PCR-survey of Hox-genes of the zebrafish: new sequence information and evolutionary implications

We analyzed the Hox gene complement of the zebrafish Danio rerio using a PCR survey. We found 18 new zebrafish HOM/Hox type sequences and one sequence of the msh group. For groups 1-3 and 8-10 we could unambiguously assign the zebrafish fragments to cognate groups. The assignment for cognate groups 4-7 had to remain tentative due to insufficient sequence variation. The number of zebrafish Hox fragments classified as members of cognate groups 1-4, 8, and 9 is identical to the number of genes in corresponding cognate groups of the mouse and human genomes. We found only two differences between the zebrafish and mouse Hox gene complement: four putative genes in group 10 (three in mammals) and only seven in the medial groups 5 to 7 (eight in mammals). Together with the previously published Hox gene sequences of the killifish, the larger number of zebrafish genes in group 10 is positive evidence for variation in the Hox gene complements among bony fish. In contrast, the Hox gene complement appears to be highly conserved among all tetrapods.