Gene Therapy Cures Color-Blind Monkeys
All male squirrel monkeys are color blind, making them ideal for the test. Furthermore, the mechanism for their color blindness (the lack of L-opsin protein) is similar to many cases of human color blindness. The same method of gene therapy that was used in the LCA tests, was adapted to help monkeys produce opsin. First, scientists knew which gene codes for L-opsin production. A virus was created to carry that gene. The virus was then injected into the monkey’s retina. Like any self-respecting virus, it infected cells and in the process passed on the new gene. These upgraded cells in the retina now had the gene to produce L-opsin and boom…monkeys see in full color.
While the research was only recently published, it took place over several years. After gene therapy, it took five months of rewards-based testing (like that in the video) to discover that the squirrel monkeys could detect shades of red. It is unclear if that time was due to the slow development or adaptation of neural pathways, or the cognitive progression of the monkeys. In fact, the mechanism for how the monkeys’ brains were changed to receive the new input is not well understood at all. The change is likely very stable – the monkeys have retained their new color perception for the more than two years that have passed since testing began.
The fact remains that we are years from seeing color blind gene therapy being offered to humans. It is obviously still in the animal testing phase. The LCA treatment was for safety testing, not efficacy testing, so there are years of study ahead in that field as well. Still, genetic treatments are advancing and could one day be used to cure advanced macular degeneration (AMD), and other common forms of blindness.
And gene therapy isn’t just limited to the eye. Cures for almost any genetic condition could be done in a similar manner to the blindness treatments. In theory, all it takes to fix an illness is finding the responsible gene and replacing it. We could see these treatments rise in availability in the next ten to twenty years.
Gene therapy could also allow us to update our genes so that we could view colors outside our natural range, or develop low-light vision as good as other animals. Enhancements for oxygen absorption could make super athletes out of everyone. Such possibilities are likely decades away, but they’re not out of the question.
Gene therapy: A cure for congenital blindness
Congenital Blindness is blindness that occurs when a child is born. There are many forms of congenital blindness. One specific form of congenital blindness is Leber’s Congenital Amaurosis.
Leber’s Congenital Amaurosis (LCA) is a form of blindness that is usually found at a very young age. It is extremely rare and occurs in 3 in 100,000 newborns.
A digram of how gene therapy works
A diagram of how gene therapy works
Though LCA does not currently have a cure, experts have been successfully using gene therapy to allow patients with the disease to gain vision. Gene therapy is a process in which a working gene is inserted into a patient to repair a malfunctioning gene.
In 2007, a team of experts at the University of Pennsylvania and Children’s Hospital of Philadelphia, conducted gene therapy on twelve patients with LCA. The above diagram shows how the gene therapy worked.
- An eye syringe containing a vector, or genetically engineered virus, is injected into the patient’s photoreceptor cells.
- The vector releases the healthy gene, in this case, the RPE65 gene.
- After gene therapy was performed on twelve patients, vision was almost completely restored to their eyes. The restored vision has been permanent from the time of the experiment (started in October 2007).
Cystic Fibrosis Gene Therapy
With gene therapy, treatment targets the cause of cystic fibrosis rather than just treating the symptoms. Although the first gene therapy experiments have involved lung cells, scientists hope that these technologies will be adapted to treat other organs affected by cystic fibrosis.
Is There a "Cystic Fibrosis Gene?"
The cause of cystic fibrosis (CF) is a defect in the cystic fibrosis transmembrane conductance regulator (CFTR) gene.
This gene for cystic fibrosis makes a protein that controls the movement of salt and water in and out of your cells. In people with cystic fibrosis, the gene does not work effectively. As a result, cells that line the passageways of the lungs, pancreas, and other organs produce abnormally thick, sticky mucus. This mucus obstructs the airways and glands, which causes the characteristic signs and symptoms of cystic fibrosis.
Other factors may influence the course of cystic fibrosis. For example, changes in genes other than CFTR might help explain why some people with the disease are more severely affected than others. However, most of these genetic changes have not been identified.
Cystic fibrosis is inherited in an autosomal recessive pattern, which means that two copies of the cystic fibrosis gene in each cell are altered. In most cases, the parents of an individual with an autosomal recessive disorder are carriers of one copy of the altered gene, but do not show signs and symptoms of the disorder.
When two cystic fibrosis carriers have a baby, the baby has a:
- One in four chance of inheriting two abnormal CFTR genes and having cystic fibrosis.
- One in four chance of inheriting two normal CFTR genes and not having cystic fibrosis or being a carrier.
- Two in four chance of inheriting one normal CFTR gene and one abnormal CFTR gene. The baby will not have cystic fibrosis, but will be a carrier like its parents.
How gene therapy could cure brain diseases
Nature’s neurology journal has a freely available article on a technique that interferes with the translation of genetic information into proteins that may help prevent inherited brain diseases.
DNA has two main functions. The ‘template function’ of DNA is to pass on genes through generations and allow different traits to be inherited.
The ‘transcriptional function’ of DNA is to allow these genes to be expressed at appropriate times and places (and not expressed at others) to allow the cell to do its work.
‘Expression’ just means ‘turned into a protein’ and genes are just blueprints for proteins.
The blueprint gets turned into a protein by messenger RNA, which ‘reads off’ the information, then moves away to assemble the protein from a store of amino acid component parts.
As different cells in the body have different functions, and individual cells need to behave differently depending on what’s happening, different proteins need to be created at different times.
Disorders like huntington's disease result from genes that cause damaging proteins to be formed. These lead to the malfunction and death of brain areas that, in turn, leads to cognitive problems, movement difficulties, mental illness and eventual death.
Using a technique called RNA interference, researchers have found they can selectively interfere with the process where messenger RNA assembles proteins from the DNA’s genetic information.
Essentially, small chunks of gene-specific RNA are introduced into the cell, these find the messenger RNA and destroy the information before it gets turned into a protein.
In other words, it prevents specific genes from being turned into proteins.
This has caused a great deal of excitement because it could lead to treatments for disorders like Huntingdon’s by simply ‘silencing’ the rogue Huntingdon’s gene.
While you might have a rogue gene, RNA interference could essentially gag it, meaning it would never have a knock-on effect in the brain.
This has been demonstrated in very limited lab tests, and the Nature article examines the prospects for it being developed into a widespread treatment.
There are still some difficulties to overcome, however. One of which is how to get the interfering RNA into the right cells in the brain, a difficulty with many treatments owing to the filtering effect of the blood-brain barrier Another is how to make sure that the technique affects only the disease process. Researchers talk about proteins being involved in ‘chemical cascades’, meaning that they are involved in huge and complex mechanisms in the body.
It’s hard to predict exactly what effect silencing a gene will have, and whether your technique for doing so will also interfere with some other processes that use some of the same mechanisms, some of which we probably don’t even know about at the present.
RNA interference is still an experimental process, but it holds great potential for treating inherited brain diseases. The Nature article is a fantastic guide to the cutting edge of the science in this area.
