Journal of cell science最新文献

During development cells must change shape and move without disrupting dynamic tissue architecture. This requires robust linkage of cell-cell adherens junctions to the force-generating actomyosin cytoskeleton. Drosophila Canoe and mammalian Afadin play key roles. One central task for the field is defining mechanisms by which upstream inputs from Ras-family GTPases regulate Canoe/Afadin. They are unusual in sharing two tandem Ras-association (RA) domains, which, when deleted, virtually eliminate Canoe function. Work in vitro suggested RA1 and RA2 differ in GTPase affinity, but their individual functions in vivo remain unknown. Combining bioinformatic and biochemical approaches, we find that both RA1 and RA2 bind to active Rap1 with similar affinities, and their conserved N-terminal extensions enhance binding. We created Drosophila canoe mutants to test RA1 and RA2 function in vivo. Despite their similar affinities for Rap1, RA1 and RA2 play strikingly different roles. Deleting RA1 virtually eliminates Canoe function, while mutants lacking RA2 are viable and fertile but have defects in junctional reinforcement in embryos and during pupal eye development. These data significantly expand our understanding of regulation of adherens junction:cytoskeletal linkage.

Ultraviolet (UV) rays prompt a natural response in epidermal cells, particularly within melanocytes. The changes in gene expression and related signaling pathways in melanocytes following exposure to UVR are still not entirely understood. Our findings reveal that UVB irradiation suppresses the expression of Dicer. This repression is intricately linked to the activation of the PI3K, RSK, and WNT/β-catenin signaling pathways and is directly associated with transcriptional repression by β-catenin. Notably, we have identified specific binding sites for the LEF/β-catenin complex in the Dicer promoter. Collectively, these results emphasize the significance of the UV-induced pathway involving LEF/β-catenin, which impacts Dicer expression. UV radiation also reduced the levels of specific miRNAs known to be important in the biology of melanocytes. This pathway holds potential importance in governing melanocyte physiology.

The increasing technical complexity of all aspects involving bioimages, ranging from their acquisition to their analysis, has led to a diversification in the expertise of scientists engaged at the different stages of the discovery process. Although this diversity of profiles comes with the major challenge of establishing fruitful interdisciplinary collaboration, such collaboration also offers a superb opportunity for scientific discovery. In this Perspective, we review the different actors within the bioimaging research universe and identify the primary obstacles that hinder their interactions. We advocate that data sharing, which lies at the heart of innovation, is finally within reach after decades of being viewed as next to impossible in bioimaging. Building on recent community efforts, we propose actions to consolidate the development of a truly interdisciplinary bioimaging culture based on open data exchange and highlight the promising outlook of bioimaging as an example of multidisciplinary scientific endeavour.

Advances in imaging, segmentation and tracking have led to the routine generation of large and complex microscopy datasets. New tools are required to process this 'phenomics' type data. Here, we present 'Cell PLasticity Analysis Tool' (cellPLATO), a Python-based analysis software designed for measurement and classification of cell behaviours based on clustering features of cell morphology and motility. Used after segmentation and tracking, the tool extracts features from each cell per timepoint, using them to segregate cells into dimensionally reduced behavioural subtypes. Resultant cell tracks describe a 'behavioural ID' at each timepoint, and similarity analysis allows the grouping of behavioural sequences into discrete trajectories with assigned IDs. Here, we use cellPLATO to investigate the role of IL-15 in modulating human natural killer (NK) cell migration on ICAM-1 or VCAM-1. We find eight behavioural subsets of NK cells based on their shape and migration dynamics between single timepoints, and four trajectories based on sequences of these behaviours over time. Therefore, by using cellPLATO, we show that IL-15 increases plasticity between cell migration behaviours and that different integrin ligands induce different forms of NK cell migration.

The enteric nervous system (ENS) consists of an extensive network of neurons and glial cells embedded within the wall of the gastrointestinal (GI) tract. Alterations in neuronal distribution and function are strongly associated with GI dysfunction. Current methods for assessing neuronal distribution suffer from undersampling, partly due to challenges associated with imaging and analyzing large tissue areas, and operator bias due to manual analysis. We present the Gut Analysis Toolbox (GAT), an image analysis tool designed for characterization of enteric neurons and their neurochemical coding using two-dimensional images of GI wholemount preparations. GAT is developed in Fiji, has a user-friendly interface, and offers rapid and accurate segmentation via custom deep learning (DL)-based cell segmentation models developed using StarDist, as well as a ganglia segmentation model in deepImageJ. We apply proximal neighbor-based spatial analysis to reveal differences in cellular distribution across gut regions using a public dataset. In summary, GAT provides an easy-to-use toolbox to streamline routine image analysis tasks in ENS research. GAT enhances throughput, allowing rapid unbiased analysis of larger tissue areas, multiple neuronal markers and numerous samples.

Plant protoplasts provide starting material for of inducing pluripotent cell masses that are competent for tissue regeneration in vitro, analogous to animal induced pluripotent stem cells (iPSCs). Dedifferentiation is associated with large-scale chromatin reorganisation and massive transcriptome reprogramming, characterised by stochastic gene expression. How this cellular variability reflects on chromatin organisation in individual cells and what factors influence chromatin transitions during culturing are largely unknown. Here, we used high-throughput imaging and a custom supervised image analysis protocol extracting over 100 chromatin features of cultured protoplasts. The analysis revealed rapid, multiscale dynamics of chromatin patterns with a trajectory that strongly depended on nutrient availability. Decreased abundance in H1 (linker histones) is hallmark of chromatin transitions. We measured a high heterogeneity of chromatin patterns indicating intrinsic entropy as a hallmark of the initial cultures. We further measured an entropy decline over time, and an antagonistic influence by external and intrinsic factors, such as phytohormones and epigenetic modifiers, respectively. Collectively, our study benchmarks an approach to understand the variability and evolution of chromatin patterns underlying plant cell reprogramming in vitro.

Candida albicans is the most prevalent fungal pathogen associated with candidemia. Similar to other fungi, the complex life cycle of C. albicans has been challenging to study with high-resolution microscopy due to its small size. Here, we employed ultrastructure expansion microscopy (U-ExM) to directly visualise subcellular structures at high resolution in the yeast and during its transition to hyphal growth. N-hydroxysuccinimide (NHS)-ester pan-labelling in combination with immunofluorescence via snapshots of various mitotic stages provided a comprehensive map of nucleolar and mitochondrial segregation dynamics and enabled the resolution of the inner and outer plaque of spindle pole bodies (SPBs). Analyses of microtubules (MTs) and SPBs suggest that C. albicans displays a side-by-side SPB arrangement with a short mitotic spindle and longer astral MTs (aMTs) at the pre-anaphase stage. Modifications to the established U-ExM protocol enabled the expansion of six other human fungal pathogens, revealing that the side-by-side SPB configuration is a plausibly conserved feature shared by many fungal species. We highlight the power of U-ExM to investigate subcellular organisation at high resolution and low cost in poorly studied and medically relevant microbial pathogens.

Trichomonas vaginalis causes trichomoniasis, the most common non-viral sexually transmitted disease worldwide. As an extracellular parasite, adhesion to host cells is essential for the development of infection. During attachment, the parasite changes its tear ovoid shape to a flat ameboid form, expanding the contact surface and migrating through tissues. Here, we have identified a novel structure formed at the posterior pole of adherent parasite strains, resembling the previously described uropod, which appears to play a pivotal role as an anchor during the attachment process. Moreover, our research demonstrates that the overexpression of the tetraspanin T. vaginalis TSP5 protein (TvTSP5), which is localized on the cell surface of the parasite, notably enhances the formation of this posterior anchor structure in adherent strains. Finally, we demonstrate that parasites that overexpress TvTSP5 possess an increased ability to adhere to host cells, enhanced aggregation and reduced migration on agar plates. Overall, these findings unveil novel proteins and structures involved in the intricate mechanisms of T. vaginalis interactions with host cells.

Ever since Robert Hooke's 17th century discovery of the cell using a humble compound microscope, light-matter interactions have continuously redefined our understanding of cell biology. Fluorescence microscopy has been particularly transformative and remains an indispensable tool for many cell biologists. The subcellular localization of biomolecules is now routinely visualized simply by manipulating the wavelength of light. Fluorescence polarization microscopy (FPM) extends these capabilities by exploiting another optical property - polarization - allowing researchers to measure not only the location of molecules, but also their organization or alignment within larger cellular structures. With only minor modifications to an existing fluorescence microscope, FPM can reveal the nanoscale architecture, orientational dynamics, conformational changes and interactions of fluorescently labeled molecules in their native cellular environments. Importantly, FPM excels at imaging systems that are challenging to study through traditional structural approaches, such as membranes, membrane proteins, cytoskeletal networks and large macromolecular complexes. In this Review, we discuss key discoveries enabled by FPM, compare and contrast the most common optical setups for FPM, and provide a theoretical and practical framework for researchers to apply this technique to their own research questions.