Changes in the transcriptional profile of cardiac myocytes following green fluorescent protein expression

Green fluorescent protein (GFP) and its multiple forms, such as enhanced GFP (EGFP), have been widely used as marker proteins and for tracking purposes in many biological systems, including the heart and cardiac cell systems. Despite some concerns on its toxicity under certain circumstances, GFP remains amongst the most reliable and easy-to-use markers available. Using rat full genome DNA microarrays, we have investigated the broader consequences of adenoviral-driven GFP expression in cardiac myocytes. In our transcriptional profiling analysis, we set a threshold of a twofold change. We removed possible changes resulting from adenoviral infection by comparison with transcriptional profiles of cardiac myocytes with adenoviral-driven expression of an unrelated protein, the kinase MEK. Our analysis revealed changes in the expression of 212 genes. Of these genes, 174 were upregulated and 38 were downregulated following GFP expression. Many of these genes remain unannotated, but an evaluation of those with described functions for their resulting proteins indicated that many were involved in processes, including responses to stimuli/stress and signal transduction. Our analysis thus indicates the broader consequences of GFP expression in altering gene expression profiles in cardiac cells. Care should therefore be taken when using GFP expression as a control in gene expression studies.