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最近一周一项研究被大肆宣传
There’s been a lot of hype in the last couple
这项研究是关于使用基因编辑技术（CRISPR）
weeks about a study that used the gene editing technique CRISPR
来修饰人类胚胎
to modify human embryos.
这项研究于八月二日在美国《自然杂志》
The study was published on August 2nd in the journal Nature
由美国及韩国研究员发表
by American and Korean researchers.
从那以后 你可能听说过人们担忧基因工程婴儿
And since then you might have heard concerns about designer babies
在人类基因工程中疯狂横行
in human genetic engineering run amok.
但其实这项研究的真实情况没那么厉害
But the study’s real findings were a little more modest.
一个降低疾病影响的可能的方法
A possible way to decrease the impact of one disease,
还有一个关于人类基因组是如何
and a surprising discovery about how the human genome could
保护自己不被改变的惊人发现
protect itself from being changed.
CRISPR 更正式的说法是CRISPR-Cas9
CRISPR, more formally known as CRISPR-Cas9,
它是一项相对较新的基因工程技术
is a relatively new genetic engineering technique.
它让科学家能更有力 更灵活的编辑活细胞中的DNA
It gives scientists more power and flexibility
而且是前所未有的有力 灵活
to edit DNA in living cells than they’ve ever had.
因此很多实验开始了
So lots of experiments are underway
大到成人的癌症治疗 小到修饰传播病菌的蚊子
from cancer treatments in adults to modifying disease-transmitting mosquitoes.
这种方法中用到了可以剪切DNA的Cas9酶
The system uses an enzyme called Cas9 which makes cuts in DNA.
细胞一般用作化学信使的一段RNA
A piece of RNA which cells normally use as a chemical messenger,
引导Cas9酶结合到DNA序列上
guides the Cas9 to a DNA sequence
这段DNA序列是和那段信使RNA序列互补配对的
that matches up with the RNA sequence.
接着Cas9酶切开双链DNA
Then Cas9 makes a cut through both DNA strands,
这个过程叫双链断裂
it’s called a double-stranded break.
之后会发生一系列的反应
After that a couple of things could happen.
细胞会尽快把这些解螺旋的DNA末端富集起来
The cell might jam those loose DNA ends together as quickly as
即使这样可能会不可避免的出现错误
it can, even if it introduces mistakes.
但相反 有时细胞会通过复制DNA模板
But sometimes cells will fix the break
修复断裂的双链DNA
by copying a DNA template instead.
这是很可能出现的 比如
This can happen, for example,
如果一个细胞正在准备分裂
if a cell is getting ready to divide and
而且这个细胞的DNA也复制完成了
it’s made a couple of copies of its DNA.
这个细胞就可以再复制被复制的DNA来修复模板DNA
The cell can copy the copy to fix the original,
然后一切顺利完成
and everything’s good.
通过CRISPR技术 研究人员可以为细胞提供特定的DNA序列
With CRISPR, researchers can provide a specific DNA sequence for
在进行这些修复时用作模板
the cells to use as a template during these repairs.
通过那种方法 可以产生任何他们想要的改变
That way they can introduce any changes they want,
比如添加不同的基因
like adding a different version of the gene.
在这项研究中 研究员们特别观察了
In this study, the researchers were specifically looking at
一个叫MYBPC3的基因
a gene called MYBPC3,
这个基因和肥厚型心肌病有关
it’s involved in a hypertrophic cardiomyopathy.
肥厚型心肌病是一种会使心脏肌肉变厚的病
A disease that makes the heart muscle thicker.
而且它能导致个体突发性心脏衰竭 早亡
And it can lead to sudden heart failure and death in young,
另外 健康的运动员如果剧烈运动也会猝死
otherwise healthy athletes when they push their hearts too hard while exercising.
这种病可被很多治疗方法控制住
The disease can be managed with a variety of treatments,
但没有办法根治
but there’s no real cure.
而且如果刚好这个人
And if just one of a person’s
两条复制的基因链中有一条发生突变
two copies of the gene has a mutation,
他们就会被这种疾病侵袭
they’re affected by the disease and can
而且会遗传给下一代
pass it on to their children.
研究员们想利用CRISPR-Cas9技术
These researchers wanted to use CRISPR-Cas9 to
通过修饰胚胎中的基因
fix the gene in embryos to see if
来研究是否能阻止这种突变遗传给下一代
they could prevent it from being passed on from parent to child.
在实验中 他们从一个男性中
For their experiments they got a sperm from a man
取得一个带有MYBPC3突变基因的精子
with a mutant MYBPC3 gene,
并且从健康女性中取得一些未发生突变的卵细胞
and eggs from several healthy women with no mutant genes.
然后通过显微注射技术把突变体精子和带有Cas9蛋白酶的sgRNA
They injected the sperm and the Cas9 protein with sgRNA
注入健康卵细胞中
directly into the eggs, along with a single-stranded DNA template
还有一条基因正常的单链DNA模板也注入该卵细胞中
for a healthy version of the gene.
目的是让Cas9酶切下所有的突变基因
Their goal was to get Cas9 to slice out any copies
然后用正常的基因修补
of the mutant gene and repair it with a healthy gene instead.
然后带有两个正常MYBPC3基因的受精卵继续卵裂
And the fertilized eggs went on to produce embryos
有42/58的正常受精卵继续生长发育
with two healthy MYBPC3 genes in 42 out of 58 trials,
成功率高达70%以上
over 70% of the time.
在没有用CRISPR技术的对比实验中
In the control experiment without any CRISPR,
成功率在50%
it was around 50/50.
这个实验结果是符合预期的
That’s what you’d expect because the man
因为这名男性有一半突变基因 一半正常基因
had one mutant copy and one normal copy,
因此有一半的精子带有突变基因
so half of his sperm were carrying the mutant gene.
因此 这种治疗方法比没有基因修复的治疗更有效
So, the treatment worked a little more efficiently than no treatment.
还有 研究人员正在努力
Plus, the researchers were trying to avoid getting a mix of
避免在一个胚胎中既有CRISPR修复又有未修复细胞的混合情况
CRISPR treated and untreated cells in a single embryo.
他们看似是成功的修复了一个受精卵
They seemed to succeed in all but one fertilized egg,
因为他们是同时使用CRISPR技术注射进精子的
because they injected the sperm at the same time as CRISPR.
但当研究人员仔细观察这些DNA序列时
When the researchers took a closer look at the DNA sequences,
他们发现了未预想到的情况
they found something that they didn’t expect.
因为 研究员们之前标记的模板的方法
So, the scientists had marked their template in ways
虽然能显现在基因序列中
that wouldn’t change the final gene product, but
但是却不能改变基因表达的最终产物 蛋白质
would show up in sequencing.
他们做的标记也没有出现在所有
But their markers weren’t in almost all of the embryo cells
有正常基因的胚胎中
with two healthy genes.
因此 他们意识到
So, they realized that when the fertilized egg cells fixed
当受精卵细胞用Cas9修补断裂的双链时
the double-stranded breaks made by Cas9,
几乎所有的细胞完全没有用研究员们提供的模板
almost all the cells totally ignored the template that the researchers provided.
相反 这些细胞用了卵细胞中的正常基因作为模板
Instead, the cells use the healthy gene from the egg cell
来修饰精子中的致病的配体模板
as a template to fix its diseased counterpart from the sperm.
那是DNA的修复机制
That’s a mechanism for DNA repair that
而且是研究员们没想到的机制
the researchers didn’t see coming and
这种DNA修复机制表明几个重要的事实
it means a couple of big things:
第一 它表明可能有一种方式
First, it suggests that there might be a way for our
可以让我们的精子 卵子细胞抵制DNA的改变
sperm and egg cells to resist changes
而我们其它的细胞却不会抵抗这种改变
in their DNA in a way that our other cells don’t.
研究员们认为这种细胞机制应该是有意义的
So researchers think this kind of makes sense,
因为既然这些细胞中的DNA是我们要复制的
since DNA in those cells is what lets us reproduce,
那么保持它的完整性肯定很重要
so it’s really important to keep it intact.
第二 这个新发现的修复系统可能意味着
Second, this newly discovered repair system could mean that embryos will
胚胎会拒绝我们硬塞给它们的新DNA
reject a new DNA we try to give them.
因此我们也许可以利用CRISPR技术来解决类似MYBPC3基因突变的问题
So we could possibly use CRISPR to fix a problem like MYBPC3,
就是一个亲本的基因是不正常的 而另一个亲本的基因是正常的那种情况
where one parent’s gene is bad and the other is fine.
但是 如果来自父母的基因都不正常
But if genes from both parents are broken, this mechanism
这种机制很可能会抵抗排斥
might resist any attempts to introduce new DNA
任何企图想要修复它们的新基因
that’s supposed to fix them.
除了这项惊人的发现外 研究员的研究视野
Other than this surprising finding, the scope of this research is
可能会比你想的各种噱头要小的多
more modest than you might think from all the clickbait.
有时 这个父亲或母亲可能知道
Sometimes, a parent might know
他们携带着像MYBPC3之类的危险基因
that they carry a dangerous gene like MYBPC3,
或是常导致乳腺癌的BRCA突变基因
or the mutant BRCA gene that often leads to breast cancer.
因此 他们很可能会用
So, they might use in vitro fertilization with
有胚胎植入前遗传学诊断的试管受精
pre-implantation genetic diagnosis.
基本上是医生帮人们进行体外受精
Basically, that’s when a doctor helps people create fertilized eggs,
然后把受精卵培养成胚胎 并且筛选出带有致病基因的受精卵
grows them into embryos, and then screens them for disease genes
再把正常健康的受精卵植入某人的子宫内
and then implants only the healthy egg into someone’s uterus.
新研究的这项技术有助于医生培养胚胎 使培养胚胎的速度更快
The technique in this new study could help doctors grow healthy embryos
而且能提高试管受精的效率
more often and improve the efficiency of IVF, having
让父母创造少许的胚胎更简单
to create fewer embryos is easier on parents.
由于帕特里克法及国家的不同
The Patrick of laws and different countries will make it difficult for
这项新技术进展艰难
this new technique to get off the ground though.
这项使用人类胚胎研究的例子
The study using human embryos for instance was only legal
仅在美国合法 因为美国允许私人研究所运行
in the US because it was privately funded.
从遗传学角度讲 人类基因工程中
Genetically, engineering embryos to grow up
胚胎生长发育为个体人 仍然任重道远
into human beings is still way, way off.
这些研究是仅在最近几年的文化认知中才成长起来的
These were only grown in a culture for three days,
研究成果还只局限于四到六个小胚球中
and were still just a tiny ball of four to eight cells.
而且还需要很多研究
And a great deal of research is needed to refine the techniques
来改善这项研究中发展的技术
developed in this study and make sure they’re absolutely safe for
还要保证这些技术在理论上用在任何人身上都是安全的
for any theoretical human use.
所以 不管新闻标题 新闻头条是怎么说的
So, whatever the headlines are saying,
我们现在仍在进行有限而又令人惊奇的探索研究之中
we’re really looking at a narrow but surprising study.
它再次告诉了我们
It showed us once again
现在仍然有很多
that there’s still a lot
很多在身体机能方面我们不了解的内容
we don’t understand about how our bodies work,
而且对它的研究逐渐增加
and it’s an incremental piece of research
通常是科学研究中的重点
which is usually the case with science.
而且假设这项研究导致了什么不好的后果
And if anything its results make designer babies
都可能会使人们对基因工程婴儿的研究大大减少
less likely, not more.
感谢观看本集科学秀新闻节目
Thanks for watching this episode of SciShow News.
现在另一件重大科学新闻是日食
The other big science news right now is the solar eclipse
此次日食将会在下周一出现
that’s happening next Monday.
现在我们科学秀都感到非常激动
We’re very excited about here at SciShow.
那么 如果你想了解更多的科学新闻
So if you wanna learn more,
可以到科学秀里查看视频
you can check out our video on SciShow Space.
还有 如果你想知道的更多
And if you want more of this,
你可以去YouTube.com/scishow订阅
you can go to youtube.com/scishow and subscribe.