KLF9 is a transcription factor that binds GC box promoter elements and acts as a selective transcriptional regulator, activating genes with tandem GC box repeats while repressing those with single GC boxes 1. In hepatocytes and stem cells, KLF9 is induced by thyroid hormone receptors via triiodothyronine (T3) signaling and regulates hundreds of target genes involved in cell differentiation and Notch pathway signaling 1. KLF9 also functions as an epidermal circadian regulator controlling keratinocyte proliferation. Mechanistically, KLF9 integrates cardiac energy metabolism by controlling PGC-1α and mitochondrial dynamics genes; Klf9-deficient mice develop hypertrophic cardiomyopathy with impaired mitochondrial function and defective mitophagy 2. In obesity, NAT10-mediated N4-acetylcytidine modification stabilizes KLF9 mRNA, and KLF9 promotes adipogenesis by activating CEBPA/B-PPARG pathway 3. Under severe oxidative stress, Nrf2 induces KLF9 expression to suppress antioxidant enzyme genes and promote cell death 4. In pancreatic cancer, KLF9 inhibits proliferation and metastasis by directly repressing PAFAH1B3 5. DNA methylation of KLF9 is regulated by thyroid hormones and inversely correlates with gene expression 6. In liver fibrosis, KLF9 is upregulated in activated hepatic stellate cells during metabolic dysfunction-associated steatohepatitis 7. Glucocorticoids regulate KLF9 expression in brain tissue as part of stress response mechanisms 8.