Stat5a and Stat5b are 95% identical in amino acid sequence and were assumed to be redundant for responses to GH, TPO, EPO, IL-2, GM-CSF, and PRL. Mice deficient in Stat5a and/or Stat5b have been generated, and they have both specific and redundant functions downstream of numerous cytokine receptors. Stat5a-deficient bone marrow-derived macrophages and T lymphocytes exhibited defects in proliferation in response to GM-CSF and IL-2, respectively (25,26). Defects in T-cell proliferation and reductions in peripheral T-cell populations have been attributed at least in part to defects in IL-2-induced upregulation of the IL-2Ra chain. Disruption of Stat5a prevented mammary lobuloalveolar outgrowth during pregnancy and lactation after parturition, indicating a specific role for Stat5a in mammopoietic and lactogenic signaling (27). Stat5b-deficient mice demonstrated impaired IL-2- and IL-15-induced proliferation of splenocytes, reductions in natural killer (NK) cell populations, and decreases in expression of IL-2R0 chain and perforin (28). Stat5b was required for the sexual dimorphism of body growth rates and gene expression in the liver, as well as for normal lactation, reproduction, fat deposition, and hair growth (29). Deletion of both Stat5a and Stat5b abrogated responses to IL-2, IL-3, IL-5, IL-7, and GM-CSF, partially explaining reductions in B lymphocytes and peripheral T lymphocytes (30,31). Using a competitive repopulation assay, it was shown that Stat5a/b is required for long-term repopulation of the hematopoietic compartment (32). In addition, Stat5a/b mutant mice were significantly smaller than Stat5b-defi-cient animals, and the female infertility was caused by abnormal ovarian development and associated defects in progesterone secretion (33).
Was this article helpful?
Prior to planning pregnancy, you should learn more about the things involved in getting pregnant. It involves carrying a baby inside you for nine months, caring for a child for a number of years, and many more. Consider these things, so that you can properly assess if you are ready for pregnancy. Get all these very important tips about pregnancy that you need to know.