Nobel Prize for Medicine: microRNA explains how cells differ

For the final Nobel Prize winners, it’s the turn of US duo Victor Ambros and Gary Ruvkun who have scooped the gong for medicine. Here’s Will Tingle again…

The 2024 Nobel Prize in Physiology or Medicine has been awarded to the University of Massachusetts' Victor Ambros, and Harvard's Gary Ruvkun, for the discovery of a key process that controls which genes are turned on or off in different cells in our bodies.

This matters because there are more than 200 different types of cells doing very different jobs all around the body. Yet they all carry a complete and nearly identical copy of our individual DNA code.

So whether it's a liver cell breaking down the booze consumed by a Nobel Prizewinner after they popped the champagne cork, or a cone cell in the retina enabling us to see, these different cells are all dipping into the same DNA recipe book for the instructions that make them work.

The difference is that the liver cell will be reading and making a different repertoire of recipes than the retinal cell.

So how is that achieved?

Before Ambros and Ruvkun came along, the explanation centred mostly on signals called transcription factors. These are small molecules made inside cells that can lock onto DNA and physically turn groups of genes on and off.

But what  Ambros and Ruvkun showed, using microscopic worms called C.elegans, is that pieces of genetic material also do this job.

Cells "transcribe" genes from DNA into a temporary intermediary called mRNA. This is a bit like jotting down a copy of a recipe on a piece of paper to avoid having to take the entire Jame Oliver tome into the kitchen.

It's this mRNA copy that's shuttled out to the part of the cell that turns recipes into reality and effectively cooks the cake prescribed in the DNA.

But the mRNA can be ambushed en-route, Ambros and Ruvkun found, by other short pieces of genetic material called "micro RNAs".

These resemble the mRNA made from working genes, except that many of them are the genetic "mirror images" of parts of those genes. And if they meet their mRNA mirror image, they can bind on, triggering the cell to rip up the recipe and blocking the expression of the gene.

Initially the scientific community were sceptical and regarded the findings as a peculiar foible of the worms the scientists had been studying.

But in the years since, the phenomenon has been confirmed to be operating across the tree of life, at work in even bacteria through to our own cells. It is arguably one of the most important ways in which genes are regulated, and also offers us new ways to get a handle on important diseases.

Because this system is disrupted by conditions like cancer, which can make cells grow in ways they shouldn't; and infections like the herpes simplex virus exploit these mechanisms to cause repeated painful cold sores.

But thankfully, for the majority of the time, thanks to this system the 37 trillion cells in an adult human know their places and roles. And that liver cell knows that it needs to turn on the alcohol dehydrogenase gene: very important when you've just won the Nobel Prize and are celebrating with a glass or two of bubbly!