A novel member of the netrin family, beta-netrin, shares homology with thebeta chain of laminin: Identification, expression, and functional characterization

The netrins are a family of laminin-related molecules. Here, we characteriz e a new member of the family, beta -netrin. beta -Netrin is homologous to t he NH2 terminus of laminin chain short arms; it contains a laminin-like dom ain VI and 3.5 laminin EGF repeats and a netrin C domain. Unlike other netr ins, this new netrin is more related to the laminin beta chains, thus, its name beta -netrin. An initial analysis of the tissue distribution revealed that kidney, heart, ovary, retina, and the olfactory bulb were tissues of h igh expression. We have expressed the molecule in a eukaryotic cell express ion system and made antibodies to the expressed product. Both in situ hybri dization and immunohistochemistry were used to describe the cellular source of beta -netrin and where beta -netrin is deposited. beta -Netrin is a bas ement membrane component; it is present in the basement membranes of the va sculature, kidney, and ovaries. In addition, beta -netrin is expressed in a limited set of fiber tracts within the brain, including the lateral olfact ory tract and the vomeronasal nerve. Functional studies were performed and show that beta -netrin promotes neurite elongation from olfactory bulb expl ants. Together, these data suggest that beta -netrin is important in neural , kidney, and vascular development.