A collection of blog posts connected to my teaching on biomedical sciences and biochemistry degrees. All views and opinions expressed are my own, and not connected to my past, present or future employers.
To develop effective treatments and vaccines for COVID-19, we needed to understand how the virus interacted with living organisms. For this, scientists typically use model organisms like mice. However, using mice for COVID-19 research presented a significant problem.
COVID-19, caused by a coronavirus, gains entry into human cells by binding to a specific receptor on the cell surface known as ACE2 (angiotensin-converting enzyme 2). However, the ACE2 receptor in mice differs from the human version, making it impossible for the virus to bind to mouse cells. This meant that mice could not be used to study the virus in a living organism to better understand how it works and to test potential treatments.
Fortunately, genetic engineering provided a solution.
Back in 2007, during the outbreak of another coronavirus, SARS, scientists developed a line of genetically engineered mice that express the human version of the ACE2 receptor. These “humanised” mice could be infected with SARS-CoV-2, the virus responsible for COVID-19, making them an invaluable tool in the fight against the pandemic.
Using these genetically modified mice, researchers could study how COVID-19 interacted with cells, how it causes disease, and how different treatments might work in a living organism.
Gene drives are a revolutionary and controversial advancement in genetic engineering. The process allows scientists to introduce self-propagating changes into an organism's genome, bypassing traditional Mendelian inheritance. By ensuring that specific mutations become homozygous in offspring, gene drives have the potential to rapidly spread these changes throughout populations.
The applications of gene drives are both promising and far-reaching. They could play a crucial role in eradicating mosquito-borne diseases such as malaria and Zika, which continue to claim millions of lives globally. Additionally, gene drives could help tackle drug-resistant fungal pathogens that pose a significant threat to human health and be employed to control or eliminate invasive species that disrupt ecosystems.
But how does this technology work?
Gene drives use CRISPR, a gene-editing tool. In a gene drive, the CRISPR machinery is introduced along with the desired mutation. This machinery then actively copies itself onto the corresponding chromosome, ensuring the organism becomes homozygous for the mutation. This process allows the mutation to "drive" through the population, even if it does not provide a traditional selective advantage.
However, the power of gene drives comes with significant ethical concerns. The ability to alter ecosystems and species at such a fundamental level raises the question: Just because we can, should we? That is, once you introduce a change in a system using gene drive, how could you change or reverse it, or stop it spreading to other organisms?
CRISPR has emerged as a powerful genetic engineering tool. However, it does come with the ethical implications.
CRISPR
CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) is a gene-editing tool that allows scientists to alter DNA sequences within organisms. Using this technology, researchers can add, remove, or modify genetic material, leading to potential cures for genetic diseases, improved agricultural practices, and innovative solutions to environmental issues.
However, using CRISPR, especially in humans, raises significant ethical issues.
The CRISPR Babies
One of the most shocking uses of CRISPR on humans occurred when the genomes of human embryos were edited, leading to the birth of two genetically modified babies. The primary goal was to disable the CCR5 gene to produce babies that were HIV-resistant. That is, remove the receptor that HIV uses to enter human cells.
The CCR5 gene was selected because a naturally occurring mutation in this gene provides resistance to HIV and the Black Death in about 1% of Northern Europeans.
Researchers attempted to mimic this natural 32-base pair deletion using CRISPR, disrupting the CCR5 receptor's function and preventing HIV infection.
Outcomes and Concerns
The resulting edits did not replicate the exact natural mutation. One baby had a 15-base pair deletion in one copy of the gene, while the other had different insertions and deletions across both gene copies.
These unintended mutations raise serious health concerns as studies suggest that individuals with CCR5 mutations may have a 20% lower likelihood of reaching age 76 and could be more susceptible to other infections and diseases.
There is also the risk of off-target edits, where CRISPR inadvertently alters other parts of the genome, potentially leading to unforeseen health issues.
The scientific community widely condemned this work for its ethical breaches, lack of transparency, and disregard for established guidelines. The researchers involved faced legal consequences, including fines and imprisonment.
This case highlights the ethical dilemmas associated with germline editing:
Consent: The edited changes are heritable, affecting future generations who cannot consent.
Risk vs. Benefit: The potential health risks may outweigh the intended benefits, especially given existing alternatives to prevent HIV transmission.
Regulatory Oversight: The need for strict guidelines and oversight in genetic editing research is evident to prevent misuse and ensure ethical compliance.
Promising and Legal Applications of CRISPR
CRISPR has the potential for legitimate and beneficial medical applications. Here are two examples:
1. Cancer Treatment
Treatment of testicular cancer resistant to conventional therapies.
Patient-derived T cells are collected and genetically modified using CRISPR to disrupt three specific genes that regulate T cell targeting.
A lentivirus is then used to introduce a new targeting mechanism, directing the T cells to recognise and attack proteins unique to the patient's cancer cells.
The modified T cells are then reintroduced into the patient, aiming to boost the immune system's ability to fight cancer effectively.
This represents a personalised and targeted approach to cancer therapy and demonstrates CRISPR's potential to improve immunotherapy treatments.
2. Treating Childhood Blindness
CRISPR is also being used to address Leber Congenital Amaurosis 10 (LCA10), a cause of blindness in children.
The procedure targets the CEP290 gene, where specific mutations disrupt normal retinal development.
The CRISPR components are packaged into adeno-associated viruses (AAVs), and the system precisely removes the mutation in the CEP290 gene, aiming to restore proper protein function and improve vision.
1. BT Cotton: A Solution with Unintended Consequences
BT cotton is a prime example of how genetic engineering can provide a targeted solution to agricultural problems. This cotton variety has been engineered to produce a toxin derived from a specific type of bacteria. The toxin crystallises within the plant, and when an insect eats the leaves, the toxin dissolves the insect’s gut, eliminating the pest without the need for widespread insecticide use. This approach has the added benefit of protecting beneficial insects, as the crop itself becomes a selective defence mechanism.
However, this crop has had some unintended consequences. For example, in India, the high cost of BT cotton seeds has created a debt cycle for many farmers. Additionally, the market has seen a rise in counterfeit seeds, complicating the situation further.
2. Venomous Cabbage: A Controversial Defense
I do like this one.... what made the researchers think of it?
The venomous cabbage - these cabbages have been modified to express scorpion venom in their leaves. The Diamondback moth larvae, notorious for damaging cabbage crops, eat the leaves of cabbages producing the venom and dying. Luckily, this venom is not toxic to humans, making the cabbage safe to eat.
Would you be comfortable eating such a cabbage?
3. Golden Rice: Tackling Vitamin A Deficiency
I was involved in a similar project - more about that in a later video.
Golden Rice represents a more human-centric approach to genetic engineering. This rice has been enriched with beta-carotene, a compound the human body can convert into vitamin A - making it a potent tool in the fight against vitamin A deficiency, which is prevalent in many parts of the world.
The rice owes its yellow colour to the addition of genes from daffodils and bacteria.
While Golden Rice has the potential to significantly improve public health, it also raises important questions. How do we feel about consuming a staple food that contains genes from other species? This case exemplifies the broader debate surrounding genetically modified organisms (GMOs) and their role in our food supply.
What are your thoughts on these genetically engineered crops? Would you eat them? Let me know in the comments or comment on the video.
I like bananas — there, I have said it. They are one of my go-to fruits. But did you know they are in danger of being wiped out and no longer available?
About 99% of bananas we eat come from a single strain known as the Cavendish. Unfortunately, this strain faces a threat that could wipe it out.
The Cavendish Banana: A Monoculture at Risk
As popular as it is, the Cavendish banana has a significant vulnerability. It's sterile, meaning it can’t reproduce through seeds like many other plants. Instead, it’s propagated through cuttings. While this has allowed us to produce vast quantities of genetically identical bananas, it also means that if a disease affects one plant, it can quickly spread to all Cavendish bananas worldwide.
Fusarium wilt tropical race 4, or TR4, is a fungus threatening to wipe out the Cavendish banana. TR4 attacks the plant's roots, eventually killing it. Because the Cavendish is sterile, traditional breeding methods can’t be used to introduce resistance to this fungus, making the banana especially vulnerable.
Worryingly, this isn’t the first time a banana strain has faced extinction due to a fungal disease. Before the Cavendish, the Gros Michel banana was the world's favourite. However, attacked by a different strain of Fusarium wilt, leading to its near-total disappearance from the market. The Cavendish was introduced as a replacement, but now it’s facing a similar fate.
How Can We Save the Cavendish Banana?
Traditional breeding can't be used as the Cavendish is sterile. Hence, scientists are using genetic engineering to save the banana. One of the most promising approaches involves tweaking the banana’s genome to make it resistant to TR4.
One explored method is inserting a resistance gene from wild bananas into the Cavendish. The wild bananas have naturally evolved to resist the fungus, and by transferring their genes, we could give the Cavendish the same level of resistance.
However, an even more interesting approach would be to use CRISPR to make precise changes to the banana’s DNA. In the case of the Cavendish banana, CRISPR could be used to activate a gene that has been silenced but could provide resistance to TR4. Additionally, CRISPR could deactivate genes that make the Cavendish susceptible to the fungus.
Why CRISPR is a Game-Changer
The advantage of using CRISPR is that it doesn’t involve inserting foreign DNA into the banana. This means the resulting banana wouldn’t be considered transgenic, which could ease regulatory hurdles and public concerns about genetically modified organisms (GMOs).
Genetic engineering often evokes strong emotions and heated debates. When people hear the term, they might immediately think of genetically modified organisms (GMOs), "Frankenstein foods," or the ethical dilemmas surrounding altering life at its most fundamental level. But what exactly is genetic engineering, and what are the implications of this technology?
In its simplest form, genetic engineering directly manipulates an organism's DNA to achieve desired traits. Humans have used genetic engineering through selective breeding to cultivate crops and livestock that yield better produce and more reliable outcomes for centuries. But today’s technology allows scientists to bypass traditional breeding processes and make precise changes to DNA in a laboratory setting. This raises a profound question: just because we can modify life in this way, should we?
In the video, I look at the ethical and scientific complexities of genetic engineering and wonder where society should draw the line. Is it acceptable to engineer a potato or a chicken for better production? What about a cow? How about a human? These questions are not just theoretical but have real-world implications as technology continues to advance.
I also discuss how genetic engineering can be further divided into two broad categories of genetic engineering: research and applications. Research involves using genetic engineering to understand biological systems and diseases, while applications focus on improving crops, livestock, and human health. The ethical dilemmas become particularly acute when considering human health. Should genetic modifications be limited to somatic cells (which don’t get passed on to offspring), or is it ethical to alter germ cells, thereby affecting future generations?
Finally, I wrap up the video by explaining the difference between transgenic and non-transgenic organisms. Transgenic organisms have DNA from a different species introduced into their genome, while non-transgenic organisms involve changes made to the organism’s own DNA. But this distinction leads to another intriguing question: Is DNA truly species-specific?
Blog Bonus: Free information sheet summarising the video and defining the key terms - download.
Site-directed mutagenesis is a powerful technique in molecular biology that can introduce specific mutations into a DNA sequence. The method has been instrumental in understanding how proteins function and how genes are regulated.
The Process of Site-Directed Mutagenesis
Site-directed mutagenesis involves several key steps:
Preparation of DNA: The DNA sequence of interest is either cloned into a plasmid or selected from a plasmid library.
Designing the Primer: A primer is designed to bind specifically to the region of DNA where the mutation is desired. This primer is about 20 bases long, with one crucial difference—it contains the new base that will introduce the mutation. More information on Primer Design.
Creating a Single-Stranded DNA Template: The double-stranded plasmid DNA is converted into a single-stranded form. This single strand serves as the template for the primer to bind.
DNA Synthesis and Ligation: Once the primer is bound, DNA polymerase synthesises the complementary strand, incorporating the new base. DNA ligase is then added to seal the DNA strand, completing the synthesis.
Introduction into Bacteria: The newly mutated plasmid is introduced into bacteria, where the bacteria's natural DNA repair mechanisms take over. These mechanisms either repair the mismatched DNA back to its original form or incorporate the new mutation.
Applications of Site-Directed Mutagenesis
The ability to change a single base in a DNA sequence provides scientists with a powerful tool to explore how specific mutations affect protein function and gene expression. This technique has enabled numerous studies, allowing researchers to pinpoint individual amino acids' roles in proteins and dissect complex genetic regulatory networks.
From Site-Directed Mutagenesis to CRISPR
While site-directed mutagenesis has been a common lab technique for decades, the advent of CRISPR technology has revolutionised the field of genetic engineering. CRISPR offers a more efficient and precise method for making targeted genetic changes, but the foundational principles of mutagenesis laid the groundwork for these modern advances.
Blog Bonus: Free information sheet summarising the video and defining the key terms - download.
