A major focus of the lab is to study the function of AP-1 proteins in organ/whole body development and metabolism using loss-(LOF) and gain-of-function (GOF) mouse models (GEMM). We use mouse and human tissue samples for large-scale studies, such as deep sequencing (RNA-Seq, ChIP-Seq) and mass spectrometry analyses. We evaluate possible biomarkers and therapeutic approaches in small-scale preclinical studies based on these screens as well as hypothesis-driven analyses (FIGURE).
At the origins of skin inflammation
Using mice with inducible epidermal deletion of JunB and cJun (DKO*) that develop skin inflammation and a psoriatic-arthritis-like (PsA) disease, we aim to find therapeutic targets to alleviate skin and joint inflammation. Using lineage tracing in the DKO* psoriasis-like mouse model as well as a novel GEMM with epidermal stem cells (ESCs) deletion of JunB and cJun, we found that mutant ESCs initiate epidermal hyperplasia and skin inflammation by priming neighbouring non-mutant epidermal cells to acquire a psoriasis-like phenotype. These findings unravel specific roles of epidermal populations in psoriasis-like disease and provide novel mechanistic insights into epidermal cell interactions under inflammatory conditions.
Skin inflammation and Cancer
It was suggested that psoriatic patients have decreased skin cancer risk. We observed that psoriasis-like DKO* mice with severe phenotype have a significant decrease in chemically-induced skin papillomas compared to controls. Detailed characterisation suggests that in the context of chronic skin inflammation, elevated chemokines and antimicrobial proteins may modulate papilloma formation. We are now expanding our studies to additional skin inflammation models and patient samples.
Osteosarcoma, bone loss, arthritis and skin inflammation
We are studying the function of AP-1 proteins in bone development and disease using loss-( LOF ) and gain-of-function (GOF) mouse models. In mice, transgenic c-Fos expression leads to osteosarcomas (OS). Using an inducible bone-specific Wntless LOF GEMM, we found that loss of Wnt signalling delays Fos-induced OS development. Our data also demonstrate that increased Wnt7b and Wnt9a, non-canonical Wnt signalling and the Lysyl oxidase Loxl2 are causally involved in OS.
Rheumatoid, Psoriatic and Osteoarthritis (OA) are destructive joint pathologies linked to chronic inflammation. Using inducible cell type-specific AP-1 LOF mouse models, combined with experimental arthritis models, we found that c-Fos is a key regulator of surgery- and age-induced OA.
We previously identified highly elevated S100A8/A9 complex in our DKO*-GEMM as well as in human psoriatic skin samples. We generated a new DKO*-GEMM with epidermal and global deletion of S100A9 to determine the specific role of keratinocyte- and neutrophil-derived S100A9 in skin/joint inflammation. Psoriatic patient samples with and without arthritis are also examined in collaboration with Georg Schett, Erlangen, Germany.
Characterisation of the systemic inflammatory disease in epidermal-deficient JunB GEMMs indicated a skin to bone cross-talk by Il-17A-mediated inhibition of Wnt signalling in osteoblasts. These mice also suffer from dysbiosis and chronic S. aureus colonisation. We generated several GEMMs to define the role of autophagy (p62) and antimicrobial proteins (AMPs), such as S100A8/A9 and Lipocalin-2, and in the systemic effects of inflammatory skin diseases.
Lung fibrosis, inflammation and cancer
Lung fibrotic diseases and non-small cell lung cancer (NSCLC) lack effective treatments and lead to high mortality. Using GEMMs we found that Fra-2, an AP-1 transcription factor, contributes to both diseases. Fra-2 expression is increased in lung fibrosis patient samples and correlates with poor survival in human NSCLC. In lung fibrosis, Fra-2 is associated with macrophage-specific expression of Type VI collagen in a type2 immune response and mediates disease progression, while in NSCLC, Fra-2 promotes growth in K-Ras-mutated tumours. We aim to find new therapeutic targets and potential disease biomarkers downstream of AP-1. The lung fibrosis studies are conducted in collaboration with Acceleron Pharma (USA) and the cancer studies with Mariano Barbacid’s Group at CNIO, Spain.
Liver disease - metabolism, fibrosis, inflammation and cancer
AP-1 proteins are important modulators of hepatic lipid metabolism as specific AP-1 dimers can either activate or repress PPARγ transcription. Therefore, fatty liver disease and obesity most likely depend on AP-1 dimer composition. In addition, ectopic expression of specific Fos or Fra-2, but not Fra-1-containing AP-1 dimers in hepatocytes, leads to liver dysplasia, inflammation, fibrosis and tumours with HCC signatures. Mechanistically, molecular analyses point to the involvement of pathways connected to human hepatocellular carcinoma (HCC), such as the Wnt/b-catenin and Myc pathways and/or to altered cholesterol and bile acid metabolism. A robust connection between c-Fos expression and the activity of the LXR/RXR pathway, an important regulator of cholesterol homeostasis, was unravelled and most likely contributes to the oncogenic function of c-Fos in hepatocytes. We are currently testing whether any of the pathways we discovered can be exploited therapeutically to treat liver cancer in preclinical models.
Cancer-associated cachexia (CAC)
CAC is a complex wasting syndrome characterised by loss of muscle and fat along with ‘browning’, a switch from white to brown fat, as previously described. Our aim is to understand the systemic events taking place in CAC and to identify novel biomarkers and therapeutic targets. Systemic inflammation is a consistent event in CAC with innate immune cells, such as neutrophils, as a major cell type. Interestingly, Lipocalin-2, an adipokine important in innate immunity is highly upregulated in CAC and may be a potential new biomarker. We found that CAC is not prevented in a neutropenic situation suggesting that increased neutrophils may not be a key determinant for CAC. Ongoing studies show that the Renin-Angiotensin-Aldosterone System (RAAS) is dysregulated in CAC in patients and mice, potentially leading to cardiac dysfunction. We are now dissecting in mice and in human CAC samples, the involvement of the central and peripheral nervous system, the RAAS as well as the tissue-specific role of Ucp-1 (in collaboration with R. Señarís, La Compostella, Spain; M. Petruzzelli, Cambridge, UK; H. Watzke & M. Unseld, MUW Vienna; M. Poglitsch, Attoquant Inc, Vienna; R. Zechner, Graz, Austria).
Techniques and infrastructure of the research group
Erwin Wagner has pioneered technologies for engineering the mouse genome producing highly instructive mouse models. These have revealed molecular mechanisms of development, inflammation, metabolism and cancer. The laboratory expertise is primarily centered on the generation and analysis of state-of-the-art GEMMs to understand whole body physiology and better model human conditions. Novel mouse strains are generated routinely and we developed a powerful technology for switchable, reversible and tissue-specific ectopic gene expression of AP-1 monomers/dimers in the skin, liver and bone, complemented by several tissue/cell specific loss-of-function mouse models. Techniques such as expression profiling, proteomics, RNA-sequencing and ChIP-sequencing are employed to compare mouse models to human disease and to identify novel therapeutic targets that are tested in preclinical studies. Group members have access to fully equipped facilities within the MUW Center of Translational Research as well as at the Departments of Laboratory Medicine and Dermatology. Patient samples and further expertise are provided by our internal MUW and external collaborators.