Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent University, J. Plateaustraat 22, Ghent, Belgium.
Aquat Toxicol. 2010 May 5;97(3):188-95. doi: 10.1016/j.aquatox.2009.07.013. Epub 2009 Jul 25.
DNA methylation has recently been reported in Daphnia magna, which indicates the possible presence of epigenetic mechanisms regulating gene expression in this species. As such, effects of transient chemical exposure could be transferred through epigenetic inheritance to non-exposed generations. In this study, in the Zn-exposed daphnids, a large number of genes were found to be differentially transcribed, amongst which transcription and translation related genes (downregulated), genes associated with oxidative stress (upregulated) and different types of metabolism-related genes (mostly upregulated). In the two subsequent generations of non-exposed daphnids, a considerable number of differentially regulated genes were observed, indicating an effect of Zn-exposure in the non-exposed progeny. However, none of the differentially transcribed genes observed in the Zn-exposed generation were regulated in the same direction in both non-exposed subsequent generations. The exposure of D. magna to a sublethal Zn concentration for one generation did not result in a stable transgenerational epigenetic effect with consequences for reproductive output nor was a stably epigenetically inheritable effect observed on the transcription of any of the studied genes. An important observation was the large number of genes that were differentially transcribed between different control generations with no pre-exposure history. These genes were not considered in the analysis of the effect of Zn exposure on gene transcription. This differential regulation between subsequent control generations was attributed to possible differences in synchronization of the molting and reproductive cycle of the daphnids in the different generations. This finding is of major importance for the interpretation and design of future microarray experiments with adult Daphnia.
DNA 甲基化最近在大型溞（Daphnia magna）中被报道，这表明在该物种中可能存在调节基因表达的表观遗传机制。因此，短暂的化学暴露的影响可能通过表观遗传遗传传递给未暴露的后代。在这项研究中，在暴露于锌的大型溞中，发现大量基因的转录存在差异，其中转录和翻译相关基因（下调）、与氧化应激相关的基因（上调）和不同类型的代谢相关基因（大多上调）。在随后两代未暴露的大型溞中，观察到大量差异调节的基因，表明未暴露的后代中存在锌暴露的影响。然而，在暴露于锌的一代中观察到的差异转录基因在随后两代未暴露的后代中并没有朝着相同的方向调节。大型溞暴露于亚致死浓度的锌一代不会导致具有生殖输出后果的稳定跨代表观遗传效应，也没有观察到任何研究基因的转录稳定的可遗传的表观遗传效应。一个重要的观察结果是，在没有预暴露史的不同对照代之间，有大量的基因差异转录。这些基因未被纳入对锌暴露对基因转录影响的分析中。在不同代的溞的蜕皮和生殖周期的同步性方面的差异导致了随后的对照代之间的这种差异调节。这一发现对解释和设计未来具有成年大型溞的微阵列实验具有重要意义。
