Phf6 truncating mutation drives leukemogenesis via disrupted epigenetic regulation in mice

Somatic mutations in PHF6 (PHD finger protein 6) are common in hematologic malignancies and confer worse overall survival in acute myeloid leukemia patients. These mutations are predominantly frameshift or nonsense variants, resulting in a truncated PHF6 protein. However, the specific role of truncated PHF6 in leukemogenesis remains unclear. Here, we generated a transgenic mouse model, Phf6^R274XTg, expressing a patient-derived truncated Phf6 mutation specifically in hematopoietic lineages. Unlike Phf6 knock-out mice, which do not develop spontaneous diseases, Phf6^R274XTg mice developed a spectrum of spontaneous hematologic malignancies that recapitulate key features of PHF6-mutated hematologic malignancies in patients. Expression of PHF6^aa1-273 led to expansion of the hematopoietic stem cell/progenitor cell (HSC/HPC) pool and promoted myeloid-skewed differentiation. The Phf6^R274X mutation also induced substantial transcriptional dysregulation in HSC/HPCs. Single-cell RNA-seq analysis revealed a unique HSC trajectory and enhanced myeloid-biased differentiation in Phf6^R274XTg HSC/HPCs. Additionally, truncation of PHF6 altered genome-wide H3K27ac occupancy via enhanced activity of KAT6B acetyltransferase. Treatment with CTx-648, a KAT6A/KAT6B inhibitor, restored HSC function in Phf6^R274XTg mice and prolonged the survival of leukemic Phf6^R274XTg mice. These findings demonstrate a gain-of-function effect for truncated PHF6^aa1-273 in driving leukemogenesis and highlight KAT6B as a promising therapeutic target in PHF6 truncation-associated hematologic malignancies.