eLife最新文献

Although several open-source, easy-to-assemble light-sheet microscope platforms already exist-such as mesoSPIM, OpenSPIM, and OpenSpin-they are optimized for imaging large specimens and lack the resolution required to visualize subcellular features, such as organelles or cytoskeletal architectures. In contrast, lattice light-sheet microscopy (LLSM) achieves the resolution necessary to resolve such fine structures but, in its open-source implementation, can be alignment- and maintenance-intensive, often requiring specialist expertise. To address this gap, we developed Altair light-sheet fluorescence microscopy (LSFM), a high-resolution, open-source, sample-scanning light-sheet microscope specifically designed for subcellular imaging. By optimizing the optical pathway in silico, we created a custom baseplate that greatly simplifies alignment and assembly. The system integrates streamlined optoelectronics and optomechanics with seamless operation through our open-source software, navigate. Altair-LSFM achieves lateral and axial resolutions of approximately 235 and 350 nm, respectively, across a 266 µm field of view after deconvolution. We validate the system's capabilities by imaging sub-diffraction fluorescent nanospheres and visualizing fine structural details in mammalian cells, including microtubules, actin filaments, nuclei, and Golgi apparatus. We further demonstrate its live-cell imaging capabilities by visualizing microtubules and vimentin intermediate filaments in actively migrating cells.

Transition metals, such as iron and zinc, are indispensable trace elements for eukaryotic life, acting as co-factors in essential processes ranging from metabolism to DNA replication. These metals can be transported into cells by an evolutionary-conserved family of metal transporters; however, how the ubiquitous mammalian parasite Toxoplasma gondii acquires essential metals has been unknown. Here, we have identified and characterised the first iron and zinc importer in T. gondii. This transporter, named ZFT, localised to the parasite plasma membrane and is essential for the parasite's life cycle. We find ZFT is regulated by iron availability and overexpression sensitises cells to excess iron and zinc. Using a conditional knockdown system, we find that knockdown of ZFT leads to reduction in mitochondrial respiration and a switch to a more quiescent lifecycle stage. To confirm transport activity, we find that knockdown of ZFT leads to a reduction in parasite-associated zinc and iron, and ZFT expression complements loss of zinc transporter activity in a yeast model. Further, expression of ZFT in Xenopus oocytes demonstrates direct uptake of iron, which is outcompeted in the presence of zinc. Overall, we have identified the first metal uptake transporter in T. gondii and demonstrated the importance of iron and zinc to the parasite. This finding advances our understanding of how this obligate intracellular parasite acquires nutrients from its host.

Axolotls (Ambystoma mexicanum) exhibit a remarkable ability to regenerate limbs. Classical experiments have suggested that contact between cells derived from distinct orientations-dorsal, ventral, anterior, and posterior-within the regenerating blastema is necessary for accurate limb pattern formation. However, the molecular basis for this requirement has remained largely unknown. Here, we demonstrate that both dorsal and ventral tissues are required for limb formation via induction of Shh expression, which plays a crucial role in limb patterning. Using the accessory limb model, we induced position-specific blastemas lacking cells derived from a single orientation (anterior, posterior, dorsal, or ventral). Limb patterning occurred only in blastemas containing both dorsal- and ventral-derived cells. We further observed that Shh expression requires dorsoventral contact within a blastema, highlighting the necessity of dorsoventral contact for inducing Shh expression. Additionally, we identified WNT10B and FGF2 as dorsal- and ventral-mediated signals, respectively, that create the inductive environment for Shh expression. Our findings clarify the role of dorsal and ventral cells in inducing Shh, a mechanism that has rarely been studied in the context of limb regeneration and pattern formation. This model provides new insights into how cells with different positional identities drive the regeneration process.

The protective correlates of Mycobacterium tuberculosis (Mtb) infection-elicited host immune responses are incompletely understood. Here, we report pro-pathogenic crosstalk involving Ly6G⁺ granulocytes (Ly6G⁺Gra), IL-17, and COX2. We show that in the lungs of Mtb-infected wild-type mice, either BCG-vaccinated or not, most intracellular bacilli are Ly6G⁺Gra-resident 4 weeks post-infection onwards. In the genetically susceptible ifng^-/- mice, excessive Ly6G⁺Gra infiltration correlates with severe bacteremia. Neutralizing IL-17 (anti-IL17mAb) and COX2 inhibition by celecoxib reverse Ly6G⁺Gra infiltration, associated pathology, and death in ifng^-/- mice. Surprisingly, Ly6G⁺Gra also serves as the major source of IL-17 in the lungs of Mtb-infected WT or ifng^-/- mice. The IL-17-COX2-Ly6G⁺Gra interplay also operates in WT mice. Inhibiting RORγt, the key transcription factor for IL-17 production or COX2, reduces the bacterial burden in Ly6G⁺Gra, leading to reduced bacterial burden and pathology in the lungs of WT mice. In the Mtb-infected WT mice, COX2 inhibition abrogates IL-17 levels in the lung homogenates and significantly enhances BCG's protective efficacy, mainly by targeting the Ly6G⁺Gra-resident Mtb pool, a phenotype also observed when IL-17 is blocked by RORγt inhibitor. Furthermore, in pulmonary TB patients, high neutrophil count and IL-17 correlated with adverse treatment outcomes. Together, our results suggest that IL-17 and PGE2 are the negative correlates of protection, and we propose targeting the pro-pathogenic IL-17-COX2-Ly6G⁺Gra axis for TB prevention and therapy.

The behaviour of a receptor protein can be influenced by the presence of certain lipids in the membrane it is embedded in.

Even seemingly homogeneous populations of cells can express phenotypic diversity in response to environmental changes. Thus, X-ray irradiation of tissues composed of diverse cell types can have complex outcomes. We have used single-cell RNA sequencing to study the effects of X-ray radiation on the Drosophila wing imaginal disc, a relatively simple tissue composed mostly of epithelial cells. Transcriptomic clustering of cells collected from the wing disc generates clusters that are mainly grouped based on proximodistal cell location. To quantify heterogeneity of gene expression among clusters, we adapted a metric used to study market concentration, the Herfindahl-Hirschman Index. Genes involved in DNA damage repair, defense against reactive oxygen species, cell cycle progression, and apoptosis are expressed relatively uniformly. In contrast, genes encoding a subset of ligands, notably cytokines that activate the JAK/STAT pathway, some transcription factors, including Ets21C, previously implicated in regeneration, and several signaling proteins are expressed more regionally. Though the radiation-responsive transcription factor p53 is expressed relatively uniformly in the wing disc, several regionally induced genes still require p53 function, indicating that regional and radiation-induced factors combine to regulate their expression. We also examined heterogeneity within regions using a clustering approach based on cell cycle gene expression. A subpopulation of cells, characterized by high levels of tribbles expression, is amplified in irradiated discs. Remarkably, this subpopulation accounts for a considerable fraction of radiation-induced gene expression, indicating that cellular responses are non-uniform even within regions. Thus, both inter-regional and intra-regional heterogeneity are important features of tissue responses to X-ray radiation.

In the peripheral nervous system, sensory and motor axons are generally covered by wrapping glial cell processes. This neuron-glia interaction requires an intricate coordination of glial growth and differentiation. How this is controlled molecularly remains largely unknown. At the example of Drosophila larval nerves, we show that glial growth, which occurs without any cell division, is initially triggered by the FGF-receptor tyrosine kinase Heartless (Htl). In a screen for genes acting downstream of activated FGF-receptor, we identified the large membrane protein Uninflatable (Uif), which supports the growth of excessive plasma membrane domains but does not support glial axon wrapping. Uif is also known to inhibit Notch. Surprisingly, we find that Notch signaling is required in postmitotic wrapping glia. While compromised Notch signaling results in a reduced wrapping efficiency, gain of Notch activity in wrapping glia leads to a hyperwrapping phenotype. Thus, Notch signaling is both necessary and sufficient for glial wrapping in Drosophila larvae. In addition, Notch suppresses both uif and htl function and thus stabilizes the switch between glial growth and glial axon wrapping. Given the general conservation of signaling mechanisms controlling glia development in mice and flies, similar mechanisms may act in the mammalian nervous system to control final glial differentiation.

Movement flexibility and automaticity are necessary to successfully navigate different environments. When encountering difficult terrains such as a muddy trail, we can change how we step almost immediately so that we can continue walking. This flexibility comes at a cost since we initially must pay deliberate attention to how we are moving. Gradually, after a few minutes on the trail, stepping becomes automatic so that we do not need to think about our movements. Canonical theory indicates that different adaptive motor learning mechanisms confer these essential properties to movement: explicit control confers rapid flexibility, while forward model recalibration confers automaticity. Here, we uncover a distinct mechanism of treadmill walking adaptation - an automatic stimulus-response mapping - that confers both properties to movement. The mechanism is flexible as it learns stepping patterns that can be rapidly changed to suit a range of treadmill configurations. It is also automatic as it can operate without deliberate control or explicit awareness by the participants. Our findings reveal a tandem architecture of forward model recalibration and automatic stimulus-response mapping mechanisms for walking, reconciling different findings of motor adaptation and perceptual realignment.

Chromatin organisation and transcriptional regulation are tightly coordinated processes that are essential for maintaining cellular identity and function. ATP-dependent chromatin remodelling proteins play critical roles in control of genome structure and in regulating transcription across eukaryotes. Their essential nature, however, has made it difficult to define exactly how these functions are mediated. The chromatin remodeller CHD4 has been shown to be capable of sliding nucleosomes in vitro, and to regulate chromatin accessibility and gene expression in vivo. Using an inducible depletion system, here we identify a second mechanism of action for CHD4 in actively restricting the residence time of transcription factors (TFs) on chromatin. Together, these activities result in distinct, context-dependent outcomes: at highly accessible regulatory elements, CHD4 limits TF binding to maintain regulatory function, while at low-accessibility euchromatic regions, it prevents TF engagement and sustains chromatin compaction, thereby silencing cryptic enhancers. Collectively, these mechanisms enable CHD4 to reduce transcriptional noise while preserving the responsiveness of active regulatory networks.