Effects of Spring Warming on Seasonal Neuroendocrinology and Activation of the Reproductive Axis in Hibernating Arctic Ground Squirrels.
Effects of Spring Warming on Seasonal Neuroendocrinology and Activation of the Reproductive Axis in Hibernating Arctic Ground Squirrels.
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春季变暖对冬眠北极地松鼠季节性神经内分泌和生殖轴激活的影响。
DOI：
10.1093/icb/icac112
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发表时间：
2022
影响因子：
2.6
通讯作者：
Chmura HE
中科院分区：
文献类型：
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作者：
Chmura HE
许多动物调整季节性事件的时间，如繁殖，蜕皮，迁移和冬眠，以响应年际变化和定向气候驱动的温度变化。然而，温度影响季节性时间的机制相对来说还没有得到充分的研究。季节性时序涉及逆行信号传导，其中结节部（PT）中的促甲状腺激素（TSH）改变下丘脑第三脑室内衬的伸展细胞中甲状腺激素（TH）脱碘酶（Dio 2/Dio 3）的表达。这反过来又影响了三碘甲腺原氨酸（T3）的可用性内的mediobasal下丘脑增加下丘脑T3恢复夏季表型，并激活生殖轴在长日育种。最近，我们发现，逆行TH信号被激活在冬眠后期在北极地松鼠（Urocitellus parryii）在恒定的黑暗和恒定的环境温度。季节性途径对非光信号（如温度）的敏感性可能对春季在冬眠室中被隔离的冬眠物种特别重要。为了解决这个问题，我们将圈养的北极地松鼠在冬眠后期暴露于与生态相关的环境温度升高（从-6到-1 °C），并检查变暖对季节性逆行TSH/Dio/T3信号通路的影响，以及生殖轴的下游元素。我们发现，温暖的男性往往有更高的PTTSHβ表达和显着更重的睾丸质量，而TSH/Dio/T3信号通路不受温暖的女性，虽然温暖的女性卵巢质量略有下降。我们的研究结果表明，温度可能对雄性和雌性北极地松鼠的性腺生长产生不同的影响，这可能导致应对快速气候变化的时机不匹配。
Many animals adjust the timing of seasonal events, such as reproduction, molt, migration, and hibernation, in response to interannual variation and directional climate-driven changes in temperature. However, the mechanisms by which temperature influences seasonal timing are relatively under-explored. Seasonal timing involves retrograde signaling in which thyrotropin (TSH) in the pars tuberalis (PT) alters expression of thyroid hormone (TH) deiodinases (Dio2/Dio3) in tanycyte cells lining the third ventricle of the hypothalamus. This, in turn, affects the availability of triiodothyronine (T3) within the mediobasal hypothalamus—increased hypothalamic T3 restores a summer phenotype and activates the reproductive axis in long-day breeders. Recently, we showed that retrograde TH signaling is activated during late hibernation in arctic ground squirrels (Urocitellus parryii) held in constant darkness and constant ambient temperature. Sensitivity of seasonal pathways to nonphotic cues, such as temperature, is likely particularly important to hibernating species that are sequestered in hibernacula during spring. To address this issue, we exposed captive arctic ground squirrels of both sexes to an ecologically relevant increase in ambient temperature (from −6 to −1°C) late in hibernation and examined the effects of warming on the seasonal retrograde TSH/Dio/T3 signaling pathway, as well as downstream elements of the reproductive axis. We found that warmed males tended to have higher PTTSHβexpression and significantly heavier testis mass whereas the TSH/Dio/T3 signaling pathway was unaffected by warming in females, although warmed females exhibited a slight decrease in ovarian mass. Our findings suggest that temperature could have different effects on gonadal growth in male and female arctic ground squirrels, which could lead to mismatched timing in response to rapid climate change.