CHARACTERIZATION OF A HIGHLY CONSERVED HUMAN HOMOLOG TO THE CHICKEN NEURAL CELL-SURFACE PROTEIN BRAVO NR-CAM THAT MAPS TO CHROMOSOME BAND 7Q31/

The neuronal cell adhesion molecule Bravo/Nr-CAM is a cell surface pro tein of the immunoglobulin (Ig) superfamily and is closely related to the L1/NgCAM and neurofascin molecules, all of which contain six immun oglobulin domains, five fibronectin repeats, a transmembrane region, a nd an intracellular domain. Chicken Bravo/Nr-CAM has been shown to int eract with other cell surface molecules of the Ig superfamily and has been implicated in specific pathfinding roles of axonal growth cones i n the developing nervous system. We now report the characterization of cDNA clones encoding the human Bravo/Nr-CAM protein, which, like its chicken homolog, is composed of six V-like Ig domains and five fibrone ctin type III repeats, The human Bravo/Nr-CAM homolog also contains a transmembrane and intracellular domain, both of which are 100% conserv ed at the amino acid level compared to its chicken homolog. Overall, t he human Bravo/Nr-CAM homolog is 82% identical to the chicken Bravo/Nr -CAM amino acid sequence. Independent cDNAs encoding four different is oforms were also identified, all of which contain alternatively splice d variants around the fifth fibronectin type III repeat, including one isoform that had been previously identified for chicken Bravo/Nr-CAM. Northern blot analysis reveals one mRNA species of approximately 7.0 kb in adult human brain tissue. Fluorescence in situ hybridization map s the gene for human Bravo/Nr-CAM to human chromosome 7q31.1-q31.2. Th is chromosomal locus has been previously identified as containing a tu mor suppressor candidate gene commonly deleted in certain human cancer tissues. (C) 1996 Academic Press, Inc.