Abstract 311: Network Analysis of Pathways Associated with Genetic Regulation of Trimethylamine-N-Oxide

Abstract

Common complex diseases, such as atherosclerosis, diabetes and obesity, are the result of genetic, environmental and gene/environmental interactions. Genetic reference panels are powerful tools to interrogate how the environment interacts with the underlying genetic architecture to influence disease susceptibility. Recently 2 genetic reference panels have been created: the Diversity Outbred (DO) mouse population and Collaborative Cross (CC). The mice comprising the CC/DO are mosaics of C57BL6/J, A/J, NOD/ShiLtJ, NZO/HiLtJ, WSB/EiJ, CAST/EiJ, PWK/PhJ, and 129S1/SvImJ. Both the DO and CC populations have tremendous genetic diversity, containing approximately 45 million segregating single-nucleotide polymorphisms (SNPs). Our primary goal was to characterize the genetic regulation of risk factors for atherosclerosis susceptibility in the 8 founder strains of the DO/CC reference panels. Using a systems genetic approach, we perform integrative analysis of clinical traits, targeted metabolomics and RNA expression. We quantitated genome wide mRNA levels using RNA sequencing followed by network analysis. The network was then related to clinical traits and a targeted panel of 5 metabolites (trimethylamine-N-oxide (TMAO), Betaine, Choline and Creatinine) to identify key groups of genes (called modules). We performed weighted gene network co-expression analysis (WGCNA) using 17,122 genes across 46 mice (N = 5-8 mice per strain). The network contains 47 independent co-expression modules and associated these modules with plasma lipoproteins, liver triglyceride levels and the novel plasma risk factors TMAO and Betaine. For example, the turquoise module was most strongly associated with TMAO levels (p < 2 x 10-8) and the black module was associated with plasma Betaine concentrations. Both modules contain several candidate genes and enrichment analysis using Database for Annotation, Visualization and Integrated Discovery (DAVID ) v6.7 Studies are ongoing to validate the key molecular drivers of the network with a particular interest in the transcriptional network regulating plasma TMAO and Betaine concentrations.