Posts Tagged ‘gene-’
Messing with the blueprints: Gene therapy has arrived – Mayo Clinic Press
You can add Nov. 16, 2023, to July 16, 1945 the day nuclear power moved from the theoretical to the actual as an entry to the list of consequential moments for everyones favorite vertebrate, Homo sapiens.
The news was easy to miss, but there it was. The United Kingdom announced that it would be the first country in the world to approve the use of gene editing as a medical therapy, starting with two inherited types of anemia: beta-thalassemia, and the more widely known sickle cell anemia. The U.S. Food and Drug Administration (FDA) followed suit three weeks later.
Its official: we humans are going to mess with our DNA, our original blueprints. DNA is the genetic instructions dictating how we look and behave, and that define what diseases we may develop, be prone to or be free of. With our ever-improving gene-editing skills, we are now prepared to peel back the pages of this ancient and sacred text and write the story the way we want to hear it.
DNA makes up the letters of lifes instruction manual for humans or any living thing. Genes organize those letters into words and paragraphs. Chromosomes organize those genes into chapters. In humans, each cell has 23 pairs of chromosomes. Inside the cell, DNA provides the formula for manufacturing specific proteins. Its the blueprint that tells each cell what to build, and how to build it.
Unfortunately, DNA can get altered or damaged, an occurrence thats referred to as a mutation. A mutation can be either inherited or newly acquired. It can cause the gene to produce a faulty product or no product at all. In the case of sickle cell disease, a mutation in the gene that codes for hemoglobin a complex protein that allows red blood cells to shuttle oxygen from the lungs to the body can lead to a whole lot of pain and suffering.
Red blood cells are flexible, allowing them to scooch through tiny capillaries where they unload their oxygen. In sickle cell disease, the mutation in the hemoglobin molecule can cause a red blood cell to change shape from a circle to a sickle. Sickled red blood cells lack flexibility, so they plug up the very capillaries they were supposed to be sliding through. Just as a traffic accident can lead to a pileup of cars behind it, one stuck sickled cell can trigger an upstream backup of stuck sickled cells.
Traffic jams are a pain, but a sickle cell attack aptly termed a crisis produces a deep, aching pain that may be unrivaled in human suffering. As capillaries and small arteries plug up, downstream tissues are left without oxygen. These blood-starved tissues begin screaming for oxygen as if their lives depended on it which they do.
Although a sickle cell crisis can cause excruciating pain, thankfully it is only rarely lethal. With pain medications, intravenous fluids, blood transfusions and oxygen support, the pain eventually eases. But repeated episodes take their toll on the body, significantly shortening the life expectancy of those with the disease.
Those with sickle cell disease (SCD) carry two copies of a sickling-prone hemoglobin gene (HbS). One copy comes from each parent. Those with sickle cell trait (SCT) have just one copy of HbS, but thats not enough to cause sickling except in rare circumstances like scuba diving or mountain climbing.
The sickle cell gene seems to have originated in sub-Saharan Africa, where having a single copy of the gene having SCT protects against severe malaria infections. Thats because the parasite that causes malaria, which reproduces by infecting red blood cells, has a harder time doing that inside cells carrying a lone sickle gene.
Although the prevalence of the sickle cell gene remains highest in sub-Saharan Africa, slavery and migration patterns have expanded its global range, so that today SCD can affect people of Hispanic, Southern European, Middle Eastern or Asian Indian backgrounds.
In the United States, 7% to 8% of Black newborns carry the sickle cell trait. In addition, 0.7% of Hispanic newborns, 0.3% of white newborns, and 0.2% of Asian or Pacific Islander newborns carry the trait. One out of every 365 Black newborns will have SCD. In total, about 100,000 people in the U.S. and 20 million people worldwide have SCD. Thats a lot of people hoping for a cure.
Casgevy is the first FDA-approved therapy to use CRISPR gene-editing technology. CRISPR is an acronym we can all be grateful for because it eliminates a phrase we will never be able to remember: clustered regularly interspaced short palindromic repeats.
In the case of Casgevy, CRISPR is used to create a line of red blood cells that manufacture hemoglobin F (HbF) thats F as in fetus. HbF has stronger oxygen-binding characteristics than adult hemoglobin (HbA). Thats because in the womb humans are breathing through the mothers placenta, and not through the lungs, which are filled with amniotic fluid. HbF production typically gets turned off soon after birth. Thats unfortunate for those with sickle cell disease who carry HbS, not HbA because HbF helps prevent sickling.
Casgevy turns HbF production back on.
Lyfgenia works by giving people with sickle cell disease a line of blood cells that can manufacture a form of adult hemoglobin (HbA).
Neither Casgevy nor Lyfgenia completely eliminates sickle cells, but they dilute the concentration of sickle-prone cells, thereby preventing sickle cell crises.
No surprise treatment with Casgevy and Lyfgenia is more complicated than what I just described. It requires removing stem cells from the blood. Stem cells are a little like the queen bee in a hive: They produce all the cells that will keep the body vigorous and healthy. In this application, the stem cells of interest are the ones that manufacture the new red blood cells needed to replace those at the end of their 120-day life span (or 20 to 30 days for fragile sickle cells). After these blood stem cells are removed and sent to the lab for gene therapy, the patient is given chemotherapy to decrease the number of stem cells making sickled red blood cells. This makes room for the new-and-improved stem cells.
Chemotherapy comes in a variety of potencies, and in this case, its fairly potent the kind you need to be in the hospital for. Following the gene therapy infusion, itll be 3 to 6 more weeks in the hospital waiting for the body to recover from the chemotherapy and for the modified stem cells to start growing back in serious numbers.
Like nuclear power or artificial intelligence, the technology of gene therapy brings great promise but also serious risks and ethical concerns.
There are the risks of the treatment itself: Did the gene therapy get inserted into the right gene location, and is it functioning correctly? Or did it end up in the wrong spot, altering the function of genes that we meant to leave alone?
There is the ethical question of who will get stem cell therapy. The medical complexity and steep cost of stem cell therapy a cool $2.2 million for a Casgevy treatment, and $3.1 million for Lyfgenia make it a boutique item only the haves will be able to afford.
And there are the ethics of how and where we will apply the technology. Although history teaches us that H. sapiens is an inventive and curious creature, we also are a never-quite-satisfied, boundary-pushing and occasionally nefarious lot. While were using gene therapy to eliminate sickle cell disease or perhaps someday Alzheimers, cardiovascular disease or what have you someone is going to ask: Whats the harm in getting rid of things like nearsightedness, balding, belly fat, wrinkles? And while were at it, why not use gene therapy to make sure we or our offspring have what it takes to compete in the NBA or the Ivy League, Hollywood or the Navy Seals? And can we eliminate dying?
Dont think we humans will go there? Comedian and futurist Jon Stewart told Stephen Colbert he sees it going this way: The world ends. The last words man utters are somewhere in a lab. A guy goes, Huh-huh. It worked!
Scientists disagree on whether Stewart was joking but recommend further research.
Relevant reading
When Winter Came
Dr. Pierre Sartor wrote an inspiring first-person account of how he treated more than 1,000 patients and by his reckoning, lost only five which lay forgotten in a lockbox of family artifacts until it was discovered decades later by his granddaughter, Beth Obermeyer, a journalist and author of
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Messing with the blueprints: Gene therapy has arrived - Mayo Clinic Press
This Pitt program is leveling up the gene therapy workforce in Pittsburgh – University of Pittsburgh
This Pitt program is leveling up the gene therapy workforce in Pittsburgh University of Pittsburgh
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This Pitt program is leveling up the gene therapy workforce in Pittsburgh - University of Pittsburgh
What Is CRISPR Gene Editing and How Does It Work?
In 2013, two biochemists published a paper proclaiming theyd discovered a potentially game-changing method of manipulating genes. CRISPR which sounds like a veggie-forward gastro pub won them each a Nobel Prize.
In the years since, CRISPR (or Clustered Regularly Interspaced Short Palindromic Repeats) has lived up to the hype. Its altered the global scientific landscape and raised questions about what kinds of revolutionary changes scientists and healthcare providers could and should pursue.
What if we could make foods allergy-free and crops drought-resistant? What if we could eliminate invasive species and protect against infectious diseases like malaria? What if we could revive extinct species? What if we could remove or repair mutations that cause inherited conditions? Or create custom immunotherapies to treat an individuals cancer?
The prospects are that exciting.
If your understanding of genetics starts and ends with high school biology or the (very fictional) Jurassic Park movies youre not alone. This stuff is complicated. Thats why we asked genomics and immunotherapy expert Timothy Chan, MD, PhD, to break CRISPR down for us, so we can better understand why, over a decade later, its still got researchers so excited.
Before we jump into CRISPR, lets start with the concept of gene editing.
Gene editing is the process of altering genetic material (DNA). That could mean changing a few individual genes or an entire sequence. Research has been ongoing for more than a decade thats looking at using gene editing on mutations that cause serious health conditions in people. The goal of this gene editing research is to eliminate or correct the mutation thats causing the health condition, or has the potential to cause one, such as certain cancers. In other research studies, gene editing is being explored so a mutation isnt passed down to children at birth.
For example, the U.S. Food and Drug Administration (FDA) approved a gene therapy in late 2022 that introduces a gene needed for blood clotting into people with hemophilia B. Its one of several cellular and gene therapy products currently in use today.
There are many different techniques and applications for gene editing. CRISPR is one approach to gene editing thats showing promise in ongoing clinical trials.
Now that were clear on what gene editing is, lets focus on a specific approach: CRISPR.
Clustered Regularly Interspaced Short Palindromic Repeats, otherwise known as CRISPR, was originally identified in bacteria, as a bacterial defense system, says Dr. Chan.
Thats right. Bacteria have immune systems, too.
CRISPR contains spacers sequences of DNA left over from unfriendly viruses or other entities as well as repeating sections of genetic material. Those sequences provide acquired immunity, and form the building blocks of the gene editing system or process. It creates a sort of blueprint that allows enzymes in genetic material to make changes to sequences of DNA in living cells. One of the best-known enzymes used for this purpose is called Cas9, which is why youll sometimes hear people talk about CRISPR-Cas9.
Over the years, people have discovered that specific enzymes that allow CRISPR to work Cas9 is one of them.But there are other ones, and they can be tailored to target sequences of interest in the DNA for specific cuts to be made, Dr. Chan explains.
You can think of the underlying mechanism of CRISPR gene editing as being similar to the way magnetic shapes are drawn to each other or the way Lego blocks fit together.
The segments in CRISPR are transcribed into RNA. This RNA includes a guide sequence, which is a match to existing DNA in a persons body.
That guide sequence can be tailored to whatever you want, Dr. Chan says. And as a result, you can make specific alterations or mutations in a part of the genome that you are targeting with a high degree of accuracy.
Along for the ride with this guide sequence is an enzyme like Cas9.
When the guide sequence and enzyme find the desired DNA to edit, the enzyme can then get down to business. It attaches itself to this DNA and makes changes, whether thats a cut or alteration.
CRISPR technology has come a long way, Dr. Chan says. The first generation of CRISPR was a great way to inactivate genes. It only made a break in genes. Then, the DNA would get filled up with natural repair enzymes.
But new versions of CRISPR like CRISPR prime or CRISPR HD are more advanced.
These can allow actual replacements to occur, Dr. Chan continues. You can even very accurately replace one sequence one of the letters in the genome with another letter. And you can make specific mutations.
CRISPRs ability to make very specific, very small cuts has the potential to transform how healthcare providers can address certain genetic diseases.
Dr. Chan is optimistic about the future of CRISPR based on the success of ongoing clinical trials in human subjects. For any type of genetic diseases caused by a single mutated gene, you can use CRISPR to mutate it and make it normal. Thats why its useful. Its a way for us to change errors in the genome.
Right now, CRISPR is geared toward correcting a single change in genes, he adds. While combinations may be possible in the future, were just not there yet.
While gene editing is already in use, CRISPR is still in the clinical trials phase, Dr. Chan says. Its used all the time in research laboratories and industries, he notes. Many clinical trials are testing CRISPR in the setting of genetic diseases and cancer.
Interestingly, CRISPR can be used to detect certain diseases. The best-known example is the Sherlock CRISPR SARS-CoV-2 Kit: A COVID-19 test that received emergency use authorization (EAU) from the FDA in 2020.
But theres no FDA-approved CRISPR therapy right now. The clinical trials are ongoing, he says.
These include trials looking at CRISPR to correct genetic diseases such as cystic fibrosis, Huntingtons disease and muscular dystrophy.
Dr. Chan adds that there are also major clinical trials in process for blood disorders, where CRISPR is being used to correct the gene alteration that causes the condition. As one example, he cites a promising trial looking at CRISPR-Cas9 gene editing for sickle cell disease and -thalassemia, written about in an early 2021 issue of the New England Journal of Medicine. -thalassemia is an inherited blood disorder that impacts the bodys ability to create hemoglobin an iron-dense protein that serves as the primary ingredient in red blood cells.
There are also clinical trials looking to see if CRISPR can be used to treat certain cancers. Dr. Chan notes that chimeric antigen receptor (CAR)T-cell therapy is one of the first gene therapies approved for leukemias. Current research is looking at whether CRISPR technology can make this treatment even more effective.
In CAR T-cell therapy, you take out T-cells from someone and put in a receptor a new way for these cells to target something on cancer cells and then put these cells back in the patient, he explains. Researchers are running trials now where they use CRISPR to alter those T-cells to make them even more active.
CRISPR therapies can take on many different forms. CRISPR has been inserted directly into the body before. It was famously injected into the eyes of seven people with a rare hereditary blindness disorder in 2020, two of whom later told NPR that they regained some ability to see colors. There are human trials in process right now that deliver CRISPR through gels and creams, through food or drink, skin grafts or injections. Ex-vivo delivery is also common: Thats when CRISPR is used to modify a cell outside the body. The cells are then re-inserted into the body using a harmless virus.
The results have been promising so far. I do believe in the next three to five years possibly even sooner were going to see approval to treat some diseases, Dr. Chan states.
With any type of CRISPR therapy, Dr. Chan says theres a risk of getting off-target effects or unexpected side effects.
Whenever youre altering something as fundamental as DNA, you just dont know what might happen he explains. Theres always a chance for the unexpected. You can potentially have effects on your DNA that were not intended.
At the moment, he doesnt have any specific examples of what these effects might be and he notes that existing research suggests the risk is pretty low. Still, data from future research might tell a different story.
Dr. Chan nevertheless sees a lot of potential for CRISPR in the coming years.
The field is moving very quickly, he says. Were seeing continual improvement of the actual CRISPR tools being used.
Its getting more accurate and more flexible in terms of what you can do. There are various engineered modified variants of CRISPR now that are allowing very specific, very accurate changes with fewer off-target effects. So, I think the future is very bright.
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What Is CRISPR Gene Editing and How Does It Work?