Australia's Dengue Risk Driven by Human Adaptation to Climate Change

Background

The reduced rainfall in southeast Australia has placed this region''s urban and rural communities on escalating water restrictions, with anthropogenic climate change forecasts suggesting that this drying trend will continue. To mitigate the stress this may place on domestic water supply, governments have encouraged the installation of large domestic water tanks in towns and cities throughout this region. These prospective stable mosquito larval sites create the possibility of the reintroduction of Ae. aegypti from Queensland, where it remains endemic, back into New South Wales and other populated centres in Australia, along with the associated emerging and re-emerging dengue risk if the virus was to be introduced.

Methodology/Principal Findings

Having collated the known distribution of Ae. aegypti in Australia, we built distributional models using a genetic algorithm to project Ae. aegypti''s distribution under today''s climate and under climate change scenarios for 2030 and 2050 and compared the outputs to published theoretical temperature limits. Incongruence identified between the models and theoretical temperature limits highlighted the difficulty of using point occurrence data to study a species whose distribution is mediated more by human activity than by climate. Synthesis of this data with dengue transmission climate limits in Australia derived from historical dengue epidemics suggested that a proliferation of domestic water storage tanks in Australia could result in another range expansion of Ae. aegypti which would present a risk of dengue transmission in most major cities during their warm summer months.

Conclusions/Significance

In the debate of the role climate change will play in the future range of dengue in Australia, we conclude that the increased risk of an Ae. aegypti range expansion in Australia would be due not directly to climate change but rather to human adaptation to the current and forecasted regional drying through the installation of large domestic water storing containers. The expansion of this efficient dengue vector presents both an emerging and re-emerging disease risk to Australia. Therefore, if the installation and maintenance of domestic water storage tanks is not tightly controlled, Ae. aegypti could expand its range again and cohabit with the majority of Australia''s population, presenting a high potential dengue transmission risk during our warm summers.     

Pyridones as glucokinase activators: Identification of a unique metabolic liability of the 4-sulfonyl-2-pyridone heterocycle

A promising area of novel anti-diabetic therapy involves identification of small molecule activators of the glucokinase enzyme to reduce blood glucose and normalize glucose stimulated insulin secretion. Herein, we report the identification and optimization of a series of 4-sulfonyl-2-pyridone activators. The activators were evaluated for in vitro biochemical activation and pharmacokinetic properties. As part of these efforts, a unique metabolic liability of the 4-sulfonyl-2-pyridone ring system was identified wherein this heterocycle readily undergoes conjugation with glutathione under non-enzymatic conditions.     

The intermediary cell: Minor-vein anatomy and raffinose oligosaccharide synthesis in the Scrophulariaceae

Minor-vein anatomy, sugar content, sugar synthesis, and translocation were studied in mature leaves of nine members of the Scrophulariaceae to determine if there is a correlation between companion-cell type and class of sugar translocated. Three types of companion cell were found: intermediary cells with extensive plasmodesmatal connections to the bundle sheath; transfer cells with wall ingrowths and few plasmodesmata; and ordinary companion cells with few plasmodesmata and no wall ingrowths. Alonsoa warscewiczii Regal., Verbascum chaixi Vill., and Mimulus cardinalis Dougl. ex. Benth. have intermediary cells and ordinary companion cells in the minor veins. These plants synthesize large amounts of raffinose and stachyose as well as sucrose. Nemesia strumosa Benth., and Rhodochiton atrosanguineum Zucc. have both intermediary cells and transfer cells and make proportionately less raffinose oligosaccharide than the species above. In N. strumosa, a single sieve element may abut both an intermediary cell and a transfer cell. The minor veins of Asarina scandens (Cav.) Penn. have transfer cells and what appear to be modified intermediary cells that have fewer plasmodesmata than other species, and occasional wall ingrowths. Asarina scandens synthesizes little raffinose or stachyose. Cymbalaria muralis P. Gaertn et al. and Linaria maroccana Hook.f. have only transfer cells and Digitalis grandiflora Mill. has only ordinary companion cells; these species make a trace of galactinol and raffinose, but no stachyose. Translocation experiments indicate that there is long-distance movement of raffinose oligosaccharide in these plants, even when it is synthesized in very small quantities in the leaves. We conclude that intermediary cells are as distinct a cell type as the transfer cell. In contrast to transfer cells, which are specialized for uptake of solute from the apoplast, intermediary cells are specialized for symplastic transfer of photoassimilate from the mesophyll and for synthesis of raffinose oligosaccharide. This supports our contention that raffinose oligosaccharide synthesis and symplastic phloem loading are mechanistically linked (Turgeon and Gowan 1990, Plant Physiol. 94, 1244–1249). Minor-vein anatomy and sugar synthesis may be useful characters in determining the phylogenetic relationships of plants in this family.We thank Andrea Wolfe and Wayne Elisens for helpful discussions on the taxonomy of the Scrophulariaceae. This research was supported by National Science Foundation grant DCB-9104159, U.S. Department of Agriculture Competetive Grant 92-37306-7819, and Hatch funds.     

Phylogenetic distribution in the genus Mus of t-complex-specific DNA and protein markers: inferences on the origin of t-haplotypes

We have examined the phylogenetic distribution of two t-specific markers among representatives of various taxa belonging to the genus Mus. The centromeric TCP-1a marker (a testicular protein variant specific for all t-haplotypes so far studied) has also been apparently detected in several non-t representatives of the Mus IVA, Mus IVB, and probably M. cervicolor species. By contrast, a t-specific restriction- fragment-length polymorphism allele (RFLP) of the telomeric alpha- globin pseudogene DNA marker alpha-psi-4 was found only in animals belonging to the M. musculus-complex species either bearing genuine t- haplotypes or, like the M. m. bactrianus specimen studied here, likely to do so. This t-specific alpha-psi-4 RFLP allele was found to be as divergent from the RFLP alleles of the latter, non-t, taxonomical groups as it is from Mus 4A, Mus 4B, or M. spretus ones. These results suggest the presence of t-haplotypes and of t-specific markers in populations other than those belonging to the M. m. domesticus and M. m. musculus subspecies, implying a possible origin for t-haplotypes prior to the radiation of the most recent offshoot of the Mus genus (i.e., the spretus/domesticus divergence), some 1-3 Myr ago.      

Threonine 22 phosphorylation attenuates Hsp90 interaction with cochaperones and affects its chaperone activity

Heat shock protein 90 (Hsp90) is an essential molecular chaperone whose activity is regulated not only by cochaperones but also by distinct posttranslational modifications. We report here that casein kinase 2 phosphorylates a conserved threonine residue (T22) in α helix-1 of the yeast Hsp90 N-domain both in?vitro and in?vivo. This α helix participates in?a hydrophobic interaction with the catalytic loop in Hsp90's middle domain, helping to stabilize the chaperone's ATPase-competent state. Phosphomimetic mutation of this residue alters Hsp90 ATPase activity and chaperone function and impacts interaction with the cochaperones Aha1 and Cdc37. Overexpression of Aha1 stimulates the ATPase activity, restores cochaperone interactions, and compensates for the functional defects of these Hsp90 mutants.     

The control of δ-crystallin gene expression during lens cell development: Dissociation of cell elongation,cell division, δ-crystallin synthesis,and δ-crystallin mRNA accumulation

Previous studies have shown that freshly explanted 6-day-old embryonic chick lens epithelial cells elongate, differentially increase their synthesis of δ-crystallin, and accumulate δ-crystallin mRNA when cultured with fetal calf serum; in contrast, precultured serum-starved 6-day-old and freshly explanted 19-day-old embryonic epithelial cells divide when treated with fetal calf serum. We have explored whether the stimulation of δ-crystallin gene expression (as measured by δ-crystallin synthesis and δ-crystallin mRNA accumulation) is affected by inhibiting lens cell elongation with colchicine, and whether δ-crystallin gene expression is increased in lens epithelial cells stimulated to divide by treatment with fetal calf serum, as it is in those stimulated to elongate by treatment with serum. Three new findings were made in this study. First, the stimulation of δ-crystallin gene expression does not require elongation of the cultured lens cells. Second, a decreased proportion of δ-crystallin synthesis is observed in lens epithelial cells during normal development and during serum starvation; in neither case is this decrease associated with a reduction in the number of δ-crystallin mRNA sequences per cell. Finally, serum stimulation of lens cell division does not increase the proportion of δ-crystallin synthesis, but can promote the accumulation of δ-crystallin mRNA. Thus, the relative proportion of δ-crystallin synthesized during chick lens development is not solely a function of the number of δ-crystallin mRNA sequences in the lens cells.     

The contractile basis of amoeboid movement: V. The control of gelation, solation, and contraction in extracts from dictyostelium discoideum

Motile extracts have been prepared from Dictyostelium discoideum by homogenization and differential centrifugation at 4 degrees C in a stabilization solution (60). These extracts gelled on warming to 25 degrees Celsius and contracted in response to micromolar Ca++ or a pH in excess of 7.0. Optimal gelation occurred in a solution containing 2.5 mM ethylene glycol-bis (β-aminoethyl ether)N,N,N',N'-tetraacetate (EGTA), 2.5 mM piperazine-N-N'-bis [2-ethane sulfonic acid] (PIPES), 1 mM MgC1(2), 1 mM ATP, and 20 mM KCI at ph 7.0 (relaxation solution), while micromolar levels of Ca++ inhibited gelation. Conditions that solated the gel elicited contraction of extracts containing myosin. This was true regardless of whether chemical (micromolar Ca++, pH >7.0, cytochalasin B, elevated concentrations of KCI, MgC1(2), and sucrose) or physical (pressure, mechanical stress, and cold) means were used to induce solation. Myosin was definitely required for contraction. During Ca++-or pH-elicited contraction: (a) actin, myosin, and a 95,000-dalton polypeptide were concentrated in the contracted extract; (b) the gelation activity was recovered in the material sqeezed out the contracting extract;(c) electron microscopy demonstrated that the number of free, recognizable F-actin filaments increased; (d) the actomyosin MgATPase activity was stimulated by 4- to 10-fold. In the absense of myosin the Dictyostelium extract did not contract, while gelation proceeded normally. During solation of the gel in the absense of myosin: (a) electron microscopy demonstrated that the number of free, recognizable F- actin filaments increased; (b) solation-dependent contraction of the extract and the Ca++-stimulated MgATPase activity were reconstituted by adding puried Dictyostelium myosin. Actin purified from the Dictyostelium extract did not gel (at 2 mg/ml), while low concentrations of actin (0.7-2 mg/ml) that contained several contaminating components underwent rapid Ca++ regulated gelation. These results indicated : (a) gelation in Dictyostelium extracts involves a specific Ca++-sensitive interaction between actin and several other components; (b) myosin is an absolute requirement for contraction of the extract; (c) actin-myosin interactions capable of producing force for movement are prevented in the gel, while solation of the gel by either physical or chemical means results in the release of F-actin capable of interaction with myosin and subsequent contraction. The effectiveness of physical agents in producting contraction suggests that the regulation of contraction by the gel is structural in nature.     

Moving Domain Computational Fluid Dynamics to Interface with an Embryonic Model of Cardiac Morphogenesis

Peristaltic contraction of the embryonic heart tube produces time- and spatial-varying wall shear stress (WSS) and pressure gradients (∇P) across the atrioventricular (AV) canal. Zebrafish (Danio rerio) are a genetically tractable system to investigate cardiac morphogenesis. The use of Tg(fli1a:EGFP)^y1 transgenic embryos allowed for delineation and two-dimensional reconstruction of the endocardium. This time-varying wall motion was then prescribed in a two-dimensional moving domain computational fluid dynamics (CFD) model, providing new insights into spatial and temporal variations in WSS and ∇P during cardiac development. The CFD simulations were validated with particle image velocimetry (PIV) across the atrioventricular (AV) canal, revealing an increase in both velocities and heart rates, but a decrease in the duration of atrial systole from early to later stages. At 20-30 hours post fertilization (hpf), simulation results revealed bidirectional WSS across the AV canal in the heart tube in response to peristaltic motion of the wall. At 40-50 hpf, the tube structure undergoes cardiac looping, accompanied by a nearly 3-fold increase in WSS magnitude. At 110-120 hpf, distinct AV valve, atrium, ventricle, and bulbus arteriosus form, accompanied by incremental increases in both WSS magnitude and ∇P, but a decrease in bi-directional flow. Laminar flow develops across the AV canal at 20-30 hpf, and persists at 110-120 hpf. Reynolds numbers at the AV canal increase from 0.07±0.03 at 20-30 hpf to 0.23±0.07 at 110-120 hpf (p< 0.05, n=6), whereas Womersley numbers remain relatively unchanged from 0.11 to 0.13. Our moving domain simulations highlights hemodynamic changes in relation to cardiac morphogenesis; thereby, providing a 2-D quantitative approach to complement imaging analysis.     

Affinity-based proteomics reveal cancer-specific networks coordinated by Hsp90

Most cancers are characterized by multiple molecular alterations, but identification of the key proteins involved in these signaling pathways is currently beyond reach. We show that the inhibitor PU-H71 preferentially targets tumor-enriched Hsp90 complexes and affinity captures Hsp90-dependent oncogenic client proteins. We have used PU-H71 affinity capture to design a proteomic approach that, when combined with bioinformatic pathway analysis, identifies dysregulated signaling networks and key oncoproteins in chronic myeloid leukemia. The identified interactome overlaps with the well-characterized altered proteome in this cancer, indicating that this method can provide global insights into the biology of individual tumors, including primary patient specimens. In addition, we show that this approach can be used to identify previously uncharacterized oncoproteins and mechanisms, potentially leading to new targeted therapies. We further show that the abundance of the PU-H71-enriched Hsp90 species, which is not dictated by Hsp90 expression alone, is predictive of the cell's sensitivity to Hsp90 inhibition.