Department of Cellular and Molecular Medicine, Centro de Investigaciones Biológicas, Madrid, Spain.
Cell Death Differ. 2010 Nov;17(11):1697-706. doi: 10.1038/cdd.2010.46. Epub 2010 May 7.
Programmed cell death is a crucial process in neural development that affects mature neurons and glial cells, as well as proliferating precursors and recently born neurons at earlier stages. However, the regulation of the early phase of neural cell death and its function remain relatively poorly understood. In mouse models defective in homologous recombination or nonhomologous end-joining (NHEJ), which are both DNA double-strand break (DSB) repair pathways, there is massive cell death during neural development, even leading to embryonic lethality. These observations suggest that natural DSBs occur frequently in the developing nervous system. In this study, we have found that several components of DSB repair pathways are activated in the developing mouse retina at stages that coincide with the onset of neurogenesis. In short-term organotypic retinal cultures, we confirmed that the repair pathways can be modulated pharmacologically. Indeed, inhibiting the DNA-dependent protein kinase (DNA-PK) catalytic subunit, which is involved in NHEJ, with NU7026 increased caspase-dependent cell death and selectively reduced the neuron population. This observation concurs with an increase in the number of apoptotic neurons found after NU7026 treatment, as also observed in the embryonic scid mouse retina, a mutant that lacks DNA-PK catalytic subunit activity. Therefore, our results implicate the generation of DSB and DNA-PK-mediated repair in neurogenesis in the developing retina.
程序性细胞死亡是神经发育过程中的一个关键过程，它影响成熟神经元和神经胶质细胞，以及增殖前体和早期阶段新出生的神经元。然而，神经细胞早期死亡的调控及其功能仍然相对不太了解。在同源重组或非同源末端连接（NHEJ）有缺陷的小鼠模型中，这两种都是 DNA 双链断裂（DSB）修复途径，在神经发育过程中会发生大量细胞死亡，甚至导致胚胎致死。这些观察结果表明，在发育中的神经系统中经常发生自然 DSB。在这项研究中，我们发现几种 DSB 修复途径的成分在与神经发生同时发生的发育中的小鼠视网膜中被激活。在短期器官型视网膜培养物中，我们证实修复途径可以通过药理学进行调节。事实上，用 NU7026 抑制参与 NHEJ 的 DNA 依赖性蛋白激酶（DNA-PK）催化亚基会增加 caspase 依赖性细胞死亡，并选择性减少神经元群体。这一观察结果与在 NU7026 处理后发现的凋亡神经元数量增加一致，在缺乏 DNA-PK 催化亚基活性的 scid 胚胎小鼠视网膜中也观察到了这一现象。因此，我们的结果表明 DSB 的产生和 DNA-PK 介导的修复参与了发育中视网膜的神经发生。
