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articipants of the second International Summit of Human Genome Editing in Hong Kong last month expected insightful discussions about the latest techniques and ethics of genome editing in the human embryo. However, one day before the conference started, big news arrived that shook the world of scientific research.

One of the invited speakers, He Jiankui from the University of Science and Technology in Shenzhen, China, claimed that he had successfully performed genome editing in a human embryo that resulted in newborn twins named Lulu and Nana. If the professor’s claim was true, this is the first time that human babies were born after their genome was specifically engineered.

He utilized a technique called CRISPR-Cas9 that was only discovered in 2012. This technique has enabled researchers to edit specific genes within the human genome at will.

The tremendous advancement has created previously unthinkable possibilities for designing human babies that are free from diseases or even enhancing certain qualities, such as intelligence.

Despite the breakneck progress, we still do not know whether this technique creates unwanted effects, let alone its medical safety. Therefore, any research involving a human embryo is strictly banned in virtually all countries.

He’s work has been universally condemned, even within his own university and his own country, China. His works raised alarming issues over scientific methodology and ethics.

Using CRISPR-Cas9, the professor removed a specific gene called CCR5 that encodes a protein receptor involved in our immunity system. The protein is also the main door for the human immunodeficiency virus (HIV) to enter the human cell. Therefore, he said he intended to ensure that newborns would be free from the human immunodeficiency virus throughout their lives.

This scientific logic is flawed. While CCR5 is indeed the leading gateway for HIV entry into our cells, it is not the only one. There are other molecular manipulations that HIV could do to enter our cells, so these genome-edited babies would not be entirely free of risk from acquired immune deficiency syndrome (AIDS). Moreover, the CCR5 protein is very likely to be involved in the immune system. Removing this gene may expose these babies to unnecessary risks from other common infections like the flu. Next, the experiment could not confirm whether all the cells — the 37.2 trillion of them — in each of the twins received the edited gene.

This so-called mosaicism may cause undesirable developmental growth. Lastly, there is no guarantee that other potentially important DNA sequences or genes were not modified by this gene modification, which could affect the twins’ well-being.

The more delicate issue is about ethics. Editing a human embryo means editing the cells involved in reproduction, which means the edited genome is permanent and would be passed on to future generations.

This is made worse when it is done without fully understanding the risks. The ethical discussion is also preceded by the question about when human life begins (after an egg is fertilized?): a very complex issue with as yet no consensus.

No doubt He’s scientific work has overstepped the ethical “red line”. The reaction from the scientific community and the public has been generally negative. However, if there is a time to start the debate about genome editing in a human embryo, the time is now.

Although CRISPR-Cas9 sounds like a perfect tool to edit our genome at will, in practice we are still just skimming the surface of the deep unknown of molecular biology. It is still a science of testing-and-trying and more basic studies need to be done faithfully to ensure that all the risks have been identified and alleviated. The time to edit the genomes of babies may come, but that time has not arrived yet.

The discussion then moves to what kind of genetic characteristics can be edited. Faulty single genes that cause lethal diseases such as cystic fibrosis or muscular atrophy must be the priorities for genome editing. Meanwhile, genome editing that confers no real medical values, such as enhancing intelligence, changing hair color, or even preventing easily manageable diseases, should be off limits.

Genome editing technology, once it is ready, should not be the cause for further inequalities in society. Who can afford this technology? As a society that is forward-looking, we should not allow this technique to be accessible only by the wealthy.

To prevent these unwanted effects, the discussions and debates need to be started now. It is all the more pressing as He has inadvertently opened Pandora’s Box.
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