PROJECT SUMMARY/ABSTRACT Rhinosinusitis (RS) is one of the most prevalent airway diseases, effecting approximately 15% of the U.S population. With symptoms of sinonasal mucus hypersecretion and plugging, severe facial pain and breathing difficulties, RS significantly affects both quality of life and socioeconomic burden. Despite these dire outcomes, the etiology of RS is completely unknown, severely hampering the development of preventative or curative treatments. This proposal investigates how aberrant patterning in the organs that provide the majority of the mucus, the nasal submucosal glands (SMGs), may be causative for chronic RS (CRS, > 12 weeks). Based on the high penetrance of CRS in patients with mutations in cystic fibrosis transmembrane conductance regulator (CFTR) gene (Cystic Fibrosis) and published and preliminary studies showing aberrant SMG morphology and function are common to this disease, this proposal tests the hypothesis that dysfunction in CFTR leads to aberrant SMG patterning and thus, CRS. This hypothesis will be tested via three specific aims. (1) Define cell identities and lineage dynamics during SMG development. Before molecular and cellular mechanisms of aberrant gland architecture can be understood, appreciation of normal SMG development is essential. In this Aim, transcriptomic techniques and quantitative measures of morphological changes will be employed to uncover processes governing human SMG development, which can then be utilized to delineate mechanisms of disease SMG patterning. (2) Elucidate CFTR dysfunction in SMGs as an underlying cause of CRS. This Aim will combine use of animal models and ex vivo human SMG manipulation, to test the hypothesis that mis-regulation in CFTR is a cause of tissue remodeling and CRS. (3) Identify molecular and cellular signatures of SMG remodeling in human adult CRS. This final aim will examine morphological and transcriptomic gland phenotypes common to healthy, non-CF CRS, and CF CRS patients, providing insight into alterations in gland structure and function, and thus contribution to CRS. To ensure experiment completion, training in new techniques will be carried out in the K99 phase, including 3D imaging, RNA sequencing and organoid culture. Interactions with collaborators and members of an advisory committee, and attendance of workshops and seminars, will also support project completion and career development. If successful, the proposed research will not only expand our knowledge on SMG development and biology, but will also provide targets for novel therapeutics to be tested in patients of CRS.