Cell adhesion molecules influence cell growth, differentiation, embryogenesis, immune response and cancer metastasis by networking information from the extracellular matrix to the cell. Sidekick-1 (SDK1) is a 2,213 amino acid single-pass membrane protein that functions as a cell adhesion molecule by guiding axonal terminals to specific synapses in developing neurons. Existing as three alternatively spliced isoforms, Sidekick-1 is expressed in retinal neurons and contains thirteen fibronectin type-III domains and six Ig-like C2-type (immunoglobulin-like) domains. Sidekick-1 expression is upregulated in glomeruli of patients with HIV-associated nephropathy, where it leads to podocyte dysfunction. The gene encoding Sidekick-1 maps to human chromosome 7p22.2 and murine chromosome 5 G2.