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 gene clusters, designated alpha, beta and gamma, all of which contain multiple tandemly arranged genes. PCDHB4 (Protocadherin beta-4) is a 795 amino acid single pass transmembrane protein that is one of 16 proteins in the protocadherin beta cluster. Unlike the alpha and gamma gene clusters whose genes are spliced to downstream constant region exons during transcription, members of the beta cluster (such as PCDHB4) do not use constant-region exons to produce mRNAs. As a result, each protocadherin beta gene encodes the transmembrane, extracellular and short cytoplasmic domains of the protein. PCDHB4 is likely a calcium-dependent cell adhesion protein that is involved in the maintenance of neural connections in the brain.