ANGPTL2 and CP define complementary circadian-associated signals in atrial fibrillation: integrative transcriptomics and external validation.

Introduction: Atrial fibrillation (AF) develops through the interplay of electrical, structural, inflammatory, and metabolic remodeling. However, the circadian-associated molecular characteristics of the diseased human atrium remain incompletely understood. Methods: We integrated differential expression analysis, circadian gene intersection, weighted gene co-expression network analysis, and complementary feature selection algorithms in a discovery cohort. The prioritized candidate genes were subsequently validated using an independent atrial dataset, human atrial rhythmicity data, single-nucleus transcriptomics, and experimental evidence derived from human and mouse atrial tissues. We additionally performed cross-cohort drug repurposing screening and exploratory molecular docking. Results: ANGPTL2 and CP were identified as prioritized candidate genes associated with circadian rhythms. Both genes were consistently upregulated in fibrillating atria but exhibited distinct expression profiles: ANGPTL2 demonstrated stronger discriminatory power at the tissue level, whereas CP showed a larger but more heterogeneous expression alteration. Both genes displayed rhythmic expression patterns in human atrial appendage tissue and were predominantly enriched in vascular and stromal cell populations, establishing a link between temporal atrial biology and inflammatory-metabolic remodeling as well as copper-redox remodeling. The upregulation of their transcripts and proteins was further validated across independent human samples and an arrhythmia-prone mouse model. No compound met the prespecified multi-source criteria for cross-cohort drug repurposing. An independent exploratory analysis of clinically used antiarrhythmic drugs identified favorable molecular docking profiles for both target proteins. Discussion: ANGPTL2 and CP are externally validated circadian rhythm-associated candidate genes for atrial fibrillation (AF), and may yield experimentally testable candidate gene-drug pairs. However, these findings do not establish causal regulation by the circadian clock, direct molecular binding, or clinical therapeutic efficacy.