Could this spell the end for mosquitos?
这意味着蚊子的“世界末日”吗？
Mosquitoes are one of humanity's greatest nemeses, estimated to spread infections to nearly 700 million people per year and cause more than one million deaths.
蚊子是人类最大的天敌之一，大约每年有7亿人患上由蚊子传播的疾病，并导致超过100万人死亡。
Researchers have used CRISPR/Cas9 gene editing to target a specific gene tied to fertility in male mosquitoes.The researchers were then able to discern how this mutation can suppress the fertility of female mosquitoes.
近日，研究人员对与雄性蚊子生育能力有关的基因使用CRISPR/Cas9基因编辑技术（使目标基因发生突变），然后就能够知道这种突变如何能抑制雌性蚊子的繁殖能力。
基因编辑是一种新兴的比较精确的能对生物体基因组特定目标基因进行修饰的一种基因工程技术。CRISPR-Cas9基因编辑技术，则是对靶向基因进行特定DNA修饰的技术，这项技术也是用于基因编辑中前沿的方法。以CRISPR-Cas9基础的基因编辑技术在一系列基因治疗的应用领域都展现出极大的应用前景，例如血液病、肿瘤和其他遗传疾病。
Craig Montell, professor of molecular, cellular, and developmental biology at the University of California, Santa Barbara, and coauthors were working to improve a vector-control practice called the sterile insect technique (SIT). To manage populations, scientists raise a lot of sterile male insects. They then release these males in numbers that overwhelm their wild counterparts.
加州大学圣巴巴拉分校的分子、细胞和发育生物学教授克雷格·蒙特尔和他的合作者正在改进一种被称为不育昆虫技术（SIT）的病媒介控制方法。为了控制种群数量，科学家们饲养了大量的不育雄性昆虫。然后他们释放了这些在数量上超过了野生同类的昆虫。
The idea is that females that mate with sterile males before finding a fertile one are themselves rendered infertile, thereby decreasing the size of the next generation. Repeating this technique several times has the potential to crash the population. What's more, because each generation is smaller than the last, releasing a similar number of sterile males has a stronger effect over time.
不育昆虫技术（SIT）的原理是，雌性昆虫在找到能生育的雄性昆虫之前与不育的雄性昆虫交配，其自身就会变得不育，从而减少下一代的数量。重复使用这项技术可能会导致种群崩溃。更重要的是，因为每一代的数量都比上一代少，随着时间的推移，（在每一代）释放相同数量的不育雄性效果会增强。
CRISPR IS A BETTER ALTERNATIVE TO CHEMICALS
相对于化学物质，CRISPR是一种更好的选择
SIT has proven effective in managing a number of agricultural pests, including the medfly (Mediterranean fruit fly), a major pest in California. It has also been attempted with A. aegypti mosquitoes.
SIT（不育昆虫技术）已被证明可以有效地控制许多农业害虫，包括地中海果蝇——一种加州的主要害虫。这种技术也曾被用于埃及伊蚊体内。
In the past, scientists used chemicals or radiation to sterilize male A. aegypti.However, the chemicals or radiation affected the animals' health to such an extent that they were less successful in mating with females, which undercuts the effectiveness of the sterile insect technique.
过去，科学家使用化学物质和辐射使雄性埃及伊蚊绝育。但是，这些化学物质和辐射对动物的健康影响很大，导致它们与雌性交配的成功率降低，这削弱了不育昆虫技术的有效性。
Montell figured there had to be a more targeted approach with less collateral damage. He and his colleagues, including co-first authors Jieyan Chen and Junjie Luo, set out to mutate a gene in mosquitoes that specifically caused male sterility without otherwise affecting the insects' health. The best candidate they found was b2-tubulin (B2t); mutation of the related B2t gene in fruit flies is known to cause male sterility.
蒙特尔认为，必须有一种更有针对性、附带伤害更小的方法。他和同事们（包括共同第一作者陈洁彦和罗俊杰），开始在不影响昆虫健康的情况下使蚊子的一种专门导致雄性不育的基因发生突变。他们发现的最佳候选基因是B2t。因为已知果蝇的B2t的突变已知会导致雄性不育。
Using CRISPR/Cas9, the researchers knocked out B2t in male A. aegypti. They found that the mutant males produced no sperm, but unlike in previous efforts, the sterile studs were otherwise completely healthy.
研究人员使用CRISPR/Case9基因敲除雄性埃及伊蚊的B2t基因。他们发现，突变的雄性不能产生精子，但与之前的研究不同的是，不育的雄性在其他方面是完全健康的。
In one experiment, the researchers introduced 15 mutant males into a group of 15 females for 24 hours. Then they swapped the B2t males for 15 wild-type males, and left them there. "Essentially, all of the females remained sterile," Montell says. This confirmed that B2t males could suppress female fertility without producing sperm.
在一项实验中，研究人员将15只突变雄性蚊子引入一组15只雌性蚊子中，持续24小时。然后他们用15只野生型雄性 蚊子替代B2t型雄性蚊子。蒙尔特说：“基本上，所有的雌性蚊子都保持不育。”这证实了B2t型雄性蚊子可以在不产生精子的情况下抑制雌性蚊子的生育能力。
Next the team set out to determine how timing played into the effect. They exposed the females to mutant males for different lengths of time. The scientists noticed little difference after 30 minutes, but female fertility quickly dropped after that. Montell notes that females copulated twice on average even during the first 10 minutes. This indicated to him that females have to mate with many sterile males before being rendered infertile themselves.
接下来 ，研究小组开始研究时间是如何影响效果的。他们将雌性蚊子暴露在变异的雄性蚊子面前，暴露时间长短不一。30分钟后，科学家们没有发现什么变化，但此后雌性蚊子的生育能力迅速下降。蒙特尔指出，雌性蚊子平均在前10分钟内交配两次。这启发了他，雌性蚊子必须与许多不育雄性蚊子交配，才能使自己不育。
Combining the females with the B2t males for four hours cut female fertility to 20% of normal levels. After eight hours the numbers began leveling out around 10%.
将雌性蚊子与B2t雄性蚊子结合4小时后，雌性蚊子的生育能力降至正常水平的20%，8小时后，稳定在10%左右。
MOSQUITO MATING BEHAVIORS
蚊子交配行为
With the insights from the time trials, the team sought to approximate SIT under more natural conditions. They added different ratios of B2t and wild-type males at the same time to a population of 15 females for one week, and recorded female fertility. A ratio of about 5 or 6 sterile males to one wild-type male reduced female fertility by half. A ratio of 15 to 1 suppressed fertility to about 20%, where it leveled off.
根据计时实验的结果，研究团队试图在更自然的条件下模拟SIT（不育昆虫技术）。他们将不同比例的B2t和野生型雄性蚊子同时添加到15只雌性蚊子的种群中，为期一周，并记录了雌性蚊子的生育能力。大约5到6只不育雄性蚊子与1只野生型雄性蚊子的比例会使雌性蚊子的生育能力降低一半。1：15的比率使生育率降低到20%左右，并趋于稳定。
Now, Aedes aegypti populations could easily bounce back from an 80% drop in fertility, Montell says. The success of SIT comes from subsequent, successive releases of sterile males, where each release will be more effective than the last as sterile males account for an ever-growing proportion of the population.
蒙特尔说，现在埃及伊蚊的种群可以很容易地从生育力下降80%的情况中反弹回来。SIT（不育昆虫技术）的成功来自于随后的、连续地释放不育的雄性蚊子，而且每次释放都比上次更有效，因为不育雄性在种群中所占的比例越来越大。
Montell plans to continue investigating mosquito mating behaviors and fertility. They are devising a way to maintain stocks of B2t males so they are only sterile in the wild and not in the lab. In addition, they are characterizing male mating behavior to uncover new ways to suppress mosquito populations.
蒙特尔计划继续研究蚊子的交配行为和繁衍能力。他们正在设计一种方法来维持B2t雄性蚊子的数量，这样它们就只能在野外不育，在实验室则可育。此外，他们为了发现抑制蚊子的数量的新方法还研究了雄性蚊子交配行为的特征。
热词
fertility n.生育力；肥沃
overwhelm v.超过
sterile adj.不育
A. aegypti mosquito n.埃及伊蚊
medfly n.地中海果蝇
mating n./v.交配
suppress v.抑制
编译：胡梦涵
排版：胡梦涵