– Bone Morphogenetic Protein Receptor Type-1A (BMPR1A) belongs to the TKL Ser/Thr protein kinase family and TGFB receptor subfamily, including the type I receptors BMPR1A and BMPR1B and the type II receptor BMPR2. BMPR1A is a single-pass type I membrane protein and highly expressed in skeletal muscle. BMPR1A contains one GS domain and one protein protein kinase domain. BMPR1A is necessary for the extracellular matrix depostition by osteoblasts. BMPR1A can activate SMAD transcriptional regulators, binding with ligands. Defects in BMPR1A are a cause of juvenile polyposis syndrome, Cowden disease and hereditary mixed polyposis syndrome 2 (HMPS2).