Biology subjects

Leitner, L.

Publications and source records attributed to Leitner, L..

4 recordsLinked to original sources

bioRxiv2024

A Synergistic Desmin-SPARC Axis Regulates Cardiac Stem Cell Differentiation and Promotes Cardiomyogenesis through Autocrine Regulation

BACKGROUNDThe mammalian heart contains cardiac stem cells throughout life, but it has not been possible to harness or stimulate these cells to repair damaged myocardium in vivo. Assuming physiological relevance of these cells, which have evolved and have been maintained throughout evolution, we are investigating their function using mouse cardiac stem cell lines as an in vitro model system. METHODSHere we use genetically modified embryonic stem cells and cardiac stem cells from the mouse as model systems to study the influence of desmin and Secreted Protein Acidic and Rich in Cysteine (SPARC) on cardiomyogenesis in embryoid bodies and cardiac bodies. We analyze their expression in self-renewing and differentiating stem cells by fluorescence microscopy, RT-qPCR, quantitative Western blotting and fluorescence activated cell sorting, and assess their influence on the expression of myocardial transcription factors. RESULTSIn embryoid bodies, desmin induces expression and secretion of SPARC, which promotes cardiomyogenesis. Cardiac stem cells secrete substantial amounts of SPARC, which also promotes cardiomyogenesis in a concentration-dependent, autocrine manner and promotes expression of myocardial transcription factors and desmin. Desmin and SPARC interact genetically and form a positive feedback loop and secreted SPARC negatively influences sparc mRNA expression. Finally, SPARC rescues cardiomyogenic desmin-haploinsufficiency in cardiac stem cells in a glycosylation-dependent manner, increases the phosphorylation of Smad2 and induces the expression of gata4, nkx2.5 and mef2C. CONCLUSIONSDemonstration that desmin-induced autocrine secretion of SPARC in cardiac stem cells promotes cardiomyogenesis raises the possibility that a physiological function of cardiac stem cells in the adult and aging heart may be the gland-like secretion of factors such as SPARC that modulate age-related and adverse environmental influences and thereby contribute to cardiac homeostasis throughout life.

developmental biology↗

bioRxiv2022

Engineered reporter phages for rapid detection of Escherichia coli, Klebsiella spp., and Enterococcus spp. in urine

The rapid detection and species-level differentiation of bacterial pathogens facilitates antibiotic stewardship and improves disease management. Here, we develop a rapid bacteriophage-based diagnostic assay to detect the most prevalent pathogens causing urinary tract infections: Escherichia coli, Klebsiella spp., and Enterococcus spp. For each uropathogen, two virulent phages were genetically engineered to express a nanoluciferase reporter gene upon host infection. Using 206 patient urine samples, reporter phage-induced bioluminescence was quantified to identify bacteriuria and the assay was benchmarked against conventional urinalysis. Overall, E. coli, Klebsiella spp., and Enterococcus spp. were each detected with high sensitivity (68%, 78%, 85%), specificity (99%, 99%, 99%), and accuracy (90%, 94%, 96%) at a resolution of [>=]103 CFU/ml within 5 h. We further demonstrate how bioluminescence in urine can be used to predict phage antibacterial activity, demonstrating the future potential of reporter phages as companion diagnostics that guide patient-phage matching prior to therapeutic phage application.

microbiology↗

bioRxiv2022

Enhancing bacteriophage therapeutics through in situ production and release of heterologous antimicrobial effectors

Bacteriophages operate via pathogen-specific mechanisms of action distinct from conventional, broad-spectrum antibiotics and are emerging as promising alternatives. However, phage-mediated killing is often limited by bacterial resistance development (1,2). Here, we engineer phages for target-specific effector gene delivery and host-dependent production of colicin-like bacteriocins and cell wall hydrolases. Using urinary tract infection (UTI) as a model, we show how heterologous effector phage therapeutics (HEPTs) suppress resistance and improve uropathogen killing by dual phage- and effector-mediated targeting. Moreover, we designed HEPTs to control polymicrobial uropathogen communities through production of effectors with cross-genus activity. Using a phage-based companion diagnostic (3), we identified potential HEPT responder patients and treated their urine ex vivo. Compared to wildtype phage, a colicin E7-producing HEPT demonstrated superior control of patient E. coli bacteriuria. Arming phages with heterologous effectors paves the way for successful UTI treatment and represents a versatile tool to enhance and adapt phage-based precision antimicrobials.

bioengineering↗

bioRxiv2017

Dual Phenotype Of MDA-MB-468 Cancer Cells Reveals Mutual Regulation Of Tensin3 And Adhesion Plasticity

Plasticity between adhesive and less-adhesive states is important for mammalian cell behaviour. To investigate adhesion plasticity, we have selected a stable isogenic subpopulation of MDA-MB-468 breast carcinoma cells which grows in suspension. These suspension cells are unable to re-adhere to various matrices or to contract three-dimensional collagen lattices. By transcriptome analysis, we identified the focal adhesion protein tensin3 (Tns3) as a determinant of adhesion plasticity. Tns3 is strongly reduced on mRNA and protein level in suspension cells. Furthermore, challenging breast cancer cells transiently with non-adherent conditions markedly reduces Tns3 expression, which is regained upon re-adhesion. Stable knockdown of Tns3 in parental cells results in defective adhesion, spreading and migration. Tns3 knockdown cells display impaired structure and dynamics of focal adhesion complexes as determined by immunostaining. Restoration of Tns3 expression in suspension cells partially rescues adhesion and focal contact composition. Our work identifies Tns3 as a critical focal adhesion component regulated by, and functionally contributing to, the switch between adhesive and non-adhesive states in MDA-MB-468 cancer cells.\n\nSummary statementWe identify the cell-matrix adapter protein tensin3 as a determinant of adhesion plasticity, using cancer cells selected for non-adherent growth. Tensin3 expression constitutes a feedback loop controlling adhesion and motility.

cell biology↗