THE MOLECULAR-CLONING AND CHARACTERIZATION OF POTENTIAL CHICK DM-GRASP HOMOLOGS IN ZEBRAFISH AND MOUSE

A full-length zebrafish cDNA clone and a partial mouse cDNA clone simi lar to chick DM-GRASP were isolated and analyzed. The nucleotide seque nce of the full-length zebrafish clone shares 54% identity, and predic ts 39% amino acid identity, with chick DM-GRASP. The partial mouse clo ne shares 76% nucleotide identity, and predicts 76% amino acid identit y, with chick DM-GRASP. The predicted proteins encoded by both of thes e clones exhibit conserved structural domains that are characteristic of the chick protein. These features may identify them as a distinct s ubfamily within the immunoglobulin superfamily of cell adhesion molecu les. Expression of the zebrafish DM-GRASP protein is similar to chick DM-GRASP and is principally restricted to a small subset of developing sensory and motor neurons during axonogenesis. Zebrafish DM-GRASP exp ression was temporally regulated and limited to specific axon domains. This regional expression correlated with fasciculated axon domains. T hese results suggest that the zebrafish and mouse cDNA clones represen t the respective fish and mammalian homologs of chick DM-GRASP. The hi ghly selective expression of zebrafish DM-GRASP suggests that it is in volved in the selective fasciculation and guidance of axons along thei r normal pathways. (C) 1994 John Wiley and Sons, Inc.