Poster abstracts

Poster number 87 submitted by Nicholas Baker

Temporally controlled expression of a splicing factor in single cells coordinates the metabolic and proliferative activities of regenerating livers

Nick Baker (Department of Biochemistry, UIUC), Sushant Bangru (Department of Biochemistry, UIUC), Ullas V. Chembazhi (Department of Biochemistry, UIUC), Auinash Kalsotra (Department of Biochemistry, UIUC)

The liver has an extensive ability to regenerate following injury, typically via cellular proliferation of hepatocytes. However, the exact mechanics of regeneration, such as how quiescent hepatocytes transition into a proliferative state and how regenerating livers sustain normal metabolic activities while the tissue recovers from injury, are largely unknown. The role of alternative splicing and RNA binding proteins during liver regeneration has remained completely uninvestigated. Epithelial splicing regulator protein 2 (ESRP2) is an RNA splicing factor that acts as the developmental switch for splicing targets during postnatal liver maturation, including in the Hippo signaling pathway, which is critical for organ development and regeneration. ESRP2 promotes the production of adult Hippo pathway splice variants thereby limiting hepatocyte proliferation in a quiescent mature liver. We have previously demonstrated that ESRP2 and its splicing targets are transiently reprogrammed to the fetal stage during active phases of regeneration. We further hypothesized that ESRP2 is temporally controlled within regenerating hepatocytes to promote a proliferative or metabolic state. We used single-cell RNA sequencing to determine altered cell states and gene expression changes in ESRP2 KO cells compared to WT mice during the initiation and termination stages of liver regeneration. Here we show that regenerating hepatocytes bifurcate into proliferating or metabolically-hyperactive cell states, such that ESRP2 is highly expressed in the metabolically active hepatocytes and is nearly absent in the proliferating hepatocytes. Remarkably, the adult quiescent ESRP2 KO hepatocytes exhibit an altered starting cell state, which is more closely related to the fetal stage. We further show that forced expression of ESRP2 in the mouse liver inhibits the proliferation of hepatocytes, whereas ESRP2 deletion in hepatocytes increases their proliferative index during liver regeneration. Taken together, these data imply that tightly controlled expression of ESRP2 coordinates the metabolic and proliferative activities of regenerating livers.

Dysregulated activation of fetal liver programme in acute liver failure. Hyun et al. Gut. (2019)
Alternative splicing rewires Hippo signaling pathway in hepatocytes to promote liver regeneration. Bangru et al. Nat Struct Mol Biol. (2018)

Keywords: Liver, Regeneration, scRNA-seq