Montero Juan A, Sanchez-Fernandez Cristina, Lorda-Diez Carlos I, Garcia-Porrero Juan A, Hurle Juan M
Departamento de Anatomía y Biología Celular and IDIVAL, Universidad de Cantabria, Santander 39011, Spain.
Sci Rep. 2016 Oct 18;6:35478. doi: 10.1038/srep35478.
DNA damage independent of caspase activation accompanies programmed cell death in different vertebrate embryonic organs. We analyzed the significance of DNA damage during the regression of the interdigital tissue, which sculpts the digits in the embryonic limb. Interdigit remodeling involves oxidative stress, massive apoptosis and cell senescence. Phosphorylation of H2AX mediated by ATM precedes caspase dependent apoptosis and cell senescence during interdigit regression. The association of γH2AX with other downstream DNA repair factors, including MDC1, Rad50 and 53BP1 suggests a defensive response of cells against DNA damage. The relative distribution of cells γH2AX-only positive, TUNEL-only positive, and cells double positive for both markers is consistent with a sequence of degenerative events starting by damage of the DNA. In support of this interpretation, the relative number of γH2AX-only cells increases after caspase inhibition while the relative number of TUNEL-only cells increases after inhibition of ATM. Furthermore, cultured interdigits survived and maintained intense chondrogenic potential, even at advanced stages of degeneration, discarding a previous commitment to die. Our findings support a new biological paradigm considering embryonic cell death secondary to genotoxic stimuli, challenging the idea that considers physiological cell death a cell suicide regulated by an internal death clock that pre-programmes degeneration.
在不同脊椎动物胚胎器官的程序性细胞死亡过程中，DNA损伤独立于半胱天冬酶激活而发生。我们分析了指（趾）间组织退化过程中DNA损伤的意义，指（趾）间组织在胚胎肢体中塑造指（趾）。指（趾）间重塑涉及氧化应激、大量细胞凋亡和细胞衰老。在指（趾）间退化过程中，由ATM介导的H2AX磷酸化先于半胱天冬酶依赖性细胞凋亡和细胞衰老。γH2AX与其他下游DNA修复因子（包括MDC1、Rad50和53BP1）的关联表明细胞对DNA损伤的防御反应。仅γH2AX阳性细胞、仅TUNEL阳性细胞以及两种标记均为双阳性细胞的相对分布与由DNA损伤引发的一系列退化事件一致。支持这一解释的是，半胱天冬酶抑制后仅γH2AX细胞的相对数量增加，而ATM抑制后仅TUNEL细胞的相对数量增加。此外，即使在退化的晚期阶段，培养的指（趾）间组织仍能存活并保持强烈的软骨生成潜能，摒弃了先前的死亡承诺。我们的研究结果支持一种新的生物学范式，即认为胚胎细胞死亡继发于遗传毒性刺激，这对认为生理性细胞死亡是由预编程退化的内部死亡时钟调节的细胞自杀这一观点提出了挑战。
