A recessive mutation leading to vertebral ankylosis in zebrafish is associated with amino acid alterations in the homologue of the human membrane-associated guanylate kinase DLG3

We describe the characterization of the zebrafish homologue of the human ge ne DLG3. The zebrafish dlg3 gene encodes a membrane-associated guanylate ki nase containing a single PDZ domain. This gene was cloned using a gene-trap construct inserted in the gene's first intron. The insertion co-segregates with a viable mutation called humpback (hmp), which leads to formation of ankylotic vertebrae in adult fishes. Insertion and mutation have both been mapped to chromosome 12, in a segment which is syntenic with region p12 to q12 of human chromosome 17. The hmp mutant phenotype, however, appears to b e due to two point mutations in the guanylate kinase domain rather than to the transgene insertion itself. The results of this study are discussed in the light of the possible function of the guanylate kinase domain. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.