SynCAM (Synaptic Cell Adhesion Molecule), also known as TSLC1 (tumor suppressor in lung cancer-1), SgIGSF, or CADM1, is a homophilic, transmembrane Ig-domain containing protein with intracellular PDZ protein-binding motifs. Although originally identified as a tumor suppressor of small lung cell carcinomas, SynCAM appears to be primarily involved in intracellular adhesion and synapse formation. The majority of SynCAM is localized to synaptic sites where it initiates synaptic assembly and synapse differentiation throughout the central nervous system. SynCAM also mediates the cellular adhesion of spermatogenic cells to Sertoli cells and mast cells to fibroblasts.