Biology subjects

Krivanek, J.

Publications and source records attributed to Krivanek, J..

9 recordsLinked to original sources

bioRxiv2026

SorCS2 controls Wnt signaling homeostasis during neurodevelopment by regulating Ror2 activity and trafficking

Wnt signaling orchestrates key developmental processes, yet mechanisms restricting its spatial and temporal activity remain incompletely understood. Here we identify SorCS2, a VPS10p-domain sorting receptor, as a conserved regulator of Wnt signaling homeostasis. Integrating proteomics, cell biology, embryology, and vertebrate models, we show that SorCS2 interacts with the noncanonical Wnt receptor Ror2 and controls its trafficking, Wnt5a-induced internalization, and lysosomal degradation. In mouse dopaminergic progenitors, SorCS2 deficiency enhances responsiveness to canonical and noncanonical Wnt ligands, increases Ror2 phosphorylation, and amplifies downstream signaling of both Wnt signaling cascades. Loss of SorCS2 further disrupts the ligand-receptor feedback loop, leading to elevated Ror2, Wnt5a, and Wnt1 expression, accelerated proliferation and neurogenesis, and increased expression of Tcf4, a gene implicated in neuropsychiatric disorders. Across vertebrate systems, SorCS2-dependent control of Ror2 signaling is required for anterior-posterior axis elongation, convergent extension, somitogenesis, and brain morphogenesis. These findings define a SorCS2-dependent sorting mechanism that fine-tunes morphogen receptor signaling during vertebrate neurodevelopment.

developmental biology↗

bioRxiv2026

Continuous pharyngeal endoderm links external and internal gills

Amphibians develop both external and internal gills during ontogeny, offering an opportunity to investigate the developmental relationship between these positionally distinct respiratory organs. Although internal gills of vertebrates are widely accepted to arise from pharyngeal endoderm, external gills have long been regarded as purely ectodermal outgrowths, obscuring their relationship to other vertebrate gills. Here, we combine histological analysis with direct lineage tracing in the Mexican axolotl (Ambystoma mexicanum) and the African clawed frog (Xenopus laevis) to resolve the embryonic origin of amphibian gills. We show that the external gill develops as a continuous epithelial extension of the pharyngeal endoderm, which forms its basal epithelium and reaches the distal gill tip. In the frog, this extension remains continuous with the epithelium giving rise to the internal gills. Rather than representing separate epithelial structures, external and internal gills therefore arise from a shared epithelial domain of the pharyngeal endoderm. These findings resolve a longstanding question concerning the embryonic origin of amphibian gills and provide a developmental viewpoint for understanding how spatially diverse vertebrate gills can evolve through repeated modification of a conserved endodermal tissue.

developmental biology↗

bioRxiv2026

Evolutionary origin of terpenoid biosynthesis in termites

Termites produce the most diverse array of terpenoids among metazoans, comprising over 200 structures. However, their biosynthesis has not yet been elucidated. Here, we identify a gene family which arose through the duplication of geranylgeranyl pyrophosphate synthase in the common ancestor of Neoisoptera, the terpene-producing termite lineage. We functionally characterized several proteins from this family as terpene synthases generating biologically relevant sesqui-and diterpenes. These include the queen pheromone (3R,6E)-nerolidol in Embiratermes neotenicus and the precursor of polycyclic defensive diterpenes (E,E,E)-neocembrene in Nasutitermes takasagoensis. We explore transposable element-mediated genomic mechanisms and selection pressures acting in the evolution of this gene family and report an amino acid site crucial for cyclization capacity as well as the enantiospecificity of the characterized enzymes. We conclude that we have identified an enzyme family underlying the remarkable richness of termite terpenoids, which likely contributed to the ecological success of Neoisoptera.

biochemistry↗

bioRxiv2025

Characterising the periodontal granulation tissue using scRNAseq.

AimsOur research investigated the cellular composition and molecular mechanisms of periodontal granulation tissue using single-cell RNA sequencing (scRNA-seq), aiming to enhance the understanding of periodontal disease pathogenesis and identify potential targets for regenerative therapies. Materials and MethodsGranulation tissue samples were collected from patients undergoing periodontal surgery. Fresh tissues were processed into single-cell suspensions and subjected to scRNA-seq. The data were integrated with existing datasets from healthy gingiva and periodontal ligament. Computational analyses were performed, and validation through immunofluorescence staining. ResultsTen distinct cell clusters were identified across the samples. Granulation tissue exhibited a higher abundance of immune cells compared to healthy tissues. A novel endothelial cell subpopulation, exclusive to granulation tissue, was discovered, characterized by NOTCH3 expression and involvement in ossification pathways. Additionally, granulation tissue Fibroblast subpopulations demonstrated a progenitor-like state, characterized by extracellular matrix reorganization and low differentiation, similar to cancer-associated fibroblasts. Conclusion(s)This study advances the understanding of periodontal disease by characterizing key regulatory cell populations within granulation tissue. The identification of the novel endothelial subpopulation offers new insights into the diseases pathogenesis and presents potential targets for regenerative therapies. These findings suggest opportunities for developing biomaterials that modulate specific cellular pathways to improve periodontal disease treatment.

cell biology↗

bioRxiv2024

Mesenchymal Meis2 controls whisker development independently from trigeminal sensory innervation

Hair follicle development is initiated by reciprocal molecular interactions between the placode-forming epithelium and the underlying mesenchyme. Cell fate transformation in dermal fibroblasts generates a cell niche for placode induction by activation of signaling pathways WNT, EDA, and FGF in the epithelium. These successive paracrine epithelial signals initiate dermal condensation in the underlying mesenchyme. Although epithelial signaling from the placode to mesenchyme is better described, little is known about primary mesenchymal signals resulting in placode induction. Here we show that Meis2 expression in cells derived from the neural crest is critical for whisker formation, and also for branching of trigeminal nerves. While whisker formation is independent of the trigeminal sensory innervation, MEIS2 in mesenchymal dermal cells orchestrates the initial steps of epithelial placode formation and subsequent dermal condensation. MEIS2 regulates the expression of transcription factor Foxd1, which is typical of pre-dermal condensation. However, deletion of Foxd1 does not affect whisker development. Overall, our data suggest an early role of mesenchymal MEIS2 during whisker formation and provide evidence that whiskers can normally develop in the absence of sensory innervation or Foxd1 expression.

developmental biology↗

bioRxiv2024

Identification of the trail-following pheromone receptor in termites

Chemical communication is the cornerstone of eusocial insect societies since it mediates the social hierarchy, division of labor, and concerted activities of colony members. The chemistry of social insect pheromones received considerable attention in both major groups of social insects, the eusocial Hymenoptera and termites. By contrast, current knowledge on molecular mechanisms of social insect pheromone detection by odorant receptors (ORs) is limited to hymenopteran social insects and no OR was yet functionally characterized in termites, the oldest eusocial insect clade. Here, we present the first OR deorphanization in termites. We selected four OR sequences from the previously annotated antennal transcriptome of the termite Prorhinotermes simplex (Rhinotermitidae), expressed them in Empty Neuron Drosophila, and functionally characterized using single sensillum recording (SSR) and a panel of termite semiochemicals. In one of the selected ORs, PsimOR14, we succeeded in obtaining strong and reliable responses to the main component of P. simplex trail-following pheromone, the monocyclic diterpene neocembrene. PsimOR14 showed a narrow tuning to neocembrene; only one additional compound out of 67 tested (geranylgeraniol) generated non-negligible responses. Subsequently, we used SSR in P. simplex workers and identified the olfactory sensillum specifically responding to neocembrene, thus likely expressing PsimOR14. We report on homology-based modelling of neocembrene binding by PsimOR14 and show how different ligands impact the receptor dynamicity using molecular dynamics simulations. Finally, we demonstrate that PsimOR14 is significantly more expressed in worker antennae compared to soldiers, which correlates with higher sensitivity of workers to neocembrene.

animal behavior and cognition↗

bioRxiv2024

Unveiling Vertebrate Development Dynamics in Frog Xenopus laevis using Micro-CT Imaging

BackgroundXenopus laevis, the African clawed frog, is a versatile vertebrate model organism employed across various biological disciplines, prominently in developmental biology to elucidate the intricate processes underpinning body plan reorganization during metamorphosis. Despite its widespread utility, a notable gap exists in the availability of comprehensive datasets encompassing Xenopus late developmental stages. FindingsIn the present study, we harnessed micro-computed tomography (micro-CT), a non-invasive 3D imaging technique utilizing X-rays to examine structures at a micrometer scale, to investigate the developmental dynamics and morphological changes of this crucial vertebrate model. Our approach involved generating high-resolution images and computed 3D models of developing Xenopus specimens, spanning from premetamorphosis tadpoles to fully mature adult frogs. This extensive dataset enhances our understanding of vertebrate development and is adaptable for various analyses. For instance, we conducted a thorough examination, analyzing body size, shape, and morphological features, with a specific emphasis on skeletogenesis, teeth, and organs like the brain at different stages. Our analysis yielded valuable insights into the morphological changes and structure dynamics in 3D space during Xenopus development, some of which were not previously documented in such meticulous detail. This implies that our datasets effectively capture and thoroughly examine Xenopus specimens. Thus, these datasets hold the solid potential for additional morphological and morphometric analyses, including individual segmentation of both hard and soft tissue elements within Xenopus. ConclusionsOur repository of micro-CT scans represents a significant resource that can enhance our understanding of Xenopus development and the associated morphological changes. The widespread utility of this amphibian species, coupled with the exceptional quality of our scans, which encompass a comprehensive series of developmental stages, opens up extensive opportunities for their broader research application. Moreover, these scans have the potential for use in virtual reality, 3D printing, and educational contexts, further expanding their value and impact. Graphical abstract & lay summary3D images of selected developmental stages of X. laevis in a comparison (scale bar = 10 mm). O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=67 SRC="FIGDIR/small/598452v1_ufig1.gif" ALT="Figure 1"> View larger version (14K): org.highwire.dtl.DTLVardef@1bc4664org.highwire.dtl.DTLVardef@1b1750dorg.highwire.dtl.DTLVardef@17bddaaorg.highwire.dtl.DTLVardef@115de4e_HPS_FORMAT_FIGEXP M_FIG C_FIG Lay summaryX-ray tomography was used to examine the African clawed frog (Xenopus laevis). An extensive data set of specimens from tadpoles to adult frogs provides novel insights into the changes and developmental dynamics of selected structures, which opens avenues to an improved understanding of this crucial animal model.

developmental biology↗

bioRxiv2024

Extended longevity of termite kings and queens is accompanied by extranuclear localization of telomerase in somatic organs and caste-specific expression of its isoforms

Kings and queens of termites are endowed with an extraordinary longevity coupled with lifelong fecundity. We recently reported that termite kings and queens display a dramatically increased enzymatic activity and abundance of telomerase in their somatic organs when compared to short-lived workers and soldiers. We hypothesized that this telomerase activation may represent a non-canonical pro-longevity function, independent of its canonical role in telomere maintenance. Here, we explore this avenue and investigate whether the presumed non-canonical role of telomerase may be due to alternative splicing of the catalytic telomerase subunit TERT and whether the subcellular localization of TERT isoforms differs among organs and castes in the termite Prorhinotermes simplex. We empirically confirm the expression of four in silico predicted splice variants (psTERT1-A, psTERT1-B, psTERT2-A, psTERT2-B), defined by N-terminal splicing implicating differential localizations, and C-terminal splicing giving rise to full-length and truncated isoforms. We show that the transcript proportions of the psTERT are caste- and tissue-specific and that the extranuclear full-length isoform TERT1-A is relatively enriched in the soma of neotenic kings and queens compared to their gonads and to the soma of workers. We also show that extranuclear TERT protein quantities are significantly higher in the soma of kings and queens compared to workers, namely due to the cytosolic TERT. Independently, we confirm by microscopy the extranuclear TERT localization in somatic organs. We conclude that the presumed pleiotropic action of telomerase combining the canonical nuclear role in telomere maintenance with extranuclear functions is driven by complex TERT splicing.

molecular biology↗

bioRxiv2020

miR-183/96/182 cluster is an important morphogenetic factor targeting PAX6 expression in differentiating human retinal organoids

MicroRNAs (miRNAs), a class of small, non-coding RNA molecules represent important regulators of gene expression. Recent reports have implicated their role in the cell specification process acting as "fine-tuners" to ensure the precise gene expression at the specific stage of cell differentiation. Here we used retinal organoids differentiated from human pluripotent stem cells (hPSCs) as a model to closely investigate the role of a sensory organ-specific and evolutionary conserved miR-183/96/182 cluster. Using a miRNA tough decoy approach, we inhibited the miR-183/96/182 cluster in hPSCs. Inhibition of the miRNA cluster resulted in an increased expansion of neuroepithelium leading to abnormal "bulged" neural retina in organoids, associated with upregulation of neural-specific and retinal-specific genes. Importantly, we identified PAX6, a well-known essential gene in neuroectoderm specification, as a target of the miR-183/96/182 cluster members. Taken together, the miR-183/96/182 cluster not only represents an important regulator of PAX6 expression, but it also plays a crucial role in retinal tissue morphogenesis.

molecular biology↗