Th17 cells have critical roles in mucosal defense and are major contributors to inflammatory disease. Their differentiation requires the nuclear hormone receptor RORγt working with multiple other essential transcription factors (TFs). We have used an iterative systems approach, combining genome-wide TF occupancy, expression profiling of TF mutants, and expression time series to delineate the Th17 global transcriptional regulatory network. We find that cooperatively-bound BATF and IRF4 contribute to initial chromatin accessibility, and with STAT3 initiate a transcriptional program that is then globally tuned by the lineage-specifying TF RORγt, which plays a focal deterministic role at key loci. Integration of multiple datasets allowed inference of an accurate predictive model that we computationally and experimentally validated, identifying multiple new Th17 regulators, including Fosl2, a key determinant of cellular plasticity. This interconnected network can be used to investigate new therapeutic approaches to manipulate Th17 functions in the setting of inflammatory disease.

Gain-of-function mutations in NOTCH1 are common in T-cell lymphoblastic leukemias (T-ALL), making this receptor a promising target for drugs such as γ-secretase inhibitors, which block a proteolytic cleavage required for NOTCH1 activation. However, the enthusiasm for these therapies has been tempered by tumor resistance and the paucity of information on the oncogenic programs regulated by oncogenic NOTCH1. Here we show that NOTCH1 regulates PTEN expression and the activity of the PI3K-AKT signaling pathway in normal and leukemic T cells. Notch signaling and the PI3K-AKT pathway synergize in vivo in a Drosophila model of Notch-induced tumorigenesis, and mutational loss of PTEN is associated with resistance to NOTCH1 inhibition in human T-ALL. Overall, these findings identify the transcriptional control of PTEN and the regulation of the PI3K/ AKT pathway as key elements of the leukemogenic program activated by NOTCH1 and provide the basis for the design of new therapeutic strategies for T-ALL.NOTCH receptors directly transduce extracellular signals at the cell surface into changes in gene expression that regulate differentiation, self renewal, proliferation and apoptosis 1 . Constitutively active forms of the NOTCH1 receptor contribute to over 50% of human T-cell lymphoblastic leukemias and lymphomas (T-ALL) 2 , and have also been implicated in the pathogenesis of solid tumors, such as breast carcinomas, gliomas and neuroblastoma 3-5 . #Adolfo A. Ferrando (af2196@columbia.edu) and Maria Dominguez (m.dominguez@umh.es) are co-senior corresponding authors.

No abstract

Notch signals are necessary for the functional outcomes of T cell receptor beta-selection, including differentiation, proliferation and rescue from apoptosis. The mechanism underlying this requirement for T cell development is unknown. Here we show that Notch receptor and Delta-like 1 ligand interactions promoted the survival of CD4(-)CD8(-) pre-T cells through the maintenance of cell size, glucose uptake and metabolism. Furthermore, the trophic effects of Notch signaling were mediated by the pathway of phosphatidylinositol-3-OH kinase and the kinase Akt, such that expression of active Atk overcame the requirement for Notch in beta-selection. Collectively, our results demonstrate involvement of Notch receptor-ligand interactions in the regulation of cellular metabolism, thus enabling the autonomous signaling capacity of the pre-T cell receptor complex.