Hippo suppression of NFkB controls pancreas morphogenesis and beta cell fate

点击翻译按钮获取中文摘要

More than 30 million Americans have pre- or existing diabetes. An innovative approach to treat diabetes is to generate functional beta cells, which originate from a multipotent progenitor population in the early pancreas bud. This approach is currently in clinical trials, but a recognized problem is suboptimal progenitor generation. While mechanisms regulating later pancreas development have been well defined, how pancreas progenitor specification is regulated remains unclear. This proposal will examine genetic pathways downstream of the Hippo signaling pathway using transgenic mouse models, as well as tissue culture techniques that include organ explants and pancreatic organoids. Bioinformatic approaches will be used to (1) determine if Hippo signaling regulates pancreatic progenitor specification, morphogenesis, or cell differentiation, and (2) determine crosstalk mechanisms between Yap1/Taz and NFκB that regulate progenitor specification and beta cell differentiation in the pancreas. We have found that deleting the Lats kinases dysregulates epithelial cell proliferation, leading to aberrant morphogenesis and cell differentiation, supporting the idea that pancreatic morphogenesis is closely tied to cell differentiation. Using transcriptional profiling, we have found that Yap1/Taz promote NFκB activator genes and here we will define the mechanisms involved. In this proposal, we propose the unique idea that Hippo pathway components act as a rheostat to control levels of NFκB activity during this process, sculpting the epithelial niche that generates beta cells. This niche is a specialized and transient epithelial plexus at the core of the embryonic pancreas. We hypothesize that Lats1/2 activity is required homeostatically to inactivate Yap1/Taz and thereby suppress aberrant NFκB signaling in the normal pancreas. Elevated NFκB activity in pancreatic epithelium results in dysregulated EMT initiation and loss of β-cell fate, due to disruption of the epithelial plexus niche. We hypothesize that elevated Yap1 activity stimulates NFκB signaling at least in part via the pantetheinase Vanin1 (Vnn1). Our aims will use in vivo and in vitro models to investigate these observations. Our hypotheses will be tested via: 1) an examination of how loss of Lats1 and Lats2 affects epithelial integrity and initiation of epithelial-to-mesenchymal transitions (EMTs); 2) an examination of whether overexpression of Yap1 mimics the Lats1/2 double deletion (1/2DKO) in single or clusters of epithelial cells, as well as an assessment of downstream targets known to be affected in 1/2DKO; and 3) an evaluation of the role of the NFkB pathway in pancreatic epithelial homeostasis and an examination of the role of Vnn1 in this process. We hope this work will enhance translational impact of downstream targets in pancreas progenitors and beta cells, with the goal of therapeutic beta cell replacement and regeneration to treat diabetes.