我們離轉基因人類有多遠?

BERKELEY, Calif. — AN advisory committee of the Food and Drug Administration is set to begin two days of meetings tomorrow to consider radical biological procedures that, if successful, would produce genetically modified human beings. This is a dangerous step. These techniques would change every cell in the bodies of children born as a result of their use, and these alterations would be passed down to future generations.

加利福尼亞州伯克利——食品與藥品管理局（Food and Drug Administration，簡稱FDA）的一個顧問委員會定於明天開始一個爲期兩天的會議，對一種全新的生物手段加以考量，這種手段一旦成功，將產生經過基因修改的人類。這是危險的一步。這些技術將改變一個新生兒全身上下的每一個細胞，其後代也將繼承這些改變。

The F.D.A. calls them mitochondrial manipulation technologies. The procedures involve removing the nuclear material either from the egg or embryo of a woman with inheritable mitochondrial disease and inserting it into a healthy egg or embryo of a donor whose own nuclear material has been discarded. Any offspring would carry genetic material from three people — the nuclear DNA of the mother and father, and the mitochondrial DNA of the donor.

FDA稱之爲線粒體操作技術。相關的步驟涉及將患有遺傳性線粒體疾病的女性的卵子或胚胎的核質取出，嵌入到捐贈者的健康卵子或胚胎中，捐贈者本身的核質已經丟棄。所有子女都將攜帶三個人的基因物質，分別是父親和母親的核DNA以及捐贈者的線粒體DNA。

Roughly 1,000 to 4,000 children born in the United States each year will develop a mitochondrial disease, most by age 10, with symptoms that can range from mild to devastating. These diseases typically prevent mitochondria from converting food into energy and are the result of genetic abnormalities, although some cases can be caused by exposures to toxins. Disorders caused by mutations in the mitochondrial DNA are passed down from the mother.

美國每年有1000到4000名新生兒患有線粒體疾病，大多數在10歲以前發病，症狀有的輕微，有的極爲嚴重。這類疾病通常會阻止線粒體將食物轉化爲能量，是基因異常的結果，不過某些情況下也可能因接觸毒素導致。線粒體DNA變異導致的障礙症會通過母親傳給下一代。

Developers of these modification techniques say they are a way for women with mitochondrial disease to give birth to healthy children to whom they are related genetically. Some are also promoting their use for age-related infertility. These are worthy goals. But these procedures are deeply problematic in terms of their medical risks and societal implications. Will the child be born healthy, or will the cellular disruptions created by this eggs-as-Lego-pieces approach lead to problems later on? What about subsequent generations? And how far will we go in our efforts to engineer humans?

基因修改技術的開發人員稱，使用這種技術可以讓患有線粒體疾病的女性生下健康的孩子，同時與孩子還有基因關聯。另外一些人強調這種技術可用於與年齡相關的不孕不育。這些都是有價值的目標。但是這些手段在醫療風險和社會意義方面有着深層次的問題。生下的孩子是不是健康，或者，這種拿細胞當樂高積木的方法產生的細胞干擾是否會導致日後的問題？後代又會如何？我們在人類轉基因上將要走多遠？

These sorts of concerns were first voiced decades ago, well before the human genome had even been "mapped." Those were the days when our accelerating knowledge about genetics led to over-optimistic hopes for quick fixes to an array of afflictions and grandiose visions of designing genetically enhanced babies to be more intelligent, athletic, musically talented and the like.

這些都是幾十年前就已經提出的擔憂，而那時連對人類基因組的“繪圖”都遠未開始。在那個年代，遺傳學的迅速發展令我們產生了過分樂觀的希望，認爲它可以幫我們找到治療諸多疾病的捷徑，並描畫出經過基因改善的嬰兒的宏偉設計藍圖，希望通過改進把孩子變得更聰明，在運動和音樂等方面更具天賦。

More recently, many scholars, scientists and policy makers have urged a different approach: We should carefully and thoughtfully apply the tools of human genetic engineering to treat medical conditions in people, but we should not use them to manipulate the genetic traits of future children. Genetic modifications of sperm, eggs and early embryos should be strictly off limits. Otherwise, we risk venturing into human experimentation and high-tech eugenics.

而近些年來，許多學者、科學家和政策制定者開始呼籲選擇另一種路線：我們應該小心而周密地去運用人類基因手段治療疾病，但我們不應該用這些手段去操控未來孩子的基因性狀。精子、卵子和早期胚胎的基因修改應該受到嚴格限制，否則我們就可能陷入人類實驗和高科技優生學的危險境地。

Unfortunately, there are now worrisome signs that opposition to inheritable genetic modifications, written into law by dozens of countries, according to our count, may be weakening. British regulators are also considering mitochondrial manipulations, and proponents there, like their counterparts in the United States, want to move quickly to clinical trials.

不幸的是，目前出現了一些令人擔憂的跡象，根據我們的統計，對遺傳性基因修改的牴觸正在減弱——這種修改在許多國家是被法律禁止的。英國監管機構也在考慮線粒體操控技術，那裏的倡導者跟在美國的同道一樣，希望儘快展開臨牀試驗。

Researchers at Oregon Health and Science University have produced five macaque monkeys using one of these techniques. Four are now adults and all five appear healthy. But we won't know for years how subsequent generations may be affected.

俄勒岡健康與科學大學(Oregon Health and Science University)的研究人員使用其中一項技術培養了五隻獼猴。五隻猴子目前看來都是健康的，其中四隻已經成年。但我們要再等幾年才能知道後代會受到什麼影響。

And the O.H.S.U. researchers themselves report a difference between their experience with the macaques and their work so far on fertilized human eggs. More than half of the human zygotes — single cells formed by the merging of an egg and sperm — had abnormalities not observed in the fertilized eggs of the monkeys. "It looks like human oocytes are more sensitive," the lead researcher, Shoukhrat Mitalipov, a reproductive biologist, told Nature.

該大學的研究人員自己也在報告中提到，這次獼猴實驗和他們迄今用受過精的人類卵子進行的研究是有差異的。超過一半的人類受精卵——卵子和精子結合形成的單個細胞——出現了在猴子受精卵中沒有觀察到的異常。“看起來人類的卵細胞更敏感，”生殖生物學家、本次研究的首席研究員舒哈拉特·米塔利波夫(Shoukhrat Mitalipov)對《自然》(Nature)雜誌說。

Some media accounts about these techniques have misleadingly referred to "saving lives," as if they were aimed at people who are sick and suffering. Others have failed to note how very few women would be candidates for even considering them. And they could turn to safer and simpler alternatives. An affected woman could adopt or use in vitro fertilization with another woman's eggs. Of course, the resulting child would not be genetically related to her, but neither would the child be put at grave risk by an extreme procedure.

部分媒體在報道中誤導性地稱之爲“救命的”技術，彷彿它們面向的是受病痛困擾的人。還有一些報道沒能明確一點，要去考慮使用這些技術的女性少之又少。她們有更安全、更簡單的方案可選。患病的女性可以選擇領養，或使用另一名女性的卵子進行體外受精。當然，這樣一來她和孩子將不存在基因上的關聯，但同時也讓孩子免於承擔極端手段帶來的可怕風險。

The F.D.A. advisory panel says that its meeting will consider only scientific aspects of mitochondrial manipulation and that any "ethical and social policy issues" are outside its scope. But those are precisely the issues that we must address. Simply being able to do something doesn't mean we should do it.

FDA顧問專家組稱，此次會議對線粒體操作的思考將僅限於科學層面，任何“倫理和社會政策問題”都不在關注範疇內。然而我們需要面對的恰恰就是這些問題。具備做某件事的能力並不等於我們就應該去做它。