Department of Biology and Evolution, University of Ferrara, Ferrara, Italy.
PLoS Biol. 2011 Sep;9(9):e1001142. doi: 10.1371/journal.pbio.1001142. Epub 2011 Sep 6.
The circadian clock is synchronized with the day-night cycle primarily by light. Fish represent fascinating models for deciphering the light input pathway to the vertebrate clock since fish cell clocks are regulated by direct light exposure. Here we have performed a comparative, functional analysis of the circadian clock involving the zebrafish that is normally exposed to the day-night cycle and a cavefish species that has evolved in perpetual darkness. Our results reveal that the cavefish retains a food-entrainable clock that oscillates with an infradian period. Importantly, however, this clock is not regulated by light. This comparative study pinpoints the two extra-retinal photoreceptors Melanopsin (Opn4m2) and TMT-opsin as essential upstream elements of the peripheral clock light input pathway.
生物钟主要通过光与昼夜节律同步。鱼类是破解脊椎动物时钟光输入途径的迷人模型，因为鱼类细胞时钟受直接光照调节。在这里，我们对斑马鱼进行了比较功能分析，斑马鱼通常暴露在昼夜循环中，而穴居鱼则在永久黑暗中进化。我们的研究结果表明，穴居鱼保留了一个可被食物驯化的生物钟，该生物钟以亚日周期振荡。然而，重要的是，这个时钟不受光调节。这项比较研究指出，两个额外的视网膜光感受器黑素视蛋白（Opn4m2）和 TMT-opsin 是外周时钟光输入途径的必需上游元件。
