Atrial Proteomic Profiling Reveals a Switch Towards Profibrotic Gene Expression Program in CREM-IbΔC-X Mice with Persistent Atrial Fibrillation

Background Overexpression of the CREM (cAMP response element-binding modulator) isoform CREM-IbΔC-X in transgenic mice (CREM-Tg) causes the age-dependent development of spontaneous AF. Purpose To identify key proteome signatures and biological processes accompanying the development of persistent AF through integrated proteomics and bioinformatics analysis. Methods Atrial tissue samples from three CREM-Tg mice and three wild-type littermates were subjected to unbiased mass spectrometry-based quantitative proteomics, differential expression and pathway enrichment analysis, and protein-protein interaction (PPI) network analysis. Results A total of 98 differentially expressed proteins were identified. Gene ontology analysis revealed enrichment for biological processes regulating actin cytoskeleton organization and extracellular matrix (ECM) dynamics. Changes in ITGAV, FBLN5, and LCP1 were identified as being relevant to atrial fibrosis and remodeling based on expression changes, co-expression patterns, and PPI network analysis. Comparative analysis with previously published datasets revealed a shift in protein expression patterns from ion-channel and metabolic regulators in young CREM-Tg mice to profibrotic remodeling factors in older CREM-Tg mice. Furthermore, older CREM-Tg mice exhibited protein expression patterns that resembled those of humans with persistent AF. Conclusions This study uncovered distinct temporal changes in atrial protein expression patterns with age in CREM-Tg mice consistent with the progressive evolution of AF. Future studies into the role of the key differentially abundant proteins identified in this study in AF progression may open new therapeutic avenues to control atrial fibrosis and substrate development in AF. Graphical abstract Graphical abstract summarizing key findings of this paper. The atrial proteome in 9-month-old CREM- Tg mice with chronic persistent AF (perAF) was compared with age-matched WT littermates. In addition, proteome changes in these old CREM-Tg mice were compared with proteome changes previously identified in young CREM-Tg mice with paroxysmal AF (pAF). Moreover, an interspecies comparison was performed between old CREM-Tg mice and human patients with perAF. The major findings are that in pAF, key changes were identified in proteins involved in metabolism, energy production, DNA synthesis, and cell proliferation and growth. On the other hand, in mice and humans with perAF, key changes were found in the expression of proteins involved in collagen production, extracellular matrix remodeling, actin cytoskeleton organization, and tissue repair. ![Figure][1] ### Competing Interest Statement XHTW is a founding partner and shareholder of Elex Biotech Inc, a start-up company that developed drug molecules that target ryanodine receptors to treat cardiac arrhythmia disorders. Other authors have no conflict of interest to declare. * AF : atrial fibrillation BP : biological process CREM : cAMP-response element modulator DEP differentially expressed protein ECG : electrocardiogram ECM : extracellular matrix FBLN5 : fibulin 5 GO : gene ontology GSEA : gene set enrichment analysis ITGAV integrin alpha V LCP1 : lymphocyte cytosolic protein 1 MS : mass spectrometry pAF : paroxysmal atrial fibrillation PCA : principal component analysis perAF : persistent atrial fibrillation PPI : protein-protein interaction WT : wild type [1]: pending:yes