Short double-stranded ribonucleic acid as inhibitor of gene expression by the interference mechanism

The rapid development of the small interfering ribonucleic acid (siRNA)-induced inhibition of the gene expression at the RNA level offers to research groups a new strategy for the understanding of gene functions. The siRNA approach is close to antisense oligonucleotide technology and takes advantage of the progress of chemically synthesized oligoribonucleotides. This approach for the mammalian cells was described by Elbashir et al. at the beginning of 2001, and in this chapter we describe methods for the design of siRNA molecules, solutions for efficiently transfecting cells, and methods for analyzing the inhibition of targeted genes. Methods for in vivo approach are also proposed.