Biology subjects

Walther, R. F.

Publications and source records attributed to Walther, R. F..

5 recordsLinked to original sources

bioRxiv2025

A Natural Programmable Metamaterial Controls 3D Curvature of Compound Eyes

The panoramic vision of the convex compound eyes, common to insects and crustaceans, relies on micrometer-scale curvature variations1. These variations create specialized visual zones adapted to specific tasks, including detecting prey, mates, or predators2,3. However, the mechanisms by which such fine-scale curvature is encoded during development remain unknown. Here we show that the developing eye of Drosophila melanogaster functions as a natural metamaterial that programs the organs precise 3D curvature. We discover a supracellular triangular mesh in the basal retina with a specific pattern of triangles sizes. Computational simulations demonstrate its role directing the small scale curvature variations of the eye. Genetic disruption of this micropattern prevents local curvature establishment. Furthermore, the presence of a homologous mesh-curvature relationship in Drosophila mauritiana indicates evolutionary conservation of this mechanism. These results reveal a novel mechanism of morphogenesis control in which the supracellular 2D patterning give rise to a biological programmable metamaterial that encodes 3D curvature with great precision4. Our in vivo finding offers a novel framework for the design of shape-programmable 3D biological surfaces with broad implications from synthetic morphogenesis to clinical applications.

developmental biology↗

bioRxiv2024

Super-Resolution Simplified: Sub-10nm Imaging Over Large Areas and Deep Penetration via SDC-OPR and DNA-PAINT

Single Molecule Localization Microscopy (SMLM) has traditionally faced challenges to optimize signal-to-noise ratio, penetration depth, field-of-view (FOV), and spatial resolution simultaneously. Here, we show that DNA-PAINT imaging on a Spinning Disk Confocal with Optical Photon Reassignment (SDC-OPR) system overcomes these trade-offs, enabling high-resolution imaging across multiple cellular layers and large FOVs. We demonstrate the systems capability with DNA origami constructs and biological samples, including nuclear pore complexes, mitochondria, and microtubules, achieving a spatial resolution of 6 nm in the basal plane and sub-10 nm localization precision at depths of 9 {micro}m within a 53 x 53 {micro}m{superscript 2} FOV. Additionally, imaging of the developing Drosophila eye epithelium at depths up to 9 {micro}m with sub-13 nm average localization precision, reveals distinct E-cadherin populations in adherens junctions. Quantitative analysis of Collagen IV deposition in this epithelium indicated an average of 46 {+/-} 27 molecules per secretory vesicle. These results underscore the versatility of DNA-PAINT on an SDC-OPR for advancing super-resolution imaging in complex biological systems.

biophysics↗

bioRxiv2022

A Dystroglycan-Laminin-Integrin axis controls cell basal geometry remodeling in the developing Drosophila retina

Cell shape remodeling is a principal driver of epithelial tissue morphogenesis. While progress continues to be made in our understanding of the pathways that control the apical (top) geometry of epithelial cells, we know comparatively little about those that control cell basal (bottom) geometry. To examine this issue, we used the fly ommatidium, which is the basic visual unit of the compound eye. The ommatidium is shaped as a hexagonal prism, and generating this three-dimensional structure requires ommatidial cells to adopt specific apical and basal polygonal geometries. Using this model system, we find that generating cell type-specific basal geometries starts with patterning of the basement membrane, whereby Laminin accumulates at discrete locations across the basal surface of the retina. We show that the Dystroglycan surface receptor promotes this localized Laminin accumulation. Moreover, our results reveal that localized accumulation of Laminin-Dystroglycan induces polarization of Integrin adhesion in ommatidial cells. This underpins cell basal geometry remodeling by anchoring the basal surface of cells to the basement membrane at specific, discrete locations. Altogether, our work shows that patterning of a basement membrane by generating discrete Laminin domains, can direct Integrin adhesion. In the retina, this pathway generates specific basal polygonal geometries to organize a complex multicellular structure in three-dimensions.

developmental biology↗

bioRxiv2019

Cdc42 promotes epithelial morphogenesis by coupling Par-complex and Crumbs recruitment via Par6-aPKC

Epithelial morphogenesis depends on Cdc42, which acts in part through the Par-complex (Baz/Par3-Par6-aPKC), and Crumbs (Crb/CRB3). However, how these proteins come together and interact during morphogenesis is not well understood. Here we show that in Drosophila cells, Cdc42 is active at the apical membrane and cell-cell contacts, and couples apical recruitment of Par6-aPKC and Crb to promote apical identify. This coupling depends on Cdc42 and aPKC binding to Par6, and is mediated by Par6 binding to Crb. Conversely, Crb promotes the apical retention of Par6-aPKC, and thus Cdc42-Par6-aPKC and Crb promote each others apical accumulation to specify the apical membrane and Zonula Adherens (ZA). Altogether, our work shows that epithelial morphogenesis relies on a two tiered-mechanism whereby Cdc42 coordinates Par-complex assembly and apical recruitment of Crb through Par6-aPKC.

cell biology↗

bioRxiv2017

Rap1, AF6 and Pak4 cooperate with Par3 to promote ZA assembly and remodeling in the fly photoreceptor

The epithelial Zonula adherens (ZA) is a main adhesion compartment that enables organogenesis by allowing epithelial cells to assemble into sheets. How ZA assembly is regulated during epithelial cell morphogenesis is not fully understood. We show that during ZA morphogenesis, the function of the small GTPase Rap1 and the F-actin binding protein AF6/Cno are both linked to that of the P21-activated kinase Pak4/Mbt. We find that Rap1 and Mbt regulate each others localization at the ZA and cooperate in promoting ECadherin stabilization. During this process Cno regulates the recruitment of Baz at the ZA, a process that is also regulated by Arm phosphorylation by Mbt. Altogether, we propose that Rap1, Cno and Mbt regulate ZA morphogenesis by coordinating ECadherin stabilization and Baz recruitment and retention. In addition, our work uncovers a new link between two main oncogenes, Rap1 and Pak4/Mbt, in a model developing epithelial cell.

cell biology↗