Platelets are produced by bone marrow megakaryocytes through cytoplasmic protrusions, named native proplatelets (nPPT), into blood vessels. Proplatelets also refer to protrusions observed in megakaryocyte culture (cPPT) that are morphologically different. Contrary to cPPT, the mechanisms of nPPT formation are poorly understood. We show here in living mice that nPPT elongation is in equilibrium between protrusive and retraction forces mediated by myosin-IIA. We also found, using WT and β1-tubulin-deficient mice, that microtubule behavior differs between cPPT and nPPT, being absolutely required in vitro, while less critical in vivo. Remarkably, microtubule depolymerization in myosin-deficient mice did not affect nPPT elongation. We then calculated that blood Stokes'forces may be sufficient to promote nPPT extension, independently of myosin and microtubules. Together, we propose a new mechanism for nPPT extension that might explain contradictions between severely affected cPPT production and moderate platelet count defects in some patients and animal models.

Solitary bees are among the most important pollinators worldwide however population declines especially in croplands has been noticed. The novel pesticide sulfoxaflor is a competitive modulator of nicotinic acetylcholine receptors (nAChR) in insects. While there is evidence of a negative impact of neonicotinoids on bees of several social organization levels, our overall knowledge on the impact of sulfoxaflor on bees is poor. Here we present for the first time a study showing effects of field realistic doses of sulfoxaflor on solitary bees. Bees submitted to long term exposure of field realistic doses of sulfoxaflor (5 µg dm-3, 10 µg dm-3, 50 µg dm-3) and control were observed regarding their survival rate. Moreover, we recorded metrics related to flower visitation and flight performance. We discover that the highest field realistic dose is lethal to Osmia bicornis along five days of exposure. The effect of sulfoxaflor reduces the outcome of foraging, important features for fruit and seed production of cross-pollinated plant species. Bees exposed to pesticide visited flowers mostly walking rather than flying. Flight performance was also impaired by the pesticide.

In acute ischemic stroke due to large vessel occlusion (LVO) infarcts rapidly grow into the penumbra, which represents dysfunctional, but still viable brain tissue amenable to rescue by vessel recanalization. However, infarct progression and/or delayed patient presentation are serious and frequent limitations of this so far only acute therapy. Thus, a major goal of translational research is to “freeze” the penumbra already during LVO (before opening the vessel) and thereby extend individual time windows for non-futile recanalization. We used the filament occlusion model of the middle cerebral artery (MCAO) in mice and assessed progressive infarction under occlusion at 2, 3, and 4 h after onset. We show that blocking the activatory platelet receptor glycoprotein (GP)VI substantially delayed progressive neocortical infarction compared to isotype control antibody treated mice. Moreover, the local vascular recruitment of infiltrating neutrophils and T-cells was mitigated. In conclusion, our experimental data support ongoing clinical trials blocking platelet GPVI in acute ischemic stroke.

Paternal obesity is known to have a negative impact on the male’s reproductive health as well as the health of his offspring. Although epigenetic mechanisms have been implicated in the non-genetic transmission of acquired traits, the effect of paternal obesity on gene expression in the preimplantation embryo has not been fully studied. To this end, we investigated whether paternal obesity is associated with gene expression changes in eight-cell stage embryos fathered by males on a high-fat diet. We used single embryo RNA-seq to compare the gene expression profile of embryos generated by males on a high fat (HFD) versus control (CD) diet. This analysis revealed significant upregulation of the Samd4b and Gata6 gene in embryos in response to a paternal HFD. Furthermore, we could show a significant increase in expression of both Gata6 and Samd4b during differentiation of stromal vascular cells into mature adipocytes. These findings suggest that paternal obesity may induce changes in the male germ cells which are associated with the gene expression changes in the resulting preimplantation embryos.

The neuropeptide pigment-dispersing factor (PDF) is a key player to orchestrate the central clock of Drosophila melanogaster. In the fly brain PDF is expressed by the ventral lateral neurons which are the central pacemakers of the Drosophila circadian system and therefore align different clock neurons and modulate downstream circuits. The terminals of the small ventral lateral neurons (s-LNv) undergo daily circadian morphological changes which also affects the synaptic organization of these neurons. However, PDF function and release seems to be unaffected by the circadian plasticity. In Drosophila presynaptic sites are organized by the active zone protein Bruchpilot (BRP), a homolog of the mammalian ELKS protein. BRP and other active zone scaffold proteins are crucial for the recruiting and membrane fusion of small synaptic vesicles that contain amino-acid or monoamide transmitters. Neuropeptides, like PDF, are produced from larger preproproteins within the regulated secretory pathway. The preproproteins are directed to the lumen of the rough endoplasmic reticulum where, after removal of the signal peptide, the resulting proprotein can be modified and is then exported to the trans-Golgi network. Finally, the proproteins are packaged within dense-core vesicles (DCV) and transported to release sites. Within the trans-Golgi and the dense-core vesicles, the bioactive peptides are processed from the proprotein by a set of specific enzymes. Neuropeptide release sites seem to be non-correlated to active zones (AZ), indicating an independence of PDF release from synaptic scaffold proteins. This study aims to elucidate the relevance of AZ for the release of neuropeptides, especially for PDF, by taking both anatomical and functional aspects into consideration. I employed endogenous BRP labeling to examine the spatial correlation between immunolabeled PDF-containing DCV and BRP-labeled AZs in the s-LNv. The number of BRP-labeled puncta in the s-LNv terminals remained stable between morning (Zeitgeber time 2) and night (Zeitgeber time 14) but the puncta-density changed during circadian plasticity. This is an indicator for recycling of BRP in the s-LNv terminals. The relative distance between BRP- and PDF-labeled puncta was higher in the morning, around the reported time of PDF release. This is also the time of day when the terminal arborization complexity is most prominent. Investigation of the publically available ssTEM dataset (FAFB) suggests that spontaneous DCV release profiles in the s-LNv lacked spatial correlation to BRP-organized AZs (T-bars). Functional impairment of PDF signaling via RNAi expression in the sLNvs leads to a shift of circadian locomotor activity and a weaker rhythmicity under constant darkness. Both were not affected by downregulation of brp in the s-LNvs. However, the knockdown of the peptide release factor cadps or proteins involved in the SNARE complex significantly impaired rhythmic strength. To further investigate the impact of brp knockdown in DCV release, I employed another RNAi screen in the Inka cells, which produce the ecdysis triggering hormone (ETH). Knockdown of eth, cadps and SNARE proteins led to severely impaired behaviour, while knockdown of brp and other AZ scaffold proteins did not phenocopy the impairment of ETH signaling. Taken together, the data collected in this study suggest that DCV release of PDF and ETH is independent of BRP-organized AZs, supporting the hypothesis of different release processes for neuropeptides and classical neurotransmitters. Further investigations are necessary to elucidate the recruitment and targeting of DCV release. Anatomical investigation of CNS in the Drosophila brain proves challenging for structures that are as tiny as ACs since their size lies beyond the diffraction limit of light. Many studies employ electron microscopy (EM) to visualize structures in the scale of nanometers. However, fixation methods for EM reduce the toolset for immunostaining methods because epitopes, neccessary to identify the regions of interests (ROIs) in histology samples are blocked or denaturated. Correlative light and electron microscopy (CLEM) offer a solution to this dilemma by combining the best of both worlds. In this study I adjusted a protocol, which was originally published for C. elegans to Drosophila brain-tissue samples. I was able to label PDF immunostained on serial plastic sections and reconstruct a ROI with a z-resolution of 100nm.