Novel and future applications of microarrays in toxicological research.

Microarray technologies have both fascinated and frustrated the toxicological community since their introduction around a decade ago. Fascination arose from the possibility offered by the technology to gain a profound insight into the cellular response to chemically mediated stress, and the potential that this genomic signature would be indicative of the biological mechanism by which that stress was induced. Frustrations have arisen primarily from technical factors such as data variance, the requirement for the application of advanced statistical and mathematical analysis, and difficulties associated with actually recognising signature gene expression patterns, and discerning mechanisms. Toxicogenomics was predicted to make toxicological assessment and extrapolation easier, faster and cheaper. The reality has been somewhat different; toxicogenomics is difficult. However, its potential when properly applied has been indicated by some well designed toxicogenomics studies, particularly in the differentiation of genotoxins from non-genotoxins. Technology waits though for no man. While the toxicological community has been working to apply transcriptomics (mRNA levels) in toxicology, the technology has moved beyond this application into new arenas. Some have application to toxicology and are reviewed here, except transcriptomics which has been extensively written about before. This review discusses the application of microarray technologies applied to the genome per se (amplifications, deletions, epigenetic change), mRNA translation and its control mechanisms through miRNA. Which of the new genomics technoï¿(1/2)logies will find most application in toxicology? In the opinion of the author there are three potentially major applications: i) arrayCGH in assessment and recognition of genotoxicity; ii) epigenetic assessment in developmental and transgenerational toxicology; and iii) miRNA assessment in all toxicology types, but particularly developmental toxicology.