Defective dendrite elongation but normal fertility in mice lacking the Rho-like GTPase activator Dbl

Dbl is the prototype of a large family of GDP-GTP exchange factors for small GTPases of the Rho family. In vitro, Dbl is known to activate Rho and Cdc42 and to induce a transformed phenotype. Dbl is specifically expressed in brain and gonads, but its in vivo functions are largely unknown. To assess its role in neurogenesis and gametogenesis, targeted deletion of the murine Dbl gene was accomplished in embryonic stem cells. Dbl-null mice are viable and did not show either decreased reproductive performances or obvious neurological defects. Histological analysis of mutant testis showed normal morphology and unaltered proliferation and survival of spermatogonia. Dbl-null brains indicated a correct disposition of the major neural structures. Analysis of cortical stratification indicated that Dbl is not crucial for neuronal migration. However, in distinct populations of Dbl-null cortical pyramidal neurons, the length of dendrites was significantly reduced, suggesting a role for Dbl in dendrite elongation.     

Direct Costs of Dengue Hospitalization in Brazil: Public and Private Health Care Systems and Use of WHO Guidelines

Background

Dengue, an arboviral disease, is a public health problem in tropical and subtropical regions worldwide. In Brazil, epidemics have become increasingly important, with increases in the number of hospitalizations and the costs associated with the disease. This study aimed to describe the direct costs of hospitalized dengue cases, the financial impact of admissions and the use of blood products where current protocols for disease management were not followed.

Methods and Results

To analyze the direct costs of dengue illness and platelet transfusion in Brazil based on the World Health Organization (WHO) guidelines, we conducted a retrospective cross-sectional census study on hospitalized dengue patients in the public and private Brazilian health systems in Dourados City, Mato Grosso do Sul State, Brazil. The analysis involved cases that occurred from January through December during the 2010 outbreak. In total, we examined 8,226 mandatorily reported suspected dengue cases involving 507 hospitalized patients. The final sample comprised 288 laboratory-confirmed dengue patients, who accounted for 56.8% of all hospitalized cases. The overall cost of the hospitalized dengue cases was US $210,084.30, in 2010, which corresponded to 2.5% of the gross domestic product per capita in Dourados that year. In 35.2% of cases, blood products were used in patients who did not meet the blood transfusion criteria. The overall median hospitalization cost was higher (p = 0.002) in the group that received blood products (US $1,622.40) compared with the group that did not receive blood products (US $550.20).

Conclusion

The comparative costs between the public and the private health systems show that both the hospitalization of and platelet transfusion in patients who do not meet the WHO and Brazilian dengue guidelines increase the direct costs, but not the quality, of health care.     

Proline-rich tyrosine kinase 2 and Rac activation by chemokine and integrin receptors controls NK cell transendothelial migration

Protein tyrosine kinase activation is an important requisite for leukocyte migration. Herein we demonstrate that NK cell binding to endothelium activates proline-rich tyrosine kinase 2 (Pyk-2) and the small GTP binding protein Rac that are coupled to integrin and chemokine receptors. Chemokine-mediated, but not integrin-mediated, Pyk-2 and Rac activation was sensitive to pretreatment of NK cells with pertussis toxin, a pharmacological inhibitor of G(i) protein-coupled receptors. Both Pyk-2 and Rac are functionally involved in chemokine-induced NK cell migration through endothelium or ICAM-1 or VCAM-1 adhesive proteins, as shown by the use of recombinant vaccinia viruses encoding dominant negative mutants of Pyk-2 and Rac. Moreover, we found that Pyk-2 is associated with the Rac guanine nucleotide exchange factor Vav, which undergoes tyrosine phosphorylation upon integrin triggering. Finally, we provide direct evidence for the involvement of Pyk-2 in the control of both chemokine- and integrin-mediated Rac activation. Collectively, our results indicate that Pyk-2 acts as a receptor-proximal link between integrin and chemokine receptor signaling, and the Pyk-2/Rac pathway plays a pivotal role in the control of NK cell transendothelial migration.     

Synergism between curdlan and GM-CSF confers a strong inflammatory signature to dendritic cells

A simultaneous engagement of different pathogen recognition receptors provides a tailor-made adaptive immunity for an efficient defense against distinct pathogens. For example, cross-talk of TLR and C-type lectin signaling effectively shapes distinct gene expression patterns by integrating the signals at the level of NF-κB. In this study, we extend this principle to a strong synergism between the dectin-1 agonist curdlan and an inflammatory growth factor, GM-CSF. Both together act in synergy in inducing a strong inflammatory signature that converts immature dendritic cells (DCs) to potent effector DCs. A variety of cytokines (IL-1β, IL-6, TNF-α, IL-2, and IL-12p70), costimulatory molecules (CD80, CD86, CD40, and CD70), chemokines (CXCL1, CXCL2, CXCL3, CCL12, CCL17), as well as receptors and molecules involved in fugal recognition and immunity such as Mincle, dectin-1, dectin-2, and pentraxin 3 are strongly upregulated in DC treated simultaneously with curdlan and GM-CSF. The synergistic effect of both stimuli resulted in strong IκBα phosphorylation, its rapid degradation, and enhanced nuclear translocation of all NF-κB subunits. We further identified MAPK ERK as one possible integration site of both signals, because its phosphorylation was clearly augmented when curdlan was coapplied with GM-CSF. Our data demonstrate that the immunomodulatory activity of curdlan requires an additional signal provided by GM-CSF to successfully initiate a robust β-glucan-specific cytokine and chemokine response. The integration of both signals clearly prime and tailor a more effective innate and adaptive response against invading microbes and fungi.     

Disruption of Mtmr2 produces CMT4B1-like neuropathy with myelin outfolding and impaired spermatogenesis

Mutations in MTMR2, the myotubularin-related 2 gene, cause autosomal recessive Charcot-Marie-Tooth (CMT) type 4B1, a demyelinating neuropathy with myelin outfolding and azoospermia. MTMR2 encodes a ubiquitously expressed phosphatase whose preferred substrate is phosphatidylinositol (3,5)-biphosphate, a regulator of membrane homeostasis and vesicle transport. We generated Mtmr2-null mice, which develop progressive neuropathy characterized by myelin outfolding and recurrent loops, predominantly at paranodal myelin, and depletion of spermatids and spermatocytes from the seminiferous epithelium, which leads to azoospermia. Disruption of Mtmr2 in Schwann cells reproduces the myelin abnormalities. We also identified a novel physical interaction in Schwann cells, between Mtmr2 and discs large 1 (Dlg1)/synapse-associated protein 97, a scaffolding molecule that is enriched at the node/paranode region. Dlg1 homologues have been located in several types of cellular junctions and play roles in cell polarity and membrane addition. We propose that Schwann cell-autonomous loss of Mtmr2-Dlg1 interaction dysregulates membrane homeostasis in the paranodal region, thereby producing outfolding and recurrent loops of myelin.