LRFN1 is a 771 amino acid single-pass type I membrane protein that belongs to the LRFN family. Containing a fibronectin type-III domain, an Ig-like (immunoglobulin-like) domain, a LRRCT domain, a LRRNT domain and seven LRR (leucine-rich) repeats, LRFN1 is thought to promote neurite outgrowth in hippocampal neurons and is involved in the regulation and maintenance of excitatory synapses. LRFN1 forms heteromeric complexes with LRFN2, LRFN3, LFRN4 and LFRN5, but does not have the ability to form homomeric complexes across cell junctions of adjacent cells like other LRFN family members. The PDZ-binding motif of LRFN1 is required for neurite outgrowth promotion and for SAP 97-, NE-dlg- and PSD-95-binding. LRFN1 is encoded by a gene located on human chromosome 19q13.2 and mouse chromosome 7 A3.