What is CRISPR?
I love writing Science Avenue because it’s a learning process from start to finish. Even if I’m writing about things that I’m familiar with—like 3D printing or solar energy—I still find things I don’t know, or learn about the constant leaps and bounds happening in modern science. In short, thanks to the trend in science to move forward in favour of advancement and progress, even the simple act of web-searching a subject reveals an endless trove of new information.
The beauty of science is its adaptive nature. Science forces even its most ardent practitioners to confront new facts and to look at the wonders of our universe through a different, more focused lens. For a tourist like myself, studying science is like learning about the ingredients in my favourite recipes. I assume most of what I know about my ratatouille based on its flavours alone, but I know nothing about the specific herbs, spices, and seasonings used to prepare the meal.
Of course, Google is not nearly the only place to find surprises. I often find myself in learning moments where I’m told about something that—first of all—I’d never think to look into, and—second of all—I’d probably never find on my own.
I didn’t stumble across Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) in a reading binge. Quite the contrary, I learned about CRISPRs thanks to a friend whose research regularly utilizes these short segments of prokaryotic DNA. Then another friend told me about them. And then another. It turns out that everyone knows about CRISPRs, and I’m the only one in the dark.
For the population who, like me, doesn’t know, CRISPRs are short segments of DNA belonging to single-celled organisms lacking membrane-bound organelles (prokaryotes) that contain base sequence repetitions. CRISPRs are part of the prokaryotic immune system, and they protect prokaryotes from external genetic elements.
According to research published out of the University of Paris and research published by BioMed Central, CRISPRs are found in 40 per cent of bacteria and 90 per cent of archaea—a separate kingdom of prokaryotes.
How does CRISPR work?
Cas9 (CRISPR associated protein 9) is an enzyme associated with the CRISPR immune system in a number of prokaryotes. In eukaryotes (certain unicellular organisms with membrane-bound organelles, as well as all multicellular organisms), the RNA interface mechanism performs a similar task as Cas9/CRISPR and all of the other CRISPR associated proteins.
The CRISPR/Cas mechanism works by identifying chunks of foreign, unwanted, or harmful DNA present in prokaryotes. Once identified, cas genes—like Cas9—interrogate these foreign chunks, and the CRISPR/Cas mechanism removes them from the prokaryote by cleaving them out.
Why is CRISPR important?
When harmful, unwanted, or foreign DNA enters a prokaryote, it mixes into the organism’s normal genetic sequence. If normal bacterial DNA contains no foreign genetic material, infected bacterial DNA contains sequences of foreign genetic material. However, the CRISPR/Cas mechanism activates in the presence of foreign genetic material. During the integration process, Cas proteins insert foreign DNA between CRISPR segments. This results in foreign DNA that can be easily identified to ensure successful removal.
For prokaryotes, the CRISPR/Cas mechanism is simply genetic-business-as-usual. After all, bacteria have been around for almost 3.5 billion years—they’re not really too fascinated by the intricacies of an ancient, but startlingly efficient, method of immune response.
Instead, the CRISPR/Cas mechanism is exciting for modern researchers for its use in gene editing. In laboratory settings, CRISPR/Cas allows for relatively straightforward gene identification and editing. Everything from inserting genes to removing genetic material can be accomplished through the application of the CRISPR/Cas mechanism.
What is the future of CRISPR?
Although the presence of CRISPR/Cas has skyrocketed in recent years, the mechanism is not the only available tool for genetic biologists. Zinc finger nucleases are artificial enzymes created to target and restrict DNA sequences. Transcription activator-like effector nucleases (TALENs) are also artificial enzymes created to target and restrict DNA sequences.
Alongside CRISPR, zinc finger nucleases and TALENs are currently the most widely-used gene editing tools in the scientific field.
I’m typically excited for the absurd possibilities. However, I struggle to think of something more absurd than using a natural prokaryotic immune response to protect our species—and countless others—from the very same bacteria that would otherwise prove to be our downfall. The irony is almost genetic.