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Feature Articles : Apr 15, 2007 (Vol. 27, No. 8)

Biomarket Trends: Shape of RNAi Screening Is Changing Rapidly

Thoroughness Requires Incorporation of More Than Just mRNA Assays
  • Jonathan Witonsky

In 2006, revenues in the total RNAi market amounted to approximately $85.1 million. Revenues were generated from the sales of content, delivery tools, and screening and analysis tools. Sales of content are expected to contribute the largest source of revenue to the total RNAi market through 2012. However, as researchers focus on conducting more comprehensive analyses and knockdown screenings, it is expected that by 2012, the screening and analysis tools market will be almost as large as the RNAi content market.

A number of different tools are being utilized for the screening and analysis of cells that have undergone knockdown with RNAi content. By far, the most common downstream applications are concerned with measuring knockdown at the genomic level. Because the direct impact on RNAi is on the silencing of gene expression, the primary interest of the majority of researchers is measuring mRNA levels.

Quantitative Real-time PCR

Quantitative real-time PCR has emerged as the standard technology to be paired with RNAi research. Because of the strong parallel between these two technologies, it is also expected that the majority of researchers who have not experimented with RNAi but who utilize quantitative real-time PCR will eventually attempt RNAi-facilitated research. Therefore, the majority of new RNAi customers are expected to initially focus on screening and analyzing mRNA knockdown.

Although the majority of researchers are solely concerned with the interference effect on the level of mRNA, it is generally understood that mRNA levels alone do not necessarily correlate with a biological change.

Researchers have observed that a significant change to mRNA levels do not always lead to sufficient protein knockdown, therefore disallowing the examination of any phenotypic alteration. Without a method to evaluate protein knockdown, researchers are incapable of obtaining a comprehensive assessment of their system of interest.

To take advantage of this market opportunity, several RNAi providers are offering solutions to effectively quantify both mRNA and protein levels. These market participants have received positive feedback from their customers for RNAi-specific solutions that further enable protein analysis.

Gel Electrophoresis

For example, there have been demonstrations of how 2-D gel electrophoresis analyses in RNAi studies can enable researchers to track the up- and down-regulation of proteins as a result of knockdown. Presently, antibody-based Western blot is the tool generally used to evaluate protein knockdown. Phenotypic assays, including morphological assays, enzymatic assays, biochemical assays, and cell-based assays, are also widely applied to examine the effects of RNAi knockdown.

Although most researchers are just employing quantitative real-time PCR, the fastest growing research segment involves the combination of mRNA, protein, and phenotypic assays. It is estimated that, in 2005, slightly over 60% of RNAi screens involve only mRNA analysis. However, in 2012 it is forecasted that slightly over 15% of RNAi screens are likely to involve only mRNA analysis, whereas over 70% of RNAi screens are likely to involve a combination of mRNA, protein, and phenotypic assays.