Biology subjects

Michler, J.

Publications and source records attributed to Michler, J..

4 recordsLinked to original sources

bioRxiv2023

In vivo screening of tumor-hepatocyte interactions identifies Plexin B2 as a gatekeeper of liver metastasis

It is estimated that only 0.02% of disseminated tumor cells are able to seed overt metastases1. While this indicates the presence of environmental constraints to metastatic seeding, the landscape of host factors controlling this process remains largely unknown. Combining transposon technology2 and fluorescent niche labeling3, we developed an in vivo CRISPR activation screen to systematically investigate the influence of hepatocytes on metastatic seeding in the liver. Our approach enabled the identification of Plexin B2 as a critical host-derived regulator of metastasis. Plexin B2 upregulation in hepatocytes dramatically enhances grafting in colorectal and pancreatic cancer syngeneic models, and promotes seeding and survival of patient-derived organoids. Notably, ablation of Plexin B2 in hepatocytes prevents mesenchymal-to-epithelial transition of extravasated tumor cells and thereby almost entirely suppresses liver metastasis. We dissect a mechanism by which Plexin B2 interacts with class 4 semaphorins on tumor cells, activating Rac1 signaling and actin cytoskeleton remodeling, thereby promoting the acquisition of epithelial traits. Our findings highlight the essential role of signals from the liver parenchyma for the survival of disseminated tumor cells, prior to the establishment of a growth promoting niche. They further suggest that acquisition of epithelial traits is required for the adaptation of extravasated cells to their new tissue environment. Targeting of Plexin B2 on hepatocytes shields the liver from colonizing cells and thus presents an innovative therapeutic strategy for preventing metastasis. Finally, our screening technology, which evaluates host-derived extrinsic signals rather than tumor-intrinsic factors for their ability to promote metastatic seeding, is broadly applicable and lays a framework for the screening of environmental constraints on metastasis in other organs and cancer types.

cancer biology↗

bioRxiv2022

Fate and plasticity of SARS-CoV-2-specific B cells during memory and recall response in humans

B cell responses to different pathogens recruit tailored effector mechanisms, resulting in functionally specialized subsets. For human memory B cells (MBCs), these include CD21+ resting, CD21-CD27+ activated, and CD21-CD27- atypical cells. Whether these subsets follow deterministic or interconnected fates is unknown. We demonstrate in COVID-19 patients that single clones of SARS-CoV-2-specific MBCs followed multiple fates with distinctive phenotypic and functional characteristics. 6-12 months after infection, most circulating MBCs were CD21+ resting cells, which also accumulated in peripheral lymphoid organs where they acquired markers of tissue residency. Conversely, at acute infection and following SARS-CoV-2-specific immunization, CD21- MBCs became the predominant subsets, with atypical MBCs expressing high T-bet, inhibitory molecules, and distinct chemokine receptors. B cell receptor sequencing allowed tracking of individual MBC clones differentiating into CD21+, CD21-CD27+, and CD21-CD27- cell fates. Collectively, single MBC clones can adopt functionally different trajectories, thus contributing to immunity to infection.

immunology↗

bioRxiv2022

The elasto-plastic nano- and microscale compressive behaviour of rehydrated mineralised collagen fibres

The multiscale architectural design of bio-based nanostructured materials such as bone enables them to combine unique structure-mechanical properties that surpass classical engineering materials. In biological tissues, water as one of the main components plays an important role in the mechanical interplay, but its influence has not been quantified at the length scale of a mineralised collagen fibre. Here, we combine in situ experiments and a statistical constitutive model to identify the elasto-plastic micro- and nanomechanical fibre behaviour under rehydrated conditions. Micropillar compression and simultaneous synchrotron small angle X-ray scattering (SAXS) and X-ray diffraction (XRD) were used to quantify the interplay between fibre, mineralised collagen fibrils and mineral nanocrystals. Rehydration led to a 65% to 75% decrease of fibre yield stress and compressive strength, and a 70% decrease of stiffness with a 3x higher effect on stress than strain values. While in good agreement with bone extracellular matrix, the decrease is 1.5-3x higher compared to micro-indentation and macro-compression. Hydration has a higher influence on mineral than fibril strain while the highest difference to the macroscale was observed comparing mineral and tissue levels. Results suggest that the effect of hydration is strongly mediated by ultrastructural interfaces while corroborating the previously reported water-mediated structuring of bone apatite providing insights towards the mechanical consequences. Results show that the missing reinforcing capacity of surrounding tissue is more pronounced in wet than dry conditions when testing an excised array of fibrils, mainly related to the swelling of fibrils in the matrix. Differences leading to higher compressive strength between mineralised tissues do not seem to depend on the rehydration state while fibril mobilisation follows a similar regime in wet and dry conditions. The lack of kink bands point towards the role of water as an elastic embedding, thus, adapting the way energy is absorbed. Statement of significanceCharacterising structure-property-function relationships of biomaterials helps us to elucidate the underlying mechanisms that enables the unique properties of these architectured materials. Experimental and computational methods can advance our understanding towards their complex behaviour providing invaluable insights towards bio-inspired material development. In our study, we present a novel method for biomaterials characterisation. We close a gap of knowledge at the micro- and nanometre length scale by combining synchrotron experiments and a statistical model to describe the behaviour of a rehydrated single mineralised collagen fibre. Results suggest a high influence of hydration on structural interfaces, and the role of water as an elastic embedding. Using a statistical model, we are able to deduce the differences in wet and dry elasto-plastic properties of fibrils and fibres close to their natural hydration state.

bioengineering↗

bioRxiv2021

CD8+ T cell signature in acute SARS-CoV-2 infection identifies memory precursors

Immunological memory is a hallmark of adaptive immunity and facilitates an accelerated and enhanced immune response upon re-infection with the same pathogen1,2. Since the outbreak of the ongoing coronavirus disease 19 (COVID-19) pandemic, a key question has focused on whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T cells stimulated during acute infection give rise to long-lived memory T cells3. Using spectral flow cytometry combined with cellular indexing of transcriptomes and T cell receptor (TCR) sequencing we longitudinally characterize individual SARS-CoV-2-specific CD8+ T cells of COVID-19 patients from acute infection to one year into recovery and find a distinct signature identifying long-lived memory CD8+ T cells. SARS-CoV-2-specific memory CD8+ T cells persisting one year after acute infection re-express CD45RA and interleukin-7 receptor (CD127), upregulate T cell factor-1 (TCF1), and maintain low CCR7, thus resembling CD45RA+ effector-memory T (TEMRA) cells. Tracking individual clones of SARS-CoV-2-specific CD8+ T cells, we reveal that an interferon signature marks clones giving rise to long-lived cells, whereas prolonged proliferation and mammalian target of rapamycin (mTOR) signaling are associated with clone contraction and disappearance. Collectively, we identify a transcriptional signature differentiating short-from long-lived memory CD8+ T cells following an acute virus infection in humans.

immunology↗