文章來源:未知 文章作者:meng 發布時間:2010-03-16 00:28 字體: [ ]  進入論壇

A quest that began over a decade ago with a chance observation has reached a milestone1: the identification of a gene2 that may regulate(調節,規定) regeneration in mammals(哺乳動物) . 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(扁形蟲) , sponges(海綿動物) , and some species of salamander(蠑螈目動物) . 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(兩棲類) . 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(蠑螈) 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(反響,影響) 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(分離,擊倒) mouse to help solve a mystery first encountered in 1996 regarding another mouse strain in her laboratory. MRL(最大殘留限量) mice, which were being tested in an autoimmunity experiment, had holes pierced(穿通,刺過) 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(切爾諾貝利) reactor15 radiation accident, noticed immediately that these cells were atypical(非典型的,不規則的) , 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(情況屬實) . 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(細胞死亡) 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.事實證明這部影片是電影史上的一個里程碑。
  • I think this is a very important milestone in the relations between our two countries.我認為這是我們兩國關系中一個十分重要的里程碑。
2 gene WgKxx     
  • A single gene may have many effects.單一基因可能具有很多種效應。
  • The targeting of gene therapy has been paid close attention.其中基因治療的靶向性是值得密切關注的問題之一。
3 proceedings Wk2zvX     
  • He was released on bail pending committal proceedings. 他交?;袷駝諍蟶?。
  • to initiate legal proceedings against sb 對某人提起訴訟
4 regenerate EU2xV     
  • Their aim is to regenerate British industry.他們的目的是復興英國的工業。
  • Although it is not easy,you have the power to regenerate your life.盡管這不容易,但你有使生活重獲新生的能力。
5 amphibians c4a317a734a700eb6f767bdc511c1588     
兩棲動物( amphibian的名詞復數 ); 水陸兩用車; 水旱兩生植物; 水陸兩用飛行器
  • The skin of amphibians is permeable to water. 兩棲動物的皮膚是透水的。
  • Two amphibians ferry them out over the sands. 兩輛水陸兩用車把他們渡過沙灘。
6 embryonic 58EyK     
  • It is still in an embryonic stage.它還處于萌芽階段。
  • The plan,as yet,only exists in embryonic form.這個計劃迄今為止還只是在醞釀之中。
7 molecular mE9xh     
  • The research will provide direct insight into molecular mechanisms.這項研究將使人能夠直接地了解分子的機理。
  • For the pressure to become zero, molecular bombardment must cease.當壓強趨近于零時,分子的碰撞就停止了。
8 cellular aU1yo     
  • She has a cellular telephone in her car.她的汽車里有一部無線通訊電話機。
  • Many people use cellular materials as sensitive elements in hygrometers.很多人用蜂窩狀的材料作為測量溫度的傳感元件。
9 genes 01914f8eac35d7e14afa065217edd8c0     
n.基因( gene的名詞復數 )
  • You have good genes from your parents, so you should live a long time. 你從父母那兒獲得優良的基因,所以能夠活得很長。 來自《簡明英漢詞典》
  • Differences will help to reveal the functions of the genes. 它們間的差異將會幫助我們揭開基因多種功能。 來自英漢非文學 - 生命科學 - 生物技術的世紀
10 repercussions 4fac33c46ab5414927945f4d05f0769d     
n.后果,反響( repercussion的名詞復數 );余波
  • The collapse of the company will have repercussions for the whole industry. 這家公司的垮臺將會給整個行業造成間接的負面影響。
  • Human acts have repercussions far beyond the frontiers of the human world. 人類行為所產生的影響遠遠超出人類世界的范圍。 來自《簡明英漢詞典》
11 inactivating c42e192a01b90388aabb427adf42df50     
v.使不活潑,阻止活動( inactivate的現在分詞 )
  • By inactivating this gene in mice, it is possible to mimic the TSC syndrome. 這種基因的失活的小鼠,可以模仿臺糖綜合征。 來自互聯網
  • The efficacy of alkaline glutaraldehyde in inactivating poliovirus was higher than that of acidic glutaraldehyde. 堿性戊二醛對脊髓灰質炎病毒的滅活效果比酸性戊二醛強。 來自互聯網
12 investigators e970f9140785518a87fc81641b7c89f7     
n.調查者,審查者( investigator的名詞復數 )
  • This memo could be the smoking gun that investigators have been looking for. 這份備忘錄可能是調查人員一直在尋找的證據。
  • The team consisted of six investigators and two secretaries. 這個團隊由六個調查人員和兩個秘書組成。 來自《簡明英漢詞典》
13 genetic PgIxp     
  • It's very difficult to treat genetic diseases.遺傳性疾病治療起來很困難。
  • Each daughter cell can receive a full complement of the genetic information.每個子細胞可以收到遺傳信息的一個完全補償物。
14 ongoing 6RvzT     
  • The problem is ongoing.這個問題尚未解決。
  • The issues raised in the report relate directly to Age Concern's ongoing work in this area.報告中提出的問題與“關心老人”組織在這方面正在做的工作有直接的關系。
15 reactor jTnxL     
  • The atomic reactor generates enormous amounts of thermal energy.原子反應堆發出大量的熱能。
  • Inside the reactor the large molecules are cracked into smaller molecules.在反應堆里,大分子裂變為小分子。
16 DNA 4u3z1l     
(縮)deoxyribonucleic acid 脫氧核糖核酸
  • DNA is stored in the nucleus of a cell.脫氧核糖核酸儲存于細胞的細胞核里。
  • Gene mutations are alterations in the DNA code.基因突變是指DNA密碼的改變。
17 tumor fKxzm     
  • He was died of a malignant tumor.他死于惡性腫瘤。
  • The surgeons irradiated the tumor.外科醫生用X射線照射那個腫瘤。
18 noted 5n4zXc     
  • The local hotel is noted for its good table.當地的那家酒店以餐食精美而著稱。
  • Jim is noted for arriving late for work.吉姆上班遲到出了名。
19 mechanism zCWxr     
  • The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人體的組成部件。
  • The mechanism of the machine is very complicated.這臺機器的結構是非常復雜的。
20 embryos 0e62a67414ef42288b74539e591aa30a     
n.晶胚;胚,胚胎( embryo的名詞復數 )
  • Somatic cells of angiosperms enter a regenerative phase and behave like embryos. 被子植物體細胞進入一個生殖階段,而且其行為象胚。 來自辭典例句
  • Evolution can explain why human embryos look like gilled fishes. 進化論能夠解釋為什么人類的胚胎看起來象除去了內臟的魚一樣。 來自辭典例句
21 correlation Rogzg     
  • The second group of measurements had a high correlation with the first.第二組測量數據與第一組高度相關。
  • A high correlation exists in America between education and economic position.教育和經濟地位在美國有極密切的關系。