Biology Open最新文献

Adhesion-based migration is regulated by focal adhesions: multi-protein nanostructures linking the intracellular cytoskeleton to the extracellular substrate. Efficient adhesion-based migration has been shown to be regulated by focal adhesion dynamics such as lifetime, size and turnover, which in turn are influenced by the molecular composition of focal adhesions. We recently identified the formation of cell-substrate adhesion populations in Dictyostelium discoideum with differing molecular compositions, but it is unclear how these distinct compositions influence Dictyostelium adhesion dynamics and cell migration. Here, we further investigate the role of VinculinB - the Dictyostelium homologue of Vinculin - localization on Dictyostelium adhesion lifetime and protein turnover during cell migration. We show that co-localization of VinculinB to PaxillinB-positive cell-substrate adhesions increases adhesion lifetime without changing PaxillinB turnover. We further show that truncation of the PaxillinB N-terminus, which perturbs VinculinB co-localization to adhesions, surprisingly also increases adhesion lifetime and decreases PaxillinB turnover at adhesions. These findings suggest that similar to mammalian focal adhesions, molecular composition of Dictyostelium cell-substrate adhesion regulates their adhesion lifetimes and protein turnover, providing insight into how cell-substrate adhesions function during Dictyostelium cell migration.

Behavioral variation within a population can be influenced by physical factors such as size, sex, and body condition. This variation may contribute to intraspecific niche breadth by enabling individuals to exploit different niches. To examine how anatomy shapes behavior, we conducted open field tests on desert kangaroo rats (Dipodomys deserti, n=16) and compared their activity to sex, morphology, and body condition. We constructed an arena within the species' natural habitat to simulate ecologically relevant conditions and recorded behavior over 15 min. We quantified speed and distance traveled, used principal component analysis to explore behavioral patterns, and used linear models to test for associations between behavior, locomotor traits, and anatomical variables. We found that individuals with lower body condition scores spent more time exploring, males were more exploratory than females, and individuals with longer feet - a proxy for skeletal size - traveled further. However, behavior and locomotor performance were not significantly correlated. Lastly, individuals moved faster and farther on full moon nights compared to new moon nights, indicating that moonlight influences movement strategy - potentially reflecting trade-offs between foraging and predation risk. These findings highlight species-specific drivers of behavioral variation and underscore the importance of understanding behavioral variability of desert mammals.

Zebrafish (Danio rerio) are widely used in neurobehavioral research due to their translational relevance in studying fear. Eight different fish species and variations were tested to induce fear responses in zebrafish, including one positive control (convict cichlid, Amatitlania nigrofasciata) and negative control (tiger barb, Puntigrus tetrazona) through a shared-environment test. The observation was done in three dimensions (3D) and two dimensions (2D) to assess the impact of dimensionality on the outcome. A single-camera system was used to capture two viewpoints by mirror reflection installed above the fish tank and reconstructed to 3D using F3LA software. Zebrafish showed a similar behavioral response towards Demason's cichlid (Pseudotrophus demasoni) and threadfin acara (Acarichthys heckelii) as they did to A. nigrofasciata, with some minor differences, and a lesser response to green Gymnocorymbus ternetzi, during the shared-environment tests. Meanwhile, presence of B. melanopterus caused zebrafish to have a higher tendency to freeze and display higher entropy, similar to an anxiety-like response. We found no correlation between behavioral response and the body size of the test fishes. However, a correlation was observed when we tested convict cichlids of different ages. Finally, zebrafish color preference was also observed through the use of G. ternetzi with different body colors as test fish, with the zebrafish preferring orange and red G. ternetzi and mostly avoiding green G. ternetzi. We found use of 3D observation superior to 2D observation because several important endpoints are obtainable only from certain viewpoints.

Poorly conserved or taxonomically restricted genes represent a sizable portion of most genomes. Many of these genes participate in essential processes and can contribute to evolutionary innovation in species. Here, we evaluate two of the Caenorhabditis-restricted class of LIN-15B-domain-encoding genes, ivph-3 and gon-14, and compare their in vivo functions in two species, C. elegans and C. briggsae. We show that within the Elegans supergroup, ivph-3 and gon-14 exhibit sequence constraints distinct from other family members, including maintenance of a one-to-one orthology and a higher degree of sequence conservation. Coincidentally, mutants for either of the genes exhibit strong phenotypic defects that are similar within species (C. elegans or C. briggsae), but with notable differences when comparing between species. These findings highlight the genetic and genomic features associated with the evolution of a taxonomically restricted gene family.

Yeast mitochondrial malate dehydrogenase, Mdh1p, is known to form supramolecular complexes with other tricarboxylic acid (TCA) cycle and mitochondrial dehydrogenase enzymes, including the aldehyde dehydrogenase, Ald4p. These complexes have been proposed to facilitate NADH channeling. Here, we demonstrate that in cells grown to saturation and stationary phases, the endogenous Mdh1p, expressed without its mitochondrial targeting signal (MTS), stays outside mitochondria, in both a diffuse cytoplasmic distribution and localized to distinct puncta. The puncta formed by MTS-lacking Mdh1p show no co-localization with the MTS-lacking Ald4p, suggesting that they do not co-assemble into a supramolecular complex in the cytoplasm. However, we found that the MTS-lacking Mdh1p does co-localize with its cytoplasmic counterpart, Mdh2p, in puncta. Interestingly, Mdh2p has recently been reported to form heterocomplexes with the peroxisomal Mdh3p and to be transported into peroxisomes to assist in the glyoxylate cycle. We also show that the MTS-lacking Mdh1p co-localizes with a fluorescent peroxisome marker, Pex3p. Our findings suggest that different malate dehydrogenases can enter peroxisomes, potentially as a means to make the glyoxylate pathway more efficient.

The eusocial honeybee Apis mellifera is a key pollinator and model for insect development, offering insights into the evolutionary history of holometabolous insects. Honeybee embryos develop in a controlled hive environment, which has led to potential adaptations in embryogenesis compared to solitary insect species such as the fruit fly Drosophila melanogaster. However, previously applied static imaging techniques are not well-suited to study morphogenic events. Here, we combine mRNA-based transient fluorescence labeling, Perfluorodecalin as the imaging medium, and a custom sample chamber for light sheet fluorescence microscopy to enable long-term live imaging of honeybee embryos from blastoderm formation to hatching. Our approach provides the first dynamic visualization of extra-embryonic membrane formation in honeybees, which exhibits variable window closure locations at the posterior-ventral area of the embryo. This contrasts with the red flour beetle Tribolium castaneum, where the serosa window closes at a confined anterior-ventral area. Taken together, our methodological framework expands the toolkit for alternative insect models, enabling comparative studies and investigations of environmental stressors, such as pesticides, on development. Plasmids used and datasets acquired in this study are publicly available, supporting future studies on insect diversification and conservation.

Epithelial fusion is a fundamental morphogenetic process critical for the closure and compartmentalisation of developing organs. While widely studied in systems such as neural tube and palatal closure, the cellular transitions that enable fusion remain poorly understood. Here, we investigate epithelial fusion during chick otic vesicle closure and identify a transient population of cells at the epithelial interface that mediate this process. These otic epithelial edge (OE) cells exhibit distinct morphology, reduced apicobasal polarity, and dynamic junctional remodelling, including altered distribution of ZO-1, CDH1 and RAC1. Notably, OE cells lack basal contact and display high sphericity, consistent with a partial epithelial-to-mesenchymal transition (EMT) phenotype. Transcriptomic profiling of microdissected tissues reveals that OE cells constitute a transcriptionally distinct population, enriched for EMT regulators, extracellular matrix remodelling genes, and WNT pathway components. Among these, the transcription factors Grhl2 and Sp8 were specifically expressed at the OE and exhibited opposing roles in epithelial identity. CRISPR-Cas9-mediated knockdown of either gene led to disrupted CDH1 localisation, loss of OE cell morphology and failure in epithelial segregation. These results suggest that epithelial fusion requires a regulated, hybrid EMT state that balances junctional plasticity with tissue cohesion. Our findings demonstrate that fusion-competent epithelial cells are not merely passive participants but actively modulate their shape, polarity, adhesion and genetic identity to enable morphogenesis.

The GM2 gangliosidoses are lysosomal storage disorders exhibiting a spectrum of neurological phenotypes ranging from childhood death to debilitating adult-onset neurological impairment. To date, no mouse model harbouring a specific human mutation causing GM2 gangliosidosis has been created. We used CRISPR/Cas9 to generate knockin (KI) mice with the common adult-onset Hexa Gly269Ser variant as well as knockout (KO) mice with Hexa mutations expected to cause complete HexA deficiency. We also created Neu3 KO alleles that combined with Hexa KO or KI alleles were expected to create acute and chronic models of GM2 gangliosidosis, respectively. However, both models accumulated GM2 ganglioside throughout the brain when compared to controls (CON), and exhibited progressive loss of reflexes, gait abnormalities, and premature death by 24 weeks of age. Although survival and behavioural phenotypes did not differ between KO and KI models, the KI model had substantial Hexa mRNA and evidence of GM2 turnover. This KI model will be useful for developing gene editing to correct the variant causing the Gly269Ser substitution and its novel biochemical phenotype suggests it may be suitable for testing therapies that treat partial β-hexosaminidase A deficiency.

Physical confinement is not routinely considered as a factor that influences phagocytosis, which is typically investigated using unconfined in vitro assays. BV2 microglia-like cells were used to interrogate the impact of confinement on IgG-mediated phagocytosis side by side with unconfined cells. Confinement acted as a potent phagocytic driver, greatly increasing the fraction of phagocytic cells in the population compared to the unconfined setting. Arp2/3 complex and myosin II contributed to this effect. Remarkably, confinement partially rescued phagocytic uptake upon myosin II disruption. In addition, cells under confinement were partially resistant to the actin-depolymerizing drug cytochalasin D. Unexpectedly, we observed that bead uptake stimulated persistent migration, a process we term 'phagocytic priming'. Integrin-dependent adhesion was required for phagocytic priming in unconfined and confined settings but was dispensable for phagocytic uptake. The cytoskeletal requirements for phagocytic priming differed depending on confinement state. Myosin II and Arp2/3 complex were required for phagocytic priming under confinement, but not in unconfined settings. As with phagocytosis, cytoskeleton-dependent priming of motility varies based on physical confinement status. Phagocytic priming may be a crucial innate immune mechanism by which cells respond to wounds or trauma with increased surveillance of the local microenvironment.

The western honey bee, Apis mellifera, continues to experience widespread die-offs that threaten their critical ecological and agricultural roles. Given the recognized impact of viruses on the increased mortality rates, it is imperative to understand the forces shaping viral infections. In this study, we explore how hive husbandry, landscape, and immunity influence viral loads in managed bees. We characterized 43 apiaries across Central Florida for eight husbandry interventions, five landscape variables, transcription of four immune genes, and infection intensities of four viruses: Black Queen cell virus (BQCV), deformed wing virus type A (DWV-A), Lake Sinai virus (LSV-2), and Israeli acute paralysis virus (IAPV). We found that colonies surrounded by more floral resources and fresh water bodies were associated with increased viral loads and increased viral coinfections. We speculate that increased floral resources increased pollinator abundance, thereby increasing transmission rates and viral richness. We further speculate that increased open water similarly increased pollinator abundance and/or exposure to immunity-altering pesticides. Last, we show that husbandry interventions aimed at reducing Varroa destructor mites can have positive and negative off-target viral impacts. Our data underscore the importance of landscape, immunity, and husbandry in honey bee disease dynamics and highlight the complexity of their interactions.