Biology subjects

Schmitz, C.

Publications and source records attributed to Schmitz, C..

24 records · Page 2Linked to original sources

bioRxiv2020

CD300lf conditional knockout mouse reveals strain-specific cellular tropism for murine norovirus

Noroviruses are a leading cause of gastrointestinal infection in humans and mice. Understanding human norovirus (HuNoV) cell tropism has important implications for our understanding of viral pathogenesis. Murine norovirus (MNoV) is extensively used as a surrogate model for HuNoV. We previously identified CD300lf as the receptor for MNoV. Here, we generated a Cd300lf conditional knockout (CD300lfF/F) mouse to elucidate the cell tropism of persistent and non-persistent strains of murine norovirus. Using this mouse model, we demonstrate that CD300lf expression on intestinal epithelial cells (IECs), and on tuft cells in particular, is essential for transmission of the persistent MNoV strain CR6 (MNoVCR6) in vivo. In contrast, the nonpersistent MNoV strain CW3 (MNoVCW3) does not require CD300lf expression on IECs for infection. However, deletion of CD300lf in myelomonocytic cells (LysM Cre+) partially reduces CW3 viral load in lymphoid and intestinal tissues. Disruption of CD300lf expression on B cells (CD19 Cre), neutrophils (Mrp8 Cre), and dendritic cells (CD11c Cre) did not affect CW3 viral RNA levels. Finally, we show that the transcription factor STAT1, which is critical for the innate immune response, partially restricts the cell tropism of MNoVCW3 to LysM+ cells. Taken together, these data demonstrate that CD300lf expression on tuft cells is essential for MNoVCR6, that myelomonocytic cells are a major, but not exclusive, target cell of MNoVCW3, and that STAT1 signaling restricts the cellular tropism of MNoVCW3. This provides the first genetic system to study the cell type-specific role of CD300lf in norovirus pathogenesis. IMPORTANCEHuman noroviruses (HuNoVs) are a leading cause of gastroenteritis resulting in up to 200,000 deaths each year. The receptor and cell tropism of HuNoV in immunocompetent humans are unclear. We use murine norovirus (MNoV) as a model for HuNoV. We recently identified CD300lf as the sole physiologic receptor for MNoV. Here, we leverage this finding to generate a Cd300lf conditional knockout mouse to decipher the contributions of specific cell types to MNoV infection. We demonstrate that persistent MNoVCR6 requires CD300lf expression on tuft cells. In contrast, multiple CD300lf+ cell types, dominated by myelomonocytic cells, are sufficient for non-persistent MNoVCW3 infection. CD300lf expression on epithelial cells, B cells, neutrophils, and dendritic cells is not critical for MNoVCW3 infection. Mortality associated with MNoVCW3 strain in Stat1-/- mice does not require CD300lf expression on LysM+ cells, highlighting that both CD300lf receptor expression and innate immunity regulate MNoV cell tropism in vivo.

microbiology↗

bioRxiv2020

Genome-wide CRISPR screen reveals host genes that regulate SARS-CoV-2 infection

Identification of host genes essential for SARS-CoV-2 infection may reveal novel therapeutic targets and inform our understanding of COVID-19 pathogenesis. Here we performed a genome-wide CRISPR screen with SARS-CoV-2 and identified known SARS-CoV-2 host factors including the receptor ACE2 and protease Cathepsin L. We additionally discovered novel pro-viral genes and pathways including the SWI/SNF chromatin remodeling complex and key components of the TGF-{beta} signaling pathway. Small molecule inhibitors of these pathways prevented SARS-CoV-2-induced cell death. We also revealed that the alarmin HMGB1 is critical for SARS-CoV-2 replication. In contrast, loss of the histone H3.3 chaperone complex sensitized cells to virus-induced death. Together this study reveals potential therapeutic targets for SARS-CoV-2 and highlights host genes that may regulate COVID-19 pathogenesis.

genetics↗

bioRxiv2019

COLLECTIVE AGGRESSIVENESS LIMITS COLONY PERSISTENCE IN HIGH BUT NOT LOW ELEVATION SITES IN AMAZONIAN SOCIAL SPIDERS

Identifying the traits that foster group survival in contrasting environments is important for understanding local adaptation in social systems. Here we evaluate the relationship between the aggressiveness of social spider colonies and their persistence along an elevation gradient using the Amazonian spider, Anelosimus eximius. We found that colonies of A. eximius exhibit repeatable differences in their collective aggressiveness, and that colony aggressiveness is linked with persistence in a site-specific manner. Less aggressive colonies are better able to persist at high-elevation sites, which lack colony-sustaining large-bodied prey, whereas colony aggression was not related to chance of persistence at low-elevation sites. This suggests resistance to resource limitation through docility promotes colony survival at high elevations. These data reveal that the collective phenotypes that relate to colony persistence vary by site, and thus, the path of social evolution in these environments is likely to be affected.

evolutionary biology↗

bioRxiv2019

Soft tissue calcification in mice is governed by fetuin-A, pyrophosphate and magnesium

ObjectiveCalcifications can disrupt organ function in the cardiovascular system and the kidney, and are particularly common in patients with chronic kidney disease (CKD). Fetuin-A deficient mice maintained against the genetic background DBA/2 exhibit particularly severe soft tissue calcifications, while fetuin-A deficient C57BL/6 mice remain healthy. We employed molecular genetic analysis to identify risk factors of calcification in fetuin-A deficient mice. We sought to identify pharmaceutical therapeutic target that could be influenced by dietary of parenteral supplementation.\n\nApproach and ResultsWe studied the progeny of an intercross of fetuin-A deficient DBA/2 and C57BL/6 mice to identify candidate risk genes involved in calcification. We determined that a hypomorphic mutation of the Abcc6 gene, a liver ATP transporter supplying systemic pyrophosphate, and failure to regulate the TRPM6 magnesium transporter in kidney were associated with severity of calcification. Calcification prone fetuin-A deficient mice were alternatively treated with dietary phosphate restriction, magnesium supplementation, or by parenteral administration of fetuin-A or pyrophosphate. All treatments markedly reduced soft tissue calcification, demonstrated by computed tomography, histology and tissue calcium measurement.\n\nConclusionsWe show that pathological ectopic calcification in fetuin-A deficient DBA/2 mice is caused by a compound deficiency of three major extracellular and systemic inhibitors of calcification, namely fetuin-A, pyrophosphate, and magnesium. All three of these are individually known to contribute to stabilize protein-mineral complexes and thus inhibit mineral precipitation from extracellular fluid. We show for the first time a compound triple deficiency that can be treated by simple dietary or parenteral supplementation. This is of special importance in patients with advanced CKD, who commonly exhibit reduced serum fetuin-A, pyrophosphate and magnesium levels.\n\nSubject CodesAnimal Models of Human Disease, Fibrosis, Inflammation, Proteomics, Peripheral Vascular Disease

physiology↗

bioRxiv2018

Automatic navigation system for the mouse brain

Identification and delineation of brain regions in histologic mouse brain sections is especially pivotal for many neurogenomics, transcriptomics, proteomics and connectomics studies, yet this process is prone to observer error and bias. Here we present a novel brain navigation system, named NeuroInfo, whose general principle is similar to that of a global positioning system (GPS) in a car. NeuroInfo automatically navigates an investigator through the complex microscopic anatomy of histologic sections of mouse brains (thereafter: \"experimental mouse brain sections\"). This is achieved by automatically registering a digital image of an experimental mouse brain section with a three-dimensional (3D) digital mouse brain atlas that is essentially based on the third version of the Allen Mouse Brain Common Coordinate Framework (CCF v3), retrieving graphical region delineations and annotations from the 3D digital mouse brain atlas, and superimposing this information onto the digital image of the experimental mouse brain section on a computer screen. By doing so, NeuroInfo helps in solving the long-standing problem faced by researchers investigating experimental mouse brain sections under a light microscope--that of correctly identifying the distinct brain regions contained within the experimental mouse brain sections. Specifically, NeuroInfo provides an intuitive, readily-available computer microscopy tool to enhance researchers ability to correctly identify specific brain regions in experimental mouse brain sections. Extensive validation studies of NeuroInfo demonstrated that this novel technology performs remarkably well in accurately delineating regions that are large and/or located in the dorsal parts of mouse brains, independent on whether the sections were imaged with fluorescence or brightfield microscopy. This novel navigation system provides a highly efficient way for registering a digital image of an experimental mouse brain section with the 3D digital mouse brain atlas in a minute and accurate delineation of the image in real-time.

neuroscience↗

bioRxiv2018

Exposure of zebra mussels to extracorporeal shock waves demonstrates formation of new mineralized tissue inside and outside the focus zone

A substantial body of evidence supports the use of extracorporeal shock wave therapy (ESWT) for fracture nonunions in human medicine. However, the success rate (i.e., radiographic union at six months after ESWT) is only approximately 75%. Detailed knowledge regarding the underlying mechanisms that induce bio-calcification after ESWT is limited. The aim of the present study was to analyze the biological response within mineralized tissue of a new invertebrate model organism, the zebra mussel Dreissena polymorpha, after exposure with extracorporeal shock waves (ESWs). Mussels were exposed to ESWs with positive energy density of 0.4 mJ/mm2 or were sham exposed. Detection of newly calcified tissue was performed by concomitantly exposing the mussels to fluorescent markers. Two weeks later, the fluorescence signal intensity of the valves was measured. Mussels exposed to ESWs showed a statistically significantly higher mean fluorescence signal intensity within the shell zone than mussels that were sham exposed. Additional acoustic measurements revealed that the increased mean fluorescence signal intensity within the shell of those mussels that were exposed to ESWs was independent of the size and position of the focal point of the ESWs. These data demonstrate that induction of bio-calcification after ESWT may not be restricted to the region of direct energy transfer of ESWs into calcified tissue. The results of the present study are of relevance for better understanding of the molecular and cellular mechanisms that induce formation of new mineralized tissue after ESWT. Specifically, bio-calcification following ESWT may extend beyond the direct area of treatment.\n\nSummary statementThe use of zebra mussels in research on extracorporeal shock wave (ESW) therapy for fracture nonunions allows new insights into the complex process of induction of biomineralization by ESWs.

biophysics↗