TGFBR1 (ALK5) is a transcription growth factor beta receptor that works with TGFB1 and other TGF-beta ligands to regulate development of the central nervous system, adult neurogenesis, neuronal survival and protection, and astrocyte differentiation. In neurons and in endothelial cells, TGFBR1 induces the phosphorylation of SMAD2 and SMAD3 which in turn modulate nuclear gene expression. Mutations in TGFBR1 are correlated with Loeys-Dietz aortic aneurysm syndrome (LDS). In immunohistochemistry, TGFBR1 has cytoplasmic and membranous positivity in the brain, lung, gastrointestinal tissues, liver, kidney, reproductive tissues, muscle and appendix. References: Int J Dev Neurosci. 2005 Aug;23(5):413-24, PMID: 15936920; Int J Mol Sci. 2012; 13(7): 8219–8258, PMID: 22942700; Cell Signal. 2018 Dec;52:112-120, PMID: 30184463; Cell Signal. 2018 Dec;52:112-120, PMID: 30184463; Nat Neurosci. 2014 Jul;17(7):943-52, PMID: 24859199