ACVRL1 and renal fibrosis: In renal physiology, Alk1 has been suggested to play an important role in the regulation of extracellular matrix deposition, including collagen type I and fibronectin, and Alk1 heterozygosity has been associated with increased renal fibrosis in a mouse model of obstructive nephropathy, probably due to the decrease in the Alk1/Smad1 antifibrotic/protective signaling in renal fibroblasts16.