Department of Physiology, Michigan State University, East Lansing, Michigan, United States of America.
PLoS One. 2010 Feb 12;5(2):e9204. doi: 10.1371/journal.pone.0009204.
Therapeutic approaches to preserve fertility in females undergoing cancer treatments are currently ineffective. This is partly due to limited knowledge of the molecular mechanisms that injured germ cells elicit to repair damage and survive or to abort repair and activate biochemical pathways leading to death. So far, we know that following spontaneously occurring or drug-induced DNA damage, the efficiency of DNA repair is a critical determinant of the cell's fate. The protein encoded by the Rad51 gene is one of several components recruited for homologous recombination-dependent DNA double-strand break repair in both somatic cells and germ cells. Recently, we showed that microinjection of recombinant Rad51 into AKR/J mouse oocytes decreased the extent of spontaneous DNA double-strand breaks, suppressed apoptosis, and restored the developmental competence in AKR/J embryos. Herein we characterized the nature of chemotherapy-induced lesions in oocytes, and the associated individual components of the DNA damage sensor and repair apparatus. For comparison, we also assessed parallel spontaneous changes in aging oocytes.
Data collected were derived from: analysis of apoptosis; immunodepletion; oocyte microinjections; immunocytochemistry; immunofluorescence; and CHIP-like assays.
Our data show that: (i) DNA damage in oocytes can be induced by both chemotherapy and spontaneously by the aging process; (ii) oocytes possess the machinery and capability for repairing such DNA damage; (iii) Rad51 is a critical player in the repair of both chemotherapy-induced and spontaneously-sustained DNA damage; and (iv) in response to damage, oocytes exhibit an inverse functional relationship between presence of Bax and activity of Rad51.
CONCLUSION/SIGNIFICANCE: Our results establish Rad51 and/or Bax as potential candidates that can be targeted for development of individualized chemotherapeutic interventions that are effective, but minimal in toxicity. The use of Rad51 and Bax modulating compounds could offer women the opportunity to maintain fully functional germ cells despite cancer treatments or aging.
目前，针对接受癌症治疗的女性进行生育力保护的治疗方法效果不佳。这在一定程度上是由于对损伤的生殖细胞引发的修复损伤和存活或中止修复并激活导致死亡的生化途径的分子机制了解有限。到目前为止，我们知道，在自发发生或药物诱导的 DNA 损伤后，DNA 修复的效率是细胞命运的关键决定因素。Rad51 基因编码的蛋白质是体细胞和生殖细胞中招募用于同源重组依赖性 DNA 双链断裂修复的几种成分之一。最近，我们表明，将重组 Rad51 微注射到 AKR/J 小鼠卵母细胞中可减少自发 DNA 双链断裂的程度，抑制凋亡，并恢复 AKR/J 胚胎的发育能力。在此，我们描述了卵母细胞中化疗诱导损伤的性质，以及与 DNA 损伤传感器和修复装置相关的各个组成部分。为了进行比较，我们还评估了衰老卵母细胞中平行的自发变化。
收集的数据来自：凋亡分析；免疫耗竭；卵母细胞微注射；免疫细胞化学；免疫荧光；和 CHIP 样测定。
我们的数据表明：（i）卵母细胞中的 DNA 损伤可由化疗和衰老过程自发诱导；（ii）卵母细胞具有修复这种 DNA 损伤的机制和能力；（iii）Rad51 是修复化疗诱导和自发持续的 DNA 损伤的关键因素；（iv）在受到损伤后，卵母细胞中 Bax 的存在与 Rad51 的活性之间呈反向功能关系。
结论/意义：我们的结果确立了 Rad51 和/或 Bax 作为潜在的候选者，可作为开发有效但毒性最小的个体化化疗干预措施的目标。使用 Rad51 和 Bax 调节化合物可以为女性提供机会，使她们能够在接受癌症治疗或衰老的情况下保持完全功能的生殖细胞。
