Biology subjects

Engel, U.

Publications and source records attributed to Engel, U..

7 recordsLinked to original sources

bioRxiv2026

Inflammatory injury drives CIN and STING loss in polyploidpancreatic acinar cells

Epidemiological studies link pancreatic inflammation to increased cancer risks with elevated levels of chromosomal instability (CIN), yet the underlying cause remains unclear. The exocrine pancreas and lactating mammary gland harbor polyploid cells to boost secretory efficiency. Using organoid and in vivo models of pancreatic injury, we show that polyploid acinar cells contribute to regeneration via acinar-to-ductal metaplasia. The metaplasia induced cell size reduction is associated with crowding and spindle misorientation, leading to mitotic errors such as lagging chromosomes, chromatin bridges, and micronuclei. Micronucleated cells are not always eliminated or arrested in the cell cycle but can continue to proliferate and expand. Polyploid cells in post-lactational mammary gland organoids equally exhibited proliferation-related CIN. Single-cell proteomics of acinar cells shows STING1 loss and increased ATR levels in polyploid cells, enabling continued proliferation. These findings uncover physiological links between polyploidy, tissue repair, and CIN, offering new insights into cancer risks after tissue remodeling.

cell biology↗

bioRxiv2025

Fully three-dimensional force inference in intestinal organoids reveals ratchet-like bud stabilization

The intestinal epithelium in vertebrates has a characteristic arrangement of protruding villi and receding crypts, which are generated and stabilized by selforganized cell forces. Intestinal organoids recapitulate this development and can be used to shed light on the underlying mechanical processes. Here we combine advanced image processing and the bubbly vertex model for epithelial cell shape to achieve a fully three-dimensional reconstruction of cell shapes, forces and tissue geometries during the development of mouse intestinal organoids. We show that the transition from spherical to budded morphologies is caused by a global increase in tension at the inner side and a decrease in luminal pressure, which however are not maintained after budding, suggesting ratchet-like non-reversibility. Through computer simulations of a vertex model for growing tissue with T1-transitions and comparison with the experimental data, we show that this ratchet is likely of geometrical origin. We further find that the system is mechanically stabilized on the outer side by increases in line tensions and reorganization of the actomyosin network, stabilizing a polygonal organization that also seems to enforce the geometrical ratchet. Our approach demonstrates how one can achieve a complete mechanical analysis of a complex tissue-like system.

biophysics↗

bioRxiv2025

Image-based screens identify regulators of endogenous Dvl2 biomolecular condensates

Dishevelled (Dvl) proteins are essential transducers in Wnt signaling pathways, which have been implicated in development, stem cell maintenance, and human diseases such as cancer. Several studies have shown that Dvl proteins form dynamic biomolecular condensates. However, how cellular signals and cell states influence the formation of biomolecular condensates remains poorly understood. Here, we analyzed cells with endogenous Dvl2 condensates using image-based cell sorting in combination with phosphoproteomics and identified protein enrichment for Wnt/PCP signaling and the G2/M cell cycle transition. We then performed an image-based high-throughput screen to identify small molecule kinase inhibitors that affect Dvl2 liquid-liquid phase separation. Strikingly, CK1{delta}/{varepsilon} inhibition blocked Dvl2 condensate formation. Its effect on Wnt signaling was modulated in genetic epistasis experiments with loss-of-function alleles of APC, Axin1, and MCC. Our study highlights the interplay between post-translational modifications and condensate dynamics, opening new avenues for research on their role in cellular signaling and disease intervention.

cell biology↗

bioRxiv2024

Restraining Wnt activation and intestinal tumorigenesis by a Rab35 dependent GTPase relay

Maintenance of homeostatic processes ensure curtailment of intestinal tumorigenesis. Inactivating mutations to Adenomatous Polyposis Coli (Apc) result in aberrantly activated Wnt signalling and initiates colorectal cancer (CRC) in approx. 80% of cases, yet our understanding of the subcellular mechanisms that modulate dysregulated pathway activity is limited. Here, using a conditional in vivo genetic screen, we identify Rab35 GTPase as a novel tumour suppressor that modulates regional Wnt activity after loss of Apc in progenitor cells. Single cell analysis revealed that progenitor cells respond to Apc depletion by increasing the expression of a GTPase activating protein, which we named blackbelt, and triggering Rab35 disassociation from the plasma membrane. Mechanistically, we demonstrate that Rab35 controls the localisation and activation of the Rho GTPase, Cdc42, which functions as a relay to regulate JNK signalling. This in turn tunes the Wnt pathway upstream of {beta}-catenin to direct proliferation and differentiation of progenitor cells. Importantly, we show that maintaining active JNK signalling is important for the propagation of Apc mutant mouse colon organoids. Our findings highlight a novel GTPase cascade that sustains aberrant Wnt activity in specific segments of the intestine and provides impetus to therapeutically exploit this pathway to target CRC.

cancer biology↗

bioRxiv2023

A signalling rheostat controls chromosome segregation fidelity during early lineage specification and neurogenesis by modulating DNA replication stress

The development and homeostasis of organisms rely on the correct replication, maintenance and segregation of their genetic blueprints. How these intracellular processes are monitored across generations of different human cellular lineages, and why the spatio-temporal distribution of mosaicism varies during development remain unknown. Here, we identify several lineage specification signals that regulate chromosome segregation fidelity in both human and mouse pluripotent stem cells. Through epistatic analyses, we find that that WNT, BMP and FGF form a signalling "rheostat" upstream of ATM that monitors replication fork velocity, origin firing and DNA damage during S-phase in pluripotency, which in turn controls spindle polymerisation dynamics and faithful chromosome segregation in the following mitosis. Cell signalling control of chromosome segregation fidelity declines together with ATM activity after pluripotency exit and specification into the three human germ layers, or further differentiation into meso- and endoderm lineages, but re-emerges during neuronal lineage specification. In particular, we reveal that a tug-of-war between FGF and WNT signalling in neural progenitor cells results in DNA damage and chromosome missegregation during cortical neurogenesis, which could provide a rationale for the high levels of mosaicism in the human brain. Our results highlight a moonlighting role of morphogens, patterning signals and growth factors in genome maintenance during pluripotency and lineage specification, which could have important implications for our understanding on how mutations and aneuploidy arise during human development and disease. One sentence summaryDevelopmental signals link genome maintenance to cell fate

cell biology↗

bioRxiv2021

Nanodomain-mediated lateral sorting drives polarization of the small GTPase ROP2 in the plasma membrane of root hair cells

Formation of root hairs involves the targeted recruitment of the cellular growth machinery to the root hair initiation domain (RHID), a specialized site at the plasma membrane (PM) of trichoblast cells. Early determinants in RHID establishment are small GTPases of the Rho-of-plants (ROP) protein family, which are required for polarization of downstream effectors, membrane modification and targeted secretion during tip growth. It remains, however, not fully understood how ROP GTPases themselves are polarized. To investigate the mechanism underlying ROP2 recruitment, we employed Variable Angle Epifluorescence Microscopy (VAEM) and exploited mCitrine fluorophore blinking for single molecule localization, particle tracking and super-resolved imaging of the trichoblast plasma membrane. We observed the association of mCit-ROP2 within distinct membrane nanodomains, whose polar occurrence at the RHID was dependent on the presence of the RopGEF GEF3, and found a gradual, localized decrease of mCit-ROP2 protein mobility that preceded polarization. We provide evidence for a step-wise model of ROP2 polarization that involves (i) an initial non-polar recruitment to the plasma membrane via interactions with anionic phospholipids, (ii) ROP2 assembly into membrane nanodomains independent of nucleotide-binding state and, sub-sequently, (iii) lateral sorting into the RHID, driven by GEF3-mediated localized reduction of ROP2 mobility.

cell biology↗

bioRxiv2020

Wnt signaling recruits KIF2A to the spindle to ensure chromosome congression and alignment during mitosis

Canonical Wnt signaling plays critical roles in development and tissue renewal by regulating {beta}-catenin target genes. Recent evidence showed that {beta}-catenin-independent Wnt signaling is also required for faithful execution of mitosis. This mitotic Wnt signaling functions through Wnt-dependent stabilization of proteins (Wnt/STOP), as well as through components of the LRP6 signalosome. However, the targets and specific functions of mitotic Wnt signaling still remain uncharacterized. Using phosphoproteomics, we identified that Wnt signaling regulates the microtubule depolymerase KIF2A during mitosis. We found that Dishevelled recruits KIF2A via its N-terminal and motor domains, which is further promoted upon LRP6 signalosome formation during mitosis. We show that Wnt signaling modulates KIF2A interaction with PLK1, which is critical for KIF2A localization at the spindle. Accordingly, Wnt signaling promotes chromosome congression and alignment by monitoring KIF2A protein levels at the spindle poles both in somatic cells and in pluripotent stem cells. Our findings highlight a novel function of Wnt signaling during cell division, which could have important implications for genome maintenance, notably in stem cells. SIGNIFICANCEWnt signaling plays essential roles in embryonic patterning, stem cell renewal, and cell cycle progression from G1 to S phase via the regulation of {beta}-catenin target genes. Here, we show that Wnt signaling also promotes faithful execution of mitosis by ensuring chromosome congression and alignment before cell division, including in pluripotent stem cells. We demonstrate that the Wnt signaling transducer Dishevelled recruits the mitotic kinesin KIF2A, and mediates its binding to the spindle. KIF2A is a microtubule depolymerase that controls chromosome alignment and congression during mitosis. Consequently, we found that inhibition of Wnt signaling leads to KIF2A-dependent chromosome congression and alignment defects.

cell biology↗