What is RNAi?

RNA interference (RNAi) is a natural process that involves short fragments of double-stranded RNA to disrupt specific gene function. When introduced into cells, short interfering RNAs (siRNAs) target and cleave the mRNAs of genes with the same sequence. This prevents the target gene from producing the corresponding protein, effectively silencing gene expression. RNAi was first discovered in plants and nematodes as it helped protect against viral infection or transposon activity. Later studies found that RNAi pathways exist in most eukaryotes including fungi, invertebrates and mammals.

Mechanism of RNAi

RNAi technology begins when long double-stranded RNA (dsRNA) molecules are introduced into the cell either directly or endogenously produced. The dsRNA is cleaved by the Dicer enzyme into short 21–23 nucleotide siRNAs. Each siRNA is then incorporated into the RNA-induced silencing complex (RISC) containing Argonaute proteins. The antisense strand of the siRNA guides RISC to mRNAs that contain a complementary sequence. Upon binding, the mRNA is cleaved by Argonaute, interrupting translation and marking the mRNA for degradation. This silencing effect is sequence-specific and only affects the targeted gene. A single siRNA can induce silencing in hundreds of mRNA copies, amplifying the RNAi response.

Applications of RNAi Technology

RNAi has become a powerful tool for studying gene function and validating drug targets in mammalian systems. Some key applications of RNAi technology include:

- Functional genomics: RNAi screens can systematically evaluate gene function on a genome-wide scale. This helps identify new genes involved in various biological pathways and disease processes.

- Therapeutics: RNAi shows promise for developing drugs against previously "undruggable" targets like prion diseases. Many clinical trials are evaluating RNAi therapies for conditions like hereditary ATTR amyloidosis, alpha-1 antitrypsin deficiency and various cancers.

- Plant protection: RNAi-based pest-resistant crops are being developed by silencing essential genes in agricultural pests. This provides an alternative to insecticides while reducing yield losses.

- Veterinary medicine: RNAi can treat pet animals for genetic disorders and infectious diseases like rabies or equine influenza that impact livestock health and welfare.

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