The role of alternative splicing in hepatic metabolism

The liver is crucial for maintenance of metabolic homeostasis in eukaryotes. Dysregulation of metabolism in liver leads to obesity, type 2 diabetes, non-alcoholic fatty liver disease and cardiovascular disease. Liver disease alone costs approximately $157 billion per year, a huge burden on healthcare services and society globally. Pathways including glycolysis, lipogenesis and bile acid metabolism are frequently dysregulated and are subject to regulatory changes at the transcriptional, post-translational and signalling levels. However, alternative pre-mRNA splicing, a major contributor to both transcriptome composition and proteomic diversity has not been widely investigated in the context of hepatic metabolic disorders. This thesis demonstrates that there is a consistent mis-regulation of splicing factors and splicing events in liver under the influence of obesogenic diets (high fat, HFD and high fructose, FD). The motif of the splicing factor RBFOX2 is highly enriched surrounding alternatively spliced exons in healthy livers (control diet, CD) during feeding and fasting cycles, and between AS exons of obese livers (HFD vs CD and FD vs CD). Enhanced individual nucleotide crosslinking immunoprecipitation (eiCLIP) of RBFOX2 in primary hepatocytes showed that RBFOX2 targets are involved in cholesterol and lipid trafficking, homeostasis and regulation. Generation of a liver-specific RBFOX2 knockout mouse model (LΔRbfox2) showed that in high fructose loading, LΔRbfox2 mice have disrupted cholesterol and phospholipid metabolism. In response to increased lipogenesis from fructose consumption RBFOX2 regulates a network of targets. Use of splice switching oligos (SSOs) enabled subtle manipulation of RBFOX2 splicing targets to regulate lipid metabolic pathways. This may enhance and inform therapeutic strategies to combat metabolic dysregulation and liver disease. Open Access