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. PCDHA1 (protocadherin alpha 1), also known as PCDH-ALPHA1, is a 950 amino acid, single-pass type I membrane protein that contains six cadherin domains. Functioning as a potential calcium-dependent cell-adhesion protein, PCDHA1 has been suspected to play a role in the creation and maintenance of neuronal connections. Three isoforms of PCDHA1 exists due to alternative splicing events.