Application of the RNA Interference (RNAi) Technology to Angiogenesis Research

Abstract

Important discoveries within the past decade,which demonstrated the ability of small duplex RNAs to profoundly regulate gene expression, have opened the door to a new era of gene regulation research while providing a powerful tool to specifically down-regulate genes. Originally discovered in the nematode C. elegans, RNA interference, or RNAi, is defined as the sequence specific silencing of gene expression brought about by the introduction of exogenous double stranded RNA (Fire et al. 1998). In the initial experiments, researchers found that the injection of long (>500bp) dsRNA into nematodes interfered with the expression of specific genes that were homologous in sequence to the injected dsRNAs. Since this initial discovery, it has been shown that long dsRNA is not the direct effector of RNAi. It is cleaved into 21–23 nt duplex RNAs, termed small interfering RNAs, or siRNAs, which are the bona fide effectors of RNAi (Elbashir et al. 2001a). Prior to this discovery, it was not possible to induce RNAi in mammalian cells since the introduction of long dsRNAs induces the interferon response, leading to cell cycle alterations and apoptosis (Elbashir et al. 2001a). However, duplex RNA less than 30 nucleotides in length does not trigger the interferon response (Elbashir et al. 2001a, Elbashir et al. 2001b), and it has become possible to silence specific genes in mammalian cells with the use of siRNA.