Editing human embryos to prevent genetic disorders

Scientists have successfully removed a piece of faulty DNA that causes hereditary heart disease from embryos for the first time – this new technique could lead to 10,000 genetically inherited disorders being prevented

Clustered regularly interspaced short palindromic repeats (CRISPR) are segments of prokaryotic DNA containing short, repetitive base sequences. These play a key role in a bacterial defence system and form the basis of a genome editing technology known as CRISPR/Cas9 allowing the permanent modification of genes within organisms.

CRISPR has revolutionised molecular biology, allowing scientists to edit DNA.

The applications are vast and it could soon be possible to remove genetic faults, preventing diseases such as cystic fibrosis, breast cancer and hereditary heart disease.

More than 10,000 single faulty gene inherited disorders have been identified by scientific research, affecting millions of people worldwide.

Scientists based at Oregon Health & Science University US, the Salk Institute US and Institute for Basic Science in South Korea used CRISPR technology to focus on cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) affects one in every 500 people and can lead to the heart suddenly stopping beating. Caused by an error in a single gene, anyone carrying it has a 50% chance of passing it to their children. Current treatment options provide symptomatic relief, but are not able to address the genetic cause of the disease.

Scientists injected sperm from a man with HCM into healthy donated eggs alongside CRISPR sequences. The defect was corrected in 72% of embryos, with the genetic repair occurring during conception.

Dr Shoukhrat Mitalipov, a key figure in the research team, said: "Every subsequent generation would carry this repair because we have removed the disease-causing gene variant from that family's lineage. By using this technique, it is possible to reduce the burden of this heritable disease on the family and eventually, the human population."

This discovery could dramatically impact medicine in the future but also raises some difficult ethical questions. Never before have scientists caused a change in the DNA of an individual that can be passed on to their offspring. Correcting the faulty gene in HCM would mean that a healthy gene is passed to the next generation and HCM is removed from the family line.

Darren Griffin, a Professor of Genetics at the University of Kent, said: "Perhaps the biggest question and probably the one that will be debated the most, is whether we should be physically altering the genes of an IVF embryo at all."

"This is not a straightforward question; equally, the debate on how morally acceptable it is not to act when we have the technology to prevent these life-threatening diseases must also come into play."

Previously, there have been multiple attempts to utilise CRISPR technology to correct defects but techniques used were unable to correct every cell, producing a ‘mosaic’ of healthy and diseased cells.

The next question for consideration is the safety of the technology, which will require extensive research to even begin to answer.

Professor Robin Lovell-Badge, from the Francis Crick Institute, said: "A method of being able to avoid having affected children passing on the affected gene could be really very important for those families. In terms of when, definitely not yet. It is going to be quite a while before we know that it is going to be safe."

References

  1. Hong Ma, et al., "Correction of a pathogenic gene mutation in human embryos," Nature (2017).

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