanding of how different signaling pathways interact in the developing spinal cord, which may be instructive in designing cell-based therapeutic approaches to treat spinal cord diseases and injuries.