ALK2

ALK2, also known as ACVR1, is a type I serine/threonine kinase receptor of the transforming growth factor-β (TGF-β) superfamily that functions as a bona fide bone morphogenetic protein (BMP) receptor and transduces osteogenic signaling through BMP-dependent pathways^[1][2]. Mechanistically, ALK2 forms ligand-induced receptor complexes that activate downstream SMAD1/5/8 signaling, thereby regulating cellular differentiation, skeletal development, and chondrogenic processes^[3][4]. ALK2 has a central role in BMP receptor biology, and functional annotation of ACVR1 has established its importance in both physiological signaling and disease-associated pathway dysregulation^[2][5]. In disease settings, gain-of-function mutations in ACVR1/ALK2 cause aberrant activation of BMP signaling and are strongly associated with fibrodysplasia ossificans progressiva (FOP), a disorder characterized by heterotopic ossification^[2][6][7]. Activating ACVR1 mutations have also been identified in diffuse intrinsic pontine glioma (DIPG), extending the pathological relevance of ALK2 beyond skeletal disease^[2][5]. Compared with related BMP type I receptors, ALK2 exhibits distinct ligand responsiveness and signaling regulation, including activation by specific BMP ligands and context-dependent interactions with activin receptor complexes that influence SMAD1/5/8 activity^[4][8]. For experimental applications, selective inhibition of ALK2 signaling has become an important strategy for investigating pathological BMP pathway activation, and compounds such as LDN-212854 have been developed to achieve ALK2-biased inhibition with improved receptor selectivity^[9]. Consequently, ALK2 serves as a critical molecular target for mechanistic studies of BMP signaling and for preclinical evaluation of therapeutic approaches directed at ACVR1-driven diseases^[2][9].