Now that the gene-editing genie is out of the bottle, what would you wish for first?
Babies with “perfect” eyes, over-the-top intelligence, and a touch of movie star charisma?
Or a world free of disease… not just for your family, but for every family in the world?
Based on recent events, many scientists are working toward the latter.
Earlier this month, scientists from the Oregon Health & Science University used a gene editing tool to correct a disease-causing mutation in an embryo.
The technique, known as CRISPR-Cas9, fixed the mutation in the embryos’ nuclear DNA that causes hypertrophic cardiomyopathy, a common heart condition that can lead to heart failure or cardiac death.
This is the first time that this gene-editing tool has been tested on clinical-quality human eggs.
Had one of these embryos been implanted into a woman’s uterus and allowed to fully develop, the baby would have been free of the disease-causing variation of the gene.
This type of beneficial change would also have been passed down to future generations.
None of the embryos in this study were implanted or allowed to develop. But the success of the experiment offers a glimpse at the potential of CRISPR-Cas9.
Still, will we ever be able to gene-edit our world free of disease?
How gene editing works
According to the Genetic Disease Foundation, there are more than 6,000 human genetic disorders.
Scientists could theoretically use CRISPR-Cas9 to correct any of these diseases in an embryo.
To do this, they would need an appropriate piece of RNA to target corresponding stretches of genetic material.
The Cas9 enzyme cuts DNA at that spot, which allows scientists to delete, repair, or replace a specific gene.
Some genetic diseases, though, may be easier to treat with this method than others.
“Most people are focusing, at least initially, on diseases where there really is only one gene involved — or a limited number of genes — and they’re really well understood,” Megan Hochstrasser, PhD, science communications manager at the Innovative Genomics Institute in California, told Healthline.
Diseases caused by a mutation in a single gene include sickle cell disease, cystic fibrosis, and Tay-Sachs disease. These affect millions of people worldwide.
These types of diseases, though, are far outnumbered by diseases like cardiovascular disease, diabetes, and cancer, which kill millions of people across the globe each year.
Genetics — along with environmental factors — also contribute to obesity, mental illness, and Alzheimer’s disease, although scientists are still working on understanding exactly how.
Right now, most CRISPR-Cas9 research focuses on simpler diseases.
“There are a lot of things that have to be worked out with the technology for it to get to the place where we could ever apply it to one of those polygenic diseases, where multiple genes contribute or one gene has multiple effects,” said Hochstrasser.
Treating adults and children, not embryos
Although “designer babies” gain a lot of media attention, much CRISPR-Cas9 research is focused elsewhere.
“Most people who are working on this are not working in human embryos,” said Hochstrasser. “They’re trying to figure out how we can develop treatments for people that already have diseases.”
These types of treatments would benefit children and adults who are already living with a genetic disease, as well as people who develop cancer.
This approach may also help the 25 million to 30 million Americans who have one of the more than 6,800 rare diseases.
“Gene editing is a really powerful option for people with rare disease,” said Hochstrasser. “You could theoretically do a phase I clinical trial with all the people in the world that have a certain [rare] condition and cure them all if it worked.”
Rare diseases affect fewer than 200,000 people in the United States at any given time, which means there is less incentive for pharmaceutical companies to develop treatments.
These less-common diseases include cystic fibrosis, Huntington’s disease, muscular dystrophies, and certain types of cancer.
Last year researchers at the University of California Berkeley made progress in developing an ex vivo therapy — where you take cells out of a person, modify them, and put them back into the body.
This treatment was for sickle cell disease. In this condition, a genetic mutation causes hemoglobin molecules to stick together, which deforms red blood cells. This can lead to blockages in the blood vessels, anemia, pain, and organ failure.
Researchers used CRISPR-Cas9 to genetically engineer stem cells to fix the sickle cell disease mutation. They then injected these cells into mice.
The stem cells migrated to the bone marrow and developed into healthy red blood cells. Four months later, these cells could still be found in the mice’s blood.
This is not a cure for the disease, because the body would continue to make red blood cells that have the sickle cell disease mutation.
But researchers think that if enough healthy stem cells take root in the bone marrow, it could reduce the severity of disease symptoms.
More work is needed before researchers can test this treatment in people.
A group of used a similar technique last year to treat people with an aggressive form of lung cancer — the first clinical trial of its kind.
In this trial, researchers modified patients’ immune cells to disable a gene that is involved in stopping the cell’s immune response.
Researchers hope that, once injected into the body, the genetically edited immune cells will mount a stronger attack against the cancer cells.
These types of therapies might also work for other blood diseases, cancers, or immune problems.
But certain diseases will be more challenging to treat this way.
“If you have a disorder of the brain, for example, you can’t remove someone’s brain, do gene editing and then put it back in,” said Hochstrasser. “So we have to figure out how to get these reagents to the places they need to be in the body.”
Preventing human disease indirectly
Not every human disease is caused by mutations in our genome.
like malaria, yellow fever, dengue fever, and sleeping sickness kill more than 1 million people worldwide each year.
Many of these diseases are transmitted by mosquitoes, but also by ticks, flies, fleas, and freshwater snails.
Scientists are working on ways to use gene editing to reduce the toll of these diseases on the health of people around the world.
“We could potentially get rid of by engineering mosquitoes that can’t transmit the parasite that causes malaria,” said Hochstrasser. “We could do this using the CRISPR-Cas9 technique to push this trait through the entire mosquito population very quickly.”
Researchers are also using CRISPR-Cas9 to create “designer” foods.
DuPont recently used gene editing to produce a new variety of waxy corn that contains higher amounts of starch, which has uses in food and industry.
Modified crops may also help reduce deaths due to malnutrition, which is responsible for nearly half of all deaths worldwide in children under 5.
Scientists could potentially use CRISPR-Cas9 to create new varieties of food that are pest-resistant, drought-resistant, or contain more micronutrients.
One benefit of CRISPR-Cas9, compared to traditional plant breeding methods, is that it allows scientists to insert a single gene from a related wild plant into a domesticated variety, without other unwanted traits.
Gene editing in agriculture may also move more quickly than research in people because there is no need for years of lab, animal, and human clinical trials.
“Even though plants grow pretty slowly,” said Hochstrasser, “it really is quicker to get [genetically engineered plants] out into the world than doing a clinical trial in people.”
Safety and ethical concerns
CRISPR-Cas9 is a powerful tool, but it also raises several concerns.
“There’s a lot of discussion right now about how best to detect so-called ‘off-target effects,’” said Hochstrasser. “This is what happens when the [Cas9] protein cuts somewhere similar to where you want it to cut.”
Off-target cuts could lead to unexpected genetic problems that cause an embryo to die. An edit in the wrong gene could also create an entirely new genetic disease that would be passed onto future generations.
Even using CRISPR-Cas9 to modify mosquitoes and other insects raises safety concerns — like what happens when you make large-scale changes to an ecosystem or a trait in a population that gets out of control.
There are also many ethical issues that come with modifying human embryos.
So will CRISPR-Cas9 help rid the world of disease?
There’s no doubt that it will make a sizeable dent in many diseases, but it’s unlikely to cure all of them any time soon.
We already have tools for avoiding genetic diseases — like early genetic screening of fetuses and embryos — but these are not universally used.
“We still don’t avoid tons of genetic diseases, because a lot of people don’t know that they harbor mutations that can be inherited,” said Hochstrasser.
Some genetic mutations also happen spontaneously. This is the case with many cancers that result from such as UV rays, tobacco smoke, and certain chemicals.
People also make choices that increase their risk of heart disease, stroke, obesity, and diabetes.
So unless scientists can use CRISPR-Cas9 to find treatments for these lifestyle diseases — or genetically engineer people to stop smoking and start biking to work — these diseases will linger in human society.
“Things like that are always going to need to be treated,” said Hochstrasser. “I don’t think it’s realistic to think we would ever prevent every disease from happening in a human.”