Biology subjects

Horne-Badovinac, S.

Publications and source records attributed to Horne-Badovinac, S..

10 recordsLinked to original sources

bioRxiv2025

Tissue geometry and mechanochemical feedback initiate rotational migration in Drosophila

Collective migration of epithelial cells drives diverse tissue remodeling processes. In many cases, a free tissue edge polarizes the cells to promote directed motion, but how edge-free or closed epithelia initiate migration remains unclear. Here, we show that the rotational migration of follicular epithelial cells in the Drosophila egg chamber is a self-organizing process. Combining experiments and theoretical modeling, we identify a positive feedback loop in which the mechanosensitive behavior of the atypical cadherin Fat2 synergizes with the rigid-body dynamics of the egg chamber to both initiate and sustain rotation. Mechanical constraints arising from cell-cell interactions and tissue geometry further align this motion around the egg chambers anterior-posterior axis. Our findings reveal a biophysical mechanism -- combining Fat2-mediated velocity-polarity alignment, rigid-body dynamics, and tissue geometry -- by which a closed epithelial tissue self-organizes into persistent, large-scale rotational migration in vivo, expanding current flocking theories.

cell biology↗

bioRxiv2025

Evidence for the major role of PH4EFB in the prolyl 4-hydroxylation of Drosophila collagen IV

Collagens are fundamental components of extracellular matrices, requiring precise intracellular post-translational modifications for proper function. Among the modifications, prolyl 4-hydroxylation is critical to stabilise the collagen triple helix. In humans, this reaction is mediated by collagen prolyl 4-hydroxylases (P4Hs). While humans possess three genes encoding these enzymes (P4Hs), Drosophila melanogaster harbour at least 26 candidates for collagen P4Hs despite its simple genome, and it is poorly understood which of them are actually working on collagen in the fly. In this study, we addressed this question by carrying out thorough bioinformatic and biochemical analyses. We demonstrate that among the 26 potential collagen P4Hs, PH4EFB shares the highest homology with vertebrate collagen P4Hs. Furthermore, while collagen P4Hs and their substrates must exist in the same cells, our transcriptomic analyses at the tissue and single cell levels showed a global co-expression of PH4EFB but not the other P4H-related genes with the collagen IV genes. Moreover, expression of PH4EFB during embryogenesis was found to precede that of collagen IV, presumably enabling efficient collagen modification by PH4EFB. Finally, biochemical assays confirm that PH4EFB binds collagen, supporting its direct role in collagen IV modification. Collectively, we identify PH4EFB as the primary and potentially constitutive prolyl 4-hydroxylase responsible for collagen IV biosynthesis in Drosophila. Our findings highlight the remarkably simple nature of Drosophila collagen IV biosynthesis, which may serve as a blueprint for defining the minimal requirements for collagen engineering.

biochemistry↗

bioRxiv2023

Cortical tension regulates Hippo signaling via Par-1-mediated Kibra degradation

The Hippo pathway is an evolutionarily conserved regulator of tissue growth. Multiple Hippo signaling components are regulated via proteolytic degradation. However, how these degradation mechanisms are themselves modulated remains unexplored. Kibra is a key upstream pathway activator that promotes its own ubiquitin-mediated degradation upon assembling a Hippo signaling complex. Here, we demonstrate that Hippo complex-dependent Kibra degradation is modulated by cortical tension. Using classical genetic, osmotic, and pharmacological manipulations of myosin activity and cortical tension, we show that increasing cortical tension leads to Kibra degradation, whereas decreasing cortical tension increases Kibra abundance. Our study also implicates Par-1 in regulating Kib abundance downstream of cortical tension. We demonstrate that Par-1 promotes ubiquitin-mediated Kib degradation in a Hippo complex-dependent manner and is required for tension-induced Kib degradation. Collectively, our results reveal a previously unknown molecular mechanism by which cortical tension affects Hippo signaling and provide novel insights into the role of mechanical forces in growth control.

cell biology↗

bioRxiv2023

Fat2 polarizes Lar and Sema5c to coordinate the motility of collectively migrating epithelial cells

Migrating epithelial cells globally align their migration machinery to achieve tissue-level movement. Biochemical signaling across leading-trailing cell-cell interfaces can promote this alignment by partitioning migratory behaviors like protrusion and retraction to opposite sides of the interface. However, how the necessary signaling proteins become organized at this site is poorly understood. The follicular epithelial cells of Drosophila melanogaster have two signaling modules at their leading-trailing interfaces--one composed of the atypical cadherin Fat2 and the receptor tyrosine phosphatase Lar, and one composed of Semaphorin 5c and its receptor Plexin A. Here we show that these modules form one interface signaling system with Fat2 at its core. Trailing edge-enriched Fat2 concentrates both Lar and Sema5c at cells leading edges, likely by slowing their turnover at this site. Once localized, Lar and Sema5c act in parallel to promote collective migration. Our data suggest a model in which Fat2 couples and polarizes the distributions of multiple effectors that work together to align the migration machinery of neighboring cells.

cell biology↗

bioRxiv2022

Fat2 polarizes the WAVE complex in trans to align cell protrusions for collective migration

For a group of cells to migrate together, each cell must couple the polarity of its migratory machinery with that of the other cells in the cohort. Although collective cell migrations are common in animal development, little is known about how protrusions are coherently polarized among groups of migrating epithelial cells. We address this problem in the collective migration of the follicular epithelial cells in Drosophila melanogaster. In this epithelium, the cadherin Fat2 localizes to the trailing edge of each cell and promotes the formation of lamellipodia at the leading edge of the cell behind. We show that Fat2 performs this function by acting in trans to restrict WAVE complex activity to one long-lived region along each cells leading edge. Without Fat2, the WAVE complex distribution expands around the cell perimeter and fluctuates over time, resulting in reduced, unpolarized protrusive activity. We further show that Fat2s influence is very local, with sub-micron-scale puncta of Fat2 concentrating the WAVE complex in corresponding puncta just across the leading-trailing cell-cell interface. These findings demonstrate that a trans interaction between Fat2 and the WAVE complex creates stable regions of protrusive activity in each cell and aligns the cells protrusions across the epithelium for directionally persistent collective migration.

developmental biology↗

bioRxiv2021

DAAM mediates the assembly of long-lived, treadmilling stress fibers in collectively migrating epithelial cells in Drosophila

Stress fibers (SFs) are actomyosin bundles commonly found in individually migrating cells in culture. However, whether and how cells use SFs to migrate in vivo or collectively is largely unknown. Studying the collective migration of the follicular epithelial cells in Drosophila, we found that the SFs in these cells show a novel treadmilling behavior that allows them to persist as the cells migrate over multiple cell lengths. Treadmilling SFs grow at their fronts by adding new integrin-based adhesions and actomyosin segments over time. This causes the SFs to have many internal adhesions along their lengths, instead of adhesions only at the ends. The front-forming adhesions remain stationary relative to the substrate and typically disassemble as the cell rear approaches. By contrast, a different type of adhesion forms at the SFs terminus that slides with the cells trailing edge as the actomyosin ahead of it shortens. We further show that SF treadmilling depends on cell movement and identify a developmental switch in the formins that mediate SF assembly, with DAAM acting during migratory stages and Diaphanous acting during post-migratory stages. We propose that treadmilling SFs keep each cell on a linear trajectory, thereby promoting the collective motility required for epithelial migration.

cell biology↗

bioRxiv2021

Kinesin-3 and kinesin-1 motors direct basement membrane protein secretion to a basal sub-region of the basolateral plasma membrane in epithelial cells

Basement membranes (BMs) are sheet-like extracellular matrices that line the basal surfaces of all epithelia. Since BM proteins form networks, they likely need to be secreted near the basal surface. However, the location of their secretion site and how it is selected are unknown. Working in the Drosophila follicular epithelium, we identified two kinesins essential for normal BM formation. Our data suggest the two kinesins work together to transport Rab10+ BM protein-filled secretory vesicles towards the basal surface along the polarized microtubule array common to epithelia. This kinesin transport biases BM protein secretion basally. When kinesins are depleted, BM proteins are mis-secreted to more apical regions of the lateral membrane, creating ectopic BM protein networks between cells that disrupt cell movements and tissue architecture. These results introduce a new transport step in the BM protein secretion pathway and highlight the importance of controlling the sub-cellular exocytic site of network-forming proteins. HighlightsO_LIA kinesin-3 and a kinesin-1 are required for normal basement membrane (BM) assembly C_LIO_LIKinesins move Rab10+ BM secretory vesicles basally on polarized microtubule arrays C_LIO_LITransport biases BM exocytosis to basal subregions of the basolateral membrane C_LIO_LILoss of kinesins creates ectopic BM networks that disrupt tissue architecture C_LI

cell biology↗

bioRxiv2020

ESCargo: a regulatable fluorescent secretory cargo for diverse model organisms

Membrane traffic can be studied by imaging a cargo protein as it transits the secretory pathway. The best tools for this purpose initially block exit of the secretory cargo from the endoplasmic reticulum (ER), and then release the block to generate a cargo wave. However, previously developed regulatable secretory cargoes are often tricky to use or specific for a single model organism. To overcome these hurdles for budding yeast, we recently optimized an artificial fluorescent secretory protein that exits the ER with the aid of the Erv29 cargo receptor, which is homologous to mammalian Surf4. The fluorescent secretory protein forms aggregates in the ER lumen and can be rapidly disaggregated by addition of a ligand to generate a nearly synchronized cargo wave. Here we term this regulatable secretory protein ESCargo (Erv29/Surf4-dependent Secretory Cargo) and demonstrate its utility not only in yeast cells, but also in cultured mammalian cells, Drosophila cells, and the ciliate Tetrahymena thermophila. Kinetic studies indicate that rapid transport out of the ER requires recognition by Erv29/Surf4. By choosing an appropriate ER signal sequence and expression vector, this simple technology can likely be used with many model organisms.

cell biology↗

bioRxiv2019

In-silico definition of the Drosophila melanogaster matrisome

The extracellular matrix (ECM) is an assembly of hundreds of proteins that structurally supports the cells it surrounds and biochemically regulates their functions. Drosophila has emerged as a powerful model organism to study fundamental mechanisms underlying ECM protein secretion, ECM assembly, and ECM roles in pathophysiological processes. However, as of today, we do not possess a well-defined list of the components forming the ECM of this organism. We previously reported the development of computational pipelines to define the matrisome - the ensemble of genes encoding ECM and ECM-associated proteins - of humans, mice, zebrafish and C. elegans. Using a similar approach, we report here that the Drosophila matrisome is composed of 641 genes. We further classify these genes into different structural and functional categories, including an expanded way to classify genes encoding proteins forming apical ECMs. We illustrate how having a comprehensive list of Drosophila matrisome proteins can be used to annotate large proteomic datasets and identify unsuspected roles for the ECM in pathophysiological processes. Last, to aid the dissemination and usage of the proposed definition and categorization of the Drosophila matrisome by the scientific community, our list has been made available through three public portals: The Matrisome Project, FlyBase, and GLAD.

cell biology↗

bioRxiv2019

Oriented basement membrane fibrils provide a memory for F-actin planar polarization via the Dystrophin-Dystroglycan complex during tissue elongation

How extracellular matrix participates to tissue morphogenesis is still an open question. In the Drosophila ovarian follicle, it has been proposed that after Fat2-dependent planar polarization of the follicle cell basal domain, oriented basement membrane (BM) fibrils and F-actin stress fibers constrain follicle growth, promoting its axial elongation. However, the relationship between BM fibrils and stress fibers and their respective impact on elongation are unclear. We found that Dystroglycan (Dg) and Dystrophin (Dys) are involved in BM fibril deposition. Moreover, they orient stress fibers, by acting locally and in parallel to Fat2. Nonetheless, Dg-Dys complex-mediated cell autonomous control of F-actin fibers orientation relies on the previous BM fibril deposition, indicating two distinct but interdependent functions. Thus, the Dg-Dys complex works as a critical organizer of the epithelial basal domain, regulating both F-actin and BM. Furthermore, BM fibrils act as a persistent cue for the orientation of stress fibers that are the main effector of elongation.

developmental biology↗