CYTOKERATIN-8 IS A SUITABLE EPIDERMAL MARKER DURING ZEBRAFISH DEVELOPMENT

We have cloned and characterized the zebrafish (Danio rerio) homologou s cytokeratin 8 (zf-K8) cDNA. This cytokeratin belongs to the gene fam ily of intermediate filaments and it is a component of the cytoskeleto n of epithelial cells. Gene expression analysis during embryonic devel opment and at adult stages presented here revealed that zf-K8 mRNA is inherited maternally and that it is present in the oocyte, the zygote and in the cleavage stage embryo. After mid blastula transition this g ene is expressed in all surface cells, notably in those of the envelop ing layer (EVL) and of the periderm, as well as in a subpopulation of the deep cells (DEL) presumed to be intestinal progenitors. During lat er embryonic stages zf-K8 mRNA is strongly expressed in the developing pectoral fin. In adult zebrafish the zf-K8 gene is not only expressed in simple epithelia such as the colorectal intestine, but also, in co ntrast to other vertebrates, it is present in stratified skin and diff erentiated fins. These observations suggest that the zf-K8 gene is an appropriate epidermal marker during zebrafish ontogenesis.