Structural Toxicity: Hypertrophy Models of Human Pluripotent Stem Cell-Derived Cardiomyocytes

Human pluripotent stem cells (hPSC) are investigated as a source of authentic human cardiac cells for drug discovery and toxicological tests. Cell-based assays performed using an automated fluorescence imaging platform and high-content analysis are valuable in characterizing hypertrophic states that may be induced in hPSC-derived cardiomyocytes upon exposure to cardiotoxic compounds. In high-purity populations of hPSC-derived cardiomyocytes loaded with cell tracer probes and other cell markers, detailed hypertrophic profiles can be assessed based on information captured at cellular and subcellular levels

Assessment of the water status of mandarin and peach canopies using visible multispectral imagery

The production of high-quality mandarin or peach fruits depends on the ability to maintain an optimal level of water stress in the plant during the sugar accumulation period. This study investigates the use of visible imaging for monitoring water stress. Experiments were conducted on satsuma mandarin (Citrus unshiu Marc. var. Satsuma) and peach (Persica vulgaris Mill.) in south-western Japan. Water stress was induced using plastic mulching at the field scale. Images of crop leaves as well as orchard canopy were taken in near-infrared (760–900 nm), red (580–680 nm) and green (490–580 nm) spectral channels for 6 days. Neutral Grey Card was used as the reflectance standard and leaf water potential was the monitored crop parameter. A reflectance difference was found between water-stressed and non-water-stressed mandarin and peach plants in red and green spectral channels both at the individual leaf level and at the field-scale canopy level. A moderately good correlation was found between red reflectance and leaf water potential as well as between green reflectance and leaf water potential. Future research should aim at developing visible imaging into a precision irrigation tool applicable to mandarin and peach crops

BLOC-2 subunit HPS6 deficiency affects the tubulation and secretion of von Willebrand factor from mouse endothelial cells

Hermansky-Pudlak syndrome (HPS) is a recessive disorder with bleeding diathesis, which has been linked to platelet granule defects. Both platelet granules and endothelial Weibel-Palade bodies (WPBs) are members of lysosome-related organelles (LROs) whose formation is regulated by HPS protein associated complexes such as BLOC (biogenesis of lysosome organelles complex) -1, -2, -3, AP-3 (adaptor protein complex-3) and HOPS (homotypic fusion and protein sorting complex). Von Willebrand factor (VWF) is critical to hemostasis, which is stored in a highly-multimerized form as tubules in the WPBs. In this study, we found the defective, but varying, release of VWF into plasma after desmopressin (DDAVP) stimulation in HPS1 (BLOC-3 subunit), HPS6 (BLOC-2 subunit), and HPS9 (BLOC-1 subunit) deficient mice. In particular, VWF tubulation, a critical step in VWF maturation, was impaired in HPS6 deficient WPBs. This likely reflects a defective endothelium, contributing to the bleeding tendency in HPS mice or patients. The differentially defective regulated release of VWF in these HPS mouse models suggests the need for precise HPS genotyping before DDAVP administration to HPS patients

Sustained E2F-Dependent Transcription Is a Key Mechanism to Prevent Replication-Stress-Induced DNA Damage

Recent work established DNA replication stress as a crucial driver of genomic instability and a key event at the onset of cancer. Post-translational modifications play an important role in the cellular response to replication stress by regulating the activity of key components to prevent replication-stress-induced DNA damage. Here, we establish a far greater role for transcriptional control in determining the outcome of replication-stress-induced events than previously suspected. Sustained E2F-dependent transcription is both required and sufficient for many crucial checkpoint functions, including fork stalling, stabilization, and resolution. Importantly, we also find that, in the context of oncogene-induced replication stress, where increased E2F activity is thought to cause replication stress, E2F activity is required to limit levels of DNA damage. These data suggest a model in which cells experiencing oncogene-induced replication stress through deregulation of E2F-dependent transcription become addicted to E2F activity to cope with high levels of replication stress

Kinetochore-localized PP1-Sds22 couples chromosome segregation to polar relaxation

Cell division requires the precise coordination of chromosome segregation and cytokinesis. This coordination is achieved by the recruitment of an actomyosin regulator, Ect2, to overlapping microtubules at the centre of the elongating anaphase spindle. Ect2 then signals to the overlying cortex to promote the assembly and constriction of an actomyosin ring between segregating chromosomes. Here, by studying division in proliferating Drosophila and human cells, we demonstrate the existence of a second, parallel signalling pathway, which triggers the relaxation of the polar cell cortex at mid anaphase. This is independent of furrow formation, centrosomes and microtubules and, instead, depends on PP1 phosphatase and its regulatory subunit Sds22 (refs 2, 3). As separating chromosomes move towards the polar cortex at mid anaphase, kinetochore-localized PP1-Sds22 helps to break cortical symmetry by inducing the dephosphorylation and inactivation of ezrin/radixin/moesin proteins at cell poles. This promotes local softening of the cortex, facilitating anaphase elongation and orderly cell division. In summary, this identifies a conserved kinetochore-based phosphatase signal and substrate, which function together to link anaphase chromosome movements to cortical polarization, thereby coupling chromosome segregation to cell division

Corrigendum: Image-based siRNA screen to identify kinases regulating Weibel-Palade body size control using electroporation.

This corrects the article DOI: 10.1038/sdata.2017.22

Modulation of endothelial organelle size as an antithrombotic strategy

BACKGROUND: It is long-established that Von Willebrand Factor (VWF) is central to haemostasis and thrombosis. Endothelial VWF is stored in cell-specific secretory granules, Weibel-Palade bodies (WPBs), organelles generated in a wide range of lengths (0.5 to 5.0 μm). WPB size responds to physiological cues and pharmacological treatment, and VWF secretion from shortened WPBs dramatically reduces platelet and plasma VWF adhesion to an endothelial surface. OBJECTIVE: We hypothesised that WPB-shortening represented a novel target for antithrombotic therapy. Our objective was to determine whether compounds exhibiting this activity do exist. METHODS: Using a microscopy approach coupled to automated image analysis, we measured the size of WPB bodies in primary human endothelial cells treated with licensed compounds for 24 h. RESULTS AND CONCLUSIONS: A novel approach to identification of antithrombotic compounds generated a significant number of candidates with the ability to shorten WPBs. In vitro assays of two selected compounds confirm that they inhibit the pro-haemostatic activity of secreted VWF. This set of compounds acting at a very early stage of the haemostatic process could well prove to be a useful adjunct to current antithrombotic therapeutics. Further, in the current SARS-CoV-2 pandemic, with a considerable fraction of critically ill COVID-19 patients affected by hypercoagulability, these WPB size-reducing drugs might also provide welcome therapeutic leads for frontline clinicians and researchers

High-content screening image dataset and quantitative image analysis of Salmonella infected human cells

This work was supported by the Medical Research Council Core funding the MRC LMCB (MC_U12266B) (JKV) and the EU FP7 Marie-Curie International Reintegration Grant PIRG08-GA-2010-276811 (JKV). ANA was funded by ARUK Fellowships Non-Clinical Career Development Fellowship Ref No: 18440. ANA and SJP were also in part funded by ARUK (Grant 21261).Objectives Salmonella bacteria can induce the unfolded protein response, a cellular stress response to misfolding proteins within the endoplasmic reticulum. Salmonella can exploit the host unfolded protein response leading to enhanced bacterial replication which was in part mediated by the induction and/or enhanced endo-reticular membrane synthesis. We therefore wanted to establish a quantitative confocal imaging assay to measure endo-reticular membrane expansion following Salmonella infections of host cells. Data description High-content screening confocal fluorescence microscopic image set of Salmonella infected HeLa cells is presented. The images were collected with a PerkinElmer Opera LX high-content screening system in seven 96-well plates, 50 field-of-views and DAPI, endoplasmic reticulum tracker channels and Salmonella mCherry protein in each well. Totally 93,300 confocal fluorescence microscopic images were published in this dataset. An ImageJ high-content image analysis workflow was used to extract features. Cells were classified as infected and non-infected, the mean intensity of endoplasmic reticulum tracker under Salmonella bacteria was calculated. Statistical analysis was performed by an R script, quantifying infected and non-infected cells for wild-type and ΔsifA mutant cells. The dataset can be further used by researchers working with big data of endoplasmic reticulum fluorescence microscopic images, Salmonella bacterial infection images and human cancer cells.Publisher PDFPeer reviewe

Phosphatidylinositol 4-kinase IIβ negatively regulates invadopodia formation and suppresses an invasive cellular phenotype

The type II PI 4-kinases enzymes synthesise the lipid phosphatidylinositol 4-phosphate (PI(4)P) which has been detected at the Golgi complex and endosomal compartments, and which recruits clathrin adaptors. Despite common mechanistic similarities between the isoforms, the extent of their redundancy is unclear.We found that depletion of PI4KIIα and PI4KIIβ using siRNA led to actin remodelling. Depletion of PI4KIIβ also induced the formation of invadopodia containing membrane type I matrix metalloproteinase (MT1-MMP).Depletion of PI4KII isoforms also differentially affected TGN pools of PI(4)P and post-TGN traffic. PI4KIIβ depletion caused increased MT1-MMP trafficking to invasive structures at the plasma membrane and was accompanied by reduced colocalisation of MT1-MMP with membranes containing the endosomal markers Rab5 and Rab7, but increased localisation with the exocytic Rab8. Depletion of PI4KIIβ was sufficient to confer an aggressive invasive phenotype on minimally invasive HeLa and MCF-7 cell lines. Mining oncogenomic databases revealed that loss of the PI4K2B allele and underexpression of PI4KIIβ mRNA is associated with human cancers. This finding supports the cell data and suggests that PI4KIIβ may be a clinically significant suppressor of invasion. We propose that PI4KIIβ synthesises a pool of PI(4)P that maintains MT1-MMP traffic in the degradative pathway and suppresses the formation of invadopodia

Cell-type-specific modulation of innate immune signalling by vitamin D in human mononuclear phagocytes

Vitamin D is widely reported to inhibit innate immune signalling and dendritic cell (DC) maturation as a potential immunoregulatory mechanism. It is not known whether vitamin D has global or gene-specific effects on transcriptional responses downstream of innate immune stimulation, or whether vitamin D inhibition of innate immune signalling is common to different cells. We confirmed vitamin D inhibition of nuclear factor-κB (NF-κB) and p38 mitogen-activated protein kinase (MAPK) signalling in monocyte-derived DC (MDDC) stimulated with lipopolysaccharide (LPS). This was associated with global but modest attenuation of LPS-induced transcriptional changes at genome-wide level. Surprisingly, vitamin D did not inhibit innate immune NF-κB activation in monocyte-derived macrophages. Consistent with our findings in MDDC, ex vivo vitamin D treatment of primary peripheral blood myeloid DC also led to significant inhibition of LPS-inducible NF-κB activation. Unexpectedly, in the same samples, vitamin D enhanced activation of both NF-κB and MAPK signalling in primary peripheral blood monocytes. In a cross-sectional clinical cohort, we found no relationship between peripheral blood vitamin D levels and LPS-inducible activation of NF-κB and MAPK pathways in monocytes of myeloid DC. Remarkably, however, in vivo supplementation of people with vitamin D deficiency in this clinical cohort also enhanced LPS-inducible MAPK signalling in peripheral blood monocytes. Therefore, we report that vitamin D differentially modulates the molecular response to innate immune stimulation in monocytes, macrophages and dendritic cells. These results are of importance in the design of studies on vitamin D supplementation in infectious and immunological diseases