Gene editing is considered one of the most amazing tools with the potential to save many lives and change the entire trajectory of how we as humans fight diseases. Let’s dive into one of the most interesting parts of this venture.
You’ve probably heard of one part of gene editing before- CRISPR CAS-9. This article will go in-depth about this technology regarding its roots, discovery, and the potential it has along with other CAS genes CRISPR can use.
Gene editing has taken over the world of biology over the past few years and has continually been making progress. There is a huge misconception about what gene editing is. Today, we’ll be focusing on CRISPR and its most commonly used CRISPR Associated Protein (CAS) gene, CAS-9.
Let’s First Dive into Sequencing!
Gene Sequencing is the process of understanding the nitrogenous base pairs in our strands of DNA.
Gene Sequencing stems from one of the biggest races known to humankind. What was this race that helped to create the basis of gene editing? This race was to see who could genome sequence the entire human body. The entire point of sequencing is to determine the nitrogen base pairs that make up our DNA.
The two parties in this race were CELERA vs. THE HUMAN GENOME PROJECT.
This race was the first attempt two companies have had to sequence the entire human body. It was an incredible feat considering they had to map out over 3 billion bases in each of our cells where they are found in the 23 chromosome pairs. Each company used a very different approach to trying and sequence the entire body. The Human Genome Project used the conventional way of sequencing the body. This is called BAC-End Shotgun Sequencing.
Celera, on the other hand, used the data available to them from The Human Genome Project and then broke up certain strands of the genome to be able to sequence it easier.
Sequencing proved to be an essential component of how Gene Editing was created and how it is continuing to grow. Not only this, but sequencing also allowed scientists to understand the development of diseases, treatment, and genetic mutations in the body.
Gene Sequencing led to many advancements in modern-day medicine towards how we look at the body. This is because it is a basis for understanding our genome and was a catalyst for other projects.
We’ve talked about the past, now it’s time we look to the future. CRISPR is an emerging technology that is exciting people all over the gene-editing field.
So What is CRISPR?
Before we dive into what exactly CRISPR is, we have to look at what CRISPR was supposed to do. CRISPR is a defensive mechanism used by bacteria to defend them from viruses also known as phages. Phages can introduce their DNA into the bacteria.
The CRISPR DNA would essentially create cRNA and proteins. The cRNA would then move into the protein which would work with the proteins to destroy the virus. They do this by changing their DNA before an infection can even occur.
Back to what CRISPR actually is:
CRISPR is the acronym for Clustered Regularly Interspaced Short Palindromic Repeats. Let’s further analyze what this means. Firstly, it is essential we understand that CRISPR is repeated. Considering the rest of the name, this means the short strands of DNA are continually repeated and have base pairs that form a palindrome.
Similarly, CRISPR is also regularly interspaced meaning that there is some space (called spacer DNA) between the DNA strands. This spacer DNA is known as the CAS genes. Because of these CAS genes, CAS proteins will also be formed which can be one of two things, helicases or nucleases. The helicases un-toil the DNA while the nucleases cut the strands.
Just like how our human body builds up immunity against diseases that we’ve had in the past, bacteria using CRISPR will also do the same. After being introduced to a virus that inserts its DNA into the bacteria, the CRISPR DNA will have a new spacer added that will work to destroy that specific phage virus DNA in the future. How does this work? The CRISPR DNA will use CAS1 and CAS2 spacers to cut out a certain part of the DNA of the virus’ injection (protospacer) and uses that to defend itself.
It’s also essential we talk about PAM. Because CRISPR will be looking for the virus’s DNA sequence to attack by matching it to the DNA sequence found in itself, the CRISPR DNA can’t attack its own DNA. This is where PAM comes in. This is known as the protospacer adjacent motif. The DNA CRISPR is trying to attack in the sequences injected into the bacteria will always end in the base pairs GG (PAM Sequence). On the other hand, the sequence in the CRISPR DNA is finalized with the base pairs GT. This protects itself against the search the CRISPR does for a specific strand of DNA.
Overall, CRISPR is a type of DNA that can be found in the genes of prokaryotic cells. CRISPR was first found in Ecoli. This type of DNA’s main responsibility is to protect these cells against viruses that infect them.
It was just this until Jennifer Doudna and Emmanuelle Charpentier changed the way the scientific community looks at this sequence of DNA. When CRISPR is combined with the enzyme, CAS-9, the beauty of gene editing can be seen. This discovery was made with the bacteria, Streptococcus Pyogenes.
Because they were working with this bacteria, the CRISPR sequence they found was using the CAS gene, CAS-9. This type of CAS gene is very special. This is because when paired with CRISPR it creates two RNA strands. These are known as crRNA and tracrRNA. Mrs. Doudna and Mrs. Charpentier put the two RNA strands together using something called the guide RNA which is the basis for this advancement. The guide RNA allows the CRISPR sequence to find any sequence scientists give it. This completely revolutionizes the game for gene editing as it is much more precise and accurate than path methods that have been used before.
What about other CAS Protiens?
CAS-9 is a type of protein that can be used to isolate and remove strands of RNA and DNA. There are two other CAS proteins we will quickly look at. These prove a basis for finding more CAS genes that can help CRISPR cure a wider variety of diseases:
- CAS-12- One of the most amazing parts of the CAS-12 protein is that it is able to cut out DNA from a single strand rather than a double strand. They are currently being used to test for COVID-19.
- CAS-13- What makes CAS-13 very different from any other CAS protein is that instead of focusing on DNA, it actually looks for RNA to remove and replace.
It is essential we look at the type of cells we are using CRISPR with. This is essential to the regulations that will be in place regarding that. One of the biggest concerns people have is whether CRISPR will be used with embryonic cells (germline cells). This can affect the offspring of people for centuries and so it is essential the government puts in place regulations to ensure people are using this for the right reasons.
Capabilities The capabilities of gene editing are truly endless.
From designer babies to curing cancer. Let’s look at some of the things that are able to be accomplished with this emerging technology.
Designer babies are one of the most heated topics in the world right now. In 2018, in China, a scientist experimented with gene editing and created the worlds’ first designer baby. He Jiankui, the scientist behind this experiment, worked to change the genome of a baby to make them resistant to a potential HIV infection.
Unfortunately, not everyone wants the same outcome of using gene editing on embryos. Many look at using this technology for cosmetic purposes. Millions of people use plastic surgery to enhance their look, why can’t they use gene editing to enhance the looks of their baby? We don’t know enough about individuals’ genomes for us to alter them for cosmetic purposes.
Curing cancer is something on the cards that can be done with CRISPR. Cancer occurs as cells divide uncontrollably. This is due to the absence of gene p53. CRISPR CAS-9 could change this. By using this gene-editing tool, gene p53 could be implemented into the cells missing them, thus allowing them to go through apoptosis.
Finally, one of the obvious things many think CRISPR can solve are genetic diseases. CRISPR CAS-9 can work to remove and replace certain strands of DNA that cause genetic diseases. This can either mitigate the effects of them or destroy the disease completely. Of course, there are major consequences to doing this as wrong genetic modifications could occur which could cause more fatal outcomes.
A lot of people don’t realize that one of the biggest similarities to CRISPR and using it to edit genes is actually genetically modified organisms (GMO). This is something that has been and still is in the news very often. Although scientifically they focus on changing different parts of what the organism is, societally they are very similar.
People have looked and continue to look at GMOs as something very scary and untrusted. They don’t believe we have been using this technology long enough for us to have a 100% accurate perception of if GMOs pose any long-term health risks. Despite this, it is proven GMOs are safe for consumption and don’t pose any long-term health risks. People may still be scared, but no one can debate that they are here to help farmers and us. The same is happening with CRISPR. With the right precautions taken, CRISPR will be safe and effective and it will only be a matter of time until it is able to help solve various genetic diseases plaguing millions of people.
Gene Editing as a whole
Gene editing as a whole is something that is exciting to many people. There are many things that fall under the umbrella of gene editing that I didn’t talk about but are also very important:
Epigenetics is something different than CRISPR. It works by altering the phenotype of a person while not affecting the genotype. Because of this, certain cells could be shown differently because of the changes to their phenotype. This can change the way we look at curing various diseases as we can change the way they are understood by our bodies.
Companies Pursuing this Field
There are many different companies focused on Gene Editing.
- Cellectis- A company that works on using CAR T-cells in their fight to cure cancer.
- CRISPR Therapeutics- Company focused on using CRISPR to cure a variety of diseases.
- Editas Medicine- A company currently in the clinical stage of research focused on using CRISPR CAS-9 to ameliorate different diseases.
No one can deny that we are all genetically different to varying degrees. This poses a plethora of problems to using CRISPR CAS-9 for edits. If the guide RNA is looking for a specific strand of DNA and can’t find it because of differentiations in our genome, problems could arise.
Gene editing is something that can affect future children of people leading to a generational divide. That is something that’s very scary to me as it can cause a further divide between different types of people. We don’t understand the full repercussions of gene editing and using it can affect the future of people based on a decision that was ill-advised or misinformed. This can cause further divide than we currently have.
Similarly, using gene editing to solve a problem can lead to other problems. Editing our genome to solve one problem can also lead to other problems we may not have known about beforehand. Again, this can cause issues for generations of people. Misinformation and misinterpretation of the technology can ruin the capabilities we have for it. One of the biggest issues people see with a specific example is editing the germline. We will need very strict regulations to protect people against these unintended consequences.
Bigger Economic Divide
Finally, gene editing will allow the rich to have an even bigger gap over the rest of society. Providing the option to eliminate all genetic issues with the use of things like CRISPR, can cause a bigger divide between the poor and rich. This is because, at first, the technology will only be available to those who can afford it. Imagine if no genetic disorders will affect the rich? How hard would it be for people coming from poorer backgrounds to make their way up into a better life? Similarly, who would have access to gene editing devices and what could they be used for?