Table_1_Reproductive Aging in Caenorhabditis elegans: From Molecules to Ecology.pdf

Aging animals display a broad range of progressive degenerative changes, and one of the most fascinating is the decline of female reproductive function. In the model organism Caenorhabditis elegans, hermaphrodites reach a peak of progeny production on day 2 of adulthood and then display a rapid decline; progeny production typically ends by day 8 of adulthood. Since animals typically survive until day 15 of adulthood, there is a substantial post reproductive lifespan. Here we review the molecular and cellular changes that occur during reproductive aging, including reductions in stem cell number and activity, slowing meiotic progression, diminished Notch signaling, and deterioration of germ line and oocyte morphology. Several interventions have been identified that delay reproductive aging, including mutations, drugs and environmental factors such as temperature. The detailed description of reproductive aging coupled with interventions that delay this process have made C. elegans a leading model system to understand the mechanisms that drive reproductive aging. While reproductive aging has dramatic consequences for individual fertility, it also has consequences for the ecology of the population. Population dynamics are driven by birth and death, and reproductive aging is one important factor that influences birth rate. A variety of theories have been advanced to explain why reproductive aging occurs and how it has been sculpted during evolution. Here we summarize these theories and discuss the utility of C. elegans for testing mechanistic and evolutionary models of reproductive aging.

衰老动物会出现广泛的进行性退行性变化，其中最引人关注的现象之一便是雌性生殖功能的衰退。以模式生物秀丽隐杆线虫（Caenorhabditis elegans）为研究对象时，其雌雄同体个体在成年后第2天达到子代产出峰值，随后迅速下降；子代产出通常在成年后第8天左右终止。由于该类动物通常可存活至成年后第15天，因此存在相当长的生殖后寿命。本文综述了生殖衰老过程中发生的分子与细胞层面改变，包括干细胞数量与活性的降低、减数分裂进程减缓、Notch信号通路（Notch signaling）活性减弱，以及生殖系与卵母细胞的形态退化。目前已发现多种可延缓生殖衰老的干预手段，包括基因突变、药物干预以及温度等环境因素。对生殖衰老的详细描述，以及可延缓该过程的干预手段，使得秀丽隐杆线虫（C. elegans）成为解析生殖衰老驱动机制的主流模式系统。生殖衰老不仅对个体生育能力具有显著影响，同时也会对种群生态学产生重要作用。种群动态由出生与死亡过程驱动，而生殖衰老是影响出生率的关键因素之一。学界已提出多种理论，用以解释生殖衰老的发生原因及其在进化过程中的塑造机制。本文将对上述理论进行总结，并探讨利用C. elegans验证生殖衰老的机制模型与进化模型的应用价值。