Life Stage and Tissue-Specific Expression of the Homeobox Gene cnox1-Pc of the Hydrozoan Podocoryne carnea

We have isolated from the hydrozoan Podocoryne carnea a genomic clone and the corresponding cDNA of a homeobox gene. This gene, called cnox1-Pc, is most closely related to the lab class of homeobox genes. In the life cycle of P. carnea, which involves an asexually reproducing, sedentary polyp and a sexual planktonic medusa stage, we found cnox1-Pc transcripts specifically expressed in the medusa stage. Expression studies on isolated medusa organs and tissues indicate that the message is absent in the tentacles and the feeding and sexual organ of the medusa and present in the striated muscle cells. During medusa bud development, expression of cnox1-Pc can be correlated with the development of the striated muscle tissue, a cell type only found in the medusa. The results suggest that cnox1-Pc is involved in pattern formation of the medusa of P. carnea and might have a regulatory role in the differentiation of striated muscle.