Seasonal differences in hypothalamic thyroid-stimulating hormone ß, gonadotropin-releasing hormone-I and deiodinase expression between migrant and resident subspecies of white-crowned sparrow (Zonotrichia leucophrys).
Seasonal differences in hypothalamic thyroid-stimulating hormone ß, gonadotropin-releasing hormone-I and deiodinase expression between migrant and resident subspecies of white-crowned sparrow (Zonotrichia leucophrys).
复制标题
白冠麻雀 (Zonotrichia leucophrys) 候鸟亚种和留鸟亚种下丘脑促甲状腺激素、促性腺激素释放激素-I 和脱碘酶表达的季节性差异。
DOI：
10.1111/jne.13032
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发表时间：
2021
影响因子：
3.2
通讯作者：
Pérez JH
中科院分区：
文献类型：
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作者：
Pérez JH
在整个类群中，非繁殖状态和繁殖状态之间的季节性转换是由大脑深层的局部甲状腺激素信号控制的，通过脱碘酶表达从类型3(DIO3)到类型2(DIO2)的相互切换。这种相互转换被认为是通过增加促甲状腺激素β(促甲状腺激素β)从结节部分释放来调节的，这是对光周期变化的反应。虽然在受控实验室环境中的少数模式生物中很好地描述了这一途径，但在自然环境条件下自由生活的动物中，这一途径在很大程度上仍未被探索。在这项比较基因表达研究中，我们研究了两个季节性繁殖的白冠麻雀亚种(Zonotrichia Leucophrys)的下丘脑甲状腺激素信号，跨越了它们的整个年度周期。迁徙的Gambel(Z.l.Gambeli)亚种和常驻的Nutall(Z.l.nuttalii)亚种在繁殖时间、生活史阶段和迁徙策略方面存在差异。虽然在越冬期间，两个亚种的Dio3基因表达升高，DIO2基因表达降低，但DIO2在生殖开始之前达到峰值。然而，不同亚种的DIO2表达高峰期的时间不同。有趣的是，TSHmrna的季节性调节只在候鸟身上观察到，在繁殖开始时表达增加，与其他高度光周期物种的观察一致。居民促性腺激素β、DIO2与促性腺激素释放激素-I m RNA及生殖指标无相关性。基于这些观察到的差异，我们讨论了对于我们理解内侧基础下丘脑基因表达的变化如何调节季节性繁殖的启动的潜在意义。
Across taxa, the seasonal transition between non‐breeding and breeding states is controlled by localised thyroid hormone signalling in the deep brain via reciprocal switching of deiodinase enzyme expression from type 3 (DIO3) to type 2 (DIO2). This reciprocal switch is considered to be mediated by increasing thyroid‐stimulating hormone β (TSHβ) release from the pars tuberalis, which occurs in response to a change in photoperiod. Although well characterised in a handful of model organisms in controlled laboratory settings, this pathway remains largely unexplored in free‐living animals under natural environmental conditions. In this comparative gene expression study, we investigated hypothalamic thyroid hormone signalling in two seasonally breeding subspecies of white‐crowned sparrow (Zonotrichia leucophrys), across the entirety of their annual cycles. The migratory Gambel's (Z.l.gambelii) and resident Nuttall's (Z.l.nuttalii) subspecies differ with respect to timing of reproduction, as well as life history stage and migratory strategies. Although DIO3 mRNA expression was elevated and DIO2 mRNA expression was reduced in the wintering period in both subspecies, DIO2 peaked in both subspecies prior to the onset of reproduction. However, there was differential timing between subspecies in peak DIO2 expression. Intriguingly, seasonal modulation of TSHβ mRNA was only observed in migrants, where expression was elevated at the start of breeding, consistent with observations from other highly photoperiodic species. There was no correlation between TSHβ, DIO2 and gonadotropin‐releasing hormone‐I mRNA or reproductive metrics in residents. Based on these observed differences, we discuss potential implications for our understanding of how changes in medial basal hypothalamic gene expression mediates initiation of seasonal reproduction.