ACVRL1 (Activin A receptor, type II-like 1, activin receptor-like kinase 1) is a type I cell-surface receptor for the TGF-beta superfamily of ligands. ACVRL1 is most highly expressed in human placenta and lung. ACVRL1 protein deficiency and mutations in the gene cause hemorrhagic telangiectasia type 2 (HHT2), also known as Rendu-Osler-Weber syndrome 2 (ORW2), and also lead to pulmonary arteriovenous malformations. ACVRL1 interaction with low-density lipoprotein (LDL) also implicates it in the early phases of atherosclerosis. In immunohistochemistry of normal tissue, ACVRL1 has cytoplasmic positivity in the lung, placenta, brain, endocrine tissues, gastrointestinal tissue, gallbladder, pancreas, kidney, testis, smooth muscle, skin, and immune tissues. References: The UniProt Consortium. Nucleic Acids Res. 47: D506-515 (2019); Nucleic Acids Res. 2016 Jan 4;44(D1):D733-45, PMID:26553804; Online Mendelian Inheritance in Man, OMIM®. Johns Hopkins University, Baltimore, MD. MIM Number: 600376: 08/22/2019: URL: https://omim.org/; Nature Communications. 7: 13516, PMID: 27869117;