Design and use of constitutively active STAT5 constructs.

The transcription factor Signal Tranducer and Activator of Transcription 5 (STAT5) plays an important role in numerous biological processes including, but not limited to, (i) homeostasis of hematopoietic stem cells, (ii) development of essentially all blood cell lineages, (iii) growth hormone effects, (iv) differentiation of mammary epithelium, and (v) central nervous system control of metabolism. Two key tools for deciphering STAT5 biology have involved the use of mice in which the Stat5a and Stat5b genes can be conditionally deleted (Stat5(FL/FL) mice) and the development of systems in which STAT5a or STAT5b is rendered constitutively active. In this chapter, the distinct mechanisms that have been developed to render STAT5 constitutively active and their use in probing biological processes are discussed.