MicroRNAs are tiny pieces of RNA that play a key role in the regulation of gene activity in animals and plants. A single microRNA can control many different genes, and a single gene can be regulated by multiple microRNAs.

“The seminal discovery of microRNA has introduced a new and unexpected mechanism of gene regulation,” said Olle Kämpe, the vice-chair of the Nobel committee for physiology and medicine.

Ambros and Ruvkun made the discovery by studying mutant strains of a roundworm called Caenorhabditis elegans. Their work began while they were working in the same lab. Ambros then moved to Harvard University and Ruvkun to Massachusetts General Hospital, where they continued studying the mutant strains.

Thomas Perlmann, the secretary general of Nobel assembly, said he had not yet contacted Ambros, but had spoken to Ruvkun and his wife. “They were thrilled about the prize and coming to Stockholm,” said Perlmann.

The 2023 Nobel prize in physiology or medicine was awarded to Katalin Karikó and Drew Weissman for working out how to tweak mRNA to avoid its destruction by the immune system, which was key to the development of mRNA vaccines, including the covid-19 ones.