The ripple effect: why promoting female leadership in global health matters.

Leadership positions in global health are greatly skewed toward men; the imbalance is more pronounced in low- and middle-income countries (LMICs). The under-representation of women in leadership is a threat to gender equality, and also impacts the improvement of women's health outcomes globally. In this perspectives piece, we assert that the promotion and retention of women in global health leadership has a ripple effect that can achieve improvement in global health outcomes. We present pragmatic, actionable solutions to promote and retain female global health leaders in this field.

Les positions de dirigeant dans la santé du monde sont largement orientées vers les hommes et ce déséquilibre est encore plus prononcé dans les pays à revenu faible et moyen. La sous-représentation des femmes en termes de dirigeant menace l'égalité des genres et a également un impact sur l'amélioration de l'état de santé des femmes dans le monde. Dans cette perspective, nous affirmons que la promotion et la rétention des femmes au sein du leadership de la santé dans le monde a un effet d'entraînement qui peut aboutir à une amélioration de l'état de santé dans le monde. Nous présentons des solutions pragmatiques et réalisables pour promouvoir et retenir des leaders féminins en matière de santé dans le monde.

Los puestos directivos en materia de salud mundial se asignan de manera desproporcionada a los hombres; este desequilibrio es aun más notorio en los países de ingresos bajos y medianos. La subrepresentación de las mujeres en los cargos de responsabilidad pone en peligro la equidad entre los hombres y las mujeres y tiene además repercusiones en los resultados de salud de las mujeres en el mundo. En el presente artículo de opinión, se sostiene que promover a las mujeres a las funciones directivas relacionadas con la salud mundial y facilitar su permanencia en ellas genera una reacción en cadena que puede dar lugar a mejores resultados de salud a escala mundial. Se proponen soluciones viables y prácticas encaminadas a estimular la presencia de las mujeres en los cargos de responsabilidad en materia de salud mundial y a respaldar su permanencia en esta actividad.

Cartilage-specific ablation of XBP1 signaling in mouse results in a chondrodysplasia characterized by reduced chondrocyte proliferation and delayed cartilage maturation and mineralization.

OBJECTIVE: To investigate the in vivo role of the IRE1/XBP1 unfolded protein response (UPR) signaling pathway in cartilage. DESIGN: Xbp1(flox/flox).Col2a1-Cre mice (Xbp1(CartΔEx2)), in which XBP1 activity is ablated specifically from cartilage, were analyzed histomorphometrically by Alizarin red/Alcian blue skeletal preparations and X-rays to examine overall bone growth, histological stains to measure growth plate zone length, chondrocyte organization, and mineralization, and immunofluorescence for collagen II, collagen X, and IHH. Bromodeoxyuridine (BrdU) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analyses were used to measure chondrocyte proliferation and cell death, respectively. Chondrocyte cultures and microdissected growth plate zones were analyzed for expression profiling of chondrocyte proliferation or endoplasmic reticulum (ER) stress markers by Quantitative PCR (qPCR), and of Xbp1 mRNA splicing by RT-PCR to monitor IRE1 activation. RESULTS: Xbp1(CartΔEx2) displayed a chondrodysplasia involving dysregulated chondrocyte proliferation, growth plate hypertrophic zone shortening, and IRE1 hyperactivation in chondrocytes. Deposition of collagens II and X in the Xbp1(CartΔEx2) growth plate cartilage indicated that XBP1 is not required for matrix protein deposition or chondrocyte hypertrophy. Analyses of mid-gestation long bones revealed delayed ossification in Xbp1(CartΔEx2) embryos. The rate of chondrocyte cell death was not significantly altered, and only minimal alterations in the expression of key markers of chondrocyte proliferation were observed in the Xbp1(CartΔEx2) growth plate. IRE1 hyperactivation occurred in Xbp1(CartΔEx2) chondrocytes but was not sufficient to induce regulated IRE1-dependent decay (RIDD) or a classical UPR. CONCLUSION: Our work suggests roles for XBP1 in regulating chondrocyte proliferation and the timing of mineralization during endochondral ossification, findings which have implications for both skeletal development and disease.

XBP1: the last two decades.

The transcription factor X box-binding protein 1 (XBP1) was isolated two decades ago in a search for regulators of major histocompatibility complex (MHC) class II gene expression. Many years of research finally revealed a protein with many functions, none of them related to the MHC. This paper provided an overview of what this multifunctional transcription factor actually does.

The transcription factor T-bet regulates mucosal T cell activation in experimental colitis and Crohn's disease.

The balance between pro and antiinflammatory cytokines secreted by T cells regulates both the initiation and perpetuation of inflammatory bowel diseases (IBD). In particular, the balance between interferon (IFN)-gamma/interleukin (IL)-4 and transforming growth factor (TGF)-beta activity controls chronic intestinal inflammation. However, the molecular pathways that evoke these responses are not well understood. Here, we describe a critical role for the transcription factor T-bet in controlling the mucosal cytokine balance and clinical disease. We studied the expression and function of T-bet in patients with IBD and in mucosal T cells in various T helper (Th)1- and Th2-mediated animal models of chronic intestinal inflammation by taking advantage of mice that lack T-bet and retroviral transduction techniques, respectively. Whereas retroviral transduction of T-bet in CD62L(+) CD4(+) T cells exacerbated colitis in reconstituted SCID mice, T-bet-deficient T cells failed to induce colitis in adoptive transfer experiments suggesting that overexpression of T-bet is essential and sufficient to promote Th1-mediated colitis in vivo. Furthermore, T-bet-deficient CD62L(-) CD4(+) T cells showed enhanced protective functions in Th1-mediated colitis and exhibited increased TGF-beta signaling suggesting that a T-bet driven pathway of T cell activation controls the intestinal balance between IFN-gamma/IL-4 and TGF-beta responses and the development of chronic intestinal inflammation in T cell-mediated colitis. Furthermore, TGF-beta was found to suppress T-bet expression suggesting a reciprocal relationship between TGF-beta and T-bet in mucosal T cells. In summary, our data suggest a key regulatory role of T-bet in the pathogenesis of T cell-mediated colitis. Specific targeting of this pathway may be a promising novel approach for the treatment of patients with Crohn's disease and other autoimmune diseases mediated by Th1 T lymphocytes.

Plasma cell differentiation requires the transcription factor XBP-1.

Considerable progress has been made in identifying the transcription factors involved in the early specification of the B-lymphocyte lineage. However, little is known about factors that control the transition of mature activated B cells to antibody-secreting plasma cells. Here we report that the transcription factor XBP-1 is required for the generation of plasma cells. XBP-1 transcripts were rapidly upregulated in vitro by stimuli that induce plasma-cell differentiation, and were found at high levels in plasma cells from rheumatoid synovium. When introduced into B-lineage cells, XBP-1 initiated plasma-cell differentiation. Mouse lymphoid chimaeras deficient in XBP-1 possessed normal numbers of activated B lymphocytes that proliferated, secreted cytokines and formed normal germinal centres. However, they secreted very little immunoglobulin of any isotype and failed to control infection with the B-cell-dependent polyoma virus, because plasma cells were markedly absent. XBP-1 is the only transcription factor known to be selectively and specifically required for the terminal differentiation of B lymphocytes to plasma cells.

Tumor necrosis factor receptor-associated factor (TRAF)2 represses the T helper cell type 2 response through interaction with NFAT-interacting protein (NIP45).

Recently we have identified a novel protein NIP45 (nuclear factor of activated T cells [NFAT]-interacting protein) which substantially augments interleukin (IL)-4 gene transcription. The provision of NIP45 together with NFAT and the T helper cell type 2 (Th2)-specific transcription factor c-Maf to cells normally refractory to IL-4 production, such as B cells or Th1 clones, results in substantial IL-4 secretion to levels that approximate those produced by primary Th2 cells. In studies designed to further our understanding of NIP45 activity, we have uncovered a novel facet of IL-4 gene regulation. We present evidence that members of the tumor necrosis factor receptor-associated factor (TRAF) family of proteins, generally known to function as adapter proteins that transduce signals from the tumor necrosis factor receptor superfamily, contribute to the repression of IL-4 gene transcription and that this effect is mediated through their interaction with NIP45.

A novel group of phospholipase A2s preferentially expressed in type 2 helper T cells.

We report a novel phospholipase A(2) (PLA(2)), group XII (GXII) PLA(2), distinct from other cysteine-rich groups with a catalytic histidine motif, by its 20-kDa size and distribution of the 14 cysteine residues within the protein. Alternative spliced forms with distinct subcellular localization, designated GXII-1 and GXII-2, were identified by reverse transcription-polymerase chain reaction. Importantly, GXII PLA(2)s, in particular GXII-2 PLA(2), and group V PLA(2), but not group X PLA(2), were selectively expressed in murine type 2 helper T (Th2) clones and in vitro differentiated mouse CD4 Th2 cells as compared with type 1 helper T clones and cells. Stimulation with anti-CD3 appreciably up-regulated expression of GXII PLA(2)s and group V PLA(2) by steady state analysis of the Th2 cells as compared with type 1 helper T cells. These results suggest that group XII and group V PLA(2)s might participate in helper T cell immune response through release of immediate second signals and generation of downstream eicosanoids.

Decreased immediate inflammatory gene induction in activating transcription factor-2 mutant mice.

Transcription factor activating transcription factor (ATF)-2 is activated by inflammatory signals transduced by the JNK and p38 MAP kinase pathways. To better define the role of ATF-2 in inflammation, adult mice expressing small amounts of a mutant ATF-2 protein were challenged with lipopolysaccharide (LPS), anti-CD3 antibody or virus. Within 3 h of challenge by LPS, ATF-2 mutant mice had decreased induction of the adhesion molecules E-selectin, P-selectin and VCAM-1 as well as the cytokines tumor necrosis factor-alpha, IL-1beta and IL-6 compared with control mice. Stimulation of T lymphocytes by anti-CD3 antibody also showed less induction of IL-1 and IL-6 in ATF-2 mutant tissues. ATF-2 mutant thymocytes treated with anti-CD3 antibody in vitro demonstrated reduced induction of c-Jun, JunB, JunD and Fra-2. However, similar to what was observed after p38 kinase inhibition in normal mice, relative ATF-2 deficiency did not prevent the development of a mononuclear cell infiltrate in the week following an inflammatory stimulus. ATF-2 mutant mice proved more susceptible to death than control mice from LPS plus D-galactosamine injection or Coxsackievirus B3 infection and had a higher incidence of mononuclear pulmonary infiltrates after exposure to Herpes simplex virus-1. ATF-2 is essential for maximal immediate induction of adhesion molecules and cytokine genes, but at later time points may even protect against overactive immune responses.

NFATc1 and NFATc2 together control both T and B cell activation and differentiation.

NFAT transcription factors play critical roles in gene transcription during immune responses. To investigate further the two most prominent NFAT family members, NFATc1 and NFATc2, we generated mice bearing lymphoid systems devoid of both. Doubly deficient T cells displayed cell surface markers of activation yet were significantly deficient in the development of multiple effector functions, including Th cytokine production, surface effector molecule expression, and cytolytic activity. Nevertheless, doubly deficient B cells were hyperactivated, as evidenced by extremely elevated serum IgG1 and IgE, as well as plasma cell expansion and infiltration of end organs. Thus, in T cells, NFATc1 and NFATc2 are dispensable for inflammatory reactivity but are required for effector differentiation, while in B cells, NFATs regulate both normal homeostasis and differentiation.

Variable effects of transgenic c-Maf on autoimmune diabetes.

Autoimmune diabetes is associated with T helper 1 polarization, but protection from disease can be provided by the application of T helper 2 (Th2) cytokines. To test whether genetic manipulation of T-cells can provide protective Th2 responses, we developed transgenic mice in which T-cells express the interleukin-4-specific transcription factor c-Maf. When crossed with a transgenic model that combines a class II restricted T-cell receptor specific for influenza hemagglutinin with islet beta-cell expression of hemagglutinin, the c-Maf transgene provided significant protection from spontaneous autoimmunity but not from adoptively transferred diabetes. In a second transgenic model in which islet cells express the lymphocytic choriomeningitis virus nucleoprotein, the virus infection triggers autoimmune diabetes within a few weeks involving both CD4 and CD8 T-cells; here too transgenic c-Maf provided significant protection. Surprisingly, when the c-Maf transgene was backcrossed with the NOD model of spontaneous disease, no protection was evident. Thus, transgenic c-Maf can strongly influence autoimmune disease development in some models, but additional factors, such as background genetic differences, can influence the potency of its effect.

A lipopolysaccharide-specific enhancer complex involving Ets, Elk-1, Sp1, and CREB binding protein and p300 is recruited to the tumor necrosis factor alpha promoter in vivo.

The tumor necrosis factor alpha (TNF-alpha) gene is rapidly activated by lipopolysaccharide (LPS). Here, we show that extracellular signal-regulated kinase (ERK) kinase activity but not calcineurin phosphatase activity is required for LPS-stimulated TNF-alpha gene expression. In LPS-stimulated macrophages, the ERK substrates Ets and Elk-1 bind to the TNF-alpha promoter in vivo. Strikingly, Ets and Elk-1 bind to two TNF-alpha nuclear factor of activated T cells (NFAT)-binding sites, which are required for calcineurin and NFAT-dependent TNF-alpha gene expression in lymphocytes. The transcription factors ATF-2, c-jun, Egr-1, and Sp1 are also inducibly recruited to the TNF-alpha promoter in vivo, and the binding sites for each of these activators are required for LPS-stimulated TNF-alpha gene expression. Furthermore, assembly of the LPS-stimulated TNF-alpha enhancer complex is dependent upon the coactivator proteins CREB binding protein and p300. The finding that a distinct set of transcription factors associates with a fixed set of binding sites on the TNF-alpha promoter in response to LPS stimulation lends new insights into the mechanisms by which complex patterns of gene regulation are achieved.

A novel transcription factor, T-bet, directs Th1 lineage commitment.

Naive T helper cells differentiate into two subsets, Th1 and Th2, each with distinct functions and cytokine profiles. Here, we report the isolation of T-bet, a Th1-specific T box transcription factor that controls the expression of the hallmark Th1 cytokine, IFNgamma. T-bet expression correlates with IFNgamma expression in Th1 and NK cells. Ectopic expression of T-bet both transactivates the IFNgamma gene and induces endogenous IFNgamma production. Remarkably, retroviral gene transduction of T-bet into polarized Th2 and Tc2 primary T cells redirects them into Th1 and Tc1 cells, respectively, as evidenced by the simultaneous induction of IFNgamma and repression of IL-4 and IL-5. Thus, T-bet initiates Th1 lineage development from naive Thp cells both by activating Th1 genetic programs and by repressing the opposing Th2 programs.

An essential role in liver development for transcription factor XBP-1.

XBP-1 is a CREB/ATF family transcription factor highly expressed in hepatocellular carcinomas. Here we report that XBP-1 is essential for liver growth. Mice lacking XBP-1 displayed hypoplastic fetal livers, whose reduced hematopoiesis resulted in death from anemia. Nevertheless, XBP-1-deficient hematopoietic progenitors had no cell-autonomous defect in differentiation. Rather, hepatocyte development itself was severely impaired by two measures: diminished growth rate and prominent apoptosis. Specific target genes of XBP-1 in the liver were identified as alphaFP, which may be a regulator of hepatocyte growth, and three acute phase protein family members. Therefore, XBP-1 is a transcription factor essential for hepatocyte growth.

The nuclear factor of activated T cells (NFAT) transcription factor NFATp (NFATc2) is a repressor of chondrogenesis.

Nuclear factor of activated T cells (NFAT) transcription factors regulate gene expression in lymphocytes and control cardiac valve formation. Here, we report that NFATp regulates chondrogenesis in the adult animal. In mice lacking NFATp, resident cells in the extraarticular connective tissues spontaneously differentiate to cartilage. These cartilage cells progressively differentiate and the tissue undergoes endochondral ossification, recapitulating the development of endochondral bone. Proliferation of already existing articular cartilage cells also occurs in some older animals. At both sites, neoplastic changes in the cartilage cells occur. Consistent with these data, NFATp expression is regulated in mesenchymal stem cells induced to differentiate along a chondrogenic pathway. Lack of NFATp in articular cartilage cells results in increased expression of cartilage markers, whereas overexpression of NFATp in cartilage cell lines extinguishes the cartilage phenotype. Thus, NFATp is a repressor of cartilage cell growth and differentiation and also has the properties of a tumor suppressor.

Sequential involvement of NFAT and Egr transcription factors in FasL regulation.

The critical function of NFAT proteins in maintaining lymphoid homeostasis was revealed in mice lacking both NFATp and NFAT4 (DKO). DKO mice exhibit increased lymphoproliferation, decreased activation-induced cell death, and impaired induction of FasL. The transcription factors Egr2 and Egr3 are potent activators of FasL expression. Here we find that Egr2 and Egr3 are NFAT target genes. Activation of FasL occurs via the NFAT-dependent induction of Egr3, as demonstrated by the ability of exogenously provided NFATp to restore Egr-dependent FasL promoter activity in DKO lymph node cells. Further, Egr3 expression is enriched in Th1 cells, suggesting a molecular basis for the known preferential expression of FasL in the Th1 versus Th2 subset.

The transcription factor c-Maf controls the production of interleukin-4 but not other Th2 cytokines.

IL-4 promotes the differentiation of naive CD4+ T cells into IL-4-producing T helper 2 (Th2) cells. Previous work provided suggestive but not conclusive evidence that the transcription factor c-Maf directed the tissue-specific expression of IL-4. It was not known whether c-Maf controlled the transcription of other Th2 cytokine genes. To elucidate the role of c-Maf in vivo, we examined cytokine production in mice lacking c-Maf (c-maf(-/-)). CD4+ T cells and NK T cells from c-maf(-/-) mice were markedly deficient in IL-4 production. However, the mice produced normal levels of IL-13 and IgE, and, when differentiated in the presence of exogenous IL-4, c-maf(-/-) T cells produced approximately normal levels of other Th2 cytokines. We conclude that c-Maf has a critical and selective function in IL-4 gene transcription in vivo.

A minimal level of MHC class II expression is sufficient to abrogate autoreactivity.

The establishment of CD4(+) T cell tolerance requires that self-reactive thymocytes are negatively selected during thymic development. A threshold of antigen concentration appears to exist for both MHC class I- and class II-mediated negative selection, below which clonal deletion of a self-reactive transgenic TCR does not occur. Similarly, both the specificity and thymic concentration of MHC molecules affect the efficiency with which autoreactive thymocytes are deleted. However, this threshold for MHC class II concentration has not been well established. Here, we show that this threshold must be extraordinarily low. We have used the human lysozyme promoter to re-express an A(beta)(b) cDNA on macrophages and other phagocytic myelomonocytic cells of class II-deficient A(beta)(b) -/- mice. Surface expression of I-A(b) could be detected on mature peritoneal macrophages and, minimally, on thymic dendritic cells; however, this level of expression was not sufficient for antigen-specific T cell activation. Nevertheless, when backcrossed onto an autoreactive K14 background, this minimal level of class II was sufficient to induce negative selection of a polyclonal self-reactive population. We conclude that provision of extremely low levels of class II to thymic dendritic cells confers on them the ability to mediate clonal deletion of autoreactive T cells.