RNA Interference in Veterinary Parasitology

Introduction RNA interference (RNAi) is a naturally occurring mechanism of gene silencing that regulates gene expression post-transcriptionally. This process utilizes small double-stranded RNA molecules—particularly small interfering RNAs (siRNAs) and microRNAs (miRNAs)—to bind complementary sequences on target messenger RNAs (mRNAs), ultimately preventing their translation into proteins. Initially observed in plants and later in nematodes, the discovery of RNAi fundamentally changed our understanding of gene regulation and introduced a powerful tool for genetic research and therapy. Discovery and Mechanism of Action The landmark discovery of RNA interference was made in the nematode Caenorhabditis elegans by scientists Andrew Fire and Craig Mello in 1998. Their research demonstrated that the injection of double-stranded RNA (dsRNA) could lead to the silencing of genes with matching sequences. This discovery earned them the Nobel Prize in Physiology or Medicine in 2006. The process of RNAi begins with the introduction or endogenous production of dsRNA, which is cleaved by the RNase III enzyme Dicer into short fragments known as siRNAs. These siRNAs are then loaded into the RNA-induced silencing complex (RISC), guiding the complex to the target mRNA through sequence complementarity. Once bound, the RISC complex cleaves the mRNA, leading to its degradation and silencing of gene expression.