Fibronectin Leucine Rich Transmembrane Protein 1 (FLRT1) is a member of the Fibronectin Leucine Rich Transmembrane protein (FLRT) family. There are three fibronectin leucine-rich repeat transmembrane (FLRT) proteins: FLRT1, FLRT2 and FLRT3, all contain 10 leucine-rich repeats (LRR), a type III fibronectin (FN) domain, followed by the transmembrane region, and a short cytoplasmic tail. FLRT proteins have dual properties as regulators of cell adhesion and potentiators of fibroblast growth factor (FGF) mediated signalling. The fibronectin domain of all three FLRTs can bind FGF receptors. This binding is thought to regulate FGF signaling during development. The LRR domains are responsible for both the localization of FLRTs in areas of cell contact and homotypic cell association. FLRT1 is expressed at brain compartmental boundaries. FLRT1 is a target for tyrosine phosphorylation mediated by FGFR1 and implicate a non-receptor Src family kinase (SFK).