Biology subjects

Schmelzer, E.

Publications and source records attributed to Schmelzer, E..

3 recordsLinked to original sources

bioRxiv2025

An AmotL2 - Yap1 Module Integrates Flow and Junctional Mechanics to Specify Vascular Pruning Hotspots

Vascular networks constantly remodel to optimise blood flow, yet how endothelial cells (ECs) integrate haemodynamic cues with junctional mechanics to execute precise branch pruning remains unclear. Using live imaging and quantitative topology analysis in the zebrafish sub-intestinal vein plexus, we define the cellular events underlying flow-guided regression. Pruning occurs in geometrically disadvantaged, low-flow branches and is executed through transient polarity fluctuations, junctional remodelling and directed EC migration. We identify AmotL2 as an essential regulator of endothelial mechanical competence. AmotL2 maintains junctional architecture, actomyosin tension and appropriate cell packing, enabling ECs to polarise and rearrange in response to local flow differences. Loss of AmotL2 disrupts tension homeostasis, increases tissue compaction and prevents branch regression despite normal perfusion. In contrast, Yap1 plays an opposing, stabilising role, and its loss results in excessive pruning and network simplification. Together, AmotL2 and Yap1 constitute a mechanosensitive balancing module that interprets flow magnitude and vascular geometry to determine branch stability. This framework describes how mechanical forces sculpt vascular architecture during development and homeostasis.

developmental biology↗

bioRxiv2023

Genetic analysis of rab7 mutants in zebrafish

Vascular network formation requires the fusion of newly formed blood vessels and the emergence of a patent lumen between the newly established connections so that blood flow can start. Lumen formation has been shown to depend on the late endosomal/lysosomal pathway in various organs of animal tubular systems. Here, we identified a late endosomal/lysosomal vesicular fraction (Rab7/Lamp2) in early zebrafish angiogenic sprouts, which appears to contribute to apical membrane growth during lumen formation. To study the effect of the late endocytic pathway on vascular development, we generated mutant alleles for all three rab7 genes in zebrafish (rab7a, rab7ba, rab7bb). All rab7 genes are expressed in wild-type zebrafish and we did not detect any compensatory effects by the other rab7 isoforms in single knockout mutants, which were all viable. Only the triple mutant was lethal suggesting some functional redundancy. However, the different rab7 isoforms fulfil also at least partially independent functions because eggs laid from mothers lacking two rab7 (rab7a and/or rab7bb). showed reduced survival and contained enlarged yolk granules, suggesting maternal contribution of these two rab7. Finally, we observed minor effects on lumen formation in embryos which still express one copy of rab7. Our results support the notion that the late endocytic/lysosomal compartment contributes to lumen expansion.

genetics↗

bioRxiv2018

Nucleus- and plastid-targeted annexin 5 promotes reproductive development in Arabidopsis and is essential for pollen and embryo formation

BackgroundPollen development is a strictly controlled post-meiotic process during which microspores differentiate into microgametophytes and profound structural and functional changes occur in organelles. Annexin 5 is a calcium- and lipid-binding protein that is highly expressed in pollen grains and regulates pollen development and physiology. To gain further insights into the role of ANN5 in Arabidopsis development, we performed detailed phenotypic characterization of Arabidopsis plants with modified ANN5 levels. In addition, interaction partners and subcellular localization of ANN5 were analyzed to investigate potential functions of ANN5 at cellular level.\n\nResultsHere, we report that RNAi-mediated suppression of ANN5 results in formation of smaller pollen grains, enhanced pollen lethality, and delayed pollen tube growth. ANN5 RNAi knockdown plants also displayed aberrant development during the transition from the vegetative to generative phase and during embryogenesis, reflected by delayed bolting time and reduced embryo size, respectively. At the subcellular level, ANN5 was delivered to the nucleus, nucleolus, and cytoplasm, and was frequently localized in plastid nucleoids, suggesting a likely role in interorganellar communication. Furthermore, ANN5-YFP co-immunoprecipitated with RABE1b, a putative GTPase, and interaction in planta was confirmed in plastidial nucleoids using FLIM-FRET analysis.\n\nConclusionsOur findings let us to propose that ANN5 influences basal cell homeostasis via modulation of plastid activity during pollen maturation. We hypothesize that the role of ANN5 is to orchestrate the plastidial and nuclear genome activities via protein-protein interactions however not only in maturing pollen but also during the transition from the vegetative to the generative growth and embryo development.

plant biology↗