Cell communication lies at the core of evolution of multi-cellular life: cells send specific signals to instruct their neighbors to adopt fates distinc of their own. An important class of such developmental signals is encoded by the Wnt gene family. Wnt proteins and their signaling cascades touch on virtually every developmental process, from establishing the polarity of a single cell within a tissue to specifying the anterior-posterior bod axis of an organism. Deregulation of Wnt signaling can have catastrophic consequences, including embryonic lethality, birth defects, and disease, most notably cancer. With their diverse and potent activities in development and disease, Wnts have captivated the attention of many researchers seeking to instruct and guide cellular fate choices. The long-term objective of the proposed research is to elevate the current understanding of the mechanisms by which Wnt proteins and their signaling pathways regulate reprogramming, a process in which mature cells acquire an embryonic stem cell-like state. While the majority of research on reprogramming has focused on nuclear events and changes in the epigenome, relatively little is known about the role of the extracellular environment, such as Wnt signals, in this process. The research proposed here builds on the critical and unpublished observation that Wnt signaling is required for reprogramming. Specifically, fibroblasts harboring mutations in the Wnt processing enzyme PORCN (obtained from patients with a rare genetic defect, called Focal Dermal Hypoplasia) fail to reprogram unless the cells are treated with biologically active Wnt protein during the course of reprogramming. The proposed research will examine in great detail the role and requirement of Wnt signaling in reprogramming. Using the recently discovered method for inducing pluripotency, the first aim of this proposal will examine the requirement and timing of Wnt signaling in converting human fibroblasts to iPS cells. In the second aim, the role of Wnt receptors encoded by the FZD gene family will be examined to identify the precise nature of the Wnt signaling loop that orchestrates the process of iPS cell generation. In a third aim, next generation sequencing technologies will be employed to identify the molecular targets of the Wnt pathway during the process of reprogramming. IMPACT: The proposed and innovative research will significantly advance the field of stem cell research by establishing a new paradigm that Wnt signaling is required for the transition from mature cell to induced pluripotent stem (iPS) cell. With its abundant roles in human disorders and diseases, such as cancer, a better understanding of Wnt signaling is essential for the development of novel therapies for currently incurable diseases.
This proposal addresses the molecular mechanism by which mature cells revert to an embryonic stem cell-like state, a process referred to as reprogramming. Particular emphasis is placed on the role of cell-cell communication, specifically WNT signaling, in promoting reprogramming. These studies offer insight into fundamental biological processes, including embryonic development, tissue homeostasis and repair, and disease.