Study of DNA repair deficient mice

我们分离了两个小鼠光解酶基因同源物（mCry 1和mCry 2），它们编码蓝光受体家族中的蛋白质。为了探索哺乳动物Cry 1和Cry 2的生物学功能，我们通过基因打靶在胚胎干细胞中产生cry 1和cry 2突变小鼠。由于这些突变小鼠是完全健康的，没有表现出明显的表型，我们分析了CRY蛋白在生物钟中的可能作用，通过测量cry敲除小鼠在正常光/暗（LD）周期和恒定黑暗（DD）下的昼夜节律轮运行行为。由于CRY蛋白能够作为蓝光受体发挥作用，因此这些蛋白可能参与光夹带能力。我们发现，小鼠缺乏Cry 1或Cry 2蛋白显示加速和延迟自由运行（DD）的自发活动的周期性，分别。这些发现表明，Cry 1和Cry 2拮抗调节时钟的周期长度。然而，上述结果表明，任何一个基因的缺陷都不会产生可检测到的运动活动的光夹带损失。由于cry 1小鼠仍然含有功能性Cry 2蛋白，我们产生了双突变动物。令我们惊讶的是，在缺乏这两种蛋白质的情况下，观察到自由运行的节律性的瞬时和完全丧失。这表明，除了可能的光感受器和拮抗时钟调节功能，这两种蛋白质是必不可少的昼夜节律的维护。

We isolated two mouse homologues of photolyase gene (mCry1 and mCry2), which encode proteins in the family of blue-light receptors. To explore the biological function of mammalian Cry1 and Cry2, we have generated cry1 and cry2 mutant mice through gene targeting in embryonic stem cells. Since these mutant mice are completely healthy and showed no overt phenotype, we analyzed the possible role for CRY proteins in the biological clock by measuring the circadian wheel-running behavior of cry-knockout mice under normal light/dark (LD) cycles and in constant darkness (DD). Since CRY proteins are able to function as blue-light receptor, these protein may be involved in the light entrainment ability. We found that mice lacking the Cry1 or Cry2 protein display accelerated and delayed free-running (DD) periodicity of locomotor activity, respectively. These findings suggest that Cry1 and Cry2 antagonistically modulate the period length of the clock. Above results indicate, however, that a deficiency in either gene does not produce a detectable loss of light entrainment of locomotor activity. Since cry1 mouse still contain a functional Cry2 protein, we generated double-mutant animals. To our surprise, in the absence of both proteins, an instantaneous and complete loss of free-running rhythmicity is observed. This suggests that, in addition to a possible photoreceptor and antagonistic clock-adjusting function, both proteins are essential for the maintenance of circadian rhytjmicity.