Biology subjects

Seybold, A.

Publications and source records attributed to Seybold, A..

4 recordsLinked to original sources

bioRxiv2026

Ultrastructure of stemness and differentiated state in Hydra epithelial cells

Epithelial cells in Hydra perform an unusual combination of functions: they divide continuously like adult stem cells while simultaneously executing the complex physiological tasks of differentiated epithelia. This challenges the traditional distinction between proliferative stem cells and terminally differentiated tissue, raising the question of how a single cell type integrates these opposing roles. Using electron microscopy, we examined morphological characteristics that define the stem-like and differentiated states of Hydras ectodermal and endodermal epithelial cells. Stemness is reflected by nuclear characteristics of active proliferation, including extensive euchromatin, large nucleoli, and the presence of nuage. However, differentiated epithelial cells exhibit strong apical-basal polarity, various endomembrane compartments for endocytosis and transport, specialized secretion mechanisms, and basal muscle processes with dense-core vesicles implicated in hormonal communication. Cryofixation improved ultrastructure preservation, elucidating the pleiomorphic configurations of complex intracellular channel systems traditionally presenting as singular vacuoles. This may shed new light on possible functions of this compartment. Taken together, Hydra epithelial cells combine ancient stem cell traits with highly specialized differentiated functions. This multifunctionality provides insight into the cellular organization of early-branching animals and suggests that multifunctional epithelia may represent an ancestral condition preceding the strict segregation of stem and differentiated cell lineages in bilaterians.

evolutionary biology↗

bioRxiv2026

Structural assembly of the glycan-rich, chitin-reinforced adhesive of Hydra is coordinated by a lectin-like protein, HvAb1

Aquatic animals deploy adhesives, in numerous essential functions, and reversibility is a key adaptation. The molecular mechanisms of reversible wet adhesion remain poorly understood. Using a model organism, the freshwater cnidarian Hydra vulgaris, we dissect the mechanism of molecular assembly in a secreted adhesive and uncover a glycan and protein-based architecture organized by a lectin-like protein, Hydra vulgaris adhesive protein 1 (HvAb1). We identify HvAb1 as a nonredundant organizer of the adhesive matrix, being basal-disc specific and secreted. Knockdown of HvAb1 severely impaired attachment and disrupted footprint architecture in a mosaic pattern, with only HvAb1-positive regions of the adhesive footprint retaining their normal structure. The adhesive is wheat germ agglutinin (WGA)-reactive and contains a fibrillar chitin-based sub-network, synthesized by a basal-disc-specific chitin synthase. Applying exogeneous chitinase abolished both WGA staining and Hydra attachment, indicating that WGA-positive components perform essential roles in adhesion. Our results therefore describe a glycan-dominated matrix, organized via a lectin-like protein (HvAb1), which is reinforced by chitin and enables reversible adhesion underwater. This establishes Hydra as a tractable model to better understand the principles of reversible adhesion underwater and, potentially, inform future bioinspired, sustainable adhesives.

zoology↗

bioRxiv2026

Annelid eye evolution revealed by developmental, ultrastructural, and connectome analyses of cerebral eyes in Malacoceros fuliginosus

Eye evolution has long attracted interest, yet how multiple cerebral eyes within a lineage originate and diversify remains unclear. Annelids display exceptional diversity in eye number and structure, but the homology and function of distinct eye pairs are poorly understood. Here we investigate the cerebral eyes of the sedentary annelid Malacoceros fuliginosus using an integrated developmental, molecular, ultrastructural, and connectomic approach. We show that both the early-developing ventral and later-developing dorsal eyes are simple, few-celled, inverted rhabdomeric eyes that express transcription factors with conserved roles in animal eye development. Two r-opsin paralogs and distinct neurotransmitters are differentially expressed in different photoreceptor cells of the eyes. Ultrastructural reconstructions across larval development reveal differences in cellular composition and growth dynamics, while axonal tracing shows that photoreceptors from ventral and dorsal eyes project to overlapping regions of the larval brain. The overall organization and projections resemble those described in the errant annelid Platynereis dumerilii. Together, these data support the hypothesis that an ancestral cerebral eye duplicated early in annelid evolution, giving rise to multiple eye pairs with stage-specific functions.

evolutionary biology↗

bioRxiv2018

The Desmosome is a Mesoscale Lipid Raft-Like Membrane Domain

Desmogleins are cadherin family adhesion molecules essential for epidermal integrity. Previous studies have shown that desmogleins associate with lipid rafts, but the significance of this association was not clear. Here, we report that the desmoglein transmembrane domain (TMD) is the primary determinant of raft association. Further, we identify a novel mutation in the DSG1 TMD (G562R) that causes severe dermatitis, multiple allergies, and metabolic wasting (SAM) syndrome. Molecular modeling predicts that this G to R mutation shortens the DSG1 TMD, and experiments directly demonstrate that this mutation compromises both lipid raft association and desmosome incorporation. Finally, cryo-electron tomography (cryo-ET) indicates that the lipid bilayer within the desmosome is ~10% thicker than adjacent regions of the plasma membrane. These findings suggest that differences in bilayer thickness influence the organization of adhesion molecules within the epithelial plasma membrane, with cadherin TMDs recruited to the desmosome via establishment of a specialized mesoscale lipid raft-like membrane domain.

cell biology↗