Biology subjects

Stumpf, S.

Publications and source records attributed to Stumpf, S..

4 recordsLinked to original sources

bioRxiv2024

Evolution of the Batoidea Pectoral Fin Skeleton: Convergence, Modularity, and Integration Driving Disparity Trends

Batoids (skates and rays) are the most speciose group of cartilaginous fishes. Their body plan represents diverse ecologies and swimming modes. Early skeletal fossil remains, and recent phylogenetic analyses suggest that convergence has occurred within the batoids several times independently. The drivers for such disparity patterns and possible association with modularity and phenotypic integration among batoids are not fully understood. Here we used geometric morphometrics and phylogenetic comparative methods to characterize the evolutionary trends of the basal fin skeleton of batoids and sharks. Our analyses show that the morphological variation has a strong phylogenetic signal. Interestingly, the most speciose orders of batoids display low morphological disparity. Reef and freshwater species, show increased evolutionary rates. Meanwhile, the swimming mode shows different rates depending on the fin structure analyzed. A higher modularity and integration signal suggest that the pectoral fin of batoids has experienced mosaic evolution. The low morphological disparity might be associated with high integration. We find support for convergence between Jurassic, Cretaceous, and Extant guitarfishes, however, not completely between sharks and batoids. Our findings suggest that habitats and swimming mode have shaped the pectoral fin evolution among batoids, and at the same time batoids have constrained their basal fin skeleton.

evolutionary biology↗

bioRxiv2022

They call me the wanderer - Neurovascular anatomy of dwarfed dinosaur implies precociality in sauropods

Macronaria, a group of mostly colossal sauropod dinosaurs, comprised the largest terrestrial vertebrates of Earths history. However, some of the smallest sauropods belong to this group as well. The Late Jurassic macronarian Europasaurus holgeri is one of the best-known sauropods worldwide. So far, the braincase material of this taxon from Germany pended greater attention. With the aid of microCT, we report on the neuroanatomy of the almost complete braincase of an adult individual, as well as the inner ears of one other adult and several juveniles (also containing so far unknown vascular cavities). The presence of large and morphologically adult inner ears in juvenile material suggests precociality. Our findings add to the diversity of neurovascular anatomy in sauropod braincases and buttress the perception of sauropods as fast-growing and autonomous giants with manifold facets of reproductive and social behavior. This suggests that - apart from sheer size - little separated the island dwarf Europasaurus from its large-bodied relatives.

paleontology↗

bioRxiv2022

Tracking infectious entry routes of SARS-CoV-2

SARS-CoV-2 cell entry starts with membrane attachment and ends with spike-protein (S) catalyzed membrane fusion depending on two cleavage steps, one usually by furin in producing cells and the second by TMPRSS2 on target cells. Endosomal cathepsins can carry out both. Using real-time 3D single virion tracking, we show fusion and genome penetration requires virion exposure to an acidic milieu of pH 6.2-6.8, even when furin and TMPRSS2 cleavages have occurred. We detect the sequential steps of S1-fragment dissociation, fusion, and content release from the cell surface in TMPRRS2 overexpressing cells only when exposed to acidic pH. We define a key role of an acidic environment for successful infection, found in endosomal compartments and at the surface of TMPRSS2 expressing cells in the acidic milieu of the nasal cavity. Significance StatementInfection by SARS-CoV-2 depends upon the S large spike protein decorating the virions and is responsible for receptor engagement and subsequent fusion of viral and cellular membranes allowing release of virion contents into the cell. Using new single particle imaging tools, to visualize and track the successive steps from virion attachment to fusion, combined with chemical and genetic perturbations of the cells, we provide the first direct evidence for the cellular uptake routes of productive infection in multiple cell types and their dependence on proteolysis of S by cell surface or endosomal proteases. We show that fusion and content release always require the acidic environment from endosomes, preceded by liberation of the S1 fragment which depends on ACE2 receptor engagement. One sentence summaryDetailed molecular snapshots of the productive infectious entry pathway of SARS-CoV-2 into cells

microbiology↗

bioRxiv2020

Landscape analysis of escape variants identifies SARS-CoV-2 spike mutations that attenuate monoclonal and serum antibody neutralization

Although neutralizing antibodies against the SARS-CoV-2 spike (S) protein are a goal of COVID-19 vaccines and have received emergency use authorization as therapeutics, viral escape mutants could compromise their efficacy. To define the immune-selected mutational landscape in S protein, we used a VSV-eGFP-SARS-CoV-2-S chimeric virus and 19 neutralizing monoclonal antibodies (mAbs) against the receptor-binding domain (RBD) to generate 50 different escape mutants. The variants were mapped onto the RBD structure and evaluated for cross-resistance to mAbs and convalescent human sera. Each mAb had a unique resistance profile, although many shared residues within an epitope. Some variants (e.g., S477N) were resistant to neutralization by multiple mAbs, whereas others (e.g., E484K) escaped neutralization by convalescent sera, suggesting some humans induce a narrow repertoire of neutralizing antibodies. Comparing the antibody-mediated mutational landscape in S with sequence variation in circulating SARS-CoV-2, we define substitutions that may attenuate neutralizing immune responses in some humans.

microbiology↗