Comparison and optimization of in situ hybridization procedures yielding rapid, sensitive mRNA detections

This paper describes methods that are commonly used for performing mRNA in situ hybridizations. Each stage of the procedure has been analyzed to identify the parameters that most significantly affect the final cell morphology and sensitivity of the system. We have identified key elements of the procedure as the fixation employed, the type of polynucleotide probe and label chosen, and the detection system used. By optimizing these critical components, we have developed a procedure for performing mRNA in situ hybridizations that takes 2–4 hours and has a sensitivity of 1–10 molecules of mRNA per cell. This system has been used to detect levels of oncogene expression in normal bone marrow and peripheral blood. It is possible to detect the expression of three oncogenes (c-myc, c-sis, and c-abl) simultaneously in a small population of cells from the peripheral blood of leukemic patients.