Study of thyroid gene expression and regulation by DNA array technology: pitfalls and necessary controls in the use...

In order to identify the genes differentially expressed by TSH stimulation in dog and human thyrocytes we have used the gene array technology. Some modifications of the standard procedure were introduced to improve the method. While the macroarray technology has been developed to identify genes differentially expressed between two tissues, we report here that certain widely publicized commercial nylon filters do not allow to achieve this result. Because each step is crucial to the method and because it relies on quantitative measurements, we report different pitfalls of the method when commercial nylon filters with spotted bacterial colonies are used. The list of the most expressed genes in dog and human thyrocytes, which constitutes the minimal transcriptome of these tissues, has nevertheless been drawn up. Control tests that should be applied before the experimental use of the very expensive arrays are proposed.