The technique referred to as RNA interference (RNAi) involves the targeted destruction of mRNAs leading to reduced levels of bioactive protein. Using RNAi could be expected to have a pharmacological benefit in which of the following disorders?

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RNA interference (RNAi) can be used to reduce the expression of mutant proteins. Huntington disease is caused by a toxic gain-of-function mutation, where the mutant protein causes disease. RNAi can target and reduce the levels of this mutant protein, potentially providing therapeutic benefits.  RNA interference (RNAi) involves a mechanism of RNA-directed regulation of gene expression principally at the level of the mRNA product of the targeted gene. Interference can involve mRNA degradation or a block to translation or both. The RNAi pathway is initiated by the enzyme dicer, which cleaves double-stranded RNA (dsRNA) to short double-stranded fragments of 20 to 25 bp. One of the 2 strands of each fragment, known as the guide strand, is then incorporated into the RNA-induced silencing complex (RISC) and base-pairs with complementary sequences. When the guide-strand base-pairs with an mRNA molecule, it induces degradation of the mRNA by argonaute, the catalytic component of the RISC complex. The short RNA fragments are known as small interfering RNA (siRNA) when they derive from exogenous sources and microRNA (miRNA) when they are produced from RNA-coding genes in the cell's own genome. Since RNAi reduces the level of the target mRNA the encoded protein is consequently reduced. Therefore, the RNAi technique can prove useful in treating diseases where expression of a mutant or aberrant protein is the cause of the symptoms such as in Huntington disease.

The Technique Referred to as RNA Interference (RNAi) Involves the Targeted