主页 > 医学前沿 >
【科普】《自然》：科学家发现独立于基因的生
生物钟控制着生命活动的内在节律，过去人们一直认为它的“驱动齿轮”是基因。而英国研究人员在新一期《自然》杂志上报告说，他们发现了独立于基因的生物钟机制，这种与新陈代谢有关的机制构成了生物钟的“第二齿轮”。
英国剑桥大学研究人员报告说，首次发现人类血液红细胞中也存在生物钟。与其他细胞拥有脱氧核糖核酸（DNA）等遗传物质不同，红细胞中没有DNA，因此它不会像过去认为的那样，根据基因发出的信号来调整活动节律。研究人员探测发现，红细胞中一种名为peroxiredoxin的抗氧化蛋白的含量会出现24小时的周期性起落，这说明有另一种生物钟机制在起作用。
英国爱丁堡大学等机构的研究人员在同期《自然》杂志上发表另一份研究报告说，他们在海藻中也发现了类似现象。虽然海藻细胞中有DNA等遗传物质，但在黑暗环境中其DNA不会作为生物钟的“驱动齿轮”而转动。研究人员在黑暗环境中也探测到海藻细胞中同一种抗氧化蛋白的含量有周期性起落现象。
这两项研究说明，除了基因以外，还存在驱动生物钟运行的“第二齿轮”。由于这种抗氧化蛋白在细胞新陈代谢中扮演着重要角色，研究人员认为“第二齿轮”的驱动力应该来自新陈代谢机制本身。
爱丁堡大学的安德鲁·米勒教授说，海藻是一种极为古老的生物，因此这种与新陈代谢有关的生物钟机制很可能已经存在数十亿年之久，并在进化中成为人类等生物体内普遍存在的现象。这一发现还说明生物钟比人们以前所知更精密、更复杂，需要更多深入研究。
此前研究发现，如果生物钟因坐飞机、上夜班等原因被扰乱，常会引起新陈代谢紊乱和不舒服，甚至有可能导致糖尿病等疾病，本次研究进展将有助于相关领域的进一步探索。
Not only does the research provide important insight into health-related problems linked to individuals with disrupted clocks -- such as pilots and shift workers -- it also indicates that the 24-hour circadian clock found in human cells is the same as that found in algae and dates back millions of years to early life on Earth.
Two new studies in the journal Nature from the Universities of Cambridge and Edinburgh give insight into the circadian clock which controls patterns of daily and seasonal activity, from sleep cycles to butterfly migrations to flower opening.
One study, from the University of Cambridge's Institute of Metabolic Science, has for the first time identified 24-hour rhythms in red blood cells. This is significant because circadian rhythms have always been assumed to be linked to DNA and gene activity, but -- unlike most of the other cells in the body -- red blood cells do not have DNA.
Akhilesh Reddy, from the University of Cambridge and lead author of the study, said: "We know that clocks exist in all our cells; they're hard-wired into the cell. Imagine what we'd be like without a clock to guide us through our days. The cell would be in the same position if it didn't have a clock to coordinate its daily activities.
"The implications of this for health are manifold. We already know that disrupted clocks -- for example, caused by shift-work and jet-lag -- are associated with metabolic disorders such as diabetes, mental health problems and even cancer. By furthering our knowledge of how the 24-hour clock in cells works, we hope that the links to these disorders -- and others -- will be made clearer. This will, in the longer term, lead to new therapies that we couldn't even have thought about a couple of years ago."
For the study, the scientists, funded by the Wellcome Trust, incubated purified red blood cells from healthy volunteers in the dark and at body temperature, and sampled them at regular intervals for several days. They then examined the levels of biochemical markers -- proteins called peroxiredoxins -- that are produced in high levels in blood and found that they underwent a 24-hour cycle. Peroxiredoxins are found in virtually all known organisms.
A further study, by scientists working together at the Universities of Edinburgh and Cambridge, and the Observatoire Oceanologique in Banyuls, France, found a similar 24-hour cycle in marine algae, indicating that internal body clocks have always been important, even for ancient forms of life.
The researchers in this study found the rhythms by sampling the peroxiredoxins in algae at regular intervals over several days. When the algae were kept in darkness, their DNA was no longer active, but the algae kept their circadian clocks ticking without active genes. Scientists had thought that the circadian clock was driven by gene activity, but both the algae and the red blood cells kept time without it.
阅读本文的人还阅读：
作者:admin@医学,生命科学 2011-01-28 08:32
医学,生命科学网