Functional comparison of human ACVR1 and zebrafish Acvr1l FOP‐associated variants in embryonic zebrafish

Abstract

Background: Fibrodysplasia ossificans progressiva (FOP), a rare disease characterized by progressive heterotopic ossification of muscle and connective tissues, is caused by autosomal dominant activating mutations in the type I receptor, ACVR1/ALK2. The classic human FOP variant, ACVR1 R206H , shows increased bone morphogenetic protein (BMP) signaling and activation by activins.Results: Here, we performed in vivo functional characterization of human ACVR1 R206H and orthologous zebrafish Acvr1l R203H using early embryonic zebrafish dorsoventral patterning as a phenotypic readout for receptor activity. Our results showed that human ACVR1 R206H and zebrafish Acvr1l R203H exhibit functional differences in early embryonic zebrafish, and that human ACVR1 R206H retained its signaling activity in the absence of a ligand-binding domain (LBD). We also showed, for the first time, that zebrafish Acvr2ba/ Acvr2bb receptors are required for human ACVR1 R206H signaling in early embryonic zebrafish.Conclusions: Together, these data provide new insight into ACVR1 R206H signaling pathways that may facilitate the design of new and effective therapies for FOP patients.