The evidence of DNA methylation in Hydra, a Cnidarian model

Abstract

Epigenetics involves modification of the activation of genes without changes in DNA sequence. One of the phenomena, DNA methylaton for the epigenetic control of DNA-protein interaction has been found in wide range of biological organisms, from bacteria to human. It is essential for normal development and it involved in genomic imprinting, X chromosome inactivation, and the process of carcinogenesis. Some epigenetic changes are inherited to the next generation, thus if the epigenomic study, in the aspect of DNA methylation, coupled with environmental stress biology might make it possible to estimate the effects of environmental changes, such as chemical pollution and/or climate changes, on the biological responses in the aspects of the past, the present, and the future. In this sense, Hydra magnipapillata is a powerful candidate for this purpose, since about 165,000 ESTs are accumulated in public database; genome project has been initiated and about 1.2 Gb nucleotides have accumulated so far; and finally the most of genes and pathways are conserved through the evolutionary history. Recently we have found the evidence which provided strong support for the existence of DNA methylation in Hydra using engineered methylated binding domain protein (MBD2bt). The procedure and results of ‘Ecogenomic’ analysis, a new approach for accessing environmental changes, is schematically illustrated. The usefulness of Hydra in ecotoxicology is also discussed.