Evidence for four Hox clusters in the killifish Fundulus heteroclitus (teleostei)

We analyzed the HOM/Hox cluster composition of the teleost Fundulus heteroclitus (Killifish) using a PCR survey. We found a total number of 30 unique homeobox sequences which could be assigned to specific cognate groups of the Hox clusters by sequence comparisons. One sequence was of the msh group. Ten homeobox fragments could be identified as orthologs with specific mammalian Hox genes of cluster A-D. The number of representatives in cognate groups 1, 4, 5, 6, 7, 8 and 9 differed from those of human and mouse. For groups 1 and 9 we found four representatives, which provides the first evidence for possible four Hox clusters in a diploid teleost, a lower vertebrate. Furthermore, it demonstrates significant differences of the Fundulus clusters compared to those of mouse and humans. The implications of our data for the interpretation of the evolution of Hox clusters are discussed.