Identification of a nonchordate-type classic cadherin in vertebrates: chicken Hz-cadherin is expressed in horizontal cells of the neural retina and contains a nonchordate-specific domain complex.

Classic cadherins mediate calcium-dependent cell-cell adhesion in a variety of animals, but there are marked differences in their domain structures between chordate and nonchordate animals. The extracellular domain of chordate-type classic cadherins (type I and type II classic cadherins) consists of five tandem repeats of conserved sequences called EC domains, whereas that of nonchordate-type classic cadherins (designated as type III classic cadherin) contains a variable number of EC domains, followed by a characteristic domain complex made of laminin-A globular domains and EGF-like repeats. In the present study, we identified a novel vertebrate type III cadherin showing high sequence similarity to Drosophila N-cadherin, and named this molecule chicken Hz-cadherin (cHz-cadherin), because of the distinct expression in horizontal cells of the neural retina. cHz-cadherin functioned as an adhesion molecule when introduced into cultured cells. Database search revealed one cHz-cadherin homologue in zebrafish and two in puffer fish, but none in other vertebrate species examined. These observations indicate that type III classic cadherins have been conserved in vertebrate species, being expressed by limited cells types, but lost in particular phylogenic groups of the vertebrates. Copyright 2004 Wiley-Liss, Inc.