Calcium-dependent cell-adhesion protein. Essential for maintenance of normal retinal and cochlear function. Antiparallel heterodimer with CDH23. Found in a complex with TMIE and LHFPL5. Interacts with LHFPL5/TMHS; this interaction is required for efficient localization to hair bundles. Interacts with MYO7A. Interacts with USH1G; this interaction may recruit USH1G to the plasma membrane. Interacts with TOMT. Isoforms CD1 and CD3 interact with TMC1 (via N-terminus) and TMC2 (via N-terminus). Efficient localization to the plasma membrane requires the presence of LHFPL5. Expressed in brain, lung, kidney, spleen and testis. Found also in the inner and outer synaptic layers, and the nerve fiber layer in adult and fetal retinas. Found in the supporting cells, outer sulcus cells and spiral ganglion of fetal cochlea. Expressed in cytotoxic tumor-derived T- and NK-cell lines as well as biopsies of nasal NK/T-cell lymphomas. Not detected in normal or in vitro activated peripheral blood cells, CD4 or CD8 lymphocytes or NK cells. Isoform 3 is expressed in brain, heart, cerebellum and kidney. CD1 isoforms, such as isoform 1, have a limited pattern of expression and is detected in testis, retina and cochlea. CD2 isoforms, such as isoforms 4 and 5, are expressed in heart, kidney, thymus, spleen, testis, retina and cochlea. CD3 isoforms, such as isoform 6, are widely expressed. Cadherin repeats 1 and 2 mediate calcium-dependent heterophilic interaction with CDH23. Three calcium ions are usually bound at the interface of each cadherin domain and rigidify the connections, imparting a strong curvature to the full-length ectodomain. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting distinct genetic loci, including the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Unlikely isoform. Probable cloning artifact. Truncated C-terminus.