Now CRISPR Being Used To Modify Deafness Gene

Denis Rebrikov wants to use CRISPR to prevent children inheriting a form of deafness

Recently, Dr. He Jiaung revealed that he has produced gene-edited babies, claiming it would prevent babies from inheriting their father’s HIV. The Chinese scientist has opened the doors for other scientists who were keen on doing similar experiments.

One of them is Denis Rebrikov, a Russian biologist who told Nature in June that he also intends to gene edit human embryos and bring them to term.

He told New Scientist magazine that five Russian couples who are deaf, have approached him to experiment with the CRISPR gene-editing technique so they can have a biological child who can hear. He plans to apply to the Russian authorities for permission in “a couple of weeks”.

 In this case,the use of CRISPR, seems stronger than for trying to make children HIV resistant, as done previously, but the risks still dwarf the benefits, say, other scientists.

“Rebrikov is determined to do some germline gene editing, and I think we should take him very seriously,” says CRISPR expert Dr. Gaetan Burgio at the Australian National University. “But it is too early, it’s too risky.”

Each parent eager for his study is deaf due to mutations in their GJB2 gene. This means both the expected parents in each couple have a recessive form of deafness. Thus, all their children could normally inherit the same condition. While the majority of genetic diseases can be prevented by screening IVF embryos ahead implantation, with no need for gene-editing. However, this is not an option for these couples.

Many reports have advised that if it can be done safely then editing the genes of small babies might be justified in this kind of situation.

Is it a dangerous process?

Rebrikov, at one of Russia’s largest fertility clinic, the Kulakov National Medical Research Center for Obstetrics, Gynecology and Perinatology ( Moscow), has sought out these unusual couples.

“It is understandable and clear to ordinary people,” he says. “Each new baby for this pair would be deaf without gene mutation editing.”

Previously, He Jiankui’s work was severely criticized due to many reasons. One of the major criticism was that there was no need to conduct such uncertain experiments to prevent these men from infecting their children with HIV. More on, Jiankui worked on gene editing without the approval of the Chinese government. It was a secret affair.

On the other hand, Nature reported that Rebrikov is openly discussing his plan to use CRISPR to create HIV-resistant babies – this time for couples where the mother is HIV-positive.

Still, many experts believe that there there is no need for risky gene editing in this case.

Rebrikov also plans to discuss and seek permission from the Russian government in a few weeks before heading with the controversial CRISPR use in deafness gene editing.

How will this work?

In west Siberia, many people have a missing DNA letter in the position 35 of the GJB2 gene. Having one copy does not affect, but those who inherit this mutation from both parents never develop the ability to hear.

crispr works

Thus Rebrikov wants to stop children from inheriting a form of deafness as a result of mutations in the GJB2 gene.

The five couples who are eager to go through the process, do not want their children to be deaf too due to this mutation. Rebrikov will use the CRISPR to modify this mutation in IVF embryos from these couples.

Homology direct repair will be applied to prevent deafness. In this method, one copy out of two copies of the GJB2 gene will be corrected in the IVF embryos.

“Technically, it is achievable,” said Burgio.

In November of last year, scientists in the field released a statement saying that this kind of germline genome editing could be unobjectionable if the risks were fully addressed and if certain criteria are met. Those criteria include a very “compelling medical need” and “an absence of reasonable alternatives”.

Preserving deaf culture

But it is not a win-win situation for Rebrikov. Many people think that deafness is not a disability- at least not life threatening- but culture and want their children to inherit the deafness condition to sustain unique deaf cultures (ed note: seriously!). However, the five couples don’t have any choice if they want to have their biological children who can hear.

There are doubts about CRISPR that have not been addressed. No method was found to ensure that gene edited children won’t have unwanted mutations, or guarantee that every cell in the children’s body will have the modified DNA.

“We continue to believe that proceeding with any clinical use of germline editing is irresponsible at this time,” the November statement says.

“The 1st human trials should start with infants or embryos with nothing to lose, with fatal conditions,” says bioethicist Julian Savulescu of the University of Oxford. “One should not be starting with an embryo which stands to lead a pretty normal life.”

How about working on more serious genetic disorders? Well, people with serious recessive disorders rarely find themselves in the same condition as the 5 couples. For instance, people with cystic fibrosis usually die very young and are actively discouraged from meeting other people to avoid swapping the bacteria that infect their lungs.

According to Savulescu, the first gene editing trial should engage couples whose children could inherit fatal conditions such as Tay-Sachs, but who deny opting for screening IVF embryos because they are against destroying embryos on a religious basis.

If germline gene-editing is some day shown to be safe, Savulescu thinks there would then be a moral imperative to use it to prevent conditions such as deafness.

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