文章来源:未知 文章作者:meng 发布时间:2010-03-16 00:28 字体: [ ]  进入论坛

A quest that began over a decade ago with a chance observation has reached a milestone1: the identification of a gene2 that may regulate(调节,规定) regeneration in mammals(哺乳动物) . The absence of this single gene, called p21, confers a healing potential in mice long thought to have been lost through evolution and reserved for creatures like flatworms(扁形虫) , sponges(海绵动物) , and some species of salamander(蝾螈目动物) . In a report published today in the Proceedings3 of the National Academy of Sciences, researchers from The Wistar Institute demonstrate that mice that lack the p21 gene gain the ability to regenerate4 lost or damaged tissue. Unlike typical mammals, which heal wounds by forming a scar, these mice begin by forming a blastema(胚芽) , a structure associated with rapid cell growth and de-differentiation as seen in amphibians5(两栖类) . According to the Wistar researchers, the loss of p21 causes the cells of these mice to behave more like embryonic6 stem cells than adult mammalian cells, and their findings provide solid evidence to link tissue regeneration to the control of cell division.

"Much like a newt(蝾螈) that has lost a limb, these mice will replace missing or damaged tissue with healthy tissue that lacks any sign of scarring," said the project's lead scientist Ellen Heber-Katz, Ph.D., a professor in Wistar's Molecular7 and Cellular8 Oncogenesis program. "While we are just beginning to understand the repercussions10(反响,影响) of these findings, perhaps, one day we'll be able to accelerate healing in humans by temporarily inactivating11 the p21 gene."

Heber-Katz and her colleagues used a p21 knockout(分离,击倒) mouse to help solve a mystery first encountered in 1996 regarding another mouse strain in her laboratory. MRL(最大残留限量) mice, which were being tested in an autoimmunity experiment, had holes pierced(穿通,刺过) in their ears to create a commonly used life-long identification marker. A few weeks later, investigators12 discovered that the earholes had closed without a trace. While the experiment was ruined, it left the researchers with a new question: Was the MRL mouse a window into mammalian regeneration?

The discovery set the Heber-Katz laboratory off on two parallel paths. Working with geneticists Elizabeth Blankenhorn, Ph.D., at Drexel University, and James Cheverud, Ph.D., at Washington University, the laboratory focused on mapping the critical genes9 that turn MRL mice into healers. Meanwhile, cellular studies ongoing14 at Wistar revealed that MRL cells behaved very differently than cells from "non-healer" mouse strains in culture. Khamilia Bedebaeva, M.D., Ph.D., having studied genetic13 effects following the Chernobyl(切尔诺贝利) reactor15 radiation accident, noticed immediately that these cells were atypical(非典型的,不规则的) , showing profound differences in cell cycle characteristics and DNA16 damage. This led Andrew Snyder, Ph.D., to explore the DNA damage pathway and its effects on cell cycle control.

Snyder found that p21, a cell cycle regulator, was consistently inactive in cells from the MRL mouse ear. P21 expression is tightly controlled by the tumor17 suppressor(抑制基因) p53, another regulator of cell division and a known factor in many forms of cancer. The ultimate experiment was to show that a mouse lacking p21 would demonstrate a regenerative response similar to that seen in the MRL mouse. And this indeed was the case(情况属实) . As it turned out, p21 knockout mice had already been created, were readily available, and widely used in many studies. What had not been noted18 was that these mice could heal their ears.

"In normal cells, p21 acts like a brake to block cell cycle progression in the event of DNA damage, preventing the cells from dividing and potentially becoming cancerous," Heber-Katz said. "In these mice without p21, we do see the expected increase in DNA damage, but surprisingly no increase in cancer has been reported."

In fact, the researchers saw an increase in apoptosis(细胞死亡) in MRL mice – also known as programmed cell death – the cell's self-destruct mechanism19 that is often switched on when DNA has been damaged. According to Heber-Katz, this is exactly the sort of behavior seen in naturally regenerative creatures.

"The combined effects of an increase in highly regenerative cells and apoptosis may allow the cells of these organisms to divide rapidly without going out of control and becoming cancerous," Heber-Katz said. "In fact, it is similar to what is seen in mammalian embryos20, where p21 also happens to be inactive after DNA damage. The down regulation of p21 promotes the induced pluripotent(多能的) state in mammalian cells, highlighting a correlation21 between stem cells, tissue regeneration, and the cell cycle."


1 milestone c78zM     
  • The film proved to be a milestone in the history of cinema.事实证明这部影片是电影史上的一个里程碑。
  • I think this is a very important milestone in the relations between our two countries.我认为这是我们两国关系中一个十分重要的里程碑。
2 gene WgKxx     
  • A single gene may have many effects.单一基因可能具有很多种效应。
  • The targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。
3 proceedings Wk2zvX     
  • He was released on bail pending committal proceedings. 他交保获释正在候审。
  • to initiate legal proceedings against sb 对某人提起诉讼
4 regenerate EU2xV     
  • Their aim is to regenerate British industry.他们的目的是复兴英国的工业。
  • Although it is not easy,you have the power to regenerate your life.尽管这不容易,但你有使生活重获新生的能力。
5 amphibians c4a317a734a700eb6f767bdc511c1588     
两栖动物( amphibian的名词复数 ); 水陆两用车; 水旱两生植物; 水陆两用飞行器
  • The skin of amphibians is permeable to water. 两栖动物的皮肤是透水的。
  • Two amphibians ferry them out over the sands. 两辆水陆两用车把他们渡过沙滩。
6 embryonic 58EyK     
  • It is still in an embryonic stage.它还处于萌芽阶段。
  • The plan,as yet,only exists in embryonic form.这个计划迄今为止还只是在酝酿之中。
7 molecular mE9xh     
  • The research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。
  • For the pressure to become zero, molecular bombardment must cease.当压强趋近于零时,分子的碰撞就停止了。
8 cellular aU1yo     
  • She has a cellular telephone in her car.她的汽车里有一部无线通讯电话机。
  • Many people use cellular materials as sensitive elements in hygrometers.很多人用蜂窝状的材料作为测量温度的传感元件。
9 genes 01914f8eac35d7e14afa065217edd8c0     
n.基因( gene的名词复数 )
  • You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因,所以能够活得很长。 来自《简明英汉词典》
  • Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪
10 repercussions 4fac33c46ab5414927945f4d05f0769d     
n.后果,反响( repercussion的名词复数 );余波
  • The collapse of the company will have repercussions for the whole industry. 这家公司的垮台将会给整个行业造成间接的负面影响。
  • Human acts have repercussions far beyond the frontiers of the human world. 人类行为所产生的影响远远超出人类世界的范围。 来自《简明英汉词典》
11 inactivating c42e192a01b90388aabb427adf42df50     
v.使不活泼,阻止活动( inactivate的现在分词 )
  • By inactivating this gene in mice, it is possible to mimic the TSC syndrome. 这种基因的失活的小鼠,可以模仿台糖综合征。 来自互联网
  • The efficacy of alkaline glutaraldehyde in inactivating poliovirus was higher than that of acidic glutaraldehyde. 碱性戊二醛对脊髓灰质炎病毒的灭活效果比酸性戊二醛强。 来自互联网
12 investigators e970f9140785518a87fc81641b7c89f7     
n.调查者,审查者( investigator的名词复数 )
  • This memo could be the smoking gun that investigators have been looking for. 这份备忘录可能是调查人员一直在寻找的证据。
  • The team consisted of six investigators and two secretaries. 这个团队由六个调查人员和两个秘书组成。 来自《简明英汉词典》
13 genetic PgIxp     
  • It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
  • Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。
14 ongoing 6RvzT     
  • The problem is ongoing.这个问题尚未解决。
  • The issues raised in the report relate directly to Age Concern's ongoing work in this area.报告中提出的问题与“关心老人”组织在这方面正在做的工作有直接的关系。
15 reactor jTnxL     
  • The atomic reactor generates enormous amounts of thermal energy.原子反应堆发出大量的热能。
  • Inside the reactor the large molecules are cracked into smaller molecules.在反应堆里,大分子裂变为小分子。
16 DNA 4u3z1l     
(缩)deoxyribonucleic acid 脱氧核糖核酸
  • DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。
  • Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。
17 tumor fKxzm     
  • He was died of a malignant tumor.他死于恶性肿瘤。
  • The surgeons irradiated the tumor.外科医生用X射线照射那个肿瘤。
18 noted 5n4zXc     
  • The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
  • Jim is noted for arriving late for work.吉姆上班迟到出了名。
19 mechanism zCWxr     
  • The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
  • The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。
20 embryos 0e62a67414ef42288b74539e591aa30a     
n.晶胚;胚,胚胎( embryo的名词复数 )
  • Somatic cells of angiosperms enter a regenerative phase and behave like embryos. 被子植物体细胞进入一个生殖阶段,而且其行为象胚。 来自辞典例句
  • Evolution can explain why human embryos look like gilled fishes. 进化论能够解释为什么人类的胚胎看起来象除去了内脏的鱼一样。 来自辞典例句
21 correlation Rogzg     
  • The second group of measurements had a high correlation with the first.第二组测量数据与第一组高度相关。
  • A high correlation exists in America between education and economic position.教育和经济地位在美国有极密切的关系。