The leucine-rich (LRR) repeat is a 20-30 amino acid motif that forms a hydrophobic Alpha/Beta horseshoe fold, allowing it to accommodate several leucine residues within a tightly packed core. All LRR repeats contain a variable segment and a highly conserved segment, the latter of which accounts for 11 or 12 residues of the entire LRR motif. LRRTM1 (leucine rich repeat transmembrane neuronal 1) is a 522 amino acid single-pass type I membrane protein that localizes to the endoplasmic reticulum and contains ten LRR repeats. Expressed predominately in forebrain tissue, LRRTM1 is thought to be involved in the development of forebrain structures, specifically by influencing axon trafficking, as well as neuronal differentiation and connectivity. Human LRRTM1 shares 96% amino acid identity with its mouse counterpart, suggesting a conserved role between species. Defects in the gene encoding LRRTM1 may be associated with the pathogenesis of several common neurodevelopmental disorders.