The clinical symptomatology in the X-linked Wiskott-Aldrich syndrome (WAS), a combined immunodeficiency and autoimmune disease resulting from WAS protein (WASp) deficiency, reflects the underlying coexistence of an impaired T helper 1 (T H 1) immunity alongside intact T H 2 immunity. This suggests a role for WASp in patterning T H subtype immunity, yet the molecular basis for the T H 1-T H 2 imbalance in human WAS is unknown. We have discovered a nuclear role for WASp in the transcriptional regulation of the T H 1 regulator gene TBX21 at the chromatin level. In primary T H 1-differentiating cells, a fraction of WASp is found in the nucleus, where it is recruited to the proximal promoter locus of the TBX21 gene, but not to the core promoter of GATA3 (a T H 2 regulator gene) or RORc (a T H 17 regulator gene). Genome-wide mapping demonstrates association of WASp in vivo with the gene-regulatory network that orchestrates T H 1 cell fate choice in the human T H cell genome. Functionally, nuclear WASp associates with H3K4 trimethyltransferase [RBBP5 (retinoblastoma-binding protein 5)] and H3K9/H3K36 tridemethylase [JMJD2A (Jumonji domain-containing protein 2A)] proteins, and their enzymatic activity in vitro and in vivo is required for achieving transcription-permissive chromatin dynamics at the TBX21 proximal promoter in primary differentiating T H 1 cells. During T H 1 differentiation, the loss of WASp accompanies decreased enrichment of RBBP5 and, in a subset of WAS patients, also of filamentous actin at the TBX21 proximal promoter locus. Accordingly, human WASpdeficient T H cells, from natural mutation or RNA interference-mediated depletion, demonstrate repressed TBX21 promoter dynamics when driven under T H 1-differentiating conditions. These chromatin derangements accompany deficient T-BET messenger RNA and protein expression and impaired T H 1 function, defects that are ameliorated by reintroducing WASp. Our findings reveal a

BackgroundInterleukin-17A (IL-17A) is the founding member of a novel family of inflammatory cytokines that plays a critical role in the pathogenesis of many autoimmune diseases, including multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). IL-17A signals through its receptor, IL-17RA, which is expressed in many peripheral tissues; however, expression of IL-17RA in the central nervous system (CNS) and its role in CNS inflammation are not well understood.MethodsEAE was induced in C57Bl/6 mice by immunization with myelin oligodendroglial glycoprotein. IL-17RA expression in the CNS was compared between control and EAE mice using RT-PCR, in situ hybridization, and immunohistochemistry. Cell-type specific expression was examined in isolated astrocytic and microglial cell cultures. Cytokine and chemokine production was measured in IL-17A treated cultures to evaluate the functional status of IL-17RA.ResultsHere we report increased IL-17RA expression in the CNS of mice with EAE, and constitutive expression of functional IL-17RA in mouse CNS tissue. Specifically, astrocytes and microglia express IL-17RA in vitro, and IL-17A treatment induces biological responses in these cells, including significant upregulation of MCP-1, MCP-5, MIP-2 and KC chemokine secretion. Exogenous IL-17A does not significantly alter the expression of IL-17RA in glial cells, suggesting that upregulation of chemokines by glial cells is due to IL-17A signaling through constitutively expressed IL-17RA.ConclusionIL-17RA expression is significantly increased in the CNS of mice with EAE compared to healthy mice, suggesting that IL-17RA signaling in glial cells can play an important role in autoimmune inflammation of the CNS and may be a potential pathway to target for therapeutic interventions.

Defects in Wiskott-Aldrich Syndrome protein (WASp) underlie development of WAS, an X-linked immunodeficiency and autoimmunity disorder of childhood. Nucleation-promoting factors (NPFs) of the WASp-family generate F-actin in the cytosol via the VCA-domain and support RNA polymerase II-dependent transcription in the nucleus. Whether nuclear-WASp requires the integration of its ARP2/3-dependent cytoplasmic function to reprogram gene transcription, however, remains unresolved. Using the model of human T helper (TH) cell differentiation, we find that WASp has a functional nuclear localizing (NLS) and nuclear exit (NES) sequences and accordingly its effects on transcription are controlled mainly at the level of its nuclear entry and exit via the nuclear pore. Human WASp does not utilize its VCA-dependent, ARP2/3-driven, cytoplasmic effector mechanisms to support histone H3K4 methyltransferase activity in the nucleus of TH1-skewed cells. Accordingly, an isolated deficiency of nuclear-WASp is sufficient to impair the transcriptional reprogramming of TBX21 and IFNG promoters in TH1-skewed cells, whereas, an isolated deficiency of cytosolic-WASp does not impair this process. In contrast, nuclear presence of WASp in TH2-skewed cells is small and its loss does not impair transcriptional reprogramming of GATA3 and IL4 promoters. Our study unveils an ARP2/3:VCA-independent function of nuclear-WASp in TH1-gene activation that is uncoupled from its cytoplasmic role in actin polymerization.