Cloning could be used to save species—or make human “organ sacks”

克隆技术：既能拯救物种，也可能制造出人类“器官袋”

EXECUTIVE SUMMARY This week I spoke to scientists who have found a way to turn male mouse embryos female. They’ve developed a CRISPR-based approach to essentially cut out the Y chromosome. It allowed them to create female clones of male mice. That’s right: female animals that are genetically identical to males, except for the missing Y chromosome. 执行摘要：本周，我采访了一些科学家，他们找到了一种将雄性小鼠胚胎转化为雌性的方法。他们开发了一种基于 CRISPR 的技术，从本质上切除了 Y 染色体。这使他们能够创造出雄性小鼠的雌性克隆体。没错：除了缺失 Y 染色体外，这些雌性动物在基因上与雄性完全相同。

Takashi Ishiuchi, a reproductive biologist at the University of Yamanashi who co-led the work, told me it felt a bit like sci-fi. Ishiuchi and his colleague Shogo Matoba of the Riken BioResource Research Center hope their approach could be helpful in conservation efforts, especially in cases where we might have only a few individuals of a species left. But cloning has multiple uses, ranging from the cool to the outright creepy. 山梨大学的生殖生物学家、该研究的共同负责人石内崇（Takashi Ishiuchi）告诉我，这感觉有点像科幻小说。石内和他在理化学研究所生物资源研究中心的同事的场章悟（Shogo Matoba）希望他们的方法能有助于物种保护工作，特别是在某些物种仅存少量个体的情况下。但克隆技术有多种用途，从酷炫到令人毛骨悚然，应有尽有。

We can’t talk about cloning without mentioning Dolly, the celebrity sheep born in 1996 and the first mammal successfully cloned from an adult cell. In that case, scientists took the DNA-containing nucleus of an adult mammary cell from one sheep and transferred it into an egg cell that had had its own nucleus removed. The resulting embryo was transferred to a surrogate sheep, which gave birth to Dolly—an animal genetically identical to the DNA donor. 谈到克隆，就不能不提 1996 年出生的明星羊“多莉”，它是第一只从成年细胞成功克隆出的哺乳动物。当时，科学家从一只羊的成年乳腺细胞中取出含有 DNA 的细胞核，并将其转移到已去除细胞核的卵细胞中。由此产生的胚胎被移植到代孕母羊体内，最终生下了多莉——一只在基因上与 DNA 供体完全相同的动物。

The scientists behind that work were interested in genetically modifying livestock. Farmers have essentially been doing this for thousands of years through selective breeding, but cloning allows scientists to create genetic replicas of animals with desirable traits. Cloning is also being used to replicate deceased pets, including, famously, those of Barbra Streisand and Tom Brady, among others. 这项研究背后的科学家们对转基因家畜很感兴趣。几千年来，农民们通过选择性育种本质上一直在做这件事，但克隆技术使科学家能够创造出具有理想性状的动物的基因复制品。克隆技术也被用于复制已故的宠物，其中著名的例子包括芭芭拉·史翠珊（Barbra Streisand）和汤姆·布雷迪（Tom Brady）等人的宠物。

For a price somewhere in the tens of thousands of dollars, a company can take cells from your pet and turn them into a living, breathing clone. Considering that cloning also requires egg cells from another animal, and a surrogate animal to carry the pregnancy, not everyone is on board with this, especially since there is no medical or environmental need for the procedures. One bioethicist, Jessica Pierce, has described this aspect of dog cloning as “the exploitation of the canine underclass.” 只需花费数万美元，公司就可以提取你宠物的细胞，并将它们变成一个活生生的克隆体。考虑到克隆还需要来自另一只动物的卵细胞，以及一只代孕动物来完成妊娠，并非所有人都支持这一点，尤其是因为这些程序在医疗或环境方面并无必要。生物伦理学家杰西卡·皮尔斯（Jessica Pierce）将这种狗类克隆行为描述为“对犬类底层阶级的剥削”。

The case for cloning is stronger when it comes to conservation—where some argue there is environmental value. Scientists have been preserving animal tissues for years. Some of these tissues are cryopreserved at low temperatures in “frozen zoos.” The facility at the San Diego Zoo, for example, currently has cells from over 1,300 species. Some of these samples were taken decades ago. 在物种保护方面，克隆技术的理由更为充分——一些人认为这具有环境价值。多年来，科学家们一直在保存动物组织。其中一些组织被低温冷冻在“冷冻动物园”中。例如，圣地亚哥动物园的设施目前拥有超过 1,300 个物种的细胞。其中一些样本是几十年前采集的。

Preserved tissues like these have enabled scientists to create clones of animals considered close to extinction, including black-footed ferrets and Przewalski’s horse. But they might also help us bring back extinct animals. In 2009, researchers in Spain described how they’d cloned an extinct wild goat, the Pyrenean ibex, using skin cells that had been cryopreserved a decade earlier. In that research, the team used egg cells from domestic goats to create a total of 439 embryos. Ultimately, only one goat—a female—was born. She died minutes later because of a defect in her lungs. Poor Pyrenean ibex. It’s the only animal we know of that has gone extinct twice. 这些保存下来的组织使科学家能够克隆出被认为濒临灭绝的动物，包括黑足鼬和普氏野马。但它们也可能帮助我们复活已灭绝的动物。2009 年，西班牙的研究人员描述了他们如何利用十年前冷冻保存的皮肤细胞，克隆出一种已灭绝的野山羊——比利牛斯羱羊。在那项研究中，团队利用家山羊的卵细胞总共创造了 439 个胚胎。最终，只有一只雌性山羊出生。但它在几分钟后因肺部缺陷而死亡。可怜的比利牛斯羱羊，它是我们所知唯一一种灭绝了两次的动物。

The biotech company Colossal Biosciences is hoping to use old—and potentially ancient—genetic material to bring back long-extinct species like the thylacine and woolly mammoth. So far, the company’s efforts have largely involved modifying the genomes of modern-day animals. Technically, it’s also possible to clone humans. As far as we know, no one has done it. But some have played with the idea. One biotech startup founder has pitched an idea for “brainless clones”—human clones that lack a brain but contain all the organs people might need to replace their own in future. My colleague Antonio Regalado described that pitch in March. (I had to pause eating my lunch while rereading it.) 生物技术公司 Colossal Biosciences 希望利用古老的——甚至是远古的——遗传物质来复活袋狼和猛犸象等早已灭绝的物种。到目前为止，该公司的努力主要涉及修改现代动物的基因组。从技术上讲，克隆人类也是可能的。据我们所知，还没有人这样做过。但有些人已经开始构思这个想法。一位生物技术初创公司的创始人提出了“无脑克隆人”的构想——即没有大脑但包含人们未来可能需要更换的所有器官的人类克隆体。我的同事安东尼奥·雷加拉多（Antonio Regalado）在三月份描述过这个构想。（我在重读时不得不停下手中的午餐。）

Scientists have done a hell of a lot with cloning over the last few decades. I’m excited—but also slightly nervous—about what the coming decades will bring. 在过去的几十年里，科学家们在克隆技术上取得了巨大的成就。对于未来几十年将带来什么，我感到兴奋，但也有一丝不安。