New approach tops PCR in toxicology testing
reaction (PCR) forms the basis of pharmacogenomic and toxicogenomic
studies, but US firm Genpathway claims to have come up with a
better alternative.
The company has just presented data showing that its TransriptionPath gene analysis product can be used to measure RNA transcription - and by extension the protein profile of a cell or tissue - with greater accuracy and sensitivity than conventional techniques that rely on measuring RNA levels directly.
Pharmacogenomic and toxicogenomic studies often require analysis of gene expression changes in tissues that were not frozen immediately, such as tissue from human cadavers or deceased animals that are not immediately ready for testing and have been stored. The problem in these cases is the inherent instability of RNA, which can mean that the amount measured is not a true representation.
Genpathway's system does not measure RNA itself, but rather the transcription complexes formed as RNA is synthesised by RNA polymerases from the DNA template.
At the at 2005 Society of Toxicology Annual Meeting, held in New Orleans on 6-10 March, Genpathway presented data from analyses of post-mortem tissues that had been stored under suboptimal conditions for up to 24 hours.
In the studies, mice were initially dosed with compounds known to induce liver toxicity for varying amounts of time. Their livers were assayed by TranscriptionPath and also for RNA levels using reverse-transcriptase PCR, a standard technique for RNA profiling.
The company's researchers found that in animals stored for three hours at room temperature plus 21 hours in the fridge - not uncommon in drug testing labs - levels of transcription were similar to those from animals that were tested immediately. In contrast, RNA levels from the stored animal tissues were very low due to degradation.
In addition, they found that even in animals stored and processed under optimal conditions, TranscriptionPath detected gene expression changes with greater accuracy compared with measurement of RNA levels.
"The improvement was particularly striking with regard to the timing of the gene expression changes and the extent of those changes," according to Genpathway.
The results of these studies confirmed previously obtained results by the company showing that RNA degrades but transcription complexes are stable, it said.
