Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, Singapore, Republic of Singapore.
PLoS One. 2013 Aug 16;8(8):e71205. doi: 10.1371/journal.pone.0071205. eCollection 2013.
The African lungfish, Protopterus annectens, can undergo aestivation during drought. Aestivation has three phases: induction, maintenance and arousal. The objective of this study was to examine the differential gene expression in the brain of P. annectens during the induction (6 days) and maintenance (6 months) phases of aestivation as compared with the freshwater control using suppression subtractive hybridization. During the induction phase of aestivation, the mRNA expression of prolactin (prl) and growth hormone were up-regulated in the brain of P. annectens, which indicate for the first time the possible induction role of these two hormones in aestivation. Also, the up-regulation of mRNA expression of tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein γ polypeptide and the down-regulation of phosphatidylethanolamine binding protein, suggest that there could be a reduction in biological and neuronal activities in the brain. The mRNA expression of cold inducible RNA-binding protein and glucose regulated protein 58 were also up-regulated in the brain, probably to enhance their cytoprotective effects. Furthermore, the down-regulation of prothymosin α expression suggests that there could be a suppression of transcription and cell proliferation in preparation for the maintenance phase. In general, the induction phase appeared to be characterized by reduction in glycolytic capacity and metabolic activity, suppression of protein synthesis and degradation, and an increase in defense against ammonia toxicity. In contrast, there was a down-regulation in the mRNA expression of prl in the brain of P. annectens during the maintenance phase of aestivation. In addition, there could be an increase in oxidative defense capacity, and up-regulation of transcription, translation, and glycolytic capacities in preparation for arousal. Overall, our results signify the importance of reconstruction of protein structures and regulation of energy expenditure during the induction phase, and the needs to suppress protein degradation and conserve metabolic fuel stores during the maintenance phase of aestivation.
非洲肺鱼，Protopterus annectens，可以在干旱期间进行夏眠。夏眠有三个阶段：诱导、维持和觉醒。本研究的目的是使用抑制差减杂交技术，比较肺鱼在夏眠诱导（6 天）和维持（6 个月）阶段与淡水对照组之间大脑中的差异基因表达。在夏眠的诱导阶段，肺鱼脑中的催乳素（prl）和生长激素的 mRNA 表达上调，这首次表明这两种激素可能在夏眠中起诱导作用。此外，mRNA 表达的酪氨酸 3-单加氧酶/色氨酸 5-单加氧酶激活蛋白 γ 多肽上调和磷酸乙醇胺结合蛋白下调，表明大脑中的生物和神经元活动可能减少。冷诱导 RNA 结合蛋白和葡萄糖调节蛋白 58 的 mRNA 表达也上调，可能增强其细胞保护作用。此外，前胸腺素 α 的表达下调表明转录和细胞增殖可能受到抑制，为维持阶段做准备。总的来说，诱导阶段似乎表现为糖酵解能力和代谢活性降低，蛋白质合成和降解受到抑制，以及对氨毒性的防御增加。相比之下，在肺鱼的夏眠维持阶段，脑中 prl 的 mRNA 表达下调。此外，可能会增加氧化防御能力，并上调转录、翻译和糖酵解能力，为觉醒做准备。总的来说，我们的结果表明，在诱导阶段重建蛋白质结构和调节能量消耗的重要性，以及在夏眠维持阶段需要抑制蛋白质降解和保存代谢燃料储备。
