Barton Tara S, Robaire Bernard, Hales Barbara F
Department of Pharmacology and Therapeutics, McGill University, 3655 Promenade Sir-William-Osler, Montreal, Quebec, Canada.
Toxicol Sci. 2007 Dec;100(2):495-503. doi: 10.1093/toxsci/kfm242. Epub 2007 Sep 13.
The detrimental effects of preconceptional paternal exposure to the alkylating anticancer agent, cyclophosphamide, include aberrant epigenetic programming, dysregulated zygotic gene activation, and abnormalities in the offspring that are transmitted to the next generation. The adverse developmental consequences of genomic instabilities transmitted via the spermatozoon emphasize the need to elucidate the mechanisms by which the early embryo recognizes DNA damage in the paternal genome. Little information exists on DNA damage detection in the zygote. We assessed the impact of paternal cyclophosphamide exposure on phosphorylated H2AX (gammaH2AX) and poly(ADP-ribose) polymerase-1(PARP-1), biomarkers of DNA damage, to determine the capacity in the rat zygote to recognize genomic damage and initiate a response to DNA lesions. An amplified biphasic gammaH2AX response was triggered in the paternal pronucleus in zygotes sired by drug-treated males; the maternal genome was not affected. PARP-1 immunoreactivity was substantially elevated in both parental genomes, coincident with the second phase of gammaH2AX induction in embryos sired by cyclophosphamide-exposed spermatozoa. Thus, paternal exposure to a DNA damaging agent rapidly activates signals implemental for DNA damage recognition in the zygote. Inefficient repair of DNA lesions may lead to persistent alterations of the histone code and chromatin integrity, resulting in aberrant embryogenesis. We propose that the response of the early embryo to disturbances in spermatozoal genomic integrity plays a vital role in determining its outcome.
受孕前父本接触烷基化抗癌药物环磷酰胺的有害影响包括异常的表观遗传编程、合子基因激活失调以及后代异常并传递至下一代。通过精子传递的基因组不稳定性对发育产生的不良后果强调了阐明早期胚胎识别父本基因组中DNA损伤机制的必要性。关于合子中DNA损伤检测的信息很少。我们评估了父本接触环磷酰胺对DNA损伤生物标志物磷酸化H2AX（γH2AX）和聚（ADP - 核糖）聚合酶 - 1（PARP - 1）的影响，以确定大鼠合子识别基因组损伤并对DNA损伤启动反应的能力。在药物处理雄性所产生的合子中，父本原核触发了放大的双相γH2AX反应；母本基因组未受影响。在两个亲本基因组中，PARP - 1免疫反应性均大幅升高，这与环磷酰胺处理精子所产生胚胎中γH2AX诱导的第二阶段一致。因此，父本接触DNA损伤剂会迅速激活合子中用于DNA损伤识别的信号。DNA损伤修复效率低下可能导致组蛋白密码和染色质完整性的持续改变，从而导致异常胚胎发生。我们认为早期胚胎对精子基因组完整性干扰的反应在决定其结果方面起着至关重要的作用。
