非常值得一读的BBC报道 | 全世界首位“三亲婴儿”诞生

小白老师说：这是今天BBC官网Health频道的头条文章，非常值得一读。我之前也推送过一篇《经济学人》有关三亲婴儿的文章，附在文末（有音频）。本文中可能的生词已经给大家做了注解。阅读愉快！

Background Information

• 所谓的“三亲婴儿”，又称3P婴儿（3P即英文three parents/person的缩写），是英国新的基因技术。为了避免夫妻把生理缺陷遗传给孩子，医生去除女性捐赠者的卵子中的细胞核，接着用母亲卵细胞中对应的遗传基因取而代之，最后再按照标准的试管婴儿技术进行培育。这样诞生的孩子将会继承一位父亲和两位母亲的遗传基因。简单地说，就是这名婴儿有三名血缘亲代，即两母一父。
• 2015年10月，英国成立立法生效允许培育具有两个基因母亲和一个基因父亲的婴儿的第一个国家。
• 2016年初，首位由“三合一”胚胎人工授精技术诞生的婴儿出世 。

First ‘three person baby’ born using new method

The world’s first baby has been born using a new “three person” fertility technique（生殖技术）, New Scientist reveals.

The five-month-old boy has the usual DNA from his mum and dad, plus a tiny bit of genetic code from a donor.

US doctors took the unprecedented step to ensure the baby boy would be free of a genetic condition that his Jordanian mother carries in her genes.

Experts say the move heralds（预示着…的来临） a new era in medicine and could help other families with rare genetic conditions.

But they warn that rigorous（严格的） checks of this new and controversial （有争议的）technology, called mitochondrial（线粒体的） donation, are needed.

It’s not the first time scientists have created babies that have DNA from three people - that breakthrough（重大突破） began in the late 1990s - but it is an entirely new and significant method.

Three person babies

Mitochondria are tiny structures inside nearly every cell of the body that convert food into usable energy.

Some women carry genetic defects（缺陷） in mitochondria and they can pass these on to their children.

In the case of the Jordanian family, it was a disorder called Leigh Syndrome（亚急性坏死性脑脊髓病） that would have proved fatal to any baby conceived. The family had already experienced the heartache of four miscarriages as well as the death of two children - one at eight months and the other at six years of age.

Leigh syndrome

• A severe neurological disorder, affecting at least one in 40,000 new-born babies.
• Usually becomes apparent during the first year of a child’s life.
• First signs include vomiting, diarrhoea and difficulty with swallowing.
• Causes the progressive loss of movement, and deterioration（退化，恶化） of mental functions.
• Symptoms are linked to the development of patches（修补） of damaged tissue which develop in the brain.
• Children with the condition usually die within two to three years, usually because of respiratory failure.
• Mutations（突变） in 75 different genes have been linked to the condition.
• Most of those mutations occur in DNA from the nucleus, but in about one in five cases the culprit is found in mitochondrial DNA.

Scientists have devised a number of fertility methods to help such families.

The US team, who travelled to Mexico to carry out the procedure because there are no laws there that prohibit it, used a method that takes all the vital DNA from the mother’s egg plus healthy mitochondria from a donor egg to create a healthy new egg that can be fertilised with the father’s sperm.

The result is a baby with 0.1% of their DNA from the donor (mitochondrial DNA) and all the genetic code for things like hair and eye colour from the mother and father.

Dr John Zhang, medical director at the New Hope Fertility Centre in New York City, and his colleagues used the method to make five embryos（胚胎） - only one of them developed normally.

Step 1: Eggs from a mother with damaged mitochondria and a donor with healthy mitochondria are collected

Step 2: The majority of the genetic material is removed from both eggs

Step 3: The mother’s genetic material is inserted into the donor egg, which can be fertilised by sperm.

The UK has already passed laws to allow the creation of babies from three people.

But the science does raise ethical questions, including how any child from the technique might feel about having DNA from three people.

Fertility experts say it is important to push ahead, but cautiously.

Some have questioned whether we are only now hearing the success story while failed attempts could have gone unreported.

Prof Alison Murdoch, part of the team at Newcastle University that has been at the forefront of three person IVF work in the UK, said: “The translation of mitochondrial donation to a clinical procedure is not a race but a goal to be achieved with caution to ensure both safety and reproducibility（繁殖）.”

Critics say the work is irresponsible.

Dr David King from the pro-choice group Human Genetics Alert, said: “It is outrageous（粗暴的，令人吃惊的） that they simply ignored the cautious approach of US regulators and went to Mexico, because they think they know better. Since when is a simplistic（过分简单） “to save lives is the ethical thing to do” a balanced medical ethics approach, especially when no lives were being saved?”

Dr Zhang and his team say they will answer these questions when they presents their findings at a meeting of the American Society for Reproductive Medicine in October.

Prof Darren Griffin, an expert in Genetics at the University of Kent, said: "This study heralds a new era in preimplantation（胚胎植入前的） genetics and represents a novel means for the treatment of families at risk of transmitting genetic disease.

“With radical new treatments like this there are always challenging ethical issues, however any concerns need to be balanced against the ramifications of not implementing such a technology when families are in need of it.”

The structure of a cell

• Nucleus: Where the majority of our DNA is held - this determines how we look and our personality
• Mitochondria: Often described as the cell’s factories, these create the energy to make the cell function
• Cytoplasm: The jelly like substance that contains the nucleus and mitochondria

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