University of Colorado-Anschutz Medical Campus, Department of Obstetrics and Gynecology, Division of Reproductive Endocrinology and Infertility, Aurora, CO, USA.
University of Colorado-Anschutz Medical Campus, Department of Obstetrics and Gynecology, Division of Reproductive Sciences, Aurora, CO, USA.
Mol Hum Reprod. 2021 Aug 7;27(8). doi: 10.1093/molehr/gaab050.
Mechanisms that directly control mammalian ovarian primordial follicle (PF) growth activation and the selection of individual follicles for survival are largely unknown. Follicle cells produce factors that can act as potent inducers of cellular stress during normal function. Consistent with this, we show here that normal, untreated ovarian cells, including pre-granulosa cells of dormant PFs, express phenotype and protein markers of the activated integrated stress response (ISR), including stress-specific protein translation (phospho-Serine 51 eukaryotic initiation factor 2α; P-EIF2α), active DNA damage checkpoints, and cell-cycle arrest. We further demonstrate that mRNAs upregulated in primary (growing) follicles versus arrested PFs mostly include stress-responsive upstream open reading frames (uORFs). Treatment of a granulosa cell (GC) line with the PF growth trigger tumor necrosis factor alpha results in the upregulation of a 'stress-dependent' translation profile. This includes further elevated P-eIF2α and a shift of uORF-containing mRNAs to polysomes. Because the active ISR corresponds to slow follicle growth and PF arrest, we propose that repair and abrogation of ISR checkpoints (e.g. checkpoint recovery) drives the GC cell cycle and PF growth activation (PFGA). If cellular stress is elevated beyond a threshold(s) or, if damage occurs that cannot be repaired, cell and follicle death ensue, consistent with physiological atresia. These data suggest an intrinsic quality control mechanism for immature and growing follicles, where PFGA and subsequent follicle growth and survival depend causally upon ISR resolution, including DNA repair and thus the proof of genomic integrity.
哺乳动物卵巢原始卵泡 (PF) 生长激活和个体卵泡存活选择的直接调控机制在很大程度上尚不清楚。卵泡细胞产生的因子在正常功能中可以作为细胞应激的有效诱导剂。与此一致，我们在这里表明，包括休眠 PF 的原始卵泡细胞在内的正常、未处理的卵巢细胞表达激活的整合应激反应 (ISR) 的表型和蛋白标志物，包括应激特异性蛋白翻译 (磷酸化丝氨酸 51 真核起始因子 2α；P-EIF2α)、活跃的 DNA 损伤检查点和细胞周期停滞。我们进一步证明，与休眠 PF 相比，在初级（生长）卵泡中上调的 mRNA 大多包括应激反应性上游开放阅读框 (uORF)。用 PF 生长触发因子肿瘤坏死因子-α处理颗粒细胞 (GC) 系，导致“应激依赖性”翻译谱的上调。这包括进一步升高的 P-EIF2α 和含有 uORF 的 mRNA 向多核糖体的转移。由于活跃的 ISR 对应于卵泡生长缓慢和 PF 停滞，我们提出修复和消除 ISR 检查点（例如检查点恢复）驱动 GC 细胞周期和 PF 生长激活 (PFGA)。如果细胞应激超过阈值或发生无法修复的损伤，则会导致细胞和卵泡死亡，这与生理性退化一致。这些数据表明，不成熟和生长中的卵泡存在内在的质量控制机制，其中 PFGA 以及随后的卵泡生长和存活取决于 ISR 的解决，包括 DNA 修复，从而证明了基因组的完整性。
