A robust method for isotopic riboprobe in situ hybridisation to localise mRNAs in routine pathology specimens

In situ Hybridisation (ISH) to detect mRNA is widely applicable to studies of human pathology and experimental models including transgenic mice, where it can provide crucial information as to where a gene is expressed, that is not available in other ways. ISH was used to establish that relatively high levels of expression of E-cadherin mRNA were associated with long-term survival in colorectal cancer, before suitable antisera became available. There is increasing awareness that ISH can be used to help select between candidate disease genes found at a linked locus, and that ISH can help validate therapeutic targets. For instance, when several closely related receptor genes are expressed in a tissue, it may be possible to determine which combinations are expressed together in a single cell type. These diverse applications demand a robust method that works on a variety of clinical and experimental materials, and is easily interpreted. To date, the ICRF in situ Hybridisation Service has hybridised over 30,000 sections of principally formalin-fixed, paraffin-embedded tissues, with a high success rate. The practicalities of our preferred method are discussed and key steps for quality control highlighted.