ACVRL1 and Hermansky-Pudlak syndrome: In an HPS animal model, we first observed that advanced lung injury and pulmonary angiogenesis coincided with the elevation of KLF6 level in PMVECs; in an in vitro experiment, KLF6 was induced, and KLF6 siRNA inhibited PMVEC-mediated angiogenesis, which was associated with the downregulation of the target gene: ALK1 and ENG.