Role of the co-transcriptional regulators Yap/Taz in the normal and fibrotic lung epithelia

Sammanfattning: Idiopathic pulmonary fibrosis (IPF) is a fatal disease that exhibits patterns of usual interstitial pneumonia with honeycombing. IPF is characterized by damaged distal lung epithelium with excessive tissue scarring and extracellular matrix remodeling. The etiology of IPF is unknown and current therapies cannot end or reverse disease progression. Aberrant reactivation of developmental pathways is evident in IPF. Among these developmental actors are the co-transcriptional regulators Yap and Taz (YT). YT modulate processes such as proliferation, differentiation, and organ size and are regulated by the Hippo pathway. YT do not have a DNA binding domain but act through interaction with other transcription factors (TFs). YT play a role in fibrotic fibroblasts, but their role is not yet known in the fibrotic lung epithelium. The aim of this thesis project is to develop the tools needed to explore the role of Hippo-YT in fibrotic lung epithelium and to identify the TFs that YT interact with to exert their various functions.We first developed a method to simultaneously isolate proximal and distal lung progenitor cells from an individual mouse with the aid of a 3D printed surgical guide and found that the precision of dissecting the lung lobes affects the purity of the isolated distal progenitors and how they behave in organoid assays. We further found the Hippo pathway to be dysregulated in the fibrotic lung epithelium which led to increases in nuclear YT as well as known downstream targets. Interestingly, we found epithelial YT signaling to be actively involved in extracellular matrix remodeling in the fibrotic lung epithelium through modulation of lysyl oxidase expression, a collagen crosslinking enzyme. Targeting YT in vivo using an FDA approved drug ameliorated the fibrotic phenotype, indicating that YT targeting may be an option to treat fibrosis. We further used cleavage under target and release using nuclease (CUT&RUN) to identify the exact motif sequences on the genome where complexes containing YT bind in the normal and fibrotic lung epithelial. We further identified putative TFs that are known to bind the motif sequences identified. We found that YT have different interaction partners in the proximal and distal lung epithelium and further identified specific YT interactions in the human fibrotic lung epithelium.This current research project sets the basis for the identification of exact targeting mechanisms for finding therapeutics for IPF. YT are known to be responsible for a wide range of biologic processes and targeting YT’s profibrotic activity and promoting their pro-regenerative activities may result in beneficial effects for IPF patients.