Abstract 262: Regional Transcriptomics of Left Atrial Cardiac Tissue in a Patient With Atrial Fibrillation

Abstract

Background: Common genetic variants and inflammatory factors are associated with atrial fibrillation (AF) risk. Although the top AF risk locus is near PITX2 (associated with pulmonary vein (PV) development), regional differential expression (DE) of AF risk genes in the left atrium (LA) and PVs is not well studied. While LAA and PV gene expression have been compared, transcriptome mapping of the entire LA has not been done. We tested the hypothesis that there is significant regional DE in LA structures. Methods: RNAseq was performed in 25 regions within the PVs (n=12), LA body (LAB) (n=10), and LA appendage (LAA) (n=3) from a 75 year old male with hypertension and AF who died of a stroke. DE analysis of regional clusters (R 3.6 Limma package) and gene set enrichment analysis (GSEA) (Broad Institute) were performed. Results: In full transcriptome (n=20664) sequencing, 118 genes were significantly (q < 0.05) upregulated in the LAA, including FOSB (fold change [FC] 67.0), IL6 (FC 15.4), TNF (FC 2.4) and NLRP3 (FC 2.4), and 56 downregulated, including developmental genes such as SHOX2 (FC -12.9) and HOXA4 (FC -4.1). LAA GSEA showed enrichment (FDR < 0.05) of inflammatory response genes and TNF-α, IL-2, IL-6, and IgG signaling pathways. 2454 genes were significantly upregulated and 3737 downregulated in the PVs while 4021 genes were upregulated and 2998 were downregulated in the LAB. In an AF implicated gene set (n=190), 28 genes were upregulated in the PVs, including SIRT1 (FC 1.7), and 31 downregulated, including PMNT (FC -2.1) and CGA (FC -3.2). NEURL1 was significantly upregulated in the inferior PV (n=4) compared to the superior PV (n=8) (FC 3.6). In the LAB, 33 genes were upregulated, including MYH7 (FC 2.2) and PMNT (FC 2.1) , and 38 downregulated including SIRT1 (FC -1.9). PITX2 did not show any significant DE in any gene set. Conclusions: This data shows that genes involved in AF pathogenesis can have substantial regional expression difference, particularly when comparing the LA body, PVs, and LAA. Inflammatory activation in the LAA may contribute to increased stroke risk.