Protocadherins are a large family of cadherin-like cell adhesion proteins that are involved in the establishment and maintenance of neuronal connections in the brain. There are three protocadherin (PCDH) gene clusters, designated alpha, beta and gamma, all of which contain multiple tandemly arranged genes. The protein products of PCDH-alpha genes interact with Integrin ∫1 to promote cell adhesion and form oligomers with PCDH-gamma proteins at specific membrane sites. PCDHA3 (Protocadherin alpha-3) is a 950 amino acid single-pass transmembrane protein that contains six cadherin domains. PCDHA3 is a unique cadherin in that it likely functions in spermatogenesis and may also have a role in organizing germ cell-specific structures, such as the flagellum, acrosome and intercellular bridge. There are two isoforms of PCDHA13 that are produced as a result of alternative splicing events.