Characterizing microRNA regulators of lung disease

Abstract

Lung diseases are one of the leading causes of mortality and morbidity worldwide. Understanding these diseases at a molecular level remains a critical component to developing effective therapeutics. Previous work has shown that gene expression alterations play an important role in disease initiation, maintenance, and progression as well as serve as diagnostic tools in disease. However, much remains to be uncovered regarding the role that microRNAs play in both healthy and diseased lung tissue. This thesis seeks to utilize methods of bioinformatics, cell biology, and molecular biology to examine the effect of miR-4423 on lung epithelial cell differentiation (Aim 1), miR-424 on never smoker derived lung adenocarcinoma (Aim 2), and miR-34c isomiRs in interstitial lung disease (ILD) (Aim 3). First, we examined the role of miR-4423 in lung mucociliary epithelium by employing the use of an air-liquid interface culture system, finding miR-4423 has an effect in ciliated cell differentiation and that a loss of miR-4423 is associated with cancer progression. These findings suggest that miR-4423’s actions in airway epithelium differentiation may potentially provide a therapeutic role in lung cancer. Next, we validated transcriptomic differences between lung tumor tissues resected from never and ever smokers. Specifically, miR-424, a predicted regulator of a large number of gene expression changes in never smoker lung adenocarcinoma, was found to regulate cell migration, potentially identifying a novel target and/or pathway for therapeutic action. Lastly, the function of microRNA isomiRs is relatively unknown. We validated miR-34c as upregulated in ILD and modulated both miR-34c and a miR-34c 5’ isomiR in lung relevant cell lines to explore their differing biological roles. We found that they are capable of targeting differing mRNA, indicating an independent role for isomiRs in disease. The studies contained in this dissertation offer valuable insight into the biology of microRNAs in the lung and how they might be employed as therapeutic targets for a number of common lung diseases. In addition, biological insights into the complexity of microRNAs in the lung highlight the need to better understand diseases influenced by microRNA expression and microRNA variants in regards to actionable therapeutics.