Robichaud Nicole F, Sassine Jeanette, Beaton Margaret J, Lloyd Vett K
Department of Biology, Mount Allison University, Sackville, NB, Canada E4L 1G7.
Genet Res Int. 2012;2012:174860. doi: 10.1155/2012/174860. Epub 2012 Apr 4.
Daphnids are fresh water microcrustaceans, many of which follow a cyclically parthenogenetic life cycle. Daphnia species 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 in Daphnia. We show that a number of histone H3 and H4 modifications are present in Daphnia embryos 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 of Daphnia includes modified histones and as these epigenetic forces act on a genetically homogeneous clonal population Daphnia offers an exceptional tool to investigate the mechanism and role of epigenetics in the life cycle and development of an ecologically important species.
水蚤是淡水微型甲壳动物，其中许多遵循周期性孤雌生殖的生命周期。水蚤物种在生态学、毒理学和进化方面已得到充分研究，但其表观遗传学在很大程度上仍未被研究，尽管性别决定、有性雌性和雄性的产生以及独特的成年形态表型是由表观遗传决定的。在此，我们报告水蚤中组蛋白修饰的特征。我们表明，水蚤胚胎中存在多种组蛋白H3和H4修饰，并且赖氨酸4位点二甲基化的组蛋白H3（H3K4me2）在细胞核中以细胞周期依赖性方式非均匀存在。此外，这种组蛋白修饰在囊胚和原肠胚细胞以及成年体细胞中存在，但在卵母细胞和滋养细胞中不存在或减少。因此，水蚤的表观遗传库包括修饰的组蛋白，由于这些表观遗传力量作用于基因同质的克隆群体，水蚤为研究表观遗传学在一个具有生态重要性的物种的生命周期和发育中的机制及作用提供了一个特殊的工具。
