Biology Open最新文献

Egg-sac brooding is a costly maternal strategy for which evolutionary persistence hinges on clear offspring benefits and effective maternal tactics to offset those costs. Using the wolf spider Pardosa pusiola, we examined (1) whether hatchling emergence depends on the presence of a conspecific mother, (2) whether egg sac opening is a flexible response to embryonic cues, and (3) how mothers modulate locomotor performance under different ecological risks (sun exposure, flooding, predation). Conspecific foster mothers matched biological mothers in synchronizing egg-sac opening with embryonic development, whereas interspecific foster mothers (Pardosa astrigera) mistimed opening in most cases. Motherless egg sacs contained fully developed but un-emerged hatchlings, confirming that maternal presence is indispensable for emergence, not for hatching itself. Under moderate sun exposure, egg-sac-carrying females escaped slower than non-carrying females. Under high sun exposure or predator stimulus, carrying females escaped as fast as or faster than non-carrying females. Under simulated flooding, carrying females suffered higher mortality, yet survivors showed no difference in escape speed compared to non-carrying females. These results demonstrate flexible egg-sac management coupled with adaptive maternal locomotion, illustrating how costly parental care can be maintained when parents adjust their behavior according to environmental risk.

The extracellular matrix (ECM) is a critical component of embryonic development, providing both structural support and a dynamic signaling environment for cell migration, adhesion, and tissue organization. Collagen, the most abundant protein in the ECM, is crosslinked by the enzyme lysyl oxidase (LOX), and that activity plays a pivotal role in creating support throughout the ECM. Dysregulated LOX activity disrupts the mechanical integrity of the ECM. Sea urchins offer a robust model for studying LOX function and ECM dynamics in embryonic development due to their rapid, transparent development and traceable cell lineages. Previous studies using the pan-monoamine oxidase/LOX inhibitor β-aminopropionitrile suggested an essential role of LOX activity in sea urchin gastrulation and maintenance of ECM integrity. Here, we integrate newly developed and traditional LOX inhibitors, with a translation blocking morpholino antisense oligonucleotide to a specific lysyl oxidase, and chemoselective fluorescent probes to LOX oxidation products, all to test the role of the ECM in development and germ cell formation. The primordial germ cells in this animal are believed to be committed at the fifth cell division as small micromeres by inheritance of yet unknown molecular constituency. We find that LOX activity is essential for an instructive environment in the development of a germ line, even though the fate of that germ line in the sea urchin is predetermined. Our findings provide insight into the dynamic interplay between ECM remodeling, gene expression, and metabolism, offering a more profound understanding of the role of the ECM in development and germ cell identity.

Skippers (Hesperiidae) form a distinct lineage of butterflies where the developmental mechanisms of color patterning have seldom been studied. Skipper wing patterns often consist of median stripes, and studies from the mid-twentieth century suggested these elements are homologous to the central symmetry system (CSS) found in nymphalid butterflies. Here we examined the expression of the signaling ligand gene WntA, known to mark the presumptive CSS patterns in nymphalids, in the silver-spotted skipper Epargyreus clarus, and found support for the homology of the CSS across 95 MY of evolutionary divergence. We generated an annotated genome for E. clarus and used RNAseq to profile gene expression along the wing proximo-distal (P-D) axis. These data suggest that the transcription factor genes lobe, u-shaped, and odd-paired are expressed in restricted P-D sections of the wing similarly to WntA, indicating potential roles in CSS patterning. In addition, developmental genes involved in wing P-D patterning in Drosophila - dachsous, four-jointed, homothorax, tiptop/teashirt, vestigial, scalloped - reveal similar expressions between Diptera and Lepidoptera on the wing P-D axis, suggesting a deep conservation of P-D patterning in insect wings. This work expands our understanding of the mechanisms shaping wing pattern evolution in butterflies.

Reproduction in chondrichthyan fishes (sharks, rays, skates, and chimaeras) is generally assumed to be a long-term, energetically costly process, given their slow generation times. However, metabolic costs of reproduction remain poorly understood due to a lack of direct, non-lethal measurements. To address this, we investigated metabolic and physiological changes during oviparous reproduction in five female epaulette sharks (Hemiscyllium ocellatum). We tracked oxygen uptake rates - a proxy for metabolic rate - across a 3-week cycle, capturing data before, during, and after egg case encapsulation and oviposition. We also measured reproductive hormones (testosterone, 17β-estradiol, progesterone) and hematological parameters (hematocrit, hemoglobin concentration). Results revealed a positive but non-significant relationship between metabolic rate and body mass, and contrary to expectations, metabolic rate did not significantly change throughout the 19-day cycle. Hormone levels remained stable, except for a transient testosterone peak early in the cycle, and hematological parameters showed no significant variation. These findings tentatively suggest epaulette sharks maintain reproductive effort without marked increases in metabolic or physiological costs. Continued research under seasonal environmental variation could clarify reproductive energetics in chondrichthyans further. This study provides the first direct measurement of metabolic effects of oviparous reproduction in chondrichthyans, challenging assumptions about energetic demands in this taxon.

The size of the nucleus is tightly coordinated with cell size across eukaryotes, yet the physiological significance of maintaining proper nuclear dimensions remains poorly understood. Here, we investigate how nuclear size dysregulation resulting from perturbed nucleocytoplasmic transport affects mitotic fidelity in Schizosaccharomyces pombe. Overexpression of a GFP-tagged nuclear export signal (NES-GFP) induced nuclear expansion, leading to severe growth defects and frequent errors in chromosome segregation during mitosis. Live-cell imaging revealed that enlarged nuclei underwent delayed mitotic progression and abnormal nuclear division. Strikingly, genetic suppression of nuclear expansion alleviated these defects, whereas enhancement of nuclear size exacerbated them. Together, these findings suggest that maintaining proper nuclear dimensions contributes to accurate chromosome segregation, although additional effects of NES-GFP overproduction and other factors influencing nuclear size should be further examined.

Great reed warblers (Acrocephalus arundinaceus) have become an important species for understanding long-distance avian migration, yet the genetic basis of their migratory timing remains unknown. While previous studies have identified candidate genes influencing migration timing in other species, their role in great reed warblers remains unexplored. Additionally, it is unclear whether the genetic basis of migratory timing differs between spring and autumn migrations. This study aims to uncover genetic factors influencing migration timing, providing insights into the evolutionary and ecological processes shaping long-distance migration. We conducted pooled whole-genome sequencing representing four great reed warbler migratory chronotypes: early spring, late spring, early autumn, and late autumn. By comparing FST and allele frequency differences, we determined that the spring migration had a larger genetic contribution than the autumn migration; however, the effect sizes were small (0.03 and 0.001, respectively). When comparing the early and late spring pools, we identified 93 candidate genes enriched for functions related to lipid hydrolysis that putatively influence great reed warbler migratory behavior. Our results provide insight into the genetic differentiation underlying migratory timing in great reed warblers, which is crucial for predicting how they will adapt to shifting environmental conditions due to climate change and habitat loss.

Creating hypomorphic mutations is crucial to study gene function in vivo, especially when null mutations result in (embryonic) lethality. This applies to enzymes involved in glycosylation that, when mutated in human patients, cause the disease congenital disorders of glycosylation (CDG). In order to resemble patient condition, it would be ideal to acutely modulate the proteins in question to directly interfere with protein levels of such essential enzymes. These methods offer to establish pathogenic enzyme levels resembling net enzyme activity reported in patients suffering from CDG, with phosphomannomutase 2-CDG (PMM2-CDG) as the most common form. We established an auxin-inducible acute protein knockdown system for the use in the teleost fish medaka (Oryzias latipes) by combining an improved degron (AID2) technology with an mAID-nanobody targeting endogenously GFP-tagged Pmm2 protein. We generated a fishline expressing a functional Pmm2-GFP fusion protein, by single copy integration of GFP into the pmm2 locus. Upon induction, the degron system efficiently reduced Pmm2-GFP levels and enzyme activity, recapitulating the activity level of the hypomorphic mutations associated with PMM2-CDG in patients. This broadly applicable approach enables the investigation of CDG disease mechanisms during early embryonic development through reduction of protein abundance, mimicking hypomorphic mutations and thus substantially expanding the range of the genetic toolbox.

Transposon silencing is essential for germline development. In Drosophila oogenesis, DNA damage caused by transposon activation affects microtubule-dependent mRNA localisation in the oocyte and impairs embryonic axes formation. Our previous EMS mutagenesis screen for gurken mRNA mislocalisation on chromosome 3L of Drosophila melanogaster identified several piRNA pathway mutants ( Hayashi et al., 2014). Here, we report the screen for chromosome 3R. We identified ten mutation groups disrupting gurken mRNA localisation and other mutations affecting different aspects of oogenesis. We found that mutations in karyopherin-β3 affect localisation and translation of gurken mRNA in a transposon silencing-independent manner. Characterisation of the new mutation in vreteno revealed that the piRNA pathway is essential for the basal stalk development, the process of holding the ovariole and encapsulating the first egg chambers. Females transheterozygous for vreteno and armitage mutations both showed abnormal basal stalks, defective egg chamber formation and loss of germline cells. We also found that the mutation in the Zinc Finger motif of Spindle-E shows a hypomorphic transposon activation phenotype, consistent with the previous study ( Ott et al., 2014). Further characterisation showed that the Zinc Finger is required for robust ping-pong piRNA biogenesis and the nuage localisation of AGO3, but not of Aubergine, suggesting that it is involved in a specific step of ping-pong biogenesis.

Genomic studies of neurodevelopmental disorders (NDDs) have identified several relevant genomic variants. EBF3 is a gene with an excess of protein-coding de novo variants and underlies Hypotonia, Ataxia, and Delayed Development Syndrome. We previously identified noncoding de novo variants in an enhancer of EBF3 and further found enrichment of deletions of this enhancer in NDDs. In this study, we generated a novel mouse line that deletes the highly conserved, orthologous mouse region within the Rr169617 regulatory region, and characterized the molecular and phenotypic aspects of this mouse model. We found a deviation from Mendelian expectation (P=0.02) with significant depletion of the deletion allele (P=5.8×10-4). Rr169617+/- mice had a reduction of Ebf3 expression by 10% and Rr169617-/- mice had a reduction by 20%. Differential expression analyses in E12.5 forebrain, midbrain, and hindbrain in Rr169617+/+ versus Rr169617-/- mice identified dysregulated genes including histone and brain development related genes. A priori phenotyping analysis (open field, hole board and light/dark transition) identified sex-specific differences in mobility only for Rr169617-/- mice across multiple behavioral assays with Rr169617-/- males less mobile than Rr169617-/- females. Furthermore, both sexes when homozygous for the enhancer deletion displayed body composition differences when compared to wildtype mice. Overall, we show that deletion within Rr169617 reduces expression of Ebf3 and results in phenotypic outcomes consistent with potential sex specific behavioral differences.