Human Embryos Genetically Modified To Eliminate The Gene Responsible For Sudden Deaths!

By: Ria Majumdar
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A major breakthrough is rocking the field of Genetics and Genomics right now, as a joint venture by geneticists from the United States, Korea and China has successfully eliminated the mutated gene MYBPC3 responsible for causing Hypertrophic Cardiac Myopathy (HCM), a genetic disorder that creates structural abnormalities in an individual's heart.

The team successfully "cured" 42 out of 58 human embryos, which is an astonishingly high success rate (72.4%) in a field that has only seen unsuccessful attempts in the past.

The research and its findings were recently published in Nature, an international journal of science, and is creating major ripples in the scientific community, as the controversy around editing human genes has stirred up once again

CRISPR-Cas9 And The Challenging Field Of Genetic Modification

While genetic modification to create designer babies may sound easy to do in science-fictional novels, in reality the process of editing DNA sequences is very difficult. Not only do you need a tool that can identify and cut specific sequences of the DNA, you also need it to be so specific that it does not introduce any mutations of its own.

That's where CRISPR-Cas9 comes in.

The word "CRISPR" is an acronym for Clustered Regularly Interspaced Short Palindromic Repeat. And it is a "genetic scissor", which can swoop in and modify animal and plant genes to produce desired results (like eliminating genetic disorders and breeding superior crops).

But CRISPR is just a broad umbrella term. The actual "genetic scissors" are simply various systems under CRISPR. ystems like Cas9, which was already considered the most advanced of the lot, until Dr. Feng Zhang created a version of it that was even more ultra-specific.

This new version was capable of identifying mutated genes that cause genetic disorders (something the other CRISPR-Cas9 versions couldn't do) and could further edit them out. The same version used by the researchers in this ground-breaking study.

An Astonishingly High Success Rate In A Historically Unsuccessful Venture

Geneticists have been trying to modify the human gene ever since they successfully managed to modify crops like corn and brinjal. But every attempt has been marked by failure and controversies. The most recent of which was an attempt by some Chinese researchers at the Sun Yat-Sen University, Guangzhou.

The team of researchers were trying to eliminate the mutated version of the HBB gene responsible for causing β-Thalassemia in humans, which is a debilitating genetic disorder that affects an individual's ability to produce haemoglobin in blood, causing moderate to severe anaemia and even death at an early age due to heart failure.

genetic modification

The stakes were high and the imperative was to succeed. Because success meant a possible cure for a disorder that affects nearly 5% of the world population at present. A number that is projected to increase in subsequent generations.

Unfortunately, the research had to be abandoned in its early stages, as the team encountered an abnormally high rate of unintended mutations in the healthy DNA parts of the embryos being tested. A phenomenon called off-target mutation, which is observed when the "genetic scissor" cuts sequences of the DNA that look similar to the target sequence, but instead introduces undesired mutations in the gene.

While this phenomenon is common in all gene-editing researches, the number of such undesired mutations are usually quite low in both animal experiments and human non-stem cell editing.

The other challenge that most gene-editing researches face is the phenomenon of Mosaicism. A condition where some cells of the individual have completely different genetic information as compared to the rest of the body. And while you can observe mosaicism even in nature, like in individuals affected by Down's syndrome, usually all mosaic embryos are naturally aborted by kill switches within the cell.

In the light of all these challenges, the feat accomplished by the researchers of the newly published study is truly astounding.

The Secret Behind The Success

genetic modification

During the course of this research, the geneticists tried 2 different techniques to edit out the mutated MYBPC3 gene.

The first technique used CRISPR-Cas9 to edit the mutation after the embryo had already been formed. A technique used very commonly during such attempts.

The results, understandably, led to failure with most of the embryos showing a mosaic of "cured" and "diseased" cells.

But the second technique was more novel.

In this approach, the researchers first used CRISPR-Cas9 to repair the sperm's genes before they fertilized the egg to produce an embryo.

The result: 42 out of 58 embryos well "fully-cured" without a single mosaic cell in the midst. A feat that, if it were being clinically tested, would have produced 42 healthy babies for the first time in families that have been plagued by a long history of HCM-related woes.

Curing The Villainous Genes Causing Hypertrophic Cardiac Myopathy

HCM is a genetic disorder that affects 1 out of every 500 individuals in the world. Which when projected out, translates to 1.46 million people who are at a high risk of dying of sudden heart attack because their abnormally large hearts cannot pump enough blood to keep up with their body's oxygen demand.

In fact, 2-8% of the Indian population suffers from this disorder. A number that generously contributes towards 9.5 lakh heart-attack-related deaths in our country every year.

Considering these scary figures, and the fact that nearly 40% of all individuals born with HCM have the mutated MYBPC3 gene, the success of this research is truly a landmark moment, as it constitutes a gigantic leap towards curing over 10,000 genetic disorders that are still considered incurable in the field of medical science.

but it is still a leap with a big hurdle in its path.

Scourge Of Controversies: Why Human Gene Editing Is Still A Big No-No

While proponents of genetic modification believe it is a sin to withhold technology that has the potential to cure devastating diseases like HIV and cancer, the opponents of human gene-editing believe that mosaicism and off-target mutations can introduce dangerous and uncontrollable genes in the human gene pool. And given the unpredictability of genetic modification, it makes sense why a success rate of 72.4% doesn't seem enough to the scientific community.

But logic isn't the only enemy in this equation. The other reason why federal laws still prohibit clinical trials of gene editing is because of the social and psychological implications of such a move.

With researches that have successfully demonstrated they can change the coat colour of mice through gene editing, the main concern is the use of this tool for producing "designer babies" with fairer skin and other superior attributes. Something that can potentially widen the existing gap between the privileged and the poor by artificially creating a genetically "superior" and "inferior" race.

And what if the child grows up to resent his parent's decision to modify him without his consent? A scenario that is indeed possible because most people do not even understand the risks mentioned in the consent forms they sign before basic medical procedures like tooth extractions and plastic surgery.

Given all these controversies around human genetic modification, it may take some more time before researches like this one get the green signal for clinical trials that have the potential to change the course of human history.

Until then, we can just wait and watch.

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