The cadherins are a family of Ca++-dependent adhesion molecules that function to mediate cell-cell binding critical to the maintenance of tissue structure and morphogenesis. Cadherins each contain a large extracellular domain at the amino terminus, which is characterized by a series of five homologous repeats, the most distal of which is thought to be responsible for binding specificity. The relatively short carboxy terminal, intracellular domain interacts with a variety of cytoplasmic proteins, including catenin beta, to regulate cadherin function. Two forms of OB-cadherin (for osteoblast-cadherin, also designated cadherin-11 or OSF-4) have been identified as OBcadherin- 1 and OB-cadherin-2. Both OB-cadherins are expressed in osteoblastic cell lines and low expression is also seen in lungs, testis and brain. OB-cadherin-2 has a truncated cytoplasmic domain.