来自弗吉尼亚大学卫生系统的两个医生首次发现消除肌肉细胞内毒性的RNA（核糖核酸）从而可以治愈强直型肌肉营养不良，这种疾患在成人身上经常发生的最普遍的肌肉营养不良。
??在美国大学有40,000人患有肌强直性肌营养不良（MMD）.这种疾患可以导致慢性持续性的肌肉萎缩，心率不齐，白内障以及胰岛素耐受。很多人知道他们一二十岁才被诊断患有MMD。
??为了证明在MMD疾病中涉及到毒性RNA这种理论，来自弗吉尼亚大学（UV）病理学家Mani Mahadevan博士领导的研究团队在小鼠中重现了这种疾病。Mahadevan谈到：“在我们的小鼠动物模型中，用毒性RNA处理小鼠，使得它们患各种类型肌强直性营养不良。这时如果你消除毒性RNA，患病的小鼠可以恢复正常”。
??Mahadevan希望该研究可以在未来的几年内引导治疗MMD的新疗法。Mahadevan谈到：“如果我们研制一种疗法来沉默毒性RNA分子的表达。那么我们将有能找到治疗MMD的方法”。Mahadevan的研究出版在2006年9月份这期的《自然－遗传学》杂志上。
??DNA转变成蛋白过程中，RNA的合成是处在第二步。这些蛋白决定在机体细胞中发挥什么功能。MMD是第一个由毒性RNA引起的疾患。
??在1992年，Mahadevan发现了引起MMD（Ⅰ型）的基因突变。突变是发生在一个叫DMPK基因中出现大量的CTG的重复序列。每一个MMD的患者在19号染色体发生突变，现在也将这作为肌强直性营养不良的遗传诊断指标之一。
??在他们最近的研究中，Mahadevan和他的同僚建立了一种新型的含有额外多个拷贝CTG重复序列的小鼠动物模型，而且每一个结合到DNA的蛋白都能在显微镜下发绿光。他们同时在小鼠身上整合了对于MMD的开关，可以通过在饮水中给予它们强力霉素来激活。
??当小鼠开始产生多拷贝带有CTG的RNA时，在几周内它们就出现很多Ⅰ型MMD的症状，包括不能自由的肌肉放松以及心率失常。当终止强力霉素的给予时，小鼠就停止产生毒性RNA并恢复正常，除了在当心脏受到严重伤害的情况下不能恢复。
??然而，迄今为止Mahadevan和其他科学家都不能准确地解释在细胞内引起某些人患肌强直性肌营养不良。Mahadevan认为：“目前盛行的理论认为RNA是停留在核内，而不是被移出来，蛋白要黏附RNA上，而不能发挥他们的功效”。
??Mahadevan said认为：“在机体的每一个细胞并不能都发现毒性RNA，然而它在肌肉、心脏和大脑细胞中有很高的水平，以及在肠道的褶上、晶状体和眼肌肉细胞内也是如此。
英文原文：
Toxic molecule may cause most common type of muscular dystrophy
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Dr. Mani Mahadevan
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Doctors at the University of Virginia Health System have shown for the first time that getting rid of poisonous RNA (ribonucleic acid) in muscle cells can reverse myotonic dystrophy, the most common type of muscular dystrophy in adults.
About 40,000 people in the United States have myotonic muscular dystrophy (MMD). The disease can cause a slow, progressive wasting of the muscles, irregular heartbeat, cataracts and insulin resistance. Many people don't know they have MMD until their teens or twenties.
To prove the theory that toxic RNA is involved in myotonic muscular dystrophy, a research team led by Dr. Mani Mahadevan, a UVa pathologist, duplicated the disease in mice. "We showed in our mouse model that when you make this poisonous RNA the mice get various aspects of myotonic dystrophy," Mahadevan said. "Then, when you take away the toxic RNA, the mice get back to normal."
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A myotonic mouse muscle with green florescent protein.
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Mahadevan hopes the research might lead to new therapies for MMD in the next few years. "If we develop a therapy to silence the expression of the toxic RNA molecule, that would be a viable approach to treat people with myotonic muscular dystrophy," he said. Mahadevan's research in published in the September 2006 issue of Nature Genetics and can be found online at: http://www.nature.com/ng/index.html
Making RNA is the second step in the conversion of DNA into proteins that determine the function of the body's cells. Myotonic muscular dystrophy is the first example of a disease caused by toxic RNA.
In 1992, Mahadevan discovered the gene mutation that causes myotonic muscular dystrophy (type 1) as part of a research group in Canada. The mutation is an increased number of CTG repeats in a gene called DMPK. Everyone with myotonic muscular dystrophy has that mutation on chromosome 19, which is now part of a genetic, diagnostic test for myotonic dystrophy.
In their latest research, Mahadevan and colleagues created a new type of mouse model with many extra copies of the CTG repeats, each attached to DNA for a protein that glows green under a microscope. They also integrated an "on switch" for MMD in the mice, activated by giving them doxycycline, an antibiotic, in their drinking water.
When mice began to produce many copies of RNA with CTG repeats, they developed the hallmarks of type 1 MMD within a few weeks, including an inability to relax muscles and heart rhythm abnormalities. When doxycycline was stopped, mice stopped producing toxic RNA and returned to normal, except in cases when the heart was severely damaged.
So far, however, Mahadevan and other scientists can't explain exactly what happens inside the cell to cause someone to get myotonic dystrophy. "The prevailing theory is that the RNA remains in the nucleus, rather than moving out of it, and proteins get stuck to the RNA and aren't able to do their job," Mahadevan said.
This toxic RNA in not found in every cell of body, Mahadevan said. Rather, it is produced in higher levels in muscle cells, in the heart and brain, in the lining of the intestines and in the lens and muscles of the eyes.
