This gene encodes an activin A type IB receptor. Activins are dimeric growth and differentiation factors which belong to the transforming growth factor-beta (TGF-beta) superfamily of structurally related signaling proteins. Activins signal through a heteromeric complex of receptor serine kinases which include at least two type I and two type II receptors. This protein is a type I receptor which is essential for signaling. Mutations in this gene are associated with pituitary tumors. Alternate splicing results in multiple transcript variants.[provided by RefSeq, Jun 2010],ACTRIB, ACVRLK4, ALK4, SKR2,Apoptosis,Cell Biology & Developmental Biology,Cytoskeleton,Cytoskeleton_Microfilaments,Signal Transduction,Stem Cells,ACVR1B