Using CRISPR/Cas9 to map mucus

One Health

Karin Strijbis
Karin Strijbis

In high school, I discovered that there are rules in genetics that guide transmission of genes, and that we can draw a storyline to trace inheritance. Years later, I’m still drawing plans. Currently, it’s a map of our gut and the ongoing surveillance by our immune system of healthy bacteria (the good guys) and pathogenic microbes (bad bugs).

Healthy bacteria line our epithelial layers, such as the skin, mouth and intestines and help us fight disease-causing microbes. So, how does our immune system distinguish between good and bad microbes?

Mucus is more than just slime

We focus on the mucus layer that covers the gut. This layer is the primary structural barrier and is diverse and complex. Patients with inflammatory bowel disease (IBD) have a very thin mucus layer. Damage to the mucosal barrier and an imbalance of the microenvironment are thought to contribute to IBD. We’re figuring out how to improve the function of mucins (the primary component of mucus) in order to strengthen the barrier.  Unfortunately, not much is known about mucins; they’re difficult to study due to their large size, diverse and complex structures and multifaceted functions.

A mucin map may lead to therapeutic discoveries

Using CRISPR/Cas9 and colon intestinal cells, we’re knocking out the different mucins in order to make a map of signaling interactions initiated by these proteins. Ironically, the mucus layer makes it quite difficult to deliver the CRISPR complex into the cell. Nevertheless, we can attach a fluorescent flag (called GFP) to certain genes involved in innate defense and watch what happens when a particular mucin is missing.

Bacteria in IBD patients are too closely associated with the epithelial surface of the cell (the outside surface interfacing with the environment), and are attacking the mucins with enzymes. We’re looking for ways to disable these enzymes and boost the mucus defense mechanisms. If a particular mucin protects against bacterial invasion, we can target it for therapeutic use.

In addition, particular mucins are also highly expressed in cancer, and cancer cells have a layer of mucus that protects them from our immune system. Understanding how mucins work will help us better target cancer cells, and potentially change the direction of a patient’s storyline.

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