Even in the era of high-throughput genomics, occasionally there is the need to charactarize the expression profiles of a few genes instead of thousands of genes. Because of this, we recently purchased Clontech’s Multiple Tissue Expression (MTE) Array. The MTE Array is a nylon membrane on which poly A+ RNAs from 76 different human tissues and cancer cell lines are spotted. The use of poly A+ RNA, instead of total RNA, increases the sensitivity of these arrays. RNA samples are normalized to the expression levels of eight housekeeping genes. The hybridization protocol is optimized for usage of Clontech’s ExpressHyb hybridization solution which comes with the array.
We used the MTE Arrays to investigate tissue-specific expression profiles of genes that were isolated from the genome-wide screening of human T-lymphocytes and Natural Killer cells using an oligonucleotide fingerprinting technique. We obtained good quality signal, with low background, in almost all of the experiments we performed without the necessity of further optimizing the hybridization conditions. Control hybridizations with a ubiquitin cDNA probe confirmed, in most of the cases, normalized amounts of poly A+ RNA on the membrane. We were particulary pleased with the smooth stripping of the MTE Arrays. We have previously had serious problems with stripping probes from filters that we had purchased from another manufacturer. The User Manual that comes with the MTE Arrays is well written with clear instructions on how membranes should be handled and how hybridizations should be performed.
The major concern that I have regarding this product is its price. In comparison to commercially available microarrays, paying $1,200 dollars for a single filter seems to be a bit much. We also encountered a technical problem concerning unequal amounts of RNA in one of the filter batches we received. This was a single case, however, and the affected membranes were immediately replaced by Clontech.
Overall, my impression of Multiple Tissue Expression Arrays from Clontech is good. It is the right choice for research projects where fast and broad screening of tissue-specific gene expression is desirable.
Michal Janitz, M.D.
Groupleader
Max Planck Institute for Molecular Genetics
Berlin, Germany