PROJECT SUMMARY / ABSTRACT Sarcoidosis is a multi-organ, immune-mediated inflammatory disease with a highly variable clinical presentation and disease course. Additionally, the mortality rate from sarcoidosis appears to be rising over the past decades. A significant challenge in the management of sarcoidosis is the lack of reliable diagnostic and prognostic biomarkers. The objective of this project is to define microRNAs (miRNAs) that can be used as diagnostic biomarkers and to associate miRNA expression with clinical characteristics in sarcoidosis for the development of prognostic biomarkers. A genomic approach to biomarker development is well suited for complex, polygenetic diseases such as sarcoidosis and will be the focus of this project. miRNAs have significant potential as biomarkers in sarcoidosis given their role as epigenetic modifiers and immune response regulators. Prior to this grant, we performed miRNA sequencing on bronchoalveolar lavage (BAL) cell samples in a discovery cohort comprised of sarcoidosis cases and healthy controls; this process identified 7 differentially expressed miRNAs, which we will use in all the aims of this current proposal. In Aim 1, we will validate the 7 differentially expressed miRNAs in a validation cohort comprised of cases, healthy controls, and interstitial lung disease controls. The miRNAs that are validated will then be tested as a diagnostic biomarker for sarcoidosis. In Aim 2, we determine if the expression levels of the 7 differentially expressed miRNAs at the time of BAL reflect clinical manifestations of sarcoidosis. We will also determine if the miRNA expression levels at the time of BAL can predict changes in clinical manifestations over two years. Finally, in Aim 3, we will characterize the stability of the 7 differentially expressed miRNAs over two years in a subset of sarcoidosis cases. This finding, along with the results from Aim 2, will help in the development of prognostic biomarkers in a future grant. This proposal will provide a strong foundation for Dr. Lin’s long-term goal of becoming an independently funded physician-scientist in the field of translational sarcoidosis and environmental/occupational pulmonary research. Specifically, this proposal will continue to build her expertise in genomic biomarker development, longitudinal study design, and statistical analyses specific to sarcoidosis research. This proposal will also generate preliminary data for her future R01 grant submissions.