PROJECT SUMMARY/ABSTRACT Despite established sex differences in COPD epidemiology and clinical manifestations, most preventive and therapeutic strategies do not take biologic sex into consideration. This is due, in large part, to a lack of understanding of the molecular mechanisms that drive these sex differences, as well as conceptual and methodological gaps in incorporating sex into research and clinical practice. The involvement of X chromosome genes in COPD has not been extensively studied, particularly incomplete X chromosome inactivation (XCI), which causes gene dosage imbalance between sexes and sex-specific effects of genetic variation. Differences related to sex chromosomes may allow genetic variations to have distinct functional effects in males and females. Our hypothesis is that variations in X chromosome gene regulation affected by incomplete XCI, and X chromosome genetic variants can help explain molecular mechanisms associated with sex differences in COPD onset and heterogeneity. We will integrate X chromosome multi-omic data from lung and blood samples from COPD cases and controls from three study populations (COPDGene, LTRC, and LTCOPD). We will study sex-biased epigenetic regulation by methylation Quantitative Trait Loci (QTL) analysis (Aim 1); sex- biased genetic regulation by expression QTL analysis (Aim 2); and sex-biased regulatory processes via gene regulatory network analysis (Aim 3). Our investigation would be the first to model the effect of XCI into gene regulatory networks to examine sex divergent regulatory processes and the effect of genetic variants associated with COPD status affection, emphysema, and lung function. We expect that our network analyses will point to genetic variants that work together to influence biological function in a sex-specific manner. Given that genes that escape XCI can vary across individuals and tissues and have been linked to disease susceptibility, we will examine escape genes in the context of mQTL, eQTL, and regulatory networks, and test for changes between COPD cases and controls. Identifying variations in XCI patterns in disease will give insights into the mechanisms associated with both disease development and sex differences in COPD. These discoveries will help us better understand the biological mechanisms of sex differences in COPD, and provide data for future functional validation, and sex-aware development of diagnostic and therapeutic tools. This K01 award will enable Dr. Lopes-Ramos to build upon her existing molecular biology and transcriptomics-focused skill sets in order to learn about epigenetics, statistical genetics, pulmonology, and integrative omic analysis and methods refinement for sex-aware modeling and statistical comparisons. Dr. Lopes-Ramos has developed a detailed training plan and assembled a mentoring team with complementary expertise. This K01 will allow the proposed research to be completed successfully and will support the development of Dr. Lopes-Ramos i...