双酚A引起的父系生殖出生缺陷小鼠模型的建立与研究

Human sperm quality has been continuously reduced for decades, mainly resuled from industrial pollution, and it has caused an increasing number of infertile men.Scientists have reported many research, in order to understand how industrial pollution affacts reproduction of men. What we are now warried about is human birth defect would be caused by sperm with bad quality. However,the hypothesis has not been evaluated experimentally, partially because the mammalian animal models have not established well for this scientific question...Biphenol (BPA) is a kind of endocine-disrupting chemicals with a weak estrogen activity and exsits extensively in our environment. It has been reported that BPA .can damage spermatogenesis, and reduce sperm quality. Our study disclosed that male ratio in offsprings of BPA-treated male mice increased by approximately 18% than the control, indicating that reproductive toxicity exerted by BPA in paternal mice is transferred to their male offsprings. Therefore, we plan to build a mouse model by which BPA can induce birth defect by causing abnormality in sperm. We will focus on study of birth defect in testis and spermatogenesis by different techniques..We also plan to find and compare epigenetic features found in sperm of BPA-treated mice and male offsprings and they will be used as an epigentic standard for evaluation of quality of this animal model. ..We have reported that sperm number dropped by about 20% in the workers who were professionally exposed to BPA. We also found the sperm number was reduced by more than 20% in BPA-trated mice. Does BPA affect spermatogenesis of mice and human in the similar way? To answer the question, we will first look for abnormality in DNA methylation in the sperm of these workers, and compare BPA-associated methylome of mouse sperm and human sperm. If the study is finished as planned in our proposal, an epigenetic biomaker for BPA exposure will finally established in sperm, and it will help us to evaluate health of baby sons of BPA-exposed men.

最近几十年来, 由于环境恶化等因素导致人类精子的数量与质量全面下降，由此引起的男性生育力下降等问题已得到了广泛的研究。由质量下降了的精子有可能提高父系出生缺陷的发生率。然而该问题一直没有得到充分的关注与阐明。有关的哺乳动物模型甚为缺乏。. 双酚A（BPA）是一种人类广泛接触的环境内分泌干扰物。报道表明双酚A能明显影响小鼠睾丸的功能，导致精子质量下降。我们的研究表明BPA染毒雄鼠子代中雄鼠的比例比对照组高出18%，证实BPA引起的精子异常能够在下一代中体现。为此，我们计划建立由双酚A 通过引起精子异常而导致的下一代雄性小鼠的生殖缺陷模型，并从遗传、环境因素交互作用的角度，比较研究这两代小鼠精子表观遗传学调控的异常，并以此建立该模型的标准。最后，我们还将比较模型小鼠的精子与双酚A职业暴露人群精子在基因组DNA甲基化方面的异常，并以此在精子中建立BPA生殖毒性的表观遗传学标记。

文献报道双酚A（BPA）暴露人群精液质量下降。我们还忧虑该下降还可能提高父系出生缺陷的发生率。对此我们开展了研究。我们成功建立了BPA染毒的雄性小鼠模型，而且其生殖毒性也在其子代雄鼠中出现，这些研究证明BPA能够通过精子异常导致雄性后代生殖出生缺陷的发生。其生殖出生缺陷在组织、细胞（精子）与子代群体等层面都有不同形式的体现。例如父本与子代的精子数量都出现明显下降。..考虑到表观遗传学是研究环境与基因交互作用的学科， 我们着重研究了BPA雄性生殖毒性跨代遗传的表观遗传学基础。我们将该父本精子DNA甲基化谱与子代精原细胞基因表达谱结合起来加以生物信息学分析，结果表明BPA有可能通过父本精子中的DNA甲基化异常改变子代精原细胞部分基因的表达水平。我们还将父本与子代精子的DNA羟甲基化谱加以生物信息学分析，结果表明9.1%的基因其BPA相关的羟甲基化在两代精子中维持稳定，提示DNA羟甲基化异常也参与了BPA生殖毒性的跨代遗传。DNA羟甲基化是否参与环境因素导致的跨代遗传，目前文献中罕见报道。因此这部分研究结果具有重要的理论意义。..本项目所研究的一系列基因中，TNNT2让我们格外重视。BPA染毒在两代精子中降低该基因启动子区的DNA甲基化水平，与该结果在理论上一致的是，BPA还在两代精子中增加其羟甲基化水平。为此，我们认为这些变化可作为本模型是否成功建立一个分子标准。..鉴于文献报道BPA暴露人群精子质量下降，我们研究了其表观遗传学基础，发现BPA暴露明显上调人类精子基因组DNA羟甲基化水平，显著改变了H3K27me3结合的基因。在上述这些受BPA暴露影响的一部分基因，其表达在卵裂期的早期人类胚胎中就已出现（最近的文献报答），提示BPA暴露有可能通过精子中表观遗传学异常进而影响人类胚胎质量。综上所述，以上我们对BPA暴露人群精子的研究结果和本动物模型的建立及其研究结果都给我们这么一个警示：如果男性暴露在BPA的环境中，此后他们生育的儿子的健康可能收到影响。遗憾的是，相关的流行病学研究并没有见于文献报道。