Biology subjects

Royer, C.

Publications and source records attributed to Royer, C..

5 recordsLinked to original sources

bioRxiv2026

Endoplasmic reticulum membrane contact sites coordinate exocytic site assembly and activity in neuroendocrine cells

Membrane contact sites (MCS) between intracellular organelles regulate lipid exchange, organelles dynamics and spatial organization of signaling pathways, yet their contribution to regulated exocytosis remains poorly understood. Here, we investigated the role of endoplasmic reticulum (ER) MCS in calcium-regulated exocytosis using primary bovine chromaffin cells. Combining electron microscopy on plasma membrane (PM) sheets with immunogold labeling, we identified ER structures contacting docked secretory granules and classified three types of MCS: ER-PM, ER-granule and tripartite ER-PM-granule contacts. These contacts are enriched at exocytic sites and contain Orai1 and STIM1, both known for mediating store-operated calcium release. Functional perturbation of the Orai/STIM pathway revealed that constitutive STIM activation or pharmacological inhibition of Orai1 reduced the number of exocytotic events, slowed catecholamine release and disrupted actin organization at granule docking sites. Together, our findings revealed a previously unrecognized role for ER MCS in organizing exocytic sites and controlling secretion efficiency in neuroendocrine cells.

cell biology↗

bioRxiv2020

ASPP2/PP1 complexes maintain the integrity of pseudostratified epithelia undergoing remodelling during morphogenesis

During development, pseudostratified epithelia undergo large scale morphogenetic events associated with increased mechanical stress. The molecular mechanisms that maintain tissue integrity in this context are poorly understood. Using a variety of genetic and imaging approaches, we uncover that the ASPP2/PP1 complex ensures proper epiblast and proamniotic cavity architecture via a mechanism that specifically prevents the most apical daughter cells from delaminating apically following cell division events. The ASPP2/PP1 complex achieves this by maintaining the integrity and organisation of the F-actin cytoskeleton at the apical surface of dividing cells. ASPP2/PP1 is also essential during gastrulation in the primitive streak, in somites and in the head fold region, suggesting that this complex is required across a wide range of pseudostratified epithelia during morphogenetic events that are accompanied by intense tissue remodelling and high cell proliferation. Finally, our study also suggests that the interaction between ASPP2 and PP1 is essential to the tumour suppressor function of ASPP2 which may be particularly relevant in the context of tissues that are subject to increased mechanical stress.

developmental biology↗

bioRxiv2019

Position-sensing established duringcompaction dictates cell fate in themammalian embryo

Precise patterning within the 3-dimensional context of tissues, organs and embryos implies that cells can sense their relative position. We still understand relatively little about how cells sense their relative position within small groups of cells. During preimplantation development, outside and inside cells rely on apicobasal polarity and the Hippo pathway to choose their fate. Despite recent findings suggesting that mechanosensing may be central to this process, the relationship between blastomere geometry (i.e. shape and position) and the Hippo pathway effector YAP remains unknown. To address this, we used a highly quantitative approach to collect and analyse information on the geometry and YAP localisation of individual blastomeres of mouse and human embryos. We find that the fraction of YAP in the nucleus responds to the proportion of exposed cell surface area rather than blastomere shape. To directly test the influence of blastomere position on YAP localisation we developed an approach using hydrogel based cylindrical cavities to alter blastomere arrangement in cultured embryos. Unbiased clustering analyses of blastomeres from such embryos reveal that the ability to respond to position emerges as early as the 8-cell stage during compaction and that altering the relative position of a blastomere within an embryo can alter its fate. Finally, we demonstrate that this response is lost upon inhibiting PKC signalling, linking it to the cell polarity. Our results pinpoint when during early embryogenesis cell specification decisions are initiated and show how blastomeres can sense their position in a polarity dependent manner to alter YAP localisation. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=149 SRC="FIGDIR/small/856161v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@845b46org.highwire.dtl.DTLVardef@18473ceorg.highwire.dtl.DTLVardef@cf0124org.highwire.dtl.DTLVardef@53fc8b_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2018

LRRK2 kinase inhibitors induce a reversible effect in the lungs of non-human primates with no measurable pulmonary deficits

Putative gain-of-function mutations in leucine-rich repeat kinase 2 (LRRK2), resulting in increased kinase activity and cellular toxicity, are a leading genetic cause of Parkinsons disease (PD). Hence, there is strong interest in developing LRRK2 kinase inhibitors as a disease-modifying therapy. Published reports that repeat dosing with two LRRK2 kinase inhibitors (GNE-7915 and GNE-0877) induce histopathological changes in the lung of non-human primates Fuji et al. 2015 (1) raised concerns about potential safety liability of LRRK2 kinase inhibitors. In the present study, we sought to determine whether previously observed effects in the lung: (a) represent on-target pharmacology, but with the potential for margin of safety, (b) are reversible upon drug withdrawal, and (c) are associated with pulmonary function deficits. To this end, we evaluated the histopathological effects, toxicokinetics and target inhibition of three structurally diverse LRRK2 kinase inhibitors, GNE-7915 (30 mg/kg, BID, as a positive control), MLi-2 (15 and 50 mg/kg, QD) and PFE-360 (3 and 6 mg/kg, QD) following 2 weeks of dosing in non-human primates. Subsets of animals dosed with GNE-7915 or MLi-2 were evaluated after 2-week dose-free periods. All three LRRK2 kinase inhibitors induced mild cytoplasmic vacuolation of type II pneumocytes, as reported previously, confirming an on-target effect of these compounds. Interestingly, despite lower doses of both PFE-360 and MLi-2 producing nearly complete inhibition of LRRK2 kinase activity in the brain as assessed by levels of pS935-LRRK2, histopathological changes in lung were absent in animals treated with low-dose PFE-360 and observed only sporadically in the low-dose MLi-2 group. The lung effect was fully reversible at 2 weeks post-dosing of GNE-7915. In a second study of identical dosing with MLi-2 and GNE-7915, no deficits were observed in a battery of translational pulmonary functional tests. In aggregate, these results do not preclude the development of LRRK2 kinase inhibitors for clinical investigation in Parkinsons disease.

pharmacology and toxicology↗

bioRxiv2017

Spatial protein analysis in developing tissues: a sampling-based image processing approach

Advances in fluorescence microscopy approaches have made it relatively easy to generate multi-dimensional image volumes and have highlighted the need for flexible image analysis tools for the extraction of quantitative information from such data. Here we demonstrate that by focusing on simplified feature-based nuclear segmentation and probabilistic cytoplasmic detection we can create a tool that is able to extract geometry based information from diverse mammalian tissue images. Our open-source image analysis platform, called SilentMark can cope with noisy images and with crowded fields of cells to quantify signal intensity in different cellular compartments. Additionally, it provides tissue geometry related information, which allows one to quantify protein distribution with respect to marked regions of interest. The lightweight SilentMark algorithms have the advantage of not requiring multiple processors and graphics cards and can be run even with just several hundred MB of memory. This makes it possible to use the method as a web application, effectively eliminating setup hurdles and compatibility issues with operating systems. We test this platform on mouse pre-implantation embryos, embryonic stem cell derived embryoid bodies and mouse embryonic heart and relate protein localisation to tissue geometry.

developmental biology↗