PROJECT SUMMARY Cystic fibrosis (CF) is one of the most common fatal pediatric respiratory diseases, affecting approximately 1 in 3500 children. The development of CFTR modulators has spawned a new era of hope for CF therapeutics. However, addressing the common F508del CFTR mutation has been challenging and CFTR modulator therapy for this mutation is only minimally effective. An improved understanding of F508del CFTR and its correction is the most critical therapeutic pursuit for CF patients. I have recently shown that the cystic fibrosis genetic modifier TGF-β diminishes CFTR function, reduces CFTR synthesis, and impedes F508del correction. I have also reported that TGF-β is significantly increased in CF lungs and mediates its effects by microRNA-based signaling. Specifically, I have found that the microRNA 145 (miR-145) mediates TGF-β inhibition of CFTR expression and function, and also limits F508del correction by CFTR modulators. Discovery of this important underlying mechanism has stimulated me to expand my career goals to microRNA therapeutics. My central hypothesis is that miR-145 antagonism interrupts TGF-β suppression of CFTR synthesis and function in airway epithelia, representing an attractive therapeutic target. With K08 support, I will receive training to 1) investigate mechanisms of miRNA regulation of CFTR 2) deliver miRNA antagonists in vivo and 3) learn methods to quantify F508del therapeutic response in CF animal models. These training goals will help advance my career focus on microRNA therapy and will be achieved through the following Specific Aims: Specific Aim 1: Determine the in vitro mechanism of miR-145 inhibition of CFTR in airway epithelia. Specific Aim 2: Establish in vivo relevance of miR-145 manipulation to improve CFTR function. Specific Aim 3: Augment CFTR correction with miR-145 antagonists in preclinical CF animal models. My training will be mentored by Dr. Steven Rowe (Director of the UAB Cystic Fibrosis Research Center and expert in CF translational science) and a panel of senior investigators in a fertile research environment with exceptional resources. Data obtained during the study period will establish the role of miR-145 inhibition to stabilize F508del modulation and introduce miRNA antagonists as a useful adjunct to CFTR directed therapeutics. Training provided by the K08 mechanism will facilitate my transition to research independence, creating a niche to investigate consequence of miRNA dysregulation in CF lungs and benefit of miR-145 antagonists to improve current and next generation F508del CFTR correction. These studies will establish a foundation for my career in CF translational science evaluating mechanisms of disease progression and therapeutic development.