• Regulation of murine normal and stress-induced erythropoiesis by Desert Hedgehog

      Lau, Ching-In; Outram, Susan V.; Saldaña, José Ignacio; Furmanski, Anna L.; Dessens, Johannes T.; Crompton, Tessa (American Society of Hematology, 2012-05-17)
      The function of Hedgehog signaling in hematopoiesis is controversial, with different experimental systems giving opposing results. Here we examined the role of Desert Hedgehog (Dhh) in the regulation of murine erythropoiesis. Dhh is one of 3 mammalian Hedgehog family proteins. Dhh is essential for testis development and Schwann cell function. We show, by analysis of Dhh-deficient mice, that Dhh negatively regulates multiple stages of erythrocyte differentiation. In Dhh-deficient bone marrow, the common myeloid progenitor (CMP) population was increased, but differentiation from CMP to granulocyte/macrophage progenitor was decreased, and the mature granulocyte population was decreased, compared with wild-type (WT). In contrast, differentiation from CMP to megakaryocyte/erythrocyte progenitor was increased, and the megakaryocyte/erythrocyte progenitor population was increased. In addition, we found that erythroblast populations were Dhh-responsive in vitro and ex vivo and that Dhh negatively regulated erythroblast differentiation. In Dhh-deficient spleen and bone marrow, BFU-Es and erythroblast populations were increased compared with WT. During recovery of hematopoiesis after irradiation, and under conditions of stress-induced erythropoiesis, erythrocyte differentiation was accelerated in both spleen and bone marrow of Dhh-deficient mice compared with WT.
    • Sonic hedgehog negatively regulates pre-TCR-induced differentiation by a Gli2-dependent mechanism

      Rowbotham, Nicola J.; Hager-Theodorides, Ariadne L.; Furmanski, Anna L.; Ross, Susan; Outram, Susan V.; Dessens, Johannes T.; Crompton, Tessa (American Society of Hematology, 2009-05-21)
      Hedgehog signaling regulates differentiation, survival, and proliferation of the earliest double-negative (DN) thymocytes, but its importance at later stages of T-cell development is controversial. Here we use loss- and gain-of-function mouse models to show that Shh, by signaling directly to the developing thymocyte, is a negative regulator of pre-TCR–induced differentiation from DN to double-positive (DP) cell. When hedgehog signaling was reduced, in the Shh−/− and Gli2−/− thymus, or by T lineage–specific transgenic expression of a transcriptional-repressor form of Gli2 (Gli2ΔC2), differentiation to DP cell after pre-TCR signal transduction was increased. In contrast, when Hh signaling was constitutively activated in thymocytes, by transgenic expression of a constitutive transcriptional-activator form of Gli2 (Gli2ΔN2), the production of DP cells was decreased. Gene expression profiling showed that physiologic Hh signaling in thymocytes maintains expression of the transcription factor FoxA2 on pre-TCR signal transduction.