RFXAP and chronic obstructive pulmonary disease: The top three significantly upregulated mRNAs in the COPD cohort were PIGZ, NCBP2L, and THTPA, while the top three significantly downregulated mRNAs were VWF, FAM90A1, and RFXAP. The volcano plot showed the expression patterns of the mRNAs, lncRNAs, and circRNAs between the two groups (Fig. 2A–C).