Tracking the Activation of Stat5 through the Expression of an Inducible Reporter Gene in a Transgenic Mouse Line

Signal transducer and activator of transcription 5 (Stat5), a latent cytoplasmic transcription factor, becomes activated by phosphorylation upon cytokine, hormone, and growth factor interactions with their appropriate receptors and induces the transcription of target genes. It plays crucial roles in principal cell fate decisions and regulates cell differentiation, development, proliferation, apoptosis, and inflammation. It is active in the mammary gland, the liver, hematopoietic cells, and other organs and has pleiotropic functions, depending on its activation pathway and its site of action. We derived transgenic mice in which the expression of a LacZ reporter gene is directed by Stat5-specific response elements and visualized the activation of Stat5 in cells of mouse organs at different developmental stages. The reporter gene activity reflects the timing and the location of Stat5 activation and was documented in mammary epithelial cells during developmental stages of the gland, cells of the liver, kidney, spleen, thymus, and uterus and in granulocytes and macrophages of the transgenic lines.