Meeting Abstract
Epigenetic regulation by DNA methylation is an important mechanism for controlling gene expression throughout vertebrate lineages. The presence, however, and patterns of DNA methylation varies widely among the invertebrates. Invertebrates generally have only a single methyl-cytosine binding domain protein (MBD), that does not always contain appropriate residues for selectively binding methylated DNA. We asked whether or not sponges, one of the earliest branching animals, possess an MBD capable of recognizing methylated DNA and recruiting the associated nucleosome remodeling and deacetylase (NuRD) complex. We found that both marine and freshwater sponges have genes for each of the NuRD core components, including an MBD ortholog (MBD2/3). We confirm the presence of DNA methylation during development of the freshwater sponge, Ephydatia muelleri. Methylation coincides with expression of EmMBD2/3 which is expressed at all developmental stages. Furthermore, we show that EmMBD2/3 selectively binds methylated DNA and forms a coiled-coil interaction critical to recruitment of NuRD. Finally, we show that reducing the expression of EmMBD2/3 during E. muelleri development leads to abnormalities at the leading edge of sponge growth in the basal pinacoderm. These data support a model in which the MBD2/3 methylation-dependent functional role emerged with the earliest metazoans and has been maintained to varying degrees across animal evolution.
