ISOLATION OF THE CDNA AND CHROMOSOMAL LOCALIZATION OF THE GENE (TAX1) ENCODING THE HUMAN AXONAL GLYCOPROTEIN TAG-1

The transient axonal glycoprotein (TAG-1) is a cell adhesion molecule that promotes neurite outgrowth and belongs to the immunoglobulin superfamily. We have isolated cDNAs encoding TAX1, the human homologue of TAG-1. Human TAX1 shows a high degree of homology to rat TAX1 and less to its chick counterpart, axonin-1, with 91 and 75% identity at the amino acid level, respectively. The numbers of immunoglobulin (IgC2) domains and fibronectin repeats present in TAG-1 are conserved among the three species. The highest degree of conservation occurs in the second IgC2 domain (98% with the rat and 82% with the chick). The human homologue also contains a putative N-terminal signal sequence and a C-terminal hydrophobic sequence, suggestive of linkage to the cell membrane via phosphatidylinositol. In addition, the two mammalian TAG-1 proteins share the RGD tripeptide, a motif known to mediate recognition of fibronectin by integrins. In situ hybridization to human metaphase chromosomes maps the TAX1 gene encoding human TAG-1 to a single location on chromosome 1q32. © 1993 Academic Press, Inc.