PRC, INRAE, CNRS, IFCE, Université de Tours, Nouzilly, France.
PRC, INRAE, CNRS, IFCE, Université de Tours, Nouzilly, France.
Vitam Horm. 2021;116:91-131. doi: 10.1016/bs.vh.2021.02.005. Epub 2021 Mar 11.
Seasonal rhythms are a pervasive feature of most living organisms, which underlie yearly timeliness in breeding, migration, hibernation or weight gain and loss. To achieve this, organisms have developed inner timing devices (circannual clocks) that endow them with the ability to predict then anticipate changes to come, usually using daylength as the proximate cue. In Vertebrates, daylength interpretation involves photoperiodic control of TSH production by the pars tuberalis (PT) of the pituitary, which governs a seasonal switch in thyroid hormone (TH) availability in the neighboring hypothalamus. Tanycytes, specialized glial cells lining the third ventricle (3V), are responsible for this TH output through the opposite, PT-TSH-driven, seasonal control of deiodinases 2/3 (Dio 2/3). Tanycytes comprise a photoperiod-sensitive stem cell niche and TH is known to play major roles in cell proliferation and differentiation, which suggests that seasonal control of tanycyte proliferation may be involved in the photoperiodic synchronization of seasonal rhythms. Here we review our current knowledge of the molecular and neuroendocrine pathway linking photoperiodic information to seasonal changes in physiological functions and discuss the potential implication of tanycytes, TH and cell proliferation in seasonal timing.
季节节律是大多数生物普遍存在的特征，它是生物繁殖、迁徙、冬眠或体重增减的年度时间性的基础。为了实现这一点，生物已经开发出内在的计时装置（年周期时钟），使它们能够预测并预期即将到来的变化，通常使用日长作为近似线索。在脊椎动物中，日长解释涉及垂体结节部（PT）对 TSH 产生的光周期控制，这控制了相邻下丘脑甲状腺激素（TH）的季节性变化。特化的神经胶质细胞，即三脑室（3V） lining 的 神经胶质细胞，通过 PT-TSH 驱动的相反的、季节性的脱碘酶 2/3（Dio 2/3）控制，负责这种 TH 输出。神经胶质细胞包含一个光周期敏感的干细胞生态位，TH 已知在细胞增殖和分化中发挥主要作用，这表明神经胶质细胞增殖的季节性控制可能参与了季节性节律的光周期同步。在这里，我们回顾了将光周期信息与生理功能的季节性变化联系起来的分子和神经内分泌途径的现有知识，并讨论了神经胶质细胞、TH 和细胞增殖在季节性计时中的潜在意义。
