Aquaporin 2 Mutations in Trypanosoma brucei gambiense Field Isolates Correlate with Decreased Susceptibility to Pentamidine and Melarsoprol

The predominant mechanism of drug resistance in African trypanosomes is decreased drug uptake due to loss-of-function mutations in the genes for the transporters that mediate drug import. The role of transporters as determinants of drug susceptibility is well documented from laboratory-selected Trypanosoma brucei mutants. But clinical isolates, especially of T. b. gambiense, are less amenable to experimental investigation since they do not readily grow in culture without prior adaptation. Here we analyze a selected panel of 16 T. brucei ssp. field isolates that (i) have been adapted to axenic in vitro cultivation and (ii) mostly stem from treatment-refractory cases. For each isolate, we quantify the sensitivity to melarsoprol, pentamidine, and diminazene, and sequence the genomic loci of the transporter genes TbAT1 and TbAQP2. The former encodes the well-characterized aminopurine permease P2 which transports several trypanocides including melarsoprol, pentamidine, and diminazene. We find that diminazene-resistant field isolates of T. b. brucei and T. b. rhodesiense carry the same set of point mutations in TbAT1 that was previously described from lab mutants. Aquaglyceroporin 2 has only recently been identified as a second transporter involved in melarsoprol/pentamidine cross-resistance. Here we describe two different kinds of TbAQP2 mutations found in T. b. gambiense field isolates: simple loss of TbAQP2, or loss of wild-type TbAQP2 allele combined with the formation of a novel type of TbAQP2/3 chimera. The identified mutant T. b. gambiense are 40- to 50-fold less sensitive to pentamidine and 3- to 5-times less sensitive to melarsoprol than the reference isolates. We thus demonstrate for the first time that rearrangements of the TbAQP2/TbAQP3 locus accompanied by TbAQP2 gene loss also occur in the field, and that the T. b. gambiense carrying such mutations correlate with a significantly reduced susceptibility to pentamidine and melarsoprol.     

Implanting Glass Spinal Cord Windows in Adult Mice with Experimental Autoimmune Encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) in adult rodents is the standard experimental model for studying autonomic demyelinating diseases such as multiple sclerosis. Here we present a low-cost and reproducible glass window implantation protocol that is suitable for intravital microscopy and studying the dynamics of spinal cord cytoarchitecture with subcellular resolution in live adult mice with EAE. Briefly, we surgically expose the vertebrae T12-L2 and construct a chamber around the exposed vertebrae using a combination of cyanoacrylate and dental cement. A laminectomy is performed from T13 to L1, and a thin layer of transparent silicone elastomer is applied to the dorsal surface of the exposed spinal cord. A modified glass cover slip is implanted over the exposed spinal cord taking care that the glass does not directly contact the spinal cord. To reduce the infiltration of inflammatory cells between the window and spinal cord, anti-inflammatory treatment is administered every 2 days (as recommended by ethics committee) for the first 10 days after implantation. EAE is induced only 2-3 weeks after the cessation of anti-inflammatory treatment.Using this approach we successfully induced EAE in 87% of animals with implanted windows and, using Thy1-CFP-23 mice (blue axons in dorsal spinal cord), quantified axonal loss throughout EAE progression. Taken together, this protocol may be useful for studying the recruitment of various cell populations as well as their interaction dynamics, with subcellular resolution and for extended periods of time. This intravital imaging modality represents a valuable tool for developing therapeutic strategies to treat autoimmune demyelinating diseases such as EAE.     

Inhibitor of Apoptosis (IAP) Proteins–Modulators of Cell Death and Inflammation

Misregulated innate immune signaling and cell death form the basis of much human disease pathogenesis. Inhibitor of apoptosis (IAP) protein family members are frequently overexpressed in cancer and contribute to tumor cell survival, chemo-resistance, disease progression, and poor prognosis. Although best known for their ability to regulate caspases, IAPs also influence ubiquitin (Ub)-dependent pathways that modulate innate immune signaling via activation of nuclear factor κB (NF-κB). Recent research into IAP biology has unearthed unexpected roles for this group of proteins. In addition, the advances in our understanding of the molecular mechanisms that IAPs use to regulate cell death and innate immune responses have provided new insights into disease states and suggested novel intervention strategies. Here we review the functions assigned to those IAP proteins that act at the intersection of cell death regulation and inflammatory signaling.Apoptosis represents a fundamental biological process that relies on the activation of caspases. Inhibitor of apoptosis (IAP) proteins represent a group of negative regulators of both caspases and cell death. Although best known for their ability to regulate caspases and cell death, it is now clear that they function as arbiters of diverse biological processes (Gyrd-Hansen and Meier 2010). Most prominently, IAPs control ubiquitin (Ub)-dependent signaling events that regulate activation of nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) pathways that in turn drive expression of genes important for inflammation, immunity, cell migration, and cell survival. IAPs thereby function as E3 Ub ligases, mediating the transfer of Ub from E2s to target substrates. This in turn modulates the signaling process through regulating protein stability as well as via nondegradative means (see below for details). Many of the cellular processes controlled by IAPs are frequently deregulated in cancer and, directly or indirectly, contribute to disease initiation, tumor maintenance, and/or progression, making IAPs obvious targets for anticancer therapy (LaCasse et al. 2008). Accordingly, small pharmacological inhibitors of IAPs, frequently referred to as Smac-mimetics (SM), were developed and are currently undergoing clinical trials for the treatment of cancer (LaCasse et al. 2008). The use of SMs in preclinical tumor models and clinical trials has provided compelling evidence for the therapeutic benefit of IAP inhibition.     

Characterization and genetic mapping of a new blood-flesh trait controlled by the single dominant locus DBF in peach

Anthocyanin-rich peaches, because of their antioxidant properties and their strong attractiveness to consumers, are increasingly considered in French peach varietal innovation programs that integrate plant genomics and classical breeding. In this study, we describe a new blood-flesh trait identified in the ‘Wu Yue Xian’ peach accession from China. ‘Wu Yue Xian’ exhibits a fully red mesocarp during the later stages of fruit development, both with green midrib leaf and normal growth of the tree. This blood-flesh phenotype clearly differs from that determined by a single recessive locus (bf) in ‘Harrow Blood’, a clone showing blood-flesh in both immature and mature fruit associated with red midrib leaf and reduced tree height. We have then provided genetic evidence that blood-flesh phenotype of ‘Wu Yue Xian’ was controlled by a single dominant locus, designated DBF (Dominant Blood-Flesh), in four successive families derived from this accession. A genetic linkage map of the blood-flesh parent (‘D6090’) of the fourth population was constructed, including 102 SSRs spanning a total distance of 562.3 cM in eight linkage groups. Whereas the bf locus is located to linkage group 4, we mapped DBF to the top of linkage group 5, thus proving that DBF and bf loci are not alleles. Among 64 predicted genes in the DBF region (505 kbp), three genes of the dihydroflavonol-4-reductase family were identified as good candidates for the control of the DBF trait. Furthermore, SSR markers flanking DBF, such as AMPP157 and AMPPG178, supply a good basis to implement marker-assisted selection for this trait.     

Climate change impacts on biodiversity in Switzerland: A review

A noticeable increase in mean temperature has already been observed in Switzerland and summer temperatures up to 4.8 K warmer are expected by 2090. This article reviews the observed impacts of climate change on biodiversity and considers some perspectives for the future at the national level.The following impacts are already evident for all considered taxonomic groups: elevation shifts of distribution towards mountain summits, spread of thermophilous species, colonisation by new species from warmer areas and phenological shifts. Additionally, in the driest areas, increasing droughts are affecting tree survival and fish species are suffering from warm temperatures in lowland regions. These observations are coherent with model projections, and future changes will probably follow the current trends.These changes will likely cause extinctions for alpine species (competition, loss of habitat) and lowland species (temperature or drought stress). In the very urbanised Swiss landscape, the high fragmentation of the natural ecosystems will hinder the dispersal of many species towards mountains. Moreover, disruptions in species interactions caused by individual migration rates or phenological shifts are likely to have consequences for biodiversity. Conversely, the inertia of the ecosystems (species longevity, restricted dispersal) and the local persistence of populations will probably result in lower extinction rates than expected with some models, at least in 21st century. It is thus very difficult to estimate the impact of climate change in terms of species extinctions. A greater recognition by society of the intrinsic value of biodiversity and of its importance for our existence will be essential to put in place effective mitigation measures and to safeguard a maximum number of native species.     

Expression pattern of the homeotic gene Bapx1 during early chick gastrointestinal tract development

Regulation of the Bone Morphogenetic Protein (BMP) signaling pathway is essential for the normal development of vertebrate gastrointestinal (GI) tract, but also for the differentiation of the digestive mesenchymal layer into smooth muscles and submucosal layer. Different studies demonstrated that Bapx1 (for bagpipe homeobox homolog 1) negatively regulates the BMP pathway, but its precise expression pattern during the development and the differentiation of the GI tract mesenchyme actually remains to be examined. Here, we present the spatio-temporal expression profile of Bapx1 in the chick GI tract. We show that Bapx1 is first expressed in the undifferentiated mesenchyme of the gizzard and the colon. After the differentiation of the digestive mesenchyme, we found Bapx1 strongly expressed in the gizzard smooth muscle and in the submucosa layer of the colon. This expression pattern provides new insights into the roles of Bapx1 during the regionalization of the GI tract and the differentiation of the digestive mesenchyme of the colon and the stomach.     

Six Homeoproteins Directly Activate Myod Expression in the Gene Regulatory Networks That Control Early Myogenesis

In mammals, several genetic pathways have been characterized that govern engagement of multipotent embryonic progenitors into the myogenic program through the control of the key myogenic regulatory gene Myod. Here we demonstrate the involvement of Six homeoproteins. We first targeted into a Pax3 allele a sequence encoding a negative form of Six4 that binds DNA but cannot interact with essential Eya co-factors. The resulting embryos present hypoplasic skeletal muscles and impaired Myod activation in the trunk in the absence of Myf5/Mrf4. At the axial level, we further show that Myod is still expressed in compound Six1/Six4:Pax3 but not in Six1/Six4:Myf5 triple mutant embryos, demonstrating that Six1/4 participates in the Pax3-Myod genetic pathway. Myod expression and head myogenesis is preserved in Six1/Six4:Myf5 triple mutant embryos, illustrating that upstream regulators of Myod in different embryonic territories are distinct. We show that Myod regulatory regions are directly controlled by Six proteins and that, in the absence of Six1 and Six4, Six2 can compensate.