Isolation of zebrafish gdf7 and comparative genetic mapping of genes belonging to the growth/differentiation factor 5, 6, 7 subgroup of the TGF-beta superfamily

The Growth/differentiation factor (Gdf) 5, 6, 7 genes form a closely relate d subgroup belonging to the TGF-P superfamily. In zebrafish, there are thre e genes that belong to the Gdf5, 6, 7 subgroup that have been named radar, dynamo, and contact. The genes radar and dynamo both encode proteins most s imilar to mouse GDF6. The orthologous identity of these genes on the basis of amino acid similarities has not been clear. We have identified gdf7, a F ourth zebrafish gene belonging to the Gdf5, 6, 7 subgroup. To assign correc t orthologies and to investigate the evolutionary relationships of the huma n, mouse, and zebrafish Gdf5, 6, 7 subgroup, we have compared genetic map p ositions of the zebrafish and mammalian genes. We have mapped zebrafish gdf 7 to linkage group (LG) 17, contact to LG9, GDF6 to human chromosome (Hsa) 8 and GDR to Hsa2p. The radar and dynamo genes have been localized previous ly to LG16 and LG19, respectively. A comparison of syntenies shared among h uman, mouse, and zebrafish genomes indicates that gdf7 is the ortholog of m ammalian GDF7/Gdf7. LG16 shares syntenic relationships with mouse chromosom e (Mmu) 4, including Gdf6. Portions of LG16 and LG19 appear to be duplicate chromosomes, thus suggesting that radar and dynamo are both orthologs of G df6. Finally, the mapping data is consistent with contact being the zebrafi sh ortholog of mammalian GDF5/Gdf5.