Cellular signal transduction is governed by multiple feedback mechanisms to elicit robust cellular decisions. We combined mathematical modeling and extensive time-resolved data sets in primary erythroid progenitor cells and dissected the roles of the two transcriptional feedback regulators of the SOCS family, CIS and SOCS3 in JAK2/STAT5 signaling. Our model revealed that both feedbacks are most effective at different ligand concentration ranges.
Division of labor by dual feedback regulators controls JAK2/STAT5 signaling over broad ligand range.
Specimen part
View SamplesTo guarantee blood supply throughout adult life hematopoietic stem cells (HSCs) need to carefully balance between self-renewing cell divisions and quiescence. Identification of genes controlling HSC self-renewal is of utmost importance given that HSCs are the only stem cells with broad clinical applications. Transcription factor PU.1 is one of the major regulators of myeloid and lymphoid development. Recent reports suggest that PU.1 mediates its functions via gradual expression level changes rather than binary on/off states. So far, this has not been considered in any study of HSCs and thus, PU.1s role in HSC function has remained largely unclear. Here we demonstrate using hypomorphic mice with an engineered disruption of an autoregulatory feedback loop that decreased PU.1 levels resulted in loss of key HSC functions, all of which could be fully rescued by restoration of proper PU.1 levels via a human PU.1 transgene. Mechanistically, we found excessive HSC cell divisions and altered expression of cell cycle regulators whose promoter regions were bound by PU.1 in normal HSCs. Adequate PU.1 levels were maintained by a mechanism of direct autoregulation restricted to HSCs through a physical interaction of a -14kb enhancer with the proximal promoter. Our findings identify PU.1 as novel regulator controling the switch between cell division and quiescence in order to prevent exhaustion of HSCs. Given that even moderate level changes greatly impact stem cell function, our data suggest important therapeutic implications for leukemic patients with reduced PU.1 levels. Moreover, we provide first proof, that autoregulation of a transcription factor, PU.1, has a crucial function in vivo. We anticipate that our concept of how autoregulation forms an active chromosomal conformation will impact future research on transcription factor networks regulating stem cell fate.
Sustained PU.1 levels balance cell-cycle regulators to prevent exhaustion of adult hematopoietic stem cells.
Specimen part
View SamplesIre1 conditional null or control mice of 3-months old were injected intraperitoneally with TM or vehicle.
The unfolded protein response transducer IRE1α prevents ER stress-induced hepatic steatosis.
Specimen part
View SamplesWe generated Ikk-KA/KA knock-in mice (KA/KA), in which an ATP binding site of Ikk Lys 44 was replaced by alanine. The knock-in mice develop severe skin lesions and begin to die after 6 to 10 months. We also found lung SCCs in some of the mice. To study lung SCC development, we stabilize the skin condition by crossing KA/KA with Lori.Ikk transgenic mice to generate KA/KA-Lori.Ikk mice, which 100% spontaneously developed lethal lung SCC at 4 to 6 months of age.
The pivotal role of IKKα in the development of spontaneous lung squamous cell carcinomas.
Age, Specimen part
View SamplesPTEN imparts tumor suppression in mice by cell autonomous and non-autonomous mechanisms. Whether these two tumor suppressor roles are mediated through similar or distinct signaling pathways is not known. Here we generated and analyzed knockin mice that express a series of human cancer-derived mutant alleles of PTEN in either stromal or tumor cell compartments of mammary glands. We find that cell non-autonomous tumor suppression by Pten in stromal fibroblasts strictly requires activation of P-Akt signaling, whereas cell autonomous tumor suppression in epithelial tumor cells is independent of overt canonical pathway activation
Noncatalytic PTEN missense mutation predisposes to organ-selective cancer development in vivo.
Age, Specimen part
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