宫内砷暴露对印记基因IGF2/H19的影响及其所致跨代遗传效应的分子机制研究

Arsenic is an environmental endocrine disruptor. Exposure to this chemical during gestation can lead to an increased frequency of adult onset disease in next generation and probable to induce transgenerational inheritance. On the basis of preliminary studies, the current study was designed to investigate the potential that arsenic promotes epigenetic transgenerational effects via the imprinted genes IGF2/H19. DNA methylation patterns and the expression of IGF2 and H19 in the testis tissue of CD1 mice were analyzed. Since the exposure of a gestating F0 generation female also directly exposes the F1 generation fetus and germ line that will generate the F2 generation, the current study will also investigate the F3 generation which is the first generation without direct exposure. The difference of DNA methylation patterns and expression among the three generations were compared and the epigenetic mechanisms involved in the transgenerational inheritance of arsenic will be studied accordingly. This project will investigate the molecular mechanism involved in the transgenerational inheritance of arsenic and will provide a theoretical basis for transgenerational effects of this chemical. It will also provide new way to investigate the health effects of environmental endocrine disruptors on human offspring.

砷是一种环境内分泌干扰物，宫内砷暴露可以引起子代成年期疾病高发并可能引发跨代遗传。本项目在前期研究基础上，拟从无机砷对印记基因IGF2/H19的调控机制出发，探索宫内砷暴露的跨代遗传效应。本项目将检测CD1小鼠睾丸组织中IGF2/H19基因的甲基化印记状态和表达特征，横向（砷暴露鼠和对照鼠）和纵向(F1、F2、F3)比较IGF2/H19在无机砷跨代遗传发生、发展过程中的印记模式。本项目以期探明IGF2/H19在无机砷跨代遗传效应中的作用及其分子机制，进而为无机砷的跨代遗传效应提供理论依据，并为环境内分泌干扰物在人类后代中引发的疾病研究建立新思路。

环境砷暴露已经成为全世界广泛关注的一个公共卫生问题。大量的研究表明慢性砷暴露与多种疾病密切相关，包括癌症、皮肤损伤、心血管疾病以及糖尿病等。越来越多的证据表明生命早期砷暴露可以引起严重的远期健康效应。近年来，许多研究表明发育早期暴露于环境毒物可以导致一些不良效应发生跨代遗传，且证实表观遗传学机制可能参与其中。砷是一种内分泌干扰物，但是有关砷的雄性生殖健康跨代遗传影响还未见有报道。因此，在本研究中我们假设孕期无机砷暴露可以引起后代（至少F3代）的雄性生殖损伤。我们将受孕的CD-1小鼠按体重随机分为对照组和85 mg/L亚砷酸钠染毒组，选择孕期8-18天进行自由饮水方式染毒。通过选择雄性后代与正常雌鼠交配，建立跨代遗传动物模型，直至F3代。我们的结果表明F0代雌鼠在孕期短暂暴露于无机砷可以引起F1和F3代雄鼠精子质量下降以及睾丸组织形态学发生改变。由于砷的这种跨代遗传毒性可能是通过雄性生殖系传递的，因此我们检测了雄鼠睾丸组织中印记基因Igf2和H19的基因表达水平和DNA甲基化水平。结果发现，无论是F1代还是F3代，砷染毒组Igf2和H19的mRNA表达水平显著高于对照组。进一步研究发现，砷染毒组Igf2 DMR2和H19 DMR的总体甲基化水平较对照组有明显降低。综上，我们的研究表明宫内砷暴露可能引起雄性生殖损伤的跨代遗传，而印记基因Igf2/H19的表观遗传学改变可能参与其中。