Biology subjects

Theopold, U.

Publications and source records attributed to Theopold, U..

6 recordsLinked to original sources

bioRxiv2023

Single-cell sequencing of tumor-associated macrophages in a Drosophila model.

IntroductionTumor-associated macrophages may act to either limit or promote tumor growth, yet the molecular basis for either path is poorly characterized. MethodsWe use a larval Drosophila model that expresses a dominant-active version of the Rasoncogene (RasV12) to study dysplastic growth during early tumor progression. We performed single-cell RNA-sequencing of macrophage-like hemocytes to characterize these cells in tumor-compared to wild type larvae. Hemocytes included manually extracted tumor-associated-as well as circulating cells. Results and discussionWe identified 5 distinct hemocyte clusters. In addition to RasV12 larvae we included a tumor model where the activation of effector caspases was inhibited, mimicking an apoptosis-resistant setting. Circulating hemocytes from both tumor models differ qualitatively from control wild-type cells - they display an enrichment for genes involved in cell division, which was confirmed using proliferation assays. Split analysis of the tumor models further reveals that proliferation is strongest in the caspase-deficient setting. Similarly, depending on the tumor model, hemocytes that attach to tumors activate different sets of immune effectors - antimicrobial peptides dominate the response against the tumor alone, while caspase inhibition induces a shift toward members of proteolytic cascades. Finally, we provide evidence for transcript transfer between hemocytes and possibly other tissues. Taken together, our data support the usefulness of Drosophila to study the response against tumors at the organismic level.

cancer biology↗

bioRxiv2022

Chitinase-like protein promotes tumorigenesis through disruption of cell polarity via enlarged vesicles.

Chitinase-like proteins (CLPs) are associated with tissue-remodeling and inflammation but also with several disorders, including fibrosis, atherosclerosis, allergies, and cancer. However, CLPs role in tumors is far from clear. Here, we utilize Drosophila melanogaster to investigate the function of CLPs (imaginal disc growth factors; Idgfs) in RasV12 dysplastic salivary glands. We find one of the Idgfs members, Idgf3, is transcriptionally induced in a JNK-dependent manner via a positive feedback loop mediated by reactive oxygen species (ROS). Moreover, Idgf3 accumulates in enlarged endosomal vesicles (EnVs) that promote tumor progression by disrupting cytoskeletal organization. The process is mediated via the downstream component, Spectrin, which localizes to the EnVs. Our data provide new insight into CLP function in tumors and identifies specific targets for tumor control.

cancer biology↗

bioRxiv2021

Anti-fibrotic activity of an antimicrobial peptide in a Drosophila model.

Fibrotic lesions accompany several pathological conditions including tumors. We show that expression of a dominant-active form of the Ras oncogene in Drosophila salivary glands (SGs) leads to redistribution of components of the basement membrane (BM) and fibrotic lesions. Similar to several types of mammalian fibrosis, the disturbed BM attracts clot components including insect transglutaminase and phenoloxidase. SG epithelial cells show reduced apico-basal polarity accompanied by a loss of secretory activity. Both the fibrotic lesions and the reduced cell polarity are alleviated by ectopic expression of the antimicrobial peptide Drosomycin (Drs), which also restores secretory activity of the SGs. In addition to ECM components, both Drs and F-actin localize to fibrotic lesions.

immunology↗

bioRxiv2019

The consequences of surviving infection across the metamorphic boundary: tradeoff insights from RNAseq and life history measures

The broad diversity of insect life has been shaped, in part, by pathogen pressure, yet the influence of injury and infection during critical periods of development is understudied. During development, insects undergo metamorphosis, wherein the organism experiences a dramatic shift in their overall morphology, and physiology. In temperate zones, metamorphosis is often directly followed by a developmental arrest called diapause, for which the insect needs to acquire enough energy reserves before the onset of winter. We investigated the long-term effects of injury and infection using two bacteria in the butterfly Pieris napi, revealing that the negative consequences of bacterial infection carry across the metamorphic boundary. Initial direct effects of infection were weight loss and slower development, as well as an increased mortality at higher infection levels. The detrimental effects were stronger in the gram-positive Micrococcus luteus compared to gram-negative Escherichia coli. Transcriptome-wide differences between the two bacteria were already observed in the gene expression profile of the first 24 hours after infection. Larvae infected with M. luteus showed a strong suppression of all non-immunity related processes, with several types of immune responses being activated. The impact of these transcriptomic changes, a tradeoff between homeostasis and immune response, were visible in the life history data, wherein individuals infected with M. luteus had the highest mortality rate, along with the lowest pupal weight, developmental rate and adult weight of all the treatments. Overall, we find that the cost of infection and wounding in the final larval instar carries over the metamorphic boundary, and is expected to negatively affect their lifetime fitness.

evolutionary biology↗

bioRxiv2019

Geographic variation in hemocyte diversity and phagocytic propensity shows a diffuse genomic signature in the green veined white butterfly

Insects rely on their innate immune system to successfully mediate complex interactions with their internal microbiota, as well as the microbes present in the environment. Given the variation in microbes across habitats, the challenges to respond to them is likely to result in local adaptation in the immune system. Here we focus upon phagocytosis, a mechanism by which pathogens and foreign particles are engulfed in order to be contained, killed and processed for antigen presentation. We investigated the phenotypic and genetic variation related to phagocytosis, in two allopatric populations of the butterfly Pieris napi. We found that the populations differ in their hemocyte composition, and overall phagocytic capability, driven by the increased phagocytic propensity of each cell type. However, no evidence for divergence in phagocytosis-related genes was observed, though an enrichment of genes involved in glutamine metabolism was found, which have recently been linked to immune cell differentiation in mammals.

evolutionary biology↗

bioRxiv2019

Tissue-autonomous immune response regulates stress signalling during hypertrophy

Postmitotic tissues are incapable of replacing damaged cells through proliferation, but need to rely on buffering mechanisms to prevent tissue disintegration. By constitutively activating the Ras/MAPK-pathway via RasV12-overexpression in the postmitotic salivary glands of Drosophila larvae, we overrode the glands adaptability to growth signals, induced hypertrophy and stress accumulation. This allowed us to decipher a novel, spatio-temporally regulated interaction between the JNK-stress response and a genuine tissue-autonomous immune response. Central to this interaction is the direct inhibition of JNK-signalling by the antimicrobial peptide Drosomycin, which blocks programmed cell death and prevents recognition of the stressed tissue by the systemic immune response. While this mechanism might allow growing salivary glands to cope with temporary stress, continuous expression of Drosomycin favors survival of unrestricted, hypertrophic RasV12-glands. Our findings indicate the necessity for refined therapeutic approaches that fundamentally acknowledge detrimental effects that stimulated immune responses have on tissues coping with damage and stress.

immunology↗