Klarsfeld André, Malpel Sébastien, Michard-Vanhée Christine, Picot Marie, Chélot Elisabeth, Rouyer François
Institut de Neurobiologie Alfred Fessard, Centre National de la Recherche Scientifique, Unité Propre de Recherche 2216, 91198 Gif-sur-Yvette, France.
J Neurosci. 2004 Feb 11;24(6):1468-77. doi: 10.1523/JNEUROSCI.3661-03.2004.
In Drosophila, light affects circadian behavioral rhythms via at least two distinct mechanisms. One of them relies on the visual phototransduction cascade. The other involves a presumptive photopigment, cryptochrome (cry), expressed in lateral brain neurons that control behavioral rhythms. We show here that cry is expressed in most, if not all, larval and adult neuronal groups expressing the PERIOD (PER) protein, with the notable exception of larval dorsal neurons (DN2s) in which PER cycles in antiphase to all other known cells. Forcing cry expression in the larval DN2s gave them a normal phase of PER cycling, indicating that their unique antiphase rhythm is related to their lack of cry expression. We were able to directly monitor CRY protein in Drosophila brains in situ. It appeared highly unstable in the light, whereas in the dark, it accumulated in both the nucleus and the cytoplasm, including some neuritic projections. We also show that dorsal PER-expressing brain neurons, the adult DN1s, are the only brain neurons to coexpress the CRY protein and the photoreceptor differentiation factor GLASS. Studies of various visual system mutants and their combination with the cry(b) mutation indicated that the adult DN1s contribute significantly to the light sensitivity of the clock controlling activity rhythms, and that this contribution depends on CRY. Moreover, all CRY-independent light inputs into this central behavioral clock were found to require the visual system. Finally, we show that the photoreceptive DN1 neurons do not behave as autonomous oscillators, because their PER oscillations in constant darkness rapidly damp out in the absence of pigment-dispersing-factor signaling from the ventral lateral neurons.
在果蝇中，光通过至少两种不同的机制影响昼夜行为节律。其中一种机制依赖于视觉光转导级联反应。另一种机制涉及一种推测的光色素——隐花色素（cry），它在控制行为节律的侧脑神经元中表达。我们在此表明，cry在大多数（如果不是全部）表达周期蛋白（PER）的幼虫和成虫神经元群体中表达，但幼虫背侧神经元（DN2s）是个显著例外，其中PER的循环与所有其他已知细胞呈反相。在幼虫DN2s中强制表达cry使它们的PER循环具有正常相位，这表明它们独特的反相节律与缺乏cry表达有关。我们能够直接在果蝇大脑原位监测CRY蛋白。它在光照下显得高度不稳定，而在黑暗中，它在细胞核和细胞质中积累，包括一些神经突起。我们还表明，表达PER的背侧脑神经元，即成虫DN1s，是唯一同时表达CRY蛋白和光感受器分化因子GLASS的脑神经元。对各种视觉系统突变体及其与cry(b)突变体组合的研究表明，成虫DN1s对控制活动节律的生物钟的光敏感性有显著贡献，且这种贡献依赖于CRY。此外，发现所有不依赖CRY的光输入到这个中央行为生物钟都需要视觉系统。最后，我们表明光感受性DN1神经元并不表现为自主振荡器，因为在没有来自腹侧外侧神经元的色素分散因子信号的情况下，它们在持续黑暗中的PER振荡会迅速衰减。
