Department of Interdisciplinary Life Sciences, Research Institute of Wildlife Ecology, University of Veterinary Medicine Vienna, Savoyenstraße 1a, Vienna, 1160, Austria.
Department of Interdisciplinary Life Sciences, Konrad Lorenz Institute of Ethology, University of Veterinary Medicine Vienna, Savoyenstraße 1a, Vienna, A-1160, Austria.
Sci Rep. 2024 Sep 28;14(1):22420. doi: 10.1038/s41598-024-73033-3.
Migration is one of the most extreme and energy demanding life history strategies to have evolved in the animal kingdom. In birds, champions of long-distance migrations, the seasonal emergence of the migratory phenotype is characterised by rapid physiological and metabolic remodelling, including substantial accumulation of fat stores and increases in nocturnality. The molecular underpinnings and brain adaptations to seasonal migrations remain poorly understood. Here, we exposed Common quails (Coturnix coturnix) to controlled changes in day length to simulate southward autumn migration, and then blocked the photoperiod until birds entered the non-migratory wintering phase. We first performed de novo RNA-Sequencing from selected brain samples (hypothalamus) collected from birds at a standardised time at night, either in a migratory state (when restlessness was highest and at their body mass peak), or in a non-migratory state and conducted differential gene expression and functional pathways analyses. We found that the migratory state was associated with up-regulation of a few, yet functionally well defined, gene expression networks implicated in fat trafficking, protein and carbohydrate metabolism. Further analyses that focused on candidate genes (apolipoprotein H or APOH, lysosomal associated membrane protein-2 or LAMP2) from samples collected during the day or night across the entire study population suggested differences in the expression of these genes depending on the time of the day with the largest expression levels being found in the migratory birds sampled at night. We also found that expression of APOH was positively associated with levels of nocturnal activity in the migratory birds; such an association was absent within the non-migratory birds. Our results provide novel experimental evidence revealing that hypothalamic changes in expression of apolipoprotein pathways, which regulate the circulatory transport of lipids, are likely key regulatory activators of nocturnal migratory movements. Our study paves the way for performing deeper functional investigations on seasonal molecular remodelling underlying the development of the migratory phenotype.
迁徙是动物王国中进化出的最极端和最耗能的生命史策略之一。在鸟类中，长距离迁徙的佼佼者，迁徙表型的季节性出现的特征是快速的生理和代谢重塑，包括大量脂肪储存的积累和夜间活动的增加。季节性迁徙的分子基础和大脑适应仍知之甚少。在这里，我们让普通鹌鹑（ Coturnix coturnix ）暴露在控制的光照时间变化下，以模拟向南的秋季迁徙，然后阻止光周期，直到鸟类进入非迁徙的冬季阶段。我们首先从在标准夜间时间收集的选定脑样本（下丘脑）中进行从头 RNA 测序，这些样本取自处于迁徙状态的鸟类（此时最烦躁不安，体重达到峰值）或处于非迁徙状态的鸟类，并进行差异基因表达和功能途径分析。我们发现，迁徙状态与少数功能明确的基因表达网络的上调有关，这些网络与脂肪转运、蛋白质和碳水化合物代谢有关。进一步的分析集中在候选基因（载脂蛋白 H 或 APOH 、溶酶体相关膜蛋白 2 或 LAMP2 ）上，这些基因是从整个研究种群中在白天或夜间采集的样本中收集的，结果表明这些基因的表达存在差异，取决于一天中的时间，最大的表达水平出现在夜间采集的迁徙鸟类中。我们还发现，APOH 的表达与迁徙鸟类夜间活动水平呈正相关；而非迁徙鸟类中则不存在这种关联。我们的研究结果提供了新的实验证据，表明调节脂质循环转运的载脂蛋白途径的下丘脑表达变化可能是夜间迁徙运动的关键调节激活剂。我们的研究为深入研究季节性分子重塑在迁徙表型发育中的作用铺平了道路。
