Modeling childhood cancer in Drosophila melanogaster.

Childhood cancer is a major cause of death in developed countries, and while treatments and survival rates have improved, long-term side effects remain a challenge. The genetic component of pediatric tumors and their aggressive progression, makes the study of childhood cancer a complex area of research. Here, we introduce the fruit fly Drosophila melanogaster as study model. We emphasize its numerous advantages, including binary gene expression systems that enable precise control over the timing and location of gene expression manipulation, the capacity to combine multiple genes associated with cancer or the testing of human cancer variants within a live, intact animal. As an illustrative example, we focus on the Drosophila cancer paradigm which involves medically relevant genes, the Notch and PI3K/Akt signaling pathways. We describe how this cancer paradigm allows assessing two critical aspects of tumorigenesis during juvenile stages: (1) viability (do animals with particular cancer mutations survive into adulthood?), and (2) tumor burden (what percentage of animals bearing the cancer mutations actually develop cancer and what is the extent of the tumor?). We highlight the potential of Drosophila as a molecular therapeutic tool for drug screening and drug repurposing of medicines already approved to treat other diseases in children, thereby accelerating the potential translation of results into humans. This preclinical animal model sustains huge potential and is cost-effective. It allows screening of thousands of compounds and genes at a relatively low cost and human efforts, opening innovative venues to explore more effective and safer treatments of childhood cancer.

A picket fence function for adherens junctions in epithelial cell polarity.

Adherens junctions are a defining feature of all epithelial cells, providing cell-cell adhesion and contractile ring formation that is essential for cell and tissue morphology. In Drosophila, adherens junctions are concentrated between the apical and basolateral plasma membrane domains, defined by aPKC-Par6-Baz and Lgl/Dlg/Scrib, respectively. Whether adherens junctions contribute to apical-basal polarization itself has been unclear because neuroblasts exhibit apical-basal polarization of aPKC-Par6-Baz and Lgl in the absence of adherens junctions. Here we show that, upon disruption of adherens junctions in epithelial cells, apical polarity determinants such as aPKC can still segregate from basolateral Lgl, but lose their sharp boundaries and also overlap with Dlg and Scrib - similar to neuroblasts. In addition, control of apical versus basolateral domain size is lost, along with control of cell shape, in the absence of adherens junctions. Manipulating the levels of apical Par3/Baz or basolateral Lgl polarity determinants in experiments and in computer simulations confirms that adherens junctions provide a 'picket fence' diffusion barrier that restricts the spread of polarity determinants along the membrane to enable precise domain size control. Movement of adherens junctions in response to mechanical forces during morphogenetic change thus enables spontaneous adjustment of apical versus basolateral domain size as an emergent property of the polarising system.

Author Correction: Functional analysis of the Drosophila RhoGAP Cv-c protein and its equivalence to the human DLC3 and DLC1 proteins.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Adherens junction remodelling during mitotic rounding of pseudostratified epithelial cells.

Epithelial cells undergo cortical rounding at the onset of mitosis to enable spindle orientation in the plane of the epithelium. In cuboidal epithelia in culture, the adherens junction protein E-cadherin recruits Pins/LGN/GPSM2 and Mud/NuMA to orient the mitotic spindle. In the pseudostratified columnar epithelial cells of Drosophila, septate junctions recruit Mud/NuMA to orient the spindle, while Pins/LGN/GPSM2 is surprisingly dispensable. We show that these pseudostratified epithelial cells downregulate E-cadherin as they round up for mitosis. Preventing cortical rounding by inhibiting Rho-kinase-mediated actomyosin contractility blocks downregulation of E-cadherin during mitosis. Mitotic activation of Rho-kinase depends on the RhoGEF ECT2/Pebble and its binding partners RacGAP1/MgcRacGAP/CYK4/Tum and MKLP1/KIF23/ZEN4/Pav. Cell cycle control of these Rho activators is mediated by the Aurora A and B kinases, which act redundantly during mitotic rounding. Thus, in Drosophila pseudostratified epithelia, disruption of adherens junctions during mitosis necessitates planar spindle orientation by septate junctions to maintain epithelial integrity.

The Hippo pathway integrates PI3K-Akt signals with mechanical and polarity cues to control tissue growth.

The Hippo signalling pathway restricts cell proliferation in animal tissues by inhibiting Yes-associated protein (YAP or YAP1) and Transcriptional Activator with a PDZ domain (TAZ or WW-domain-containing transcriptional activator [WWTR1]), coactivators of the Scalloped (Sd or TEAD) DNA-binding transcription factor. Drosophila has a single YAP/TAZ homolog named Yorkie (Yki) that is regulated by Hippo pathway signalling in response to epithelial polarity and tissue mechanics during development. Here, we show that Yki translocates to the nucleus to drive Sd-mediated cell proliferation in the ovarian follicle cell epithelium in response to mechanical stretching caused by the growth of the germline. Importantly, mechanically induced Yki nuclear localisation also requires nutritionally induced insulin/insulin-like growth factor 1 (IGF-1) signalling (IIS) via phosphatidyl inositol-3-kinase (PI3K), phosphoinositide-dependent kinase 1 (PDK1 or PDPK1), and protein kinase B (Akt or PKB) in the follicular epithelium. We find similar results in the developing Drosophila wing, where Yki becomes nuclear in the mechanically stretched cells of the wing pouch during larval feeding, which induces IIS, but translocates to the cytoplasm upon cessation of feeding in the third instar stage. Inactivating Akt prevents nuclear Yki localisation in the wing disc, while ectopic activation of the insulin receptor, PI3K, or Akt/PKB is sufficient to maintain nuclear Yki in mechanically stimulated cells of the wing pouch even after feeding ceases. Finally, IIS also promotes YAP nuclear localisation in response to mechanical cues in mammalian skin epithelia. Thus, the Hippo pathway has a physiological function as an integrator of epithelial cell polarity, tissue mechanics, and nutritional cues to control cell proliferation and tissue growth in both Drosophila and mammals.

Functional analysis of the Drosophila RhoGAP Cv-c protein and its equivalence to the human DLC3 and DLC1 proteins.

RhoGAP proteins control the precise regulation of the ubiquitous small RhoGTPases. The Drosophila Crossveinless-c (Cv-c) RhoGAP is homologous to the human tumour suppressor proteins Deleted in Liver Cancer 1-3 (DLC1-3) sharing an identical arrangement of SAM, GAP and START protein domains. Here we analyse in Drosophila the requirement of each Cv-c domain to its function and cellular localization. We show that the basolateral membrane association of Cv-c is key for its epithelial function and find that the GAP domain targeted to the membrane can perform its RhoGAP activity independently of the rest of the protein, implying the SAM and START domains perform regulatory roles. We propose the SAM domain has a repressor effect over the GAP domain that is counteracted by the START domain, while the basolateral localization is mediated by a central, non-conserved Cv-c region. We find that DLC3 and Cv-c expression in the Drosophila ectoderm cause identical effects. In contrast, DLC1 is inactive but becomes functional if the central non-conserved DLC1 domain is substituted for that of Cv-c. Thus, these RhoGAP proteins are functionally equivalent, opening up the use of Drosophila as an in vivo model to analyse pharmacologically and genetically the human DLC proteins.

Mechanical strain regulates the Hippo pathway in Drosophila.

Animal cells are thought to sense mechanical forces via the transcriptional co-activators YAP (or YAP1) and TAZ (or WWTR1), the sole Drosophila homolog of which is named Yorkie (Yki). In mammalian cells in culture, artificial mechanical forces induce nuclear translocation of YAP and TAZ. Here, we show that physiological mechanical strain can also drive nuclear localisation of Yki and activation of Yki target genes in the Drosophila follicular epithelium. Mechanical strain activates Yki by stretching the apical domain, reducing the concentration of apical Crumbs, Expanded, Kibra and Merlin, and reducing apical Hippo kinase dimerisation. Overexpressing Hippo kinase to induce ectopic activation in the cytoplasm is sufficient to prevent Yki nuclear localisation even in flattened follicle cells. Conversely, blocking Hippo signalling in warts clones causes Yki nuclear localisation even in columnar follicle cells. We find no evidence for involvement of other pathways, such as Src42A kinase, in regulation of Yki. Finally, our results in follicle cells appear generally applicable to other tissues, as nuclear translocation of Yki is also readily detectable in other flattened epithelial cells such as the peripodial epithelium of the wing imaginal disc, where it promotes cell flattening.

Pak1 Kinase Maintains Apical Membrane Identity in Epithelia.

Epithelial cells are polarized along their apical-basal axis by the action of the small GTPase Cdc42, which is known to activate the aPKC kinase at the apical domain. However, loss of aPKC kinase activity was reported to have only mild effects on epithelial cell polarity. Here, we show that Cdc42 also activates a second kinase, Pak1, to specify apical domain identity in Drosophila and mammalian epithelia. aPKC and Pak1 phosphorylate an overlapping set of polarity substrates in kinase assays. Inactivating both aPKC kinase activity and the Pak1 kinase leads to a complete loss of epithelial polarity and morphology, with cells losing markers of apical polarization such as Crumbs, Par3/Bazooka, or ZO-1. This function of Pak1 downstream of Cdc42 is distinct from its role in regulating integrins or E-cadherin. Our results define a conserved dual-kinase mechanism for the control of apical membrane identity in epithelia.

Serum-borne bioactivity caused by pulmonary multiwalled carbon nanotubes induces neuroinflammation via blood-brain barrier impairment.

Pulmonary exposure to multiwalled carbon nanotubes (MWCNTs) causes indirect systemic inflammation through unknown pathways. MWCNTs translocate only minimally from the lungs into the systemic circulation, suggesting that extrapulmonary toxicity may be caused indirectly by lung-derived factors entering the circulation. To assess a role for MWCNT-induced circulating factors in driving neuroinflammatory outcomes, mice were acutely exposed to MWCNTs (10 or 40 µg/mouse) via oropharyngeal aspiration. At 4 h after MWCNT exposure, broad disruption of the blood-brain barrier (BBB) was observed across the capillary bed with the small molecule fluorescein, concomitant with reactive astrocytosis. However, pronounced BBB permeation was noted, with frank albumin leakage around larger vessels (>10 µm), overlain by a dose-dependent astroglial scar-like formation and recruitment of phagocytic microglia. As affirmed by elevated inflammatory marker transcription, MWCNT-induced BBB disruption and neuroinflammation were abrogated by pretreatment with the rho kinase inhibitor fasudil. Serum from MWCNT-exposed mice induced expression of adhesion molecules in primary murine cerebrovascular endothelial cells and, in a wound-healing in vitro assay, impaired cell motility and cytokinesis. Serum thrombospondin-1 level was significantly increased after MWCNT exposure, and mice lacking the endogenous receptor CD36 were protected from the neuroinflammatory and BBB permeability effects of MWCNTs. In conclusion, acute pulmonary exposure to MWCNTs causes neuroinflammatory responses that are dependent on the disruption of BBB integrity.

MMP-9-Dependent Serum-Borne Bioactivity Caused by Multiwalled Carbon Nanotube Exposure Induces Vascular Dysfunction via the CD36 Scavenger Receptor.

Inhalation of multiwalled carbon nanotubes (MWCNT) causes systemic effects including vascular inflammation, endothelial dysfunction, and acute phase protein expression. MWCNTs translocate only minimally beyond the lungs, thus cardiovascular effects thereof may be caused by generation of secondary biomolecular factors from MWCNT-pulmonary interactions that spill over into the systemic circulation. Therefore, we hypothesized that induced matrix metalloproteinase-9 (MMP-9) is a generator of factors that, in turn, drive vascular effects through ligand-receptor interactions with the multiligand pattern recognition receptor, CD36. To test this, wildtype (WT; C57BL/6) and MMP-9(-/-)mice were exposed to varying doses (10 or 40 µg) of MWCNTs via oropharyngeal aspiration and serum was collected at 4 and 24 h postexposure. Endothelial cells treated with serum from MWCNT-exposed WT mice exhibited significantly reduced nitric oxide (NO) generation, as measured by electron paramagnetic resonance, an effect that was independent of NO scavenging. Serum from MWCNT-exposed WT mice inhibited acetylcholine (ACh)-mediated relaxation of aortic rings at both time points. Absence of CD36 on the aortic rings (obtained from CD36-deficient mice) abolished the serum-induced impairment of vasorelaxation. MWCNT exposure induced MMP-9 protein levels in both bronchoalveolar lavage and whole lung lysates. Serum from MMP-9(-/-)mice exposed to MWCNT did not diminish the magnitude of vasorelaxation in naïve WT aortic rings, although a modest right shift of the ACh dose-response curve was observed in both MWCNT dose groups relative to controls. In conclusion, pulmonary exposure to MWCNT leads to elevated MMP-9 levels and MMP-9-dependent generation of circulating bioactive factors that promote endothelial dysfunction and decreased NO bioavailability via interaction with vascular CD36.

Inflammatory and Vasoactive Effects of Serum Following Inhalation of Varied Complex Mixtures.

Chronic cardiovascular disease is associated with air pollution exposure in epidemiology and toxicology studies. Inhaled toxicants can induce changes in serum bioactivity that impact endothelial inflammatory gene expression in vitro and impair vasorelaxation ex vivo, which are common precursors to atherosclerosis. Comparisons between single pollutants and common combustion mixtures, in terms of driving such serum inflammatory and vasoactive effects, have not been characterized. Healthy C57BL/6 mice were exposed to a single 6-h period of contrasting pollutant atmospheres: road dust, mixed vehicle emissions (MVE; a combination of gasoline and diesel engine emissions) particulate matter, mixed vehicle emissions gases, road dust plus ozone, road dust plus MVE, and hardwood smoke. Serum obtained from mice 24 h after these exposures was used as a stimulus to assess inflammatory potential in two assays: incubated with primary murine cerebrovascular endothelial cells for 4 h to measure inflammatory gene expression or applied to naïve aortic rings in an ex vivo myographic preparation. Road dust and wood smoke exposures were most potent at inducing inflammatory gene expression, while MVE atmospheres and wood smoke were most potent at impairing vasorelaxation to acetylcholine. Responses are consistent with recent reports on MVE toxicity, but reveal novel serum bioactivity related to wood smoke and road dust. These studies suggest that the compositional changes in serum and resultant bioactivity following inhalation exposure to pollutants may be highly dependent on the composition of mixtures.

Characterization of a novel endothelial biosensor assay reveals increased cumulative serum inflammatory potential in stabilized coronary artery disease patients.

BACKGROUND: Vascular disease is promoted by systemic inflammation that can arise from sites distal to the affected vessels. We sought to characterize the net inflammatory potential of serum from patients with coronary artery disease (CAD) using cultured endothelial cells as a cumulative biosensor. METHODS AND RESULTS: Serum samples from CAD patients (N = 45) and healthy control subjects (N = 48) were incubated with primary human coronary artery endothelial cells at a 1:10 dilution for 4 h, followed by isolation of the cellular RNA. Alteration of inflammation-responsive elements (adhesion molecules and cytokines) was assessed by gene expression. Specific indicators included intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and interleukin-8 (IL-8). Additionally, the cytokine levels in serum samples from all subjects were quantified. Serum from CAD subjects induced greater endothelial ICAM-1, VCAM-1, and IL-8 expression compared to healthy control serum (p < 0.001 for each analysis). The three indicators of inflammatory potential (ICAM-1, VCAM-1, and IL-8 mRNA) trended independently of each other and also of serum inflammatory biomarkers. IL-8 expression correlated negatively with serum HDL levels but positively correlated with VLDL, plasminogen activator inhibitor-1 and C-reactive protein. Interestingly, serum levels of cytokines in CAD patients were not statistically different from healthy control subjects. A year of follow-up in a sub-group of CAD subjects revealed relatively stable measures. CONCLUSIONS: As yet unidentified circulating factors in the serum of CAD patients appear to activate endothelial cells, leading to upregulation of adhesion molecules and chemokines. This cumulative assay performed well in terms of discriminating patients with CAD compared to healthy subjects, with greater range and specificity than specific inflammatory markers.

Effects of nicotine on cardiovascular remodeling in a mouse model of systemic hypertension.

Usage of nicotine-only formulations, such as transdermal patches, nicotine gum, or electronic nicotine delivery systems is increasing, as they are perceived as healthier alternatives to traditional cigarettes. Unfortunately, there is little data available on the effect of isolated nicotine on myocardial and aortic remodeling, especially in the setting of cardiovascular disease risk factors, such as hypertension. We hypothesized that nicotine would exacerbate cardiovascular remodeling induced by angiotensin-II (Ang II) treatment. Subcutaneous osmotic minipumps were implanted to administer Ang II, Nic, nicotine plus Ang II or saline to C57Bl/6 mice for 4 weeks. Heart weights were increased by all treatments, with control < nicotine < Ang II < nicotine + Ang II. Activity levels of matrix metalloproteinase-2 mirrored these changes and demonstrated clear additivity between nicotine and Ang II. Histopathological analysis of aortas revealed that mice receiving combined nicotine and Ang II treatment induced significant hypertrophy compared to all other groups. This study reveals possible cardiotoxic interactions between nicotine and a common model of systemic hypertension. Safety testing of novel nicotine delivery devices should consider that hypertension is a common impetus to begin smoking cessation therapy, and potential interactions should be more thoroughly studied.

Angiogenesis in mesenteric microvascular networks from spontaneously hypertensive versus normotensive rats.

OBJECTIVE: Elevated blood pressure during hypertension has been associated with microvascular rarefaction, defined as a loss of microvessels. However, whether rarefaction is a result of impaired angiogenesis remains unclear. The objective of this study was to compare angiogenesis across the time course of mesenteric microvascular network remodeling in adult spontaneously hypertensive versus normotensive rats. METHODS: Angiogenic responses in 15- to 16-week-old SHR and Wistar rats at 0, 3, 5, 10 or 25 days post 20-minute exteriorization of the mesentery were quantified. RESULTS: Consistent with the phenomenon of rarefaction, vascularized area in unstimulated SHR was decreased compared to Wistar. By 25 days, SHR vascular area had increased to the Wistar level and vascular length density and capillary sprouting were comparable. At 3 and 5 days, SHR and Wistar tissues displayed an increase in the capillary sprouting and vascular density relative to their unstimulated controls. At 10 days, capillary sprouting in the SHR remained elevated. The percent change in vascular density was elevated in the SHR compared to the Wistar group at 3 and 5 days and by 25 days the rate of change was more negative. CONCLUSIONS: Our results suggest that SHR networks undergo an increased rate of growth followed by an increased rate of pruning.

Mama Pacha, por los caminos de la madre tierra. Diccionario de mitologia aymara

El presente nos entrega amplio e impresionante estudio sobre el pensamiento mitologico y creencias religiosas del grupo etnico aymara, donde seres divinos, genios, heroes, simbolos, rituales y sacerdocio, cobran vida nuevamente. Gracias al contenido de este diccionario mitologico, podremos comprender la codificacion, causas y componentes simbolicos de la religiosidad nativa

Sintesis historica de Oruro

Contiene: EL habitat orureño - El hombre orureño - La historia de Oruro