Biology subjects

Tepass, U.

Publications and source records attributed to Tepass, U..

9 recordsLinked to original sources

bioRxiv2026

Cell intrinsic dynamics guide neuroblast ingression independent of tissue fluidity

Morphogenesis involves the coordination of multiple cellular processes that occur simultaneously within developing tissues. During early Drosophila embryogenesis, neuroblast (NB) ingression occurs concurrently with germ band extension (GBE), yet whether these processes interact mechanistically remains unclear. Here, we combine mathematical modelling with quantitative live imaging to investigate whether tissue-level mechanics during GBE influence NB ingression dynamics. Mathematical modelling predicted that reducing tissue fluidity through impaired cellular rearrangements should slow NB ingression by increasing mechanical resistance. Experimental analysis of mutants in which cell intercalation and GBE are disrupted revealed a dramatic reduction in tissue fluidity. However, NB ingression rates remained largely unaffected when tissue fluidity decreased. Incorporating cell-intrinsic myosin anisotropy and endocytosis-contractility coupling into our mathematical model rescued the rate of neuroblast ingression in solid-like tissues. Thus, our findings suggest that cell-intrinsic mechanisms, rather than tissue-level fluidity, maintain ingression kinetics. More broadly, these results illustrate how developmental systems can achieve robustness by insulating critical cellular events from tissue-level mechanical variability. Statement of SignificanceMorphogenesis requires coordination of cellular processes in tissues undergoing mechanical transitions. While recent work highlights the importance of tissue fluidity in morphogenesis, whether tissue-level mechanical changes influence concurrent cellular events remains unclear. Combining mathematical modelling with quantitative live imaging, we tested whether tissue fluidization during Drosophila germ-band extension regulates neuroblast ingression. Shape-based vertex models failed to predict tissue mechanical states when myosin was disrupted. Instead, incorporating cellular rearrangement delays recapitulated phenotypes independent of cell shape. Strikingly, we showed that neuroblast ingression remains robust despite tissue solidification in vivo. Biophysical modelling suggests that coupled cell contractility and endocytosis maintains robust ingression despite tissue solidification. Our work shows that developmental programs can be mechanically insulated from tissue-scale changes, thus enabling developmental robustness.

developmental biology↗

bioRxiv2026

E-cadherin clustering as a regulator of morphogenesis

Cell adhesion enables animal multicellular development. E-cadherin and the cadherin-catenin adhesion complex at adherens junctions are engaged in dynamic interactions with actomyosin generated contractile forces to drive epithelial morphogenesis. However, our understanding of how adhesion is regulated and how the tuning of adhesion contributes to morphogenesis remains incomplete. One key determinant of E-cadherin adhesion strength is clustering of the cadherin-catenin adhesion complex, a property studied extensively in vitro. Here, we use optogenetics to enhance E-cadherin cluster formation in the Drosophila embryo. Enlarged clusters were associated with increased E-cadherin surface abundance, assembled a normal cadherin-catenin complex, and showed reduced membrane mobility and turnover consistent with an increase in cell adhesion strength. Drosophila embryos with enhanced E-cadherin clustering displayed a severe reduction in cell intercalation and convergent extension of the anterior-posterior axis. To account for these observations, we modified existing vertex models to include junction-specific viscous forces representing E-cadherin-mediated friction between cells. This dissipative adhesion model predicts that enhanced adhesion increases resistance to cell rearrangements, thereby reducing cell neighbor exchanges and impairing convergent extension. To test model predictions, we analyzed two types of morphogenetic movements in embryos with enhanced E-cadherin clustering. Neuroblast ingression, which requires both apical constriction and cell rearrangement, was severely slowed. In contrast, mesoderm invagination, which requires apical constriction without neighbor exchanges, proceeded normally. Our findings suggest that optogenetic clustering, in contrast to overexpression of E-cadherin, is a valuable tool to examine the consequences of enhancing adhesion strength in tissue morphogenesis. Moreover, we propose that regulating E-cadherin clustering is essential for movements that require cell-cell contact changes.

cell biology↗

bioRxiv2025

Mitotic polarity oscillation promotes epithelial tumor progression

Mitosis of epithelial cells requires a transient loss of epithelial polarity [1-5]. However, the nature of this mitotic polarity oscillation and its functional consequences for epithelial development are not fully understood. Here we show that the Crumbs (Crb) complex, a key regulator of epithelial polarity, is lost from the membrane during mitosis, and the Crb mutant phenotype is ameliorated when cell division is inhibited. Remarkably, an essential requirement of Crb for epithelial polarity is fully suspended when cell division is blocked in conjunction with inhibition of either cell ingression or cell intercalation. We conclude that the amount of morphogenetic stress induced by mitosis, ingression, and intercalation determines the requirement for Crb. Increased cell division and loss of cell polarity are two main drivers of epithelial cancer [6-8]. Maintaining epithelial polarity is important for limiting proliferation. Whether the loss of polarity during mitosis impacts tissue growth is less clear. We show that increasing cell division in a morphogenetically quiet epithelium not only increases tissue size but also causes hyperplastic to neoplastic transition. Conversely, reducing cell division restores epithelial polarity in neoplastic tissue of tumor mutants. Taken together, our study revealed that a major function of polarity factors in epithelial maintenance is to counteract morphogenetic stress. Moreover, we propose a feedforward mechanism that links cell division and the loss of polarity as a key driver of epithelial cancer.

cell biology↗

bioRxiv2022

Crumbs complex-directed apical membrane dynamics in epithelial cell ingression

Epithelial cells often leave their tissue context and ingress to form new cell types or acquire migratory ability to move to distant sites during development and tumor progression. Cell lose their apical membrane and epithelial adherens junctions during ingression. However, how factors that organize apical-basal polarity contribute to ingression is unknown. Here, we show that the dynamic regulation of the apical Crumbs polarity complex is crucial for normal neural stem cell ingression. Crumbs endocytosis and recycling allow ingression to occur in a normal timeframe. During early ingression, Crumbs and its complex partner the RhoGEF Cysts support myosin and apical constriction to ensure robust ingression dynamics. During late ingression, the E3-ubiquitin ligase Neuralized facilitates the disassembly of the Crumbs complex and the rapid endocytic removal of the apical cell domain. Our findings reveal a mechanism integrating cell fate, apical polarity, endocytosis, vesicle trafficking, and actomyosin contractility to promote cell ingression, a fundamental morphogenetic process observed in animal development and cancer.

developmental biology↗

bioRxiv2021

The function of α-Catenin mechanosensing in tissue morphogenesis

-catenin couples the cadherin-catenin complex to the actin cytoskeleton. The mechanosensitive -catenin M region undergoes conformational changes upon application of force to recruit binding partners. Here, we took advantage to the tension landscape in the Drosophila embryo to define three different states of -catenin mechanosensing in support of cell adhesion. Low, medium, and high tension contacts showed -catenin M region-dependent low, medium, and high levels of Vinculin and Ajuba recruitment. In contrast, Afadin/Canoe acts in parallel to -catenin at bicellular low and medium tension junctions, but requires an interaction with -catenin for its tension-sensitive enrichment at high-tension tricellular junctions. Individual M region domains make complex contributions to cell adhesion through their impact on binding partner recruitment, and redundancies with the function of Afadin/Canoe. Our data argue that -catenin and its interaction partners are part of a cooperative and partially redundant, mechanoresponsive network that supports AJs remodelling during morphogenesis.

cell biology↗

bioRxiv2019

Retromer subunit, VPS29, regulates synaptic transmission and is required for endolysosomal function in the aging brain

Retromer, including Vps35, Vps26, and Vps29, is a protein complex responsible for recycling proteins within the endolysosomal pathway. Although implicated in both Parkinsons and Alzheimers disease, our understanding of retromer function in the adult brain remains limited, in part because Vps35 and Vps26 are essential for development. In Drosophila, we find that Vps29 is dispensable for embryogenesis but required for retromer function in aging adults, including for synaptic transmission, survival, and locomotion. Unexpectedly, in Vps29 mutants, Vps35 and Vps26 proteins are normally expressed and associated, but retromer is mislocalized from neuropil to soma with the Rab7 GTPase. Further, Vps29 phenotypes are suppressed by reducing Rab7 or overexpressing the GTPase activating protein, TBC1D5. With aging, retromer insufficiency triggers progressive endolysosomal dysfunction, with ultrastructural evidence of impaired substrate clearance and lysosomal stress. Our results reveal the role of Vps29 in retromer localization and function, highlighting requirements for brain homeostasis in aging.\n\nImpact StatementVps29 promotes retromer localization in the adult Drosophila brain, engaging Rab7 and TBC1D5, and its loss triggers age-dependent neuronal impairments in endolysosomal trafficking and synaptic transmission.

cell biology↗

bioRxiv2019

Identification of genes required for apical protein trafficking in Drosophila photoreceptor cells

Drosophila photoreceptor cells (PRCs) are highly polarized epithelial cells. Their apical membrane is further subdivided into the stalk membrane and the light-sensing rhabdomere. The photo-pigment Rhodopsin1 (Rh1) localizes to the rhabdomere, whereas the apical determinant Crumbs (Crb) is enriched at the stalk membrane. The proteoglycan Eyes shut (Eys) is secreted through the apical membrane into an inter-rhabdomeral space. Rh1, Crb, and Eys are essential for PRC development, normal vision, and PRC survival. Human orthologs of all three proteins have been linked to retinal degenerative diseases. Here, we describe an RNAi-based screen examining the importance of approximately 240 trafficking-related genes in apical trafficking of Eys, Rh1, and Crb. We found 28 genes that have an effect on the localization and/or levels of these apical proteins and analyzed several factors in more detail. We show that the Arf GEF protein Sec71 is required for biosynthetic traffic of both apical and basolateral proteins, that the exocyst complex and the microtubule-based motor proteins dynein and kinesin promote the secretion of Eys and Rh1, and that Syntaxin 7/Avalanche controls the endocytosis of Rh1, Eys, and Crb.\n\nArticle summeryPhotoreceptor cells (PRCs) rely on polarized vesicle trafficking to deliver key secreted and transmembrane proteins to their correct locations. Failure to do so causes defects in PRC development, function, and survival leading to retinal disease. Using the fruit fly Drosophila as a model we have identified 28 genes that are required for the trafficking of the three apical proteins Rhodopsin 1, Crumbs, and Eyes Shut. Human homologs of all three genes are associated with retinal degeneration. We characterized several genes to reveal novel mechanisms of vesicle trafficking in photoreceptor cells at different points in the biosynthetic or endocytotic pathways.

cell biology↗

bioRxiv2019

The RhoGEF Cysts couples apical polarity proteins to Rho and myosin activity at adherens junctions

The spatio-temporal regulation of small Rho GTPases is crucial for the dynamic stability of epithelial tissues. However, how RhoGTPase activity is controlled during development remains largely unknown. To explore the regulation of Rho GTPases in vivo we analyzed the Rho GTPase guanine nucleotide exchange factor (RhoGEF) Cysts, the Drosophila orthologue of mammalian p114RhoGEF, GEF-H1, p190RhoGEF, and AKAP-13. Loss of Cysts causes a phenotype that closely resemble the mutant phenotype of the apical polarity regulator Crumbs. This phenotype can be suppressed by the loss of basolateral polarity proteins suggesting that Cysts in an integral component of the apical polarity protein network. Cysts activates Rho at adherens junctions to promote junctional enrichment of myosin II, which requires the RhoGEF domain and the coiled-coil domain containing C-terminal region of Cysts. Cysts recruitment to the apico-lateral cortex depends on Crumbs and Bazooka/Par3 and requires multiple domains within Cysts including the C-terminal region. Together, our findings indicate that Cysts links apical polarity proteins to Rho1 and myosin activation at adherens junctions to support junctional and epithelial integrity in the Drosophila ectoderm.

cell biology↗

bioRxiv2019

Role of α-Catenin and its mechanosensing properties in the regulation of Hippo/YAP-dependent tissue growth

-catenin is a key protein of adherens junctions (AJs) with mechanosensory properties. It also acts as a tumor suppressor that limits tissue growth. Here we analyzed the function of Drosophila -Catenin (-Cat) in growth regulation of the wing epithelium. We found that different -Cat levels led to a differential activation of Hippo/Yorkie or JNK signaling causing tissue overgrowth or degeneration, respectively. -Cat can modulate Yorkie-dependent tissue growth through recruitment of Ajuba, a negative regulator of Hippo signaling, to AJs but also through a mechanism that does not involve junctional recruitment of Ajuba. Further, both mechanosensory regions of -Cat, the M region and the actin-binding domain (ABD), contribute to growth regulation. Whereas M is dispensable for -Cat function in the wing, individual M domains (M1, M2, M3) have opposing effects on growth regulation. In particular, M1 limits Ajuba recruitment. Loss of M1 cause Ajuba hyper-recruitment to AJs promoting tissue-tension independent overgrowth. Although M1 binds Vinculin, Vinculin it is not responsible for this effect. Moreover, disruption of mechanosensing of the -Cat actin-binding domain affects tissue growth, with enhanced actin interactions stabilizing junctions and leading to tissue overgrowth. Together, our findings indicate that -Cat acts through multiple mechanisms to control tissue growth, including regulation of AJ stability, mechanosensitive Ajuba recruitment, and dynamic direct F-actin interactions.

cell biology↗