A large number of cadherin superfamily members have been identified to date: classic cadherins, seven-pass transmembrane (7TM) cadherins, the FAT family, desmo­somal cadherins, T-cadherin and protocadherins. With few exceptions, all members of the cadherin superfamily are transmembrane proteins and have several extracellular cadherin (EC) domains that are involved in Ca²⁺ binding. The number of EC domains varies within the members. The amino acid sequences of the cytoplasmic domain diverge significantly between the subgroups, and as a re­sult, they can bind to specific cytoplasmic proteins [1]. With more than 80 members, prothocadherins represent the largest subgroup of the cadherin superfamily. They are expressed throughout the nervous system and are consid­ered to be involved in synapse formation, specification and maintenance [2].