SRP54 mutations induce Congenital Neutropenia via dominant-negative effects on XBP1 splicing

Heterozygous de novo missense variants of SRP54 were recently identified in patients presenting with Congenital Neutropenia (CN) or its syndromic form Shwachman-Diamond Syndrome (SDS). Ever since its discovery as a driver of CN and SDS, SRP54 has been increasingly studied in the context of disease and is nowadays considered the second most common cause of CN. Despite its hitherto unknown prevalence, the molecular mechanisms leading to the development of the disease are still largely unknown and patient treatments are far from specific. In this thesis, I aimed to investigate the underlying mechanisms and processes contributing to the pathophysiology of SRP54 deficiencies. To follow this aim, I characterized and established a transgenic srp54 KO zebrafish as the first in vivo model of srp54-driven disease. Interestingly, srp54-/- zebrafish show early embryonic mortality and suffer from severe neutropenia and developmental defects affecting multiple organs. srp54+/- zebrafish on the other hand are viable and only display mild neutropenia and no overt other defects. However, when injecting srp54+/- fish with human mRNA of three mutated SRP54 variants (T115A, T117Δ and G226E) identified in patients, the neutropenia intensified, and pancreatic defects developed – a phenotype accurately mimicking the characteristics of SDS patients. Of note, the induced phenotypes showed mutation-specific differences, indicating that different SRP54 lesions exert unique dominant-negative effects on the functionality of the residual wildtype SRP54 protein. Consistent with these findings, overexpression of SRP54 missense variants in human promyelocytic HL60 cells as well as in healthy CD34+ cord blood cells impaired granulocytic maturation. Mechanistically, we found that SRP54 defects significantly reduce the efficiency of the unconventional splicing of the transcription factor X-box binding protein 1 (XBP1), which is one of the major regulators of the unfolded protein response (UPR). Vice-versa, xbp1 morphant zebrafish recapitulate phenotypes observed in srp54 mutant fish, and the injection of spliced xbp1 but not unspliced xbp1 rescues the neutropenia in srp54+/- embryos. In order to identify additional mechanisms contributing to the pathophysiology of SRP54 deficient patients, we performed single cell RNA sequencing of srp54-mutated zebrafish. Sequencing analysis revealed several differentially expressed genes with most of them converging on the major signaling branches of the UPR, indicating the cell’s efforts to circumvent the impaired XBP1 activity aiming to alleviate unresolved ER-stress

Memory CD8+ T Cells Balance Pro- and Anti-inflammatory Activity by Reprogramming Cellular Acetate Handling at Sites of Infection.

Serum acetate increases upon systemic infection. Acutely, assimilation of acetate expands the capacity of memory CD8+ T cells to produce IFN-γ. Whether acetate modulates memory CD8+ T cell metabolism and function during pathogen re-encounter remains unexplored. Here we show that at sites of infection, high acetate concentrations are being reached, yet memory CD8+ T cells shut down the acetate assimilating enzymes ACSS1 and ACSS2. Acetate, being thus largely excluded from incorporation into cellular metabolic pathways, now had different effects, namely (1) directly activating glutaminase, thereby augmenting glutaminolysis, cellular respiration, and survival, and (2) suppressing TCR-triggered calcium flux, and consequently cell activation and effector cell function. In vivo, high acetate abundance at sites of infection improved pathogen clearance while reducing immunopathology. This indicates that, during different stages of the immune response, the same metabolite-acetate-induces distinct immunometabolic programs within the same cell type

Dancing bees improve colony foraging success as long-term benefits outweigh short-term costs.

Waggle dancing bees provide nestmates with spatial information about high quality resources. Surprisingly, attempts to quantify the benefits of this encoded spatial information have failed to find positive effects on colony foraging success under many ecological circumstances. Experimental designs have often involved measuring the foraging success of colonies that were repeatedly switched between oriented dances versus disoriented dances (i.e. communicating vectors versus not communicating vectors). However, if recruited bees continue to visit profitable food sources for more than one day, this procedure would lead to confounded results because of the long-term effects of successful recruitment events. Using agent-based simulations, we found that spatial information was beneficial in almost all ecological situations. Contrary to common belief, the benefits of recruitment increased with environmental stability because benefits can accumulate over time to outweigh the short-term costs of recruitment. Furthermore, we found that in simulations mimicking previous experiments, the benefits of communication were considerably underestimated (at low food density) or not detected at all (at medium and high densities). Our results suggest that the benefits of waggle dance communication are currently underestimated and that different experimental designs, which account for potential long-term benefits, are needed to measure empirically how spatial information affects colony foraging success

A comparison of foraging success measured as mean daily gain in honey (means ± s.e.) under varying patch longevities and with various intervals between experimental switches of spatial information transfer (SI) and no spatial information transfer (NI) treatments (no switches, 2-day cycles, 3-day cycles, 12-day cycles).

<p>The benefit of SI varies with patch longevity, with increasing benefits from one day (a), 7 days (b), 14 days (c), to 28 days (d). SI is more beneficial, if patches are relatively stable over time. Switching between SI and NI treatment hides the benefit of SI to a large degree (solid circle: SI, open circles: NI).</p

Task-partitioning in insect societies: Non-random direct material transfers affect both colony efficiency and information flow

Task-partitioning is an important organisational principle in insect colonies and is thought to increase colony efficiency. In task-partitioning, tasks such as the collection of resources are divided into subtasks in which the material is passed from one worker to another. Previous models have assumed that worker–worker interactions are random, but experimental evidence suggests that receivers can have preferences to handle familiar materials. We used an agent-based simulation model to explore how non-random interactions during task-partitioning with direct transfer affect colony work efficiency. Because task-partitioning also allows receivers and donors to acquire foraging related information we analysed the effect of non-random interactions on informative interaction patterns. When receivers non-randomly rejected donors offering certain materials, donors overall experienced increased time delays, hive stay durations and a decreased number of transfer partners. However, the number of transfers was slightly increased, which can improve the acquisition and quality of information for donors. When receivers were non-randomly attracted to donors offering certain materials, donors experienced reduced transfer delays, hive stay durations and an increased number of simultaneous receivers. The number of transfers is slightly decreased. The effects of the two mechanisms “non-random rejection” and “non-random attraction” are biggest if the number of foragers and receivers is balanced. In summary, our results show that colony ergonomics are improved if receivers do not reject donors and if mechanisms exist that help receivers detect potential donors, such as learning the odour of the transferred food. Finally, our simulations suggest that non-random interactions can potentially affect the foraging patterns of colonies in changing environments.Fil: Grüter, Christoph. University Of Sussex; Reino UnidoFil: Schürch, Roger. University Of Sussex; Reino UnidoFil: Farina, Walter Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentin

A comparison of foraging success measured as daily gain in honey under high, medium and low food densities, either with spatial information transfer (SI) or without spatial information transfer (NI).

<p>Model runs lasted 48 days after an initial period of 3 days SI (the 3 day acclimatization period is not shown). The first row shows the pure SI (solid black line) and NI (dotted black line) cases. These baselines are also shown for the model runs where switching between SI and NI occurred (rows 2–4, black solid and dotted lines). Rows 2–4 show the cases for SI (white background)/NI (grey background) cycles that last 2 days, 3 days or 12 days respectively. All the simulations shown here started with the SI treatment on day 4. The last row shows the aggregated simulation results (means ± s.e.) for the three food densities and SI/NI cycles (solid circles: SI, open circles: NI) including the second set of simulations that started with the NI treatment on day 4.</p

Overview of the model parameters and the values used in our simulations.

<p>Overview of the model parameters and the values used in our simulations.</p

Wetting and spreading of a surfactant film on solid particles: influence of sharp edges and surface irregularities

In addition to particle size and surface chemistry, the shape of particles plays an important role in their wetting and displacement by the surfactant film in the lung. The role of particle shape was the subject of our investigations using a model system consisting of a modified Langmuir-Wilhelmy surface balance. We measured the influence of sharp edges (lines) and other highly curved surfaces, including sharp corners or spikes, of different particles on the spreading of a dipalmitoylphosphatidyl (DPPC) film. The edges of cylindrical sapphire plates (circular curved edges, 1.65 mm radius) were wetted at a surface tension of 10.7 mJ/m2 (standard error (SE) = 0.45, n = 20) compared with that of 13.8 mJ/m2 (SE = 0.20, n = 20) for cubic sapphire plates (straight linear edges, edge length 3 mm) (p 0.05). The surfaces of the plates showed significantly higher resistance to spreading compared to that of the edges, as substantially lower surface tensions were required to initiate wetting (p 0.05), respectively, whereas the surfaces were wetted at 3.8 mJ/m2 (SE = 0.89, n = 20) and 5.8 mJ/m2 (SE = 0.52, n = 20) (p < 0.05), respectively. Further experiments with pollen of malvaceae and maize (spiky and fine knobbly surfaces) were wetted at 10.0 mJ/m2 (SE = 0.52, n = 10) and 22.75 mJ/m2 (SE = 0.81, n = 10), respectively (p < 0.05). These results show that resistance to spreading of a DPPC film on various surfaces is dependent on the extent these surfaces are curved. This is seen with cubic sapphire plates which have at their corners a radius of curvature of about 0.75 microm, spiky malvaceae pollen with an even smaller radius on top of their spikes, or talc with various highly curved surfaces. These highly curved surfaces resisted wetting by the DPPC film to a higher degree than more moderately curved surfaces such as those of cylindrical sapphire plates, maize pollens, or polystyrene spheres, which have a surface free energy similar to that of talc but a smooth surface. The macroscopic plane surfaces of the particles demonstrated the greatest resistance to spreading. This was explained by the extremely fine grooves in the nanometer range, as revealed by electron microscopy. In summary, to understand the effects of airborne particles retained on the surfaces of the respiratory tract, and ultimately their pathological potential, not only the particle size and surface chemistry but also the particle shape should be taken in consideration

Assessment of total uncertainty in cocaine and benzoylecgonine wastewater load measurements

To check the effectiveness of campaigns preventing drug abuse or indicating local effects of efforts against drug trafficking, it is beneficial to know consumed amounts of substances in a high spatial and temporal resolution. The analysis of drugs of abuse in wastewater (WW) has the potential to provide this information. In this study, the reliability of WW drug consumption estimates is assessed and a novel method presented to calculate the total uncertainty in observed WW cocaine (COC) and benzoylecgonine (BE) loads. Specifically, uncertainties resulting from discharge measurements, chemical analysis and the applied sampling scheme were addressed and three approaches presented. These consist of (i) a generic model-based procedure to investigate the influence of the sampling scheme on the uncertainty of observed or expected drug loads, (ii) a comparative analysis of two analytical methods (high performance liquid chromatography-tandem mass spectrometry and gas chromatography-mass spectrometry), including an extended cross-validation by influent profiling over several days, and (iii) monitoring COC and BE concentrations in WW of the largest Swiss sewage treatment plants. In addition, the COC and BE loads observed in the sewage treatment plant of the city of Berne were used to back-calculate the COC consumption. The estimated mean daily consumed amount was 107 ± 21 g of pure COC, corresponding to 321 g of street-grade COC

Modeling hematopoietic disorders in zebrafish

Zebrafish offer a powerful vertebrate model for studies of development and disease. The major advantages of this model include the possibilities of conducting reverse and forward genetic screens and of observing cellular processes by; in vivo; imaging of single cells. Moreover, pathways regulating blood development are highly conserved between zebrafish and mammals, and several discoveries made in fish were later translated to murine and human models. This review and accompanying poster provide an overview of zebrafish hematopoiesis and discuss the existing zebrafish models of blood disorders, such as myeloid and lymphoid malignancies, bone marrow failure syndromes and immunodeficiencies, with a focus on how these models were generated and how they can be applied for translational research