Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China.
Mol Biol Evol. 2021 Aug 23;38(9):3925-3937. doi: 10.1093/molbev/msab125.
Arylalkylamine N-acetyltransferase (AANAT) plays a crucial role in synchronizing internal biological functions to circadian and circannual changes. Generally speaking, only one copy of AANAT gene has been found in mammals, however, three independent duplications of this gene were detected in several cetartiodactyl lineages (i.e., Suidae, Hippopotamidae, and Pecora), which originated in the middle Eocene, a geological period characterized with the increased climate seasonality. Lineage-specific expansions of AANAT and the associated functional enhancement in these lineages strongly suggest an improvement in regulating photoperiodic response to adapt to seasonal climate changes. In contrast, independent inactivating mutations or deletions of the AANAT locus were identified in the four pineal-deficient clades (cetaceans, sirenians, xenarthrans, and pangolins). Loss of AANAT function in cetaceans and sirenians could disrupt the sleep-promoting effects of pineal melatonin, which might contribute to increasing wakefulness, adapting these clades to underwater sleep. The absence of AANAT and pineal glands in xenarthrans and pangolins may be associated with their body temperature maintenance. The present work demonstrates a far more complex and intriguing evolutionary pattern and functional diversity of mammalian AANAT genes than previously thought and provides further evidence for understanding AANAT evolution as driven by rhythmic adaptations in mammals.
芳基烷基胺 N-乙酰转移酶（AANAT）在使内部生物功能与昼夜节律和年节律变化同步方面发挥着关键作用。一般来说，哺乳动物中只发现了一个 AANAT 基因副本，然而，在几个偶蹄目动物谱系（即猪科、河马科和反刍动物）中检测到了这个基因的三次独立复制，这些谱系起源于中始新世，这是一个气候季节性增强的地质时期。AANAT 的谱系特异性扩张及其在这些谱系中的相关功能增强强烈表明，调节光周期反应以适应季节性气候变化的能力得到了提高。相比之下，在四个松果腺缺失的类群（鲸类、海牛目动物、有袋目动物和穿山甲）中鉴定出 AANAT 基因座的独立失活突变或缺失。在鲸类和海牛目中 AANAT 功能的丧失可能会破坏松果腺褪黑素的促进睡眠作用，这可能有助于增加清醒度，使这些类群适应水下睡眠。在有袋目动物和穿山甲中缺乏 AANAT 和松果腺可能与它们的体温维持有关。本研究表明，哺乳动物 AANAT 基因的进化模式和功能多样性远比以前想象的更为复杂和有趣，并为理解哺乳动物 AANAT 进化是由节律适应驱动提供了进一步的证据。
