A unique mutation of ALK2, G356D, found in a patient with fibrodysplasia ossificans progressiva is a moderately activated BMP type I receptor

Disease-causing allele-specific silencing against the ALK2 mutants, R206H and G356D, in fibrodysplasia ossificans progressiva

“…These results were consistent with our previous finding that ALK2_G356D had less activity than ALK2_R206H. 17 On the basis of the data, we introduced the siR206H_A9(C14) siRNA together with the IdWT4F-luc reporter gene into patient cells expressing ALK2_R206H. The result demonstrated significant reduction of the IdWT4F-luc activity by siR206H_A9(C14) ( Figure 3b); and marked decrease in the ALK2_R206H transcript was consistently detected, whereas the level of the normal ALK2 transcript, by contrast, remained unchanged ( Figure 3c).…”

“…17 The day before transfection, C2C12 myoblast cells were trypsinized and seeded into 24-well culture plates (B1Â10 5 cells per cm 2 ) in culture medium without antibiotics. Co-transfection of the IdWT4F -luc plasmid (100 ng per well) together with normal-or mutant-type ALK2-V5 expression plasmid (200 ng per well), 15,17 designed siRNA duplexes (20 nM, final concentration) and phRL -TK plasmid (50 ng per well) as a control was carried out using Lipofectamine 2000 transfection reagent. Two days after transfection, cell lysate was prepared and the expression levels of luciferase reporter genes were examined by Dual-Luciferase reporter assay system (Promega) according to the manufacturer's instructions.…”

Peripheral Blood Mononuclear Cell Immunophenotyping in Fibrodysplasia Ossificans Progressiva Patients: Evidence for Monocyte DNAM1 Up‐regulation

“…In addition to this, few different ACVR1 substitutions affecting the GS or the kinase domain of the protein were reported (7,8). As suggested by previous in vitro studies, these mutations have a "gain of function" effect on the receptor's activity with dysregulation of the downstream pathway and increased responsivity to BMPs (6,(9)(10)(11)(12). Very recently, two seminal works have demonstrated that these mutations cause a modification of ACVR1 ligand binding properties, by conferring to the mutated receptor the ability to respond to Activin-A, a molecule that normally transduces TGF-b signaling through the Smad2/3 cascade (13,14).…”

Neofunction of ACVR1 in fibrodysplasia ossificans progressiva

“…ACVR1 mutations in atypical FOP patients have been found also in other amino acids of the GS domain or protein kinase domain (11,12). Regardless of the mutation site, mutated ACVR1 (FOP-ACVR1) has been shown to activate BMP signaling without exogenous BMP ligands (constitutive activity) and transmit much stronger BMP signaling after ligand stimulation (hyperactivity) (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25).…”

“…To reveal the molecular nature of how FOP-ACVR1 activates BMP signaling, cells overexpressing FOP-ACVR1 (12)(13)(14)(15)(16)(17)(18)(19)(20), mouse embryonic fibroblasts derived from Alk2 R206H/+ mice (21,22), and cells from FOP patients, such as stem cells from human exfoliated deciduous teeth (23), FOP patient-derived induced pluripotent stem cells (FOP-iPSCs) (24,25) and induced mesenchymal stromal cells (iMSCs) from FOP-iPSCs (FOP-iMSCs) (26) have been used as models. Among these cells, Alk2 R206H/+ mouse embryonic fibroblasts and FOP-iMSCs are preferred because of their accessibility and expression level of FOP-ACVR1 using an endogenous promoter.…”