Katsumura Takafumi, Fukuyo Yukiko, Kawamura Shoji, Oota Hiroki
Department of Anatomy, Kitasato University School of Medicine, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa, 252-0374, Japan.
Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8562, Japan.
J Physiol Anthropol. 2016 Sep 28;35(1):21. doi: 10.1186/s40101-016-0111-9.
The circadian clock is set up around a 24-h period in humans who are awake in the daytime and sleep in the nighttime, accompanied with physiological and metabolic rhythms. Most haplorhine primates, including humans, are diurnal, while most "primitive" strepsirrhine primates are nocturnal, suggesting primates have evolved from nocturnal to diurnal habits. The mechanisms of physiological changes causing the habits and of genetic changes causing the physiological changes are, however, unknown. To reveal these mechanisms, we focus on the nucleotide sequences of the regulatory region of the PERIOD1 (PER1) gene that is known as one of the key elements of the circadian clock in mammalians.
We determined nucleotide sequences of the regulatory region of PER1 concerning the gene expression for six primates and compared those with those of eight primates from the international DNA database. Based on the sequence data, we constructed a phylogenetic tree including both the diurnal/nocturnal species and investigated the guanine and cytosine (GC) content in the regulatory region.
The motif sequences regulating gene expression were evolutionary conservative in the primates examined. The phylogenetic tree simply showed phylogenetic relationship among the species and no branching pattern distinguishable between the diurnal and nocturnal groups. We found two cores showing a statistically significant difference between the diurnal and the nocturnal habits related to the GC contents of the regulatory region of PER1.
Our results suggest the possibility that the two cores in the upstream region of PER1 are related to the regulation of gene expression leading to behavioral differences between diurnal and nocturnal primates.
在白天清醒、夜间睡眠的人类中，昼夜节律钟围绕24小时周期建立，并伴随着生理和代谢节律。包括人类在内的大多数灵长目简鼻亚目动物是昼行性的，而大多数“原始的”灵长目原猴亚目动物是夜行性的，这表明灵长类动物已经从夜行性习惯进化为昼行性习惯。然而，导致这些习惯的生理变化机制以及导致生理变化的基因变化机制尚不清楚。为了揭示这些机制，我们聚焦于PERIOD1（PER1）基因调控区的核苷酸序列，该基因是哺乳动物昼夜节律钟的关键元件之一。
我们测定了6种灵长类动物中与基因表达相关的PER1调控区的核苷酸序列，并将其与国际DNA数据库中8种灵长类动物的序列进行比较。基于这些序列数据，我们构建了一个包括昼行性/夜行性物种的系统发育树，并研究了调控区中鸟嘌呤和胞嘧啶（GC）的含量。
在所研究的灵长类动物中，调控基因表达的基序序列在进化上是保守的。系统发育树仅显示了物种之间的系统发育关系，没有明显的昼行性和夜行性群体之间的分支模式。我们发现两个核心区域在与PER1调控区GC含量相关的昼行性和夜行性习惯之间存在统计学上的显著差异。
我们的结果表明，PER1上游区域的两个核心区域可能与基因表达调控有关，从而导致昼行性和夜行性灵长类动物之间的行为差异。
