Applications of CRISPR Gene Editing

By Yashika Sharma

January 30, 2023
A mouse cDNA microarray gene sequences
A mouse cDNA microarray containing gene sequences.

CRISPR gene editing has been making headlines since Jennifer Doudna and Emmanuelle Charpentier were awarded the 2020 Nobel Prize in Chemistry for their pioneering work in the development of CRISPR-Cas9 and for developing a method for genome editing.

CRISPR can be used in a vast array of fields ranging from medicine to food improvement to biofuels and even de-extinction.

While these uses are still in the realm of possibility, they illustrate the enormous potential of CRISPR to shape the future in a multitude of ways.

Applications of CRISPR in Medicine

CRISPR-Cas9 gene editing is a faster, more feasible, and better version of gene editing technologies it can be used to treat various diseases of genetic origin, but as of the current scenario therapeutic uses of CRISPR gene editing are still in the primary phases.

Cancer Treatment Using CRISPR

CRISPR gene editing technology has a promising future in oncology since it is a technique that is versatile, simple, and efficient.

Human Cancer Cells
Human Cancer Cells stained purple. Credits: Photo by National Cancer Institute on Unsplash

The technique for treating lung cancer is to hunt for lymphocytes (a type of white blood cell). In this case, scientists collected T-cells from a patient in the latter stages of cancer.

Scientists used CRISPR-Cas9 to knock off the PD1 (Programmed Death1) gene, when a lymphocyte becomes senescent, the programmed death gene annihilates it.

Cancerous cells lack the receptor on immune lymphocytes when the PD1 gene is knocked out or impaired.

As a result, there will be less interaction between malignant ligands and immunological T-cells. 1

It will also assist immune cells in identifying abnormal cells and performing their function.

In the first phase of the study, eight of nine patients who received PD1 defective T-cell treatment appeared to be healthy.

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However, researchers urged that more extensive trials be conducted to assess optimum dosage and immunological response.

Treating Blood Disorders Using CRISPR

Blood disorders like sickle cell anemia and thalassemia, which affect the quality of blood, can be treated by CRISPR-Cas.

The treatment for sickle cell anemia is being developed by CRISPR Therapeutics and Vertex Pharmaceuticals.

This cell therapy involves harnessing bone marrow stem cells (Hematopoietic Stem Cells) from patients and using CRISPR to modify those cells.

Researchers used CRISPR to modify the BCL11A gene, which shuts off the production of fetal hemoglobin, and hopes to turn the BCL11A back on so that they produce high levels of fetal hemoglobin in red blood cells.

Microscope showing blood cells
Microscope showing blood cells

All this process of modifying blood cells is done ex-vivo and the modified hematopoietic stem cells are called CTX001, after the modification of stem cells.2

Then the modified stem cells are administered back into the patient’s bloodstream in the form of a stem cell transplant.

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There’s another blood disorder called hemophilia, that CRISPR gene editing could tackle, although its clinical trials are in the preliminary stages.

Curing Duchenne’s Muscular Dystrophy Using CRISPR

Duchenne’s muscular dystrophy (DMD) is a genetic progressive muscular disorder that typically affects Boys. Girls can be carriers or can be mildly affected but it’s mostly boys who are affected.

Memical representation of ‘Homelander’, of boys being more vulnerable to DMD (Duchenne’s Muscular Dystrophy).
Sarcastic representation of ‘Homelander’, depicting boys being more vulnerable to DMD (Duchenne’s Muscular Dystrophy). Credits: Evincism

There is no cure for DMD, and persons with the disease have a very short life expectancy even though DMD produces several severe symptoms, people with the condition die in their 20s or 30s.

The most common cause of mortality in DMD patients is DCM (Dilated Cardiomyopathy) which is caused by mutations in the X-linked dystrophin gene.

These mutations include large deletions, large duplications, point mutations, and other minor mutations.

Thousands of DMD mutations have been detected in humans, raising the obvious question of how CRISPR might fix such a vast number of mutations.

Answer to that human DMD mutations are clustered in hotspots inside the DNA, meaning that most mutations are within a specific region of the DNA.

Researchers employed CRISPR-Cas to conduct a selective cut at 12 hotspot locations, potentially covering the majority of the 3000 mutations causing DMD, and performed myoediting on pluripotent stem cells extracted from patients; myoediting refers to CRISPR-Cas mediated genome editing on the heart (cardiac) or skeletal muscles.

In a 3D EHM (Engineered Heart Muscle), myoediting of the DMD mutations restored dystrophin expression.3

Treating Congenital Blindness with CRISPR

CRISPR-Cas treatments are being used to treat inherited blindness disorders, a company called “Editas Medicine” developed a gene editor using CRISPR.

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In this trial, 14 patients were given moderate doses, yet the medication was only beneficial in three of them.

For this study, CRISPR was designed to cut out the defective ‘CEP290’ gene from the photosensitive rod cells in the retina of the eye4.

Instead of taking out the cells from the patient and performing treatment ex-vivo, treatment was injected directly into the patient’s body.

The treatment showed positive safety data on adults.

Although this treatment sounds promising this does not work on all patients as not all of the patients have 2 copies of the mutated CEP290 gene.

All of these efforts to heal hereditary disorders are preliminary; science has only delved to millimeters where there is a massive ocean underneath us.

Application of CRISPR in Allergen-free Foods

Food allergies occur when our immune system is triggered by eating particular foods, our immune system takes those foods as harmful substances.

This triggered immune response can cause a variety of symptoms, including reactions, digestive problems, and difficulty in breathing.

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The most common types of allergen are present in milk, wheat, and egg (all the ingredients of your favorite birthday cake).

CRISPR-Cas9 can be used to remove the allergy-causing proteins inside these foods so that people with allergies can consume them. 

Lactose-Free Milk Production Using CRISPR

Lactose-free milk using CRISPR.
Lactose-free milk can be produced using CRISPR-Cas9. Source: Healthline

Lactose intolerance is a common condition that occurs when the body is unable to fully digest Lactose, a sugar present in milk and milk products. 

The body is unable to digest lactose due to decreased production of Lactase.

Beta-lactoglobulin (bLG) is the major allergen in cow’s milk and an alternative approach could be the creation of productive breeds with a knockout of the bLG gene. 

A group of Russian researchers performed the bioinformatic analysis of the cattle genome around the area of the bLG gene.

They came up with an analysis of potential site targets for the gene editing system, selecting the specific areas on which gene editing can be performed to knock out the bLG gene by using CRISPR-Cas9.

This method revolves around genetically modified cattle production by specific gene targeting for the production of desired end products. 

Developing Allergy-Free Eggs Using CRISPR 

Allergen-free eggs using crispr
Hypoallergenic Eggs using CRISPR-Cas9. Source: Harvard T.H Chan

Allergy to eggs is another common type of food allergy, symptoms of an egg allergy may include rashes, nausea, hives, vomiting, and difficulty in breathing.

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Some people with egg allergy also suffer from anaphylaxis, a severe and potentially life-threatening allergic reaction.

The glycoprotein ovomucoid (OVM) is the major allergenic protein present in egg whites. It constitutes around 11% of egg white protein, therefore the removal of ovomucoid can result in the production of hypoallergenic eggs.

A group of Japanese researchers genetically modified chicks to remove the OVM gene and the eggs laid by the modified hens lacked the expression of the OVM gene in egg whites.

The production of eggs wasn’t affected by the reduction of the OVM gene, although the viscosity of egg white was changed.

But the mechanism of alteration of the viscosity of egg white by deletion of the OVM gene remains unclear.5

However the OVM-free eggs need to be assessed, these eggs are the potential alternative for people with egg allergies.

Gluten-Free Wheat Production Using CRISPR

Gluten intolerance, also known as coeliac disease (CD) is a condition in which the immune system reacts to gluten, a protein present in wheat, barley, and rye.

Coeliac disease is an autoimmune condition that causes an immunological response in the small intestine. Its symptoms vary greatly, but some of them include bloating, gas, diarrhea, constipation, and abdominal pain.

A strict gluten-free diet is the only treatment for coeliac disease, and going gluten-free can cure the damage caused by gluten in the small intestine.

α-, γ-, and ω- gliadins present in gluten trigger the immune response in the intestine.

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Types of proteins present in Gluten

Gluten is made up of two types of proteins gliadins and glutenins. Gliadin is the alcohol-soluble portion of gluten whereas glutenin is the water-soluble portion of gluten.

CRISPR-targeted gene editing has the potential to produce hypoimmunogenic wheat; previously, RNAi (RNA interference) was employed to make wheat lines with lower gliadin production.

To create coeliac-free wheat lines, we can combine multiple CRISPR-induced approaches.

Controversies on Genetically Modified Food

Food that has been genetically modified (GM) or genetically engineered (GE) is a contentious issue.

GM foods are generated by inserting new genes into the DNA of a plant or animal to confer specific qualities.

One of the major concerns about GM foods is their possible influence on human health. 

Some experts feel that eating genetically modified foods may increase the chance of certain health problems, such as allergies or cancer.

However, there is currently no scientific evidence to back up this assertion.

Numerous major health organizations, like the World Health Organization (WHO) and the American Medical Association (AMA), have affirmed that genetically modified (GM) foods are safe to consume.

Another concern is the possible impact of genetically modified foods on farmers, particularly in developing countries, as well as the ethical and moral issues of patenting and ownership of GM crops and seeds.

There are also debates on GM food labeling; some claim that customers have a right to know if the food they buy is genetically modified, while others argue that obligatory labeling could lead to unnecessary confusion.

However, it is observed quite often that people with food allergies are very open to the development of healthier foods for their disorder.

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Despite these difficulties, it is crucial to emphasize that GM food is a complicated topic, and different stakeholders have different opinions; ultimately, the safety and regulation of GM food should be based on scientific data and study.

Decaffeinating Coffee by Application of CRISPR

Coffee is like liquid gold for the soul, especially for those of us who need a little extra kick in the pants to start the day.

Coffee is one of the most consumed beverages around the world. 

In humans, it generates a psychoactive response that improves alertness and attention but also has a negative impact on sleep quality. 

So coffee consumers want caffeine-free coffee to not ruin their already ruined sleep schedule. 

Currently, caffeine-free coffee is produced by decaffeinating coffee before roasting coffee beans but the process of decaffeinating coffee results in the loss of some aromatic compounds which affects the aroma of coffee and it’s not as enjoyable. 

Coffee Beans
Roasted Coffee Beans. Credits: Mark Sweep

The overall process isn’t feasible and is very time-consuming. 

By analyzing the biosynthesis of caffeine in C.canephora researchers concluded that by targeting XMT for the knockout, the very first step of caffeine biosynthesis won’t take place and many mechanisms and enzymes can be targeted to inhibit the production of caffeine in C.canephora.

A UK-based company “Tropic Biosciences” developed a variety of naturally caffeine-free coffee beans, by using CRISPR, the company was able to turn off the genes that produce caffeine in coffee.

The NMT, MXMT, DMXT, and XMT genes are important genes for the biosynthesis of caffeine in the coffee plant.

Eradicating Pests Using CRISPR Gene Editing

CRISPR-Cas9 gene editing technology has been considered a plausible solution for pest eradication as it is a genetic editing technique that allows for the precise modification of organisms’ DNA.

Researchers hope to develop a population of bugs that are unable to reproduce or otherwise survive by utilizing CRISPR-Cas to target certain genes in pests.

A group American of researchers used CRISPR on fruit flies (Drosophila melanogaster) to disrupt genes that control female viability and male fertility.

This method offers the ability to control pest populations effectively and sustainably without the use of typical chemical pesticides.

The long-term ecological impacts of utilizing CRISPR-Cas9 in this manner, however, are not fully understood, and more research is required to thoroughly evaluate the safety and effectiveness of this technique.

Better Biofuels by Application of CRISPR

Bioenergy is a type of energy generated by natural sources (or biomass) such as plants, animals, and even algae.

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Biofuel is a combustible fuel made from biomass, and it can be first or second-generation, the first generation is unprocessed biofuels made from wood chips or pellets.

The production of liquified and processed fuels such as ethanol and biodiesel is part of the second generation of biofuel.

The Air Accordion Photobioreactor system, a high-efficiency system to produce algae for nutritional products, was invented by University of Arizona professor Joel Cuello
The Air Accordion Photobioreactor system, a high-efficiency system to produce algae for nutritional products, was invented by University of Arizona professor Joel Cuello. Source: Tech Launch Arizona

Bioenergy is a much-needed alternative to fossil fuels, yet current bioenergy and biofuel production can only supply around 10% of the world’s energy needs; however, CRISPR-Cas9 has the potential to change this.

Biofuel production is mostly a fermentation or chemical reaction; however, scientists have recently used CRISPR to modify bacteria and algae to boost the production of third-generation biofuels.

A team of Californian researchers used CRISPR-Cas9 to double the quantity of biodiesel produced from the phototrophic algae “Nannochloropsis gaditana” by increasing the amount of lipid synthesis.

It is kept in extreme starvation throughout the generation of biofuel from algae to begin building up fatty lipids, but because it is kept in famine, the development of algae slows and the production of lipids drops. 

So, these scientists found 20 transcriptional sites that controlled lipid production in algae and utilized CRISPR to silence 18 of those sites in algae.

So, these scientists found 20 transcriptional sites that controlled lipid production in algae and utilized CRISPR to silence 18 of those sites in algae. Silencing those genes enhanced lipid content production in algae by 2 times over what was previously produced.6

We need more technology to produce commercially viable biofuels to contribute to world energy needs and CRISPR gene editing poses a great potential to be able to improve the production of biofuels for a better future for earthlings.

References

  1. Markeshaw Tiruneh Medhin et al., ‘Current Applications and Future Perspectives of CRISPR-Cas9 for the Treatment of Lung Cancer – PMC’, PubMed Central, 31 May 2021, “Lymphocytes do not express the PD 1 receptor well, there will be less contact between the cancerous ligand and receptor.”, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8178582/[]
  2. Haydar Frangoul et al., ‘CRISPR-Cas9 Gene Editing for Sickle Cell Disease and β-Thalassemia’, 21 January 2021, The New England Journal of Medicine, “Two patients who were treated with CTX001 have shown the intended CRISPR-Cas9 editing of BCL11A in long-term hematopoietic stem cells, with durable engraftment, high levels of fetal hemoglobin expression.”, https://www.nejm.org/doi/10.1056/NEJMoa2031054[]
  3. Chengzu Long et al., Correction of diverse muscular dystrophy mutations in human engineered heart muscle by single-site genome editing’, 31 January 2018, Science, “Contractile dysfunction was partially-to-fully restored in corrected DMD EHM by myoediting.”, https://www.science.org/doi/10.1126/sciadv.aap9004[]
  4. Jocelyn Kaiser, ‘Groundbreaking CRISPR treatment for blindness only works for subset of patients’, 17 November 2022, Science, “CRISPR was designed to snip out a problematic part of a gene called CEP290.”, https://www.science.org/content/article/groundbreaking-crispr-treatment-blindness-only-works-subset-patients[]
  5. Takehiro Mukae et al., ‘Production and characterization of eggs from hens with ovomucoid gene mutation – ScienceDirect’, Science direct, 2 November 2020, “Egg white viscosity was altered in OVM-null eggs. As OVM constitutes more than 10% of the total egg white proteins, it implies that the characteristics of egg whites differ between OVM-null and WT eggs, but the mechanism by which OVM deletion affects viscosity remains unclear.”, https://www.sciencedirect.com/science/article/pii/S0032579120307793[]
  6. Imad Ajjavi, et al., ‘Lipid production in Nannochloropsis gaditana is doubled by decreasing expression of a single transcriptional regulator | Nature Biotechnology’, Nature, 19 June 2017, “But attenuation of Zn(II)2Cys6 expression yielded strains producing twice as much lipid (∼5.0 g m−2 d−1) as that in the wild type (∼2.5 g m−2 d−1) under semicontinuous growth conditions and had little effect on growth.”, https://www.nature.com/articles/nbt.3865[]
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