SCN2

RNA interference (RNAi) is a cellular mechanism that inhibits gene expression by suppressing gene transcription or activating RNA degradation. This mechanism was discovered in plants in 1998 by Andrew Fire and Craig Mello. Today, this phenomenon can be observed in almost all eukaryotes, including protozoa, flies, nematodes, insects, parasites, and mammals.

The following protocol uses the MTT colorimetric assay as a classic literature-established method for assessing cell viability/metabolic activity in cultured mammalian cells. MTT[3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] is reduced by metabolically active cells to a colored formazan product; the amount of formazan is quantified spectrophotometrically and provides an indirect measure of metabolically active viable cells. Importantly, MTT reduction reflects cellular oxidoreductase/metabolic activity rather than an absolute direct count of living cells, so changes in cellular metabolism can alter the signal independently of cell number.