Biology subjects

Guenther, S.

Publications and source records attributed to Guenther, S..

7 recordsLinked to original sources

bioRxiv2018

Screening for insulin-independent pathways that modulate glucose homeostasis identifies androgen receptor antagonists

Pathways modulating glucose homeostasis independently of insulin would open new avenues to combat insulin resistance and diabetes. Here, we report the establishment, characterization and employment of a vertebrate insulin-free model to identify insulin-independent modulators of glucose metabolism. insulin knockout zebrafish recapitulate core characteristics of diabetes and survive only up to larval stages. Utilizing a highly efficient endoderm transplant technique, we generated viable chimeric adults that provide the large numbers of insulin mutant larvae required for our screening platform. Using glucose as a disease-relevant readout, we screened 2233 molecules and identified 3 that consistently reduced glucose levels in insulin mutants. Most significantly, we uncovered an insulin-independent beneficial role for androgen receptor antagonism in hyperglycemia, mostly by reducing fasting glucose levels. Our study proposes therapeutic roles for androgen signaling in diabetes and, more broadly, offers a novel in vivo model for rapid screening and decoupling of insulin-dependent and -independent mechanisms.

developmental biology↗

bioRxiv2018

Myh10 deficiency leads to defective extracellular matrix remodeling and pulmonary disease

Impaired alveolar formation and maintenance are features of many pulmonary diseases that are associated with significant morbidity and mortality. In a forward genetic screen for modulators of mouse lung development, we identified the non-muscle myosin II heavy chain gene, Myh10. Myh10 mutant pups exhibit cyanosis and respiratory distress, and die shortly after birth from differentiation defects in alveolar epithelium and mesenchyme. From omics analyses and follow up studies, we find decreased Thrombospondin expression accompanied with increased matrix metalloproteinase activity in both mutant lungs and cultured mutant fibroblasts, as well as disrupted extracellular matrix (ECM) remodeling. Loss of Myh10 specifically in mesenchymal cells results in ECM deposition defects and alveolar simplification. Notably, MYH10 expression is down-regulated in the lung of emphysema patients. Altogether, our findings reveal critical roles for Myh10 in alveologenesis at least in part via the regulation of ECM remodeling, which may contribute to the pathogenesis of emphysema.

developmental biology↗

bioRxiv2018

Genetic compensation is triggered by mutant mRNA degradation

Genetic compensation by transcriptional modulation of related gene(s) (also known as transcriptional adaptation) has been reported in numerous systems 1-3; however, whether and how such a response can be activated in the absence of protein feedback loops is unknown. Here, we develop and analyze several models of transcriptional adaptation in zebrafish and mouse that we show are not caused by loss of protein function. We find that the increase in transcript levels is due to enhanced transcription, and observe a correlation between the levels of mutant mRNA decay and transcriptional upregulation of related genes. To assess the role of mutant mRNA degradation in triggering transcriptional adaptation, we use genetic and pharmacological approaches and find that mRNA degradation is indeed required for this process. Notably, uncapped RNAs, themselves subjected to rapid degradation, can also induce transcriptional adaptation. Next, we generate alleles that fail to transcribe the mutated gene and find that they do not show transcriptional adaptation, and exhibit more severe phenotypes than those observed in alleles displaying mutant mRNA decay. Transcriptome analysis of these different alleles reveals the upregulation of hundreds of genes with enrichment for those showing sequence similarity with the mutated genes mRNA, suggesting a model whereby mRNA degradation products induce the response via sequence similarity. These results expand the role of the mRNA surveillance machinery in buffering against mutations by triggering the transcriptional upregulation of related genes. Besides implications for our understanding of disease-causing mutations, our findings will help design mutant alleles with minimal transcriptional adaptation-derived compensation.

genetics↗

bioRxiv2018

The potassium channel KCNJ13 is essential for smooth muscle cytoskeletal organization during mouse tracheal tubulogenesis

Tubulogenesis is essential for the formation and function of internal organs. One such organ is the trachea, which allows gas exchange between the external environment and the lungs. However, the cellular and molecular mechanisms underlying tracheal tube development remain poorly understood. Here, we show that the potassium channel KCNJ13 is a critical modulator of tracheal tubulogenesis. We identify Kcnj13 in an ethylnitrosourea forward genetic screen for regulators of mouse respiratory organ development. Kcnj13 mutants exhibit a shorter trachea as well as defective smooth muscle (SM) cell alignment and polarity. KCNJ13 is essential to maintain ion homeostasis in tracheal SM cells, which is required for actin polymerization. This process appears to be mediated, at least in part, through activation of the actin regulator AKT, as pharmacological increase of AKT phosphorylation ameliorates the Kcnj13 mutant trachea phenotypes. These results provide insights into the role of ion homeostasis in cytoskeletal organization during tubulogenesis.

developmental biology↗

bioRxiv2017

Loss of Wt1 in the murine spinal cord alters interneuron composition and locomotion

Rhythmic and patterned locomotion is driven by spinal cord neurons that form neuronal circuits, referred to as central pattern generators (CPGs). Recently, dI6 neurons were suggested to participate in the control of locomotion. The dI6 neurons can be subdivided into three populations, one of which expresses the Wilms tumor suppressor gene Wt1. However, the role that Wt1 exerts on these cells is not understood. Here, we aimed to identify behavioral changes and cellular alterations in the spinal cord associated with Wt1 deletion. Locomotion analyses of mice with neuron-specific Wt1 deletion revealed that these mice ran slower than controls with a decreased stride frequency and an increased stride length. These mice showed changes in their fore-hindlimb coordination, which were accompanied by a loss of contralateral projections in the spinal cord. Neonates with Wt1 deletion displayed an increase in uncoordinated hindlimb movements and their motor neuron output was arrhythmic with a decreased frequency. The population size of dI6, V0 and V2a neurons in the developing spinal cord of conditional Wt1 mutants was significantly altered. These results show that the development of particular dI6 neurons depends on Wt1 expression and loss of Wt1 is associated with alterations in locomotion.

neuroscience↗

bioRxiv2017

Whole genome analysis reveals pathogenic potential of multi-drug resistant wastewater Escherichia coli

Wastewater treatment plants play an important role in the release of antibiotic resistance into the environment. It has been shown that wastewater contains multi-drug resistant Escherichia coli, but information on strain diversity is surprisingly scarce. Here we present an exceptionally large dataset on multidrug resistant Escherichia coli, originating from wastewater, over a thousand isolates were phenotypically characterized for twenty antibiotics and for 103 isolates whole genomes were sequenced. To our knowledge this is the first study documenting such a comprehensive diversity of multi-drug resistant Escherichia coli in wastewater. The genomic diversity of the isolates was unexpectedly high and contained a high number of resistance and virulence genes. To illustrate the genomic diversity of the isolates we calculated the pan genome of the wastewater Escherichia coli and found it to contain over sixteen thousand genes. To analyse this diverse dataset, we devised a computational approach correlating genotypic variation and resistance phenotype, this way we were able to identify not only known, but also candidate resistance genes. Finally, we could verify that the effluent of a wastewater treatment plant will contain multi-drug resistant Escherichia coli belonging to clinically important clonal groups.

bioinformatics↗

bioRxiv2017

Single-cell transcriptional regulations and accessible chromatin landscape of cell fate decisions in early heart development

Formation and segregation of the cell lineages forming the vertebrate heart have been studied extensively by genetic cell tracing techniques and by analysis of single marker gene expression both in embryos and differentiating ES cells. However, the underlying gene regulatory networks driving cell fate transitions during early cardiogenesis is only partially understood, in part due to limited cell numbers and substantial cellular heterogeneity within the early embryo. Here, we comprehensively characterized cardiac progenitor cells (CPC) marked by Nkx2-5 and Isl1 expression from embryonic days E7.5 to E9.5 using single-cell RNA sequencing. By leveraging on cell-to-cell heterogeneity, we identified different previously unknown cardiac sub-populations. Reconstruction of the developmental trajectory revealed that Isl1+ CPC represent a transitional cell population maintaining a prolonged multipotent state, whereas extended expression of Nkx-2.5 commits CPC to a unidirectional cardiomyocyte fate. Correlation-based analysis of cells in the unstable multipotent state uncovered underlying gene regulatory networks associated with differentiation. Furthermore, we show that CPC fate transitions are associated with distinct open chromatin states, which critically depend on Isl1 for accessibility of enhancers. In contrast, forced expression of Nkx2-5 eliminated multipotency of Isl1+ cells and established a unidirectional cardiomyocyte fate. Our data provides a transcriptional map for early cardiogenic events at single-cell resolution and establishes a general model of transcriptional and epigenetic regulations during cardiac progenitor cell fate decisions.

developmental biology↗