Disease-associated mutations on the STAT5B SH2 domain regulate cholesterol and lipid metabolism in liver [RNA-seq]

Growth hormone (GH) signaling through STAT5B is a central regulator of hepatic metabolism, yet the functional consequences of disease-associated STAT5B variants remain poorly understood. Here, we generated mice carrying STAT5BY665F (gain-of-function) and STAT5BY665H (loss-of-function) alleles using CRISPR/Cas9-mediated base editing to dissect their impact on metabolic regulation. STAT5BY665F mutants developed hepatic lipid accumulation, hypercholesterolemia, and enhanced insulin sensitivity, whereas STAT5BY665H mice displayed reduced body weight and impaired insulin responsiveness. Transcriptomic analyses revealed that STAT5BY665F strongly activated lipid, cholesterol, and immune transcriptional programs, while STAT5BY665H failed to induce these pathways. ChIP-seq demonstrated extensive STAT5BY665F enhancer occupancy at metabolic and immune loci, contrasting with the minimal chromatin engagement of STAT5BY665H. Beyond the liver, STAT5BY665F broadly reprogrammed adipose tissue gene expression, activating lipid metabolism and immune regulatory networks, whereas STAT5BY665H exerted more restricted effects. Notably, transcriptional and chromatin remodeling by STAT5B variants displayed sex-dependent differences, with male livers showing more pronounced reprogramming than females. Together, these findings illustrate how alterations in STAT5B activity that alter enhancer activation led to altered metabolic function in liver and adipose tissue.