The Epigenetic Repertoire ofDaphnia magnaIncludes Modified Histones

Abstract

Daphnids are fresh water microcrustaceans, many of which follow a cyclically parthenogenetic life cycle.Daphniaspecies have been well studied in the context of ecology, toxicology, and evolution, but their epigenetics remain largely unexamined even though sex determination, the production of sexual females and males, and distinct adult morphological phenotypes, are determined epigenetically. Here, we report on the characterization of histone modifications inDaphnia. We show that a number of histone H3 and H4 modifications are present inDaphniaembryos and histone H3 dimethylated at lysine 4 (H3K4me2) is present nonuniformly in the nucleus in a cell cycle-dependent manner. In addition, this histone modification, while present in blastula and gastrula cells as well as the somatic cells of adults, is absent or reduced in oocytes and nurse cells. Thus, the epigenetic repertoire ofDaphniaincludes modified histones and as these epigenetic forces act on a genetically homogeneous clonal populationDaphniaoffers an exceptional tool to investigate the mechanism and role of epigenetics in the life cycle and development of an ecologically important species.