The functional roles of zebrafishHoxA- andHoxD-related clusters in the pectoral fin development

Abstract

SummaryThe paralogs 9-13Hoxgenes in mouseHoxAandHoxDclusters are critical for limb development. When bothHoxAandHoxDclusters are deleted in mice, significant limb truncation is observed compared to the phenotypes of single and compound mutants ofHox9-13genes in these clusters. In zebrafish, mutations inhox13genes inHoxA- andHoxD-related clusters result in abnormal morphology of pectoral fins which are homologous to forelimbs. However, the effect of the simultaneous deletions of entireHoxA- andHoxD-related clusters on zebrafish pectoral fin development remains unknown. Here, we generated mutants with several combinations ofhoxaa,hoxab, andhoxdacluster deletions and analyzed the pectoral fin development. In the triple homozygous mutants, we find that the endoskeletal disc and fin fold are significantly shortened in developing pectoral fins. In addition, we show that this anomaly is due to defects in the pectoral fin growth after the fin bud formation. Furthermore, in the surviving adult mutants, micro-CT scanning reveals a defect in the posterior portion of the pectoral fin which is thought to represent latent regions of the limb. Our results further support that the functional role ofHoxAandHoxDclusters is conserved in the paired appendage formation in bony fishes.