The most important gift your mother and father ever gave you was the two sets of three billion letters of DNA that make up your genome. But like anything with three billion components, that gift is fragile. Sunlight, smoking, unhealthy eating, even spontaneous mistakes made by your cells, all cause changes to your genome. The most common kind of change in DNA is the simple swap of one letter, or base, such as C, with a different letter, such as T, G or A. In any day, the cells in your body will collectively accumulate billions of these single-letter swaps, which are also called "point mutations."
父母親給你的最貴重的禮物, 就是兩組三十億個字母的 DNA, 它們組成了你的基因組。 但,跟所有三十億個元件 組成的東西一樣, 這個禮物也很脆弱。 日曬、抽菸、不健康的飲食, 甚至你細胞自發產生的錯誤 都有可能會改變你的基因組。 最常見的 DNA 改變 就是換掉一個字母,也就是鹼基, 比如把 C 換成一個不同的字母, 比如 T、G,或 A。 每天,你身體中的細胞 全部加起來累積有 數十億次這種單一字母替換, 亦稱為「點突變」。
Now, most of these point mutations are harmless. But every now and then, a point mutation disrupts an important capability in a cell or causes a cell to misbehave in harmful ways. If that mutation were inherited from your parents or occurred early enough in your development, then the result would be that many or all of your cells contain this harmful mutation. And then you would be one of hundreds of millions of people with a genetic disease, such as sickle cell anemia or progeria or muscular dystrophy or Tay-Sachs disease.
大部分的點突變無害。 但有時候 點突變會干擾細胞裡的 某個重要功能, 或是導致傷害性的細胞失常行為。 如果那個突變遺傳自你的父母親, 或是在你年幼時就發生了, 那麼,造成的結果就是 你很多或所有的細胞 都含有這種有害的突變。 那麼你就得到機率只有數億分之一的 基因(突變)型疾病, 比如鐮刀型紅血球疾病或是早衰症, 或是肌肉萎縮症, 或精神性痴呆症。
Grievous genetic diseases caused by point mutations are especially frustrating, because we often know the exact single-letter change that causes the disease and, in theory, could cure the disease. Millions suffer from sickle cell anemia because they have a single A to T point mutations in both copies of their hemoglobin gene. And children with progeria are born with a T at a single position in their genome where you have a C, with the devastating consequence that these wonderful, bright kids age very rapidly and pass away by about age 14. Throughout the history of medicine, we have not had a way to efficiently correct point mutations in living systems, to change that disease-causing T back into a C. Perhaps until now. Because my laboratory recently succeeded in developing such a capability, which we call "base editing."
由點突變所造成的 令人痛苦的基因型疾病 特別令人挫折, 因為我們通常確知 是哪一個字母的改變 造成這種理論上可以治癒疾病。 數百萬人飽受 鐮刀型紅血球疾病之苦, 因為他們血紅素基因的兩個複本 都有一個 A 換成 T 的突變。 早衰症的兒童則是在出生時 基因組中的某個單一位置有個 T, 但那裡本來應該是 C, 產生的結果會有很大的影響, 這些美好、聰明的孩子, 會以非常快的速度老化, 大約在十四歲時就會過世。 在醫學史上, 我們還沒有方法 可以在活體上有效地校正點突變, 將造成疾病的 T 改回原本的 C。 也許現在有辦法了。 因為我的實驗室最近 成功開發了這種能力, 我們稱之為「鹼基編輯」。
The story of how we developed base editing actually begins three billion years ago. We think of bacteria as sources of infection, but bacteria themselves are also prone to being infected, in particular, by viruses. So about three billion years ago, bacteria evolved a defense mechanism to fight viral infection. That defense mechanism is now better known as CRISPR. And the warhead in CRISPR is this purple protein that acts like molecular scissors to cut DNA, breaking the double helix into two pieces. If CRISPR couldn't distinguish between bacterial and viral DNA, it wouldn't be a very useful defense system.
關於我們如何開發出 鹼基編輯的故事, 其實始於三十億年前。 我們認為細菌是感染的源頭, 但細菌本身也有可能會受到感染, 特別是會被病毒感染。 所以,大約三十億年前, 細菌演化出一種防禦機制 來對抗病毒感染。 這就是如今較為熟知的 CRISPR 防禦機制。 CRISPR 中的導彈頭, 就是這個紫色的蛋白質, 它就像是分子剪刀, 可以剪斷 DNA, 把雙股螺旋斷成兩半。 如果 CRISPR 無法區別出 細菌和病毒 DNA 的不同, 它就不會是個很有用的防禦系統。
But the most amazing feature of CRISPR is that the scissors can be programmed to search for, bind to and cut only a specific DNA sequence. So when a bacterium encounters a virus for the first time, it can store a small snippet of that virus's DNA for use as a program to direct the CRISPR scissors to cut that viral DNA sequence during a future infection. Cutting a virus's DNA messes up the function of the cut viral gene, and therefore disrupts the virus's life cycle.
但 CRISPR 最驚人的特色是 它的剪刀可以透過編程只去搜尋、 結合和剪斷 特定的 DNA 序列。 所以,當細菌初次遇到病毒時, 它能夠儲存病毒的一小段 DNA, 當成引導 CRISPR 剪刀的程式, 在將來被感染時,能夠剪斷 該病毒的 DNA 序列。 剪斷病毒的 DNA, 會打亂它的基因功能, 進而干擾該病毒的生命週期。
Remarkable researchers including Emmanuelle Charpentier, George Church, Jennifer Doudna and Feng Zhang showed six years ago how CRISPR scissors could be programmed to cut DNA sequences of our choosing, including sequences in your genome, instead of the viral DNA sequences chosen by bacteria. But the outcomes are actually similar. Cutting a DNA sequence in your genome also disrupts the function of the cut gene, typically, by causing the insertion and deletion of random mixtures of DNA letters at the cut site.
出色的研究者,包括埃馬紐埃爾 卡彭蒂耶、喬治丘奇、 詹妮弗杜德納,及張鋒, 六年前就示範過如何 透過編程讓 CRISPR 剪刀 剪斷我們選定的 DNA 序列, 包括在你的基因組中的序列, 將細菌所選擇的 病毒 DNA 序列取代掉。 但,後果其實蠻相似的。 剪斷你基因組中的 DNA 序列 通常也會干擾被剪斷的基因的功能, 就在我們剪斷點上插入和刪除 隨機混合的 DNA 字母時發生。
Now, disrupting genes can be very useful for some applications. But for most point mutations that cause genetic diseases, simply cutting the already-mutated gene won't benefit patients, because the function of the mutated gene needs to be restored, not further disrupted. So cutting this already-mutated hemoglobin gene that causes sickle cell anemia won't restore the ability of patients to make healthy red blood cells. And while we can sometimes introduce new DNA sequences into cells to replace the DNA sequences surrounding a cut site, that process, unfortunately, doesn't work in most types of cells, and the disrupted gene outcomes still predominate.
干擾基因在某些應用上非常有用。 但,對於大部分會造成 基因型疾病的點突變, 單單只剪斷已經突變的基因, 對病人並沒有益處, 因為突變基因的功能 必須要被恢復, 而不是被進一步干擾。 所以,剪斷這個已經突變 且造成鐮刀型 紅血球疾病的血紅素基因, 並不能夠恢復病人 製造健康紅血球的能力。 雖然我們可以將新的 DNA 序列放入細胞中, 取代剪斷點周圍的 DNA 序列, 但不幸的是,這個過程 在大部分類型的細胞中行不通, 被干擾的基因仍主宰病患。
Like many scientists, I've dreamed of a future in which we might be able to treat or maybe even cure human genetic diseases. But I saw the lack of a way to fix point mutations, which cause most human genetic diseases, as a major problem standing in the way.
和許多科學家一樣, 我也夢想在未來 我們可以治療或甚至治癒 人類的基因型疾病。 但我沒發現解決點突變問題的方法, 點突變正是大部分 人類基因型疾病的成因, 是檔在我們前面的大問題。
Being a chemist, I began working with my students to develop ways on performing chemistry directly on an individual DNA base, to truly fix, rather than disrupt, the mutations that cause genetic diseases. The results of our efforts are molecular machines called "base editors." Base editors use the programmable searching mechanism of CRISPR scissors, but instead of cutting the DNA, they directly convert one base to another base without disrupting the rest of the gene. So if you think of naturally occurring CRISPR proteins as molecular scissors, you can think of base editors as pencils, capable of directly rewriting one DNA letter into another by actually rearranging the atoms of one DNA base to instead become a different base.
身為化學家,我開始 和我的學生合作, 開發新方法,直接對 個別 DNA 鹼基進行化學反應, 不是干擾,而是真正修復 導致遺傳疾病的突變。 經過努力,我們開發出了分子機器, 叫做「鹼基編輯器」。 鹼基編輯器用 CRISPR 剪刀的 可編程搜尋機制, 但不是用來剪斷 DNA, 而是直接將一個鹼基 轉換成另一個鹼基, 不干擾到基因的其它部位。 所以,如果你把渾然天成的 CRISPR 蛋白質視為分子剪刀, 那麼你可以把鹼基編輯器視為鉛筆, 能夠直接改寫 DNA 字母, 做法是重新安排一個 DNA 鹼基的原子, 讓它成為另一個不同的鹼基。
Now, base editors don't exist in nature. In fact, we engineered the first base editor, shown here, from three separate proteins that don't even come from the same organism. We started by taking CRISPR scissors and disabling the ability to cut DNA while retaining its ability to search for and bind a target DNA sequence in a programmed manner. To those disabled CRISPR scissors, shown in blue, we attached a second protein in red, which performs a chemical reaction on the DNA base C, converting it into a base that behaves like T. Third, we had to attach to the first two proteins the protein shown in purple, which protects the edited base from being removed by the cell. The net result is an engineered three-part protein that for the first time allows us to convert Cs into Ts at specified locations in the genome.
大自然中沒有鹼基編輯器。 事實上,我們設計了人類第一個 鹼基編輯器,在這裡可以看到, 我們用了三個不同的蛋白質, 它們甚至可以不用是 來自同一個有機體。 我們先從 CRISPR 剪刀著手, 讓它失去剪斷 DNA 的能力, 保持其以編程方式 搜尋和結合目標 DNA 序列的能力。 藍色標示的是失去 能力的 CRISPR 剪刀, 我們黏上第二種 蛋白質,用紅色標示, 它會在 DNA 鹼基 C 上面 發生化學反應, 將它轉換成一個 行為類似 T 的鹼基。 第三,在之前的兩個蛋白質上, 我們還要再加上 用紫色標示的蛋白質, 它能夠保護被編輯過的鹼基 不會被細胞給移除。 最後就會產生一個 人造的三部件融合蛋白質, 這是人類第一次製作出 可以在基因組中的特定位置 將 C 轉換成 T 的蛋白質。
But even at this point, our work was only half done. Because in order to be stable in cells, the two strands of a DNA double helix have to form base pairs. And because C only pairs with G, and T only pairs with A, simply changing a C to a T on one DNA strand creates a mismatch, a disagreement between the two DNA strands that the cell has to resolve by deciding which strand to replace. We realized that we could further engineer this three-part protein to flag the nonedited strand as the one to be replaced by nicking that strand. This little nick tricks the cell into replacing the nonedited G with an A as it remakes the nicked strand, thereby completing the conversion of what used to be a C-G base pair into a stable T-A base pair.
但,即使做到這樣, 我們的工作也才完成一半。 為要在細胞中達到穩定, DNA 雙股螺旋的兩股 必須要形成鹼基對。 因為 C 只能和 G 配對, 且 T 只能和 A 配對, 若只把 DNA 上的 C 改成 T, 會造成無法配對的狀況, 當 DNA 的兩股之間產生衝突, 細胞為了解決問題 必須選擇一股來替換。 我們發現可以進一步 將這個三部件融合蛋白質再改造, 將未被編輯的那一股 標記為要被取代的目標, 只要在那一股上刻記即可。 這個小小刻記便能騙過細胞, 細胞便會在重製被刻記的那一股時, 用 A 來取代未被編輯的 G, 這樣就能完成轉換, 將原本的 C-G 配對 轉換為穩定的 T-A 配對。
After several years of hard work led by a former post doc in the lab, Alexis Komor, we succeeded in developing this first class of base editor, which converts Cs into Ts and Gs into As at targeted positions of our choosing. Among the more than 35,000 known disease-associated point mutations, the two kinds of mutations that this first base editor can reverse collectively account for about 14 percent or 5,000 or so pathogenic point mutations. But correcting the largest fraction of disease-causing point mutations would require developing a second class of base editor, one that could convert As into Gs or Ts into Cs. Led by Nicole Gaudelli, a former post doc in the lab, we set out to develop this second class of base editor, which, in theory, could correct up to almost half of pathogenic point mutations, including that mutation that causes the rapid-aging disease progeria.
由博士後研究員 艾莉西斯•柯摩爾領軍, 在實驗室努力多年後, 我們成功開發出了 第一類鹼基編輯器, 它能在我們標靶的位置上, 將 C 轉換為 T, 將 G 轉換為 A。 在已知的三萬五千種 和疾病相關的點突變中, 第一鹼基編輯器可以 逆轉其中兩類突變, 這兩類加總起來就佔了五千種 (14%)點突變疾病。 但若要校正最大部分 造成疾病的點突變, 需要開發第二類鹼基編輯器, 它能將 A 轉換為 G, 將 T 轉換為 C。 由博士後研究員妮可•嘉德利領軍, 我們在實驗室裡 準備開發第二類鹼基編輯器, 理論上,幾乎可以校正 一半以上的點突變疾病。 包括會造成快速老化的早衰症突變。
We realized that we could borrow, once again, the targeting mechanism of CRISPR scissors to bring the new base editor to the right site in a genome. But we quickly encountered an incredible problem; namely, there is no protein that's known to convert A into G or T into C in DNA. Faced with such a serious stumbling block, most students would probably look for another project, if not another research advisor. (Laughter) But Nicole agreed to proceed with a plan that seemed wildly ambitious at the time. Given the absence of a naturally occurring protein that performs the necessary chemistry, we decided we would evolve our own protein in the laboratory to convert A into a base that behaves like G, starting from a protein that performs related chemistry on RNA. We set up a Darwinian survival-of-the-fittest selection system that explored tens of millions of protein variants and only allowed those rare variants that could perform the necessary chemistry to survive. We ended up with a protein shown here, the first that can convert A in DNA into a base that resembles G. And when we attached that protein to the disabled CRISPR scissors, shown in blue, we produced the second base editor, which converts As into Gs, and then uses the same strand-nicking strategy that we used in the first base editor to trick the cell into replacing the nonedited T with a C as it remakes that nicked strand, thereby completing the conversion of an A-T base pair to a G-C base pair.
我們知道可以再次藉助 CRISPR 剪刀的定位機制, 把新的鹼基編輯器 定位到基因組的特定位置。 但我們很快就會遇到一個大問題; 換句話說,在 DNA 裡 沒有已知的蛋白質可以把 A 轉變成 G 或 T 轉變成 C 。 面對這麼大的障礙, 大部分學生不是另找專題 就是另找指導教授。 (笑聲) 但妮可同意繼續這個 當時看起來相當瘋狂的研究計畫。 由於沒有這個渾然天成的蛋白質 來完成必要的化學反應, 我們決定在實驗室自己設計出 能把 A 轉換成 有 G 行為表現的蛋白質 , 我們從 RNA 上尋找有相關 類似化學表現的蛋白質著手。 我們建立了一個 達爾文適者生存的選擇系統, 它可以從好幾千萬個變體蛋白質中 篩選出稀有的變體, 只讓呈現必要化學反應的 蛋白質存活下來。 我們最後找到了這個蛋白質, 第一個在 DNA 裡可以把 A 轉變成 G 的蛋白質。 當我們把蛋白質黏到 失去剪刀效力的 CRISPR 上, 用藍色顯示, 就可以做出第二鹼基編輯器, 它可以把 A 轉變成 G。 然後利用相同的「股刻記」策略, 也就是我們在第一鹼基編輯器上 運用的策略, 可以在重製刻記股時騙過細胞, 讓還沒編輯過的 T 變成 C。 如此就完成了 AT 鹼基 轉換成 GC 鹼基的過程。
(Applause)
(掌聲)
Thank you.
謝謝。
(Applause)
(掌聲)
As an academic scientist in the US, I'm not used to being interrupted by applause.
身為一位美國的學術科學家, 我還真不習慣講到一半 被掌聲中斷。
(Laughter)
(笑聲)
We developed these first two classes of base editors only three years ago and one and a half years ago. But even in that short time, base editing has become widely used by the biomedical research community. Base editors have been sent more than 6,000 times at the request of more than 1,000 researchers around the globe. A hundred scientific research papers have been published already, using base editors in organisms ranging from bacteria to plants to mice to primates.
我們開發出這兩個類型的 鹼基編輯器, 一個是在三年前, 另一個在一年半之前。 雖然問世的時間不長, 鹼基編輯已經在生化研究領域 被廣泛運用了。 我們的鹼基編輯器 應全球一千多位研究人員的索取, 已經送出了六千多組。 有好幾百篇在有機體裡 運用鹼基編輯器的 相關科學研究論文 已經陸陸續續發佈了, 範圍從細菌到植物, 老鼠到靈長類動物都有。
While base editors are too new to have already entered human clinical trials, scientists have succeeded in achieving a critical milestone towards that goal by using base editors in animals to correct point mutations that cause human genetic diseases. For example, a collaborative team of scientists led by Luke Koblan and Jon Levy, two additional students in my lab, recently used a virus to deliver that second base editor into a mouse with progeria, changing that disease-causing T back into a C and reversing its consequences at the DNA, RNA and protein levels.
因為鹼基編輯器的技術還很新, 目前無法運用在人類的臨床實驗, 但科學家已經在動物身上, 成功地完成了相當重要的目標, 已經把人類基因型疾病的 點突變校正回來。 例如, 由盧克•寇蘭及瓊•拉維領軍, 與我實驗室的兩位學生 組成科研團隊,共同參與合作, 最近利用一個病毒 將第二鹼基編輯器 送進患有早衰症的老鼠身上, 成功地將肇病的 T 轉換回 C, 並把牠的序列逆轉回 DNA、RNA和蛋白質狀態。
Base editors have also been used in animals to reverse the consequence of tyrosinemia, beta thalassemia, muscular dystrophy, phenylketonuria, a congenital deafness and a type of cardiovascular disease -- in each case, by directly correcting a point mutation that causes or contributes to the disease. In plants, base editors have been used to introduce individual single DNA letter changes that could lead to better crops.
鹼基編輯器也已被用在動物身上, 它可以逆轉酪胺酸血症、 乙型地中海貧血症、肌肉萎縮症、 苯丙酮尿症、先天性耳聾、 還有心血管疾病的序列。 每一個案例,都能直接校正 肇病的點突變。 鹼基編輯器也被運用在植物上, 藉由改變個別的 DNA 字母 可以生產出更好的農產品。
And biologists have used base editors to probe the role of individual letters in genes associated with diseases such as cancer. Two companies I cofounded, Beam Therapeutics and Pairwise Plants, are using base editing to treat human genetic diseases and to improve agriculture. All of these applications of base editing have taken place in less than the past three years: on the historical timescale of science, the blink of an eye.
生物學家也已經利用鹼基編輯器 探測出基因裡個別字母所扮演的角色, 例如癌症疾病基因。 兩家我共同創立的公司: Beam Therapeutics 和 Pairwise Plants, 正在運用鹼基編輯技術 治療人類的基因型疾病 及改善農業。 這些鹼基編輯的應用 發生在過去不到三年的時間裡: 在科學歷史的時間尺度上 僅僅是眨眼之間。
Additional work lies ahead before base editing can realize its full potential to improve the lives of patients with genetic diseases. While many of these diseases are thought to be treatable by correcting the underlying mutation in even a modest fraction of cells in an organ, delivering molecular machines like base editors into cells in a human being can be challenging. Co-opting nature's viruses to deliver base editors instead of the molecules that give you a cold is one of several promising delivery strategies that's been successfully used. Continuing to develop new molecular machines that can make all of the remaining ways to convert one base pair to another base pair and that minimize unwanted editing at off-target locations in cells is very important. And engaging with other scientists, doctors, ethicists and governments to maximize the likelihood that base editing is applied thoughtfully, safely and ethically, remains a critical obligation.
在全盤了解鹼基編輯器的潛力前, 眼前還要再努力的工作就是 改善基因型疾病病人的生活。 雖然這些疾病被認為 可由校正潛在的突變來治療, 但即使只是在器官裡一小部分細胞, 傳送鹼基編輯器這類的分子機器 到人類的細胞裡面, 仍充滿著挑戰。 利用會讓你感冒的自然界病毒, 把鹼基編輯器傳送到細胞的方式, 是其中一個還不錯的傳送策略, 這個策略已經被成功運用。 持續開發新的分子機器, 找出剩餘還沒辦法轉換的鹼基, 盡可能不去編輯不在靶區的細胞 至關重要。 而其他科學家、醫生、 倫理學家、政府的參與也很重要, 大家一起深思熟慮看看要如何 最大化、安全地、符合倫理地 應用鹼基編輯技術, 是我們的重責大任。
These challenges notwithstanding, if you had told me even just five years ago that researchers around the globe would be using laboratory-evolved molecular machines to directly convert an individual base pair to another base pair at a specified location in the human genome efficiently and with a minimum of other outcomes, I would have asked you, "What science-fiction novel are you reading?" Thanks to a relentlessly dedicated group of students who were creative enough to engineer what we could design ourselves and brave enough to evolve what we couldn't, base editing has begun to transform that science-fiction-like aspiration into an exciting new reality, one in which the most important gift we give our children may not only be three billion letters of DNA, but also the means to protect and repair them.
雖然這些挑戰仍在, 但如果你在五年前問我, 全球的研究人員, 正在利用實驗室 設計出來的分子機器, 直接把單一鹼基對還原成 另一鹼基對, 而且是在人類基因組裡的特定位置上 有效地且最小化發生其它結果地 執行還原。 我可能會問: 「你在看哪一本科幻小說?」 感謝這群全力付出、 勤奮努力的學生們, 他們的創意讓我們可以 透過基因工程設計我們自己。 並勇敢地設計出 我們所辦不到的事, 鹼基編輯已經開始從 科幻小說裡渴望的夢想 轉變成振奮人心的真實技術, 或許我們給後代的最重要禮物, 除了三十億個字母 DNA, 還有保護及修護它們的方法。
Thank you.
謝謝。
(Applause)
(掌聲)
Thank you.
謝謝。