Explained: A first— how a customised gene-editing tool was used to treat 9-month-old boy
A nine-month-old boy, born with a rare genetic disorder, has become the first (known) person to successfully receive a custom gene-editing treatment, a report published on May 15 in the New England Journal of Medicine said.
Kyle 'KJ' Muldoon Jr suffers from CPS1 deficiency which causes toxic levels of ammonia to accumulate in his blood. To treat him, scientists and doctors from the University of Pennsylvania and the Children's Hospital of Philadelphia developed a personalised treatment based on 'base editing', a new version of the decade-old CRISPR-Cas9 technology.
Scientists say this technology can potentially treat thousands of uncommon genetic diseases. But there remain many roadblocks to its universal adoption.
What is CRISPR?
Following infection by a virus, humans generate an 'immune memory' in the form of antibodies. When they are infected by the same virus again, these antibodies quickly identify the pathogens and help neutralise them.
CRISPR, short for 'clustered regularly interspaced short palindromic repeats', is an immune system found in microbes such as bacteria which fights invading viruses. When a virus infects a bacterial cell, CRISPR too helps establish a memory — but a genetic one, not in the form of antibodies like in humans.
When a virus enters a bacterial cell, the bacterium takes a piece of the virus's genome and inserts the DNA into its own genome. CRISPR then produces a new 'guide' RNA with the help of the newly acquired DNA.
During a future attack by the same virus, the guide RNA quickly recognises the virus DNA and attaches itself to it. Then, the guide RNA directs an enzyme (a type of protein) called Cas9 to act like 'molecular scissors' to cut and eliminate the virus DNA.
In 2012, scientists Jennifer Doudna and Emmanuelle Charpentier replicated this mechanism found in microbes to develop a gene-editing tool, which they called CRISPR-Cas9, a feat which earned them the Nobel Prize for Chemistry eight years later.
How does CRISPR-Cas9 gene-editing work?
The tool works much like the 'cut-copy-paste', or 'find-replace' functionalities in common computer programmes.
Genetic information in DNA is stored as code made up of four chemical bases — adenine (A), guanine (G), cytosine (C), and thymine (T). These bases exist in pairs, which are then stacked one on top of each other, creating the horizontal layers of the double-helix structure of DNA.
Note that A always pairs with T, and C always pairs with G. Genetic disorders, like the one KJ suffers from, occur due to the presence of an abnormal DNA sequence, that is, a mispairing (A-G or G-T).
The first task for the gene-editing tool is to identify the abnormal DNA sequence behind a patient's ailment. Once the bad DNA is located, scientists create a guide RNA attached to a Cas9 enzyme, which is then introduced to the target cells of the patient.
The guide RNA recognises the bad DNA sequence, then the Cas9 enzyme cuts the DNA at the specified location in a process called a 'double-strand break' (since the cut is made on both strands of the DNA). This gets rid of the DNA sequence causing the illness.
DNA strands have a natural tendency to reattach and repair themselves, meaning there is a chance that the bad sequence regrows. To tackle this issue, scientists also supply the correct DNA sequence after the 'cutting' process which is meant to attach itself to the broken strands of DNA.
Over the years, scientists have made many improvements to the original CRISPR-Cas9 technology, making it safer and more precise. A newer, evolved version of this tool is 'base editing'.
How does base editing work?
Base editing and CRISPR-Cas9 differ significantly in how they modify DNA. Unlike CRISPR-Cas9, base editing does not make a double-strand break. Rather, it enables targeted single-base conversions with the help of a Cas9 enzyme fused to a base-modifying enzyme. This allows scientists to fix mispairing of the bases by changing one specific base. For instance, mispaired A-C bases can be corrected to A-T by converting C to T.
To treat KJ, scientists first determined which mispaired base in his DNA was causing his condition. They then programmed the base editing tool to find and rewrite the target base. This process can be likened to using a pencil and an eraser, rather than scissors and glue, as in CRISPR-Cas9.
'In the older version of CRISPR, scientists were required to provide additional DNA from outside, which would be pasted at the site where the double-strand break takes place. In base editing, however, the system by itself can make a very precise change without the need for a foreign DNA to be inserted,' Debojyoti Chakraborty, principal scientist at CSIR-Institute of Genomics and Integrative Biology, told The Indian Express. 'As a result, base editing has fewer components and is compact, making it easier to package in delivery vehicles, which can take it to target cells,' he said.
In 2023, Chakraborty and his team tried to develop a similar tool to treat a patient with a rare neurodegenerative disease. But she passed away before the experiment could be carried out.
Will base editing become commonplace soon?
Chakraborty said the successful use of base editing for treating KJ has given hope to doctors treating people with rare genetic disorders for whom no medical treatments were currently available.
However, it is unlikely that such technologies will become commonplace any time soon, first and foremost due to the prohibitive costs of such treatments. Even if it were to become widely available, base editing would not be accessible to most people. (KJ's treatment was funded by research institutes and biotechnology. While they did not make any official disclosure regarding its cost, it is likely to be in the range of hundreds of thousand dollars, maybe more).
Also, the base editing tool created to help KJ was a one-off treatment, meaning it was designed specifically for his unique genetic disorder and cannot be used to treat other individuals with different disorders. This poses a unique challenge with regards to scaling up such technologies for mass consumption, something that disincentives pharmaceutical companies to invest in their development.
Getting regulatory approvals is another issue. 'To do such a thing in India is very difficult because it also means that you will have to get rid of red tapism,' Chakraborty said.
It remains to be seen how researchers make such personalised treatments more accessible. Till then, only a few fortunate people like KJ will benefit from base editing therapies.
Hashtags
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
The Hindu
2 days ago
- The Hindu
Europe suffers its largest diphtheria outbreak in 70 years
The largest diphtheria outbreak to strike Western Europe in 70 years has been affecting vulnerable people such as migrants and the homeless since 2022, new research said Wednesday. Diphtheria is a highly contagious bacterial infection that can attack the respiratory tract and spread throughout the body, causing a sore throat, fever and other symptoms. For unvaccinated people, it can be fatal in around 30 percent of cases, and is deadlier for children, according to the World Health Organization. In 2022, there was an unusual surge in the bacteria that causes diphtheria -- Corynebacterium diphtheriae -- in several European countries, particularly among recently arrived migrants, according to a study in the New England Journal of Medicine. That year 362 cases were recorded by the European Centre for Disease Prevention and Control. Contact tracing and screening helped tamp down the outbreak, but rare infections have continued to be recorded, the researchers said. A total of 536 cases, including three deaths, have been recorded across Europe since the start of 2022. Patient samples from 10 countries showed that 98 percent of the cases were in males with an average age of 18. Almost all had recently migrated. "The outbreak, which mainly affected migrants from Afghanistan and Syria, was not the result of people being infected in their countries of origin, but during their migration journeys or in their places of accommodation in European countries," said a joint statement from France's public health agency and the Pasteur Institute. The genetic similarities between the strains seen in people from different countries suggests that there was a "recent point of contact, outside the country of origin" at the source of the outbreak, the statement added. The exact areas affected by the outbreak remains unclear. But a genetic link between the 2022 strain and the one detected in Germany this year indicates that "the bacteria continues to circulate quietly in Western Europe," the statement said. Vaccination is very effective at fending off diphtheria, and the researchers emphasised the importance of immunisation programmes for the general public. They also called for European nations to do more to ensure their most vulnerable people avoid contracting the disease. That included raising awareness of the symptoms among doctors and those in contact with migrants and the homeless, as well as increasing access to vaccines and antibiotic drugs.
Time of India
2 days ago
- Time of India
Europe suffers its largest diphtheria outbreak in 70 years
Paris: The largest diphtheria outbreak to strike Western Europe in 70 years has been affecting vulnerable people such as migrants and the homeless since 2022, new research said Wednesday. Diphtheria is a highly contagious bacterial infection that can attack the respiratory tract and spread throughout the body, causing a sore throat, fever and other symptoms. For unvaccinated people, it can be fatal in around 30 percent of cases, and is deadlier for children, according to the World Health Organization. In 2022, there was an unusual surge in the bacteria that causes diphtheria -- Corynebacterium diphtheriae -- in several European countries, particularly among recently arrived migrants, according to a study in the New England Journal of Medicine. That year 362 cases were recorded by the European Centre for Disease Prevention and Control . Contact tracing and screening helped tamp down the outbreak, but rare infections have continued to be recorded, the researchers said. A total of 536 cases, including three deaths, have been recorded across Europe since the start of 2022. Patient samples from 10 countries showed that 98 percent of the cases were in males with an average age of 18. Almost all had recently migrated. "The outbreak, which mainly affected migrants from Afghanistan and Syria, was not the result of people being infected in their countries of origin, but during their migration journeys or in their places of accommodation in European countries," said a joint statement from France's public health agency and the Pasteur Institute. The genetic similarities between the strains seen in people from different countries suggests that there was a "recent point of contact, outside the country of origin" at the source of the outbreak, the statement added. The exact areas affected by the outbreak remains unclear. But a genetic link between the 2022 strain and the one detected in Germany this year indicates that "the bacteria continues to circulate quietly in Western Europe," the statement said. Vaccination is very effective at fending off diphtheria, and the researchers emphasised the importance of immunisation programmes for the general public. They also called for European nations to do more to ensure their most vulnerable people avoid contracting the disease. That included raising awareness of the symptoms among doctors and those in contact with migrants and the homeless, as well as increasing access to vaccines and antibiotic drugs. ic-dl/giv
Indian Express
2 days ago
- Indian Express
Meet India's first gene-edited sheep, born in a Srinagar lab, now a healthy six-month-old
Six months ago, Professor Riyaz Ahmad Shah and his team at the Embryo Biotechnology Lab of Sher-e-Kashmir University of Agricultural Sciences and Technology (SKUAST) in Srinagar celebrated a quiet success – the birth of a Kashmir Merino, India's first gene-edited sheep. But the team didn't rush to announce its arrival to the world – they waited, given the inherent uncertainties of scientific breakthroughs. The announcement was finally made last week after the results were validated by gene sequencing and standardised. 'This marks a new era in genetic research and has put us on the future path of transgenics in animals (inserting a foreign gene in an animal),' says Prof Shah, Dean of the Faculty of Veterinary Sciences and Animal Husbandry at SKUAST. Gene-editing of livestock animals is a growing area of research in India with significant applications targeted at enhanced meat yield and milk production, disease resistance and resilience to impacts of climate change. Prof Shah and his team edited the sheep's myostatin gene. 'This particular gene is a negative growth regulator. By targeting this gene, we can increase the muscle mass of a sheep by 30 per cent,' says Prof Shah. Talking about the significance of the project, Dr Naresh Selokar, Senior Scientist, Animal Biotechnology at National Dairy Research Institute (NDRI) in Karnal, says, 'In the Indian context, this (gene-editing of sheep) is a very significant achievement, especially considering the trait (gene) that has been targeted. 'Given our population and the huge demand for meat, without gene-editing, it is impossible to change the trait of a farm animal or to make them disease resistant. This is already an easy and approved method for production globally… In India, we need to have more high-quality, disease-resistant produce through gene editing,' says Dr Selokar, who is credited with developing the first gene-edited embryo of a buffalo in 2024. It was in 2020 that Prof Shah and his core team at SKUAST's Embryo Biotechnology Lab — Dr Suhail Magray, Dr Muneer Dar, Dr Younus Farooq, Dr Nida Handoo, Dr Syed Hilal, Dr Abrar and Dr Nafis — embarked on their ambitious project. The embryo of the sheep was first kept under laboratory conditions for some time and then transferred to a surrogate mother, before being gene-edited in July last year. To edit the myostatin gene of the sheep, the team used CRISPR-Cas9, the genome editing technology, which won Emmanuelle Charpentier and Jennifer Doudna the Nobel Prize in Chemistry that very year. The gene-edited sheep was finally born in December last year. It's now a healthy six-month-old, housed at a farm on the Shuhama campus of the Faculty of Veterinary Science. The researchers say it weighed 3.15 kg at birth and has gained 'significant weight' since then. 'We specifically chose the myostatin gene since the goal is to increase the muscle mass of sheep. Any technological advancement in livestock and agriculture is meant to increase the farmer's income and this is an important step towards that,' says Prof Shah. Their journey, says Dr Suhail Magray, wasn't without hurdles. 'We tried different techniques to get the desired results. We failed the first three times, before we got the breakthrough,' he says. In a span of 15 years, SKUAST's Centre of Animal Biotechnology has taken a leap from cloning to gene-editing. In 2012, when the lab was in its infancy, it developed the world's first pashmina goat clone, which it named Noori, using the somatic cell nuclear transfer technique. The birth of Noori was seen as a breakthrough in cloning of endangered species. Noori was born on March 9, 2012 and died in March 2023 when it was 11 years old — the average age for the pashmina goat. Their lab is now working on another gene edit — FGF5 (Fibroblast growth factor) — that will help improve the fibre quality of sheep. 'The beginning has been made,' says Dr Magray. 'Now, we can work on other genes as well that would help to make the animals disease resistant.' With the success of their latest project, Prof Shah and his team are already preparing for the next leap — transgenics. 'We are already working on combining cloning with gene-editing to enhance the technique but our next step is to move towards transgenics,' says Prof Shah. 'Transgenics is important if we are to produce proteins of therapeutic importance – if we can, for instance, produce protein in the milk of an animal, that animal will work as a factory of proteins; animals can be pharmaceutical factories, we can have anti-cancer drugs. But for that, we have to have controlled conditions and bio-secure zones.' A pioneer in genetics, Prof Shah was a PhD student at NDRI, Karnal, and was part of the team that's credited with the first buffalo cloning in the world. The buffalo, Samrupa, didn't survive and six months later, the team developed the second buffalo clone, 'Garima'. Bashaarat Masood is a Special Correspondent with The Indian Express. He has been covering Jammu and Kashmir, especially the conflict-ridden Kashmir valley, for two decades. Bashaarat joined The Indian Express after completing his Masters in Mass Communication and Journalism from the University in Kashmir. He has been writing on politics, conflict and development. Bashaarat was awarded with the Ramnath Goenka Excellence in Journalism Awards in 2012 for his stories on the Pathribal fake encounter. ... Read More
