Appenroth Daniel, West Alexander C, Wood Shona H, Hazlerigg David G
Arctic Seasonal Timekeeping Initiative (ASTI), Arctic Chronobiology & Physiology, Arctic & Marine Biology, BFE, UiT - Arctic University of Norway, Tromsø, Norway.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2025 Jan;211(1):87-99. doi: 10.1007/s00359-024-01716-3. Epub 2024 Sep 20.
In mammals and birds, tanycytes are known to regulate thyroid hormone conversion, and this process is central to the control of seasonal reproduction. In mammals, this cell type is also implicated in retinoic acid signalling, neurogenesis, and nutritional gatekeeping, all of which have been linked to hypothalamic regulation of energy metabolism. Less is known about these potential wider roles of tanycytes in birds. To address this gap, we combined LASER capture microdissection and transcriptomics to profile the tanycytic region in male Svalbard ptarmigan, a High Arctic species with photoperiod-dependent seasonal rhythms in reproductive activation and body mass. Short photoperiod (SP) adapted birds were transferred to constant light (LL) to trigger breeding and body mass loss. After five months under LL, the development of photorefractoriness led to spontaneous re-emergence of the winter phenotype, marked by the termination of breeding and gain in body mass. The transfer from SP to LL initiated gene expression changes in both thyroid hormone and retinoic acid pathways, as described in seasonal mammals. Furthermore, transcriptomic signatures of cell differentiation and migration were observed. Comparison to data from Siberian hamsters demonstrated that a photoperiod-dependent re-organisation of the hypothalamic tanycytic region is likely a conserved feature. Conversely, the spontaneous development of photorefractoriness showed a surprisingly small number of genes that reverted in expression level, despite reversal of the reproductive and metabolic phenotype. Our data suggest general conservation of tanycyte biology between photoperiodic birds and mammals and raise questions about the mechanistic origins of the photorefractory state.
在哺乳动物和鸟类中，已知伸长细胞可调节甲状腺激素转化，而这一过程对于季节性繁殖的控制至关重要。在哺乳动物中，这种细胞类型还与视黄酸信号传导、神经发生和营养把关有关，所有这些都与下丘脑对能量代谢的调节有关。关于伸长细胞在鸟类中这些潜在的更广泛作用，人们了解较少。为了填补这一空白，我们结合激光捕获显微切割技术和转录组学，对雄性斯瓦尔巴德岩雷鸟的伸长细胞区域进行了分析，该物种是一种北极高纬度物种，其繁殖激活和体重具有依赖光周期的季节性节律。适应短光周期（SP）的鸟类被转移到持续光照（LL）环境中，以触发繁殖和体重减轻。在持续光照环境下五个月后，光不应性的发展导致冬季表型自发重新出现，其特征是繁殖终止和体重增加。如在季节性哺乳动物中所描述的那样，从短光周期到持续光照的转变引发了甲状腺激素和视黄酸途径中的基因表达变化。此外，还观察到了细胞分化和迁移的转录组特征。与西伯利亚仓鼠的数据比较表明，下丘脑伸长细胞区域依赖光周期的重组可能是一个保守特征。相反，尽管繁殖和代谢表型发生了逆转，但光不应性的自发发展显示，表达水平发生逆转的基因数量出奇地少。我们的数据表明，光周期鸟类和哺乳动物之间伸长细胞生物学具有普遍的保守性，并引发了关于光不应性状态机制起源的问题。
