What is microRNA?

MicroRNA (miRNA) are small, non-coding RNA molecules approximately 22 nucleotides in length that regulate gene expression at the post-transcriptional level. They were discovered in 1993 by Victor Ambros and Gary Ruvkun studying the nematode C. elegans — a discovery honored with the 2024 Nobel Prize in Physiology or Medicine. MicroRNAs work by binding to complementary sequences in messenger RNA (mRNA), either blocking translation or triggering mRNA degradation. The human genome encodes over 2,500 known miRNA species, and together they are estimated to regulate the expression of more than 60% of all human protein-coding genes. Because of this central regulatory role, disruptions in miRNA expression are tightly linked to virtually every human disease studied, including cancer.