Deficiency of ZFP36L1 and ZFP36L2 impairs liver homeostasis and initiates cholestatic liver injury

BACKGROUND: RNA-binding proteins, Zinc Finger Protein 36-Like 1 (ZFP36L1) and Zinc Finger Protein 36-Like 2 (ZFP36L2), post-transcriptionally regulate the expression of a large number of genes involved in various cellular processes. However, specific or redundant functions of ZFP36L1 and ZFP36L2 in liver homeostasis have never been explored. Here, we hypothesized that ZFP36L1 and ZFP36L2 are functionally redundant in the liver, and their combined deficiency would stabilize their direct mRNA targets, which would alter liver homeostasis. METHODS: We generated combined liver-specific ZFP36L1-deficient and ZFP36L2-deficient mice (L1/L2dKO) and compared their liver homeostatic parameters with flox control (L1/L2FLX) mice. We performed detailed analyses of liver histology, serum biomarkers of liver injury, liver transcriptome, bile flow rate, and biliary total bile acid (TBA) excretion. RESULTS: We demonstrated that the combined liver-specific deficiency of ZFP36L1 and ZFP36L2 in mice (L1/L2dKO) results in spontaneous cholestatic liver injury, which was characterized by elevated hepatic and serum levels of TBAs and liver injury biomarkers, including ALP, ALT, and AST, presence of bile infarcts followed by marked inflammation, cellular proliferation, and fibrosis. To determine the impact of deficiency of ZFP36L1 and ZFP36L2 on the liver transcriptome and their relevance to cholestatic liver injury, RNA sequencing of whole livers of L1/L2dKO and L1/L2FLX mice was performed, which showed significant perturbation of ZFP36L1/ZFP36L2 target genes associated with cholestasis in L1/L2dKO mice. In addition, L1/L2dKO mice exhibited reduced bile flow rate and decreased biliary TBA excretion. Subsequent analyses revealed impaired bile canalicular morphogenesis by postnatal day 7, as evidenced by F-actin and zonula occludens-1 staining patterns. CONCLUSIONS: Our findings demonstrate beneficial roles of ZFP36L1 and ZFP36L2 in maintaining liver homeostasis.