The Alpha-, Beta-, Gamma-, and Delta -catenins are proteins that bind to the highly conserved, intracellular cytoplasmic tail of E-cadherin. Together, the catenin/cadherin complexes play an important role mediating cellular adhesion. Alpha-catenin interacts with E-cadherin associated protein and also associates with other members of the cadherin family, such as N-cadherin and P-cadherin. Beta-catenin associates with the cytoplasmic portion of E-cadherin, which is necessary for the function of E-cadherin as an adhesion molecule. Beta-catenin also complexes with the tumor suppressor protein APC. Gamma-catenin, also known as plakoglobin, is a protein that binds ?catenin and N-cadherin. Gamma-catenin interacts with presenilin 1 and is expressed in the brain. The gene encoding Gamma-catenin maps to human chromosome 5p15.2. A hemizygous loss of the gene encoding Gamma-catenin leads to the mental retardation associated with Cri-du-Chat syndrome. In addition, the transmembrane phosphatase PTPm associates with catenin/ cadherin complexes and may regulate complex signaling.