Publications by authors named "Judith Konantz"

6 Publications

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Modelling pancreatic β-cell inflammation in zebrafish identifies the natural product wedelolactone for human islet protection.

Dis Model Mech 2019 01 23;12(1). Epub 2019 Jan 23.

Centre for Regenerative Therapies TU Dresden, Dresden 01307, Germany.

Islet inflammation and cytokine production are implicated in pancreatic β-cell dysfunction and diabetes pathogenesis. However, we lack therapeutics to protect the insulin-producing β-cells from inflammatory damage. Closing this clinical gap requires the establishment of new disease models of islet inflammation to facilitate screening efforts aimed at identifying new protective agents. Here, we have developed a genetic model of Interleukin-1β (Il-1β)-driven islet inflammation in zebrafish, a vertebrate that allows for non-invasive imaging of β-cells and drug discovery. Live imaging of immune cells and β-cells in our model revealed dynamic migration, increased visitation and prolonged macrophage retention in the islet, together with robust activation of NF-κB signalling in β-cells. We find that Il-1β-mediated inflammation does not cause β-cell destruction but, rather, it impairs β-cell function and identity. , β-cells exhibit impaired glucose-stimulated calcium influx and reduced expression of genes involved in function and maturity. These defects are accompanied by α-cell expansion, glucose intolerance and hyperglycemia following a glucose challenge. Notably, we show that a medicinal plant derivative (wedelolactone) is capable of reducing the immune-cell infiltration while also ameliorating the hyperglycemic phenotype of our model. Importantly, these anti-diabetic properties in zebrafish are predictive of wedelolactone's efficacy in protecting rodent and human islets from cytokine-induced apoptosis. In summary, this new zebrafish model of diabetes opens a window to study the interactions between immune and β-cells , while also allowing the identification of therapeutic agents for protecting β-cells from inflammation.
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http://dx.doi.org/10.1242/dmm.036004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6361155PMC
January 2019

Age-related islet inflammation marks the proliferative decline of pancreatic beta-cells in zebrafish.

Elife 2018 04 6;7. Epub 2018 Apr 6.

DFG-Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany.

The pancreatic islet, a cellular community harboring the insulin-producing beta-cells, is known to undergo age-related alterations. However, only a handful of signals associated with aging have been identified. By comparing beta-cells from younger and older zebrafish, here we show that the aging islets exhibit signs of chronic inflammation. These include recruitment of -expressing macrophages and the activation of NF-kB signaling in beta-cells. Using a transgenic reporter, we show that NF-kB activity is undetectable in juvenile beta-cells, whereas cells from older fish exhibit heterogeneous NF-kB activity. We link this heterogeneity to differences in gene expression and proliferation. Beta-cells with high NF-kB signaling proliferate significantly less compared to their neighbors with low activity. The NF-kB signaling cells also exhibit premature upregulation of , an age-related gene that inhibits beta-cell proliferation. Together, our results show that NF-kB activity marks the asynchronous decline in beta-cell proliferation with advancing age.
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http://dx.doi.org/10.7554/eLife.32965DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5943033PMC
April 2018

Different developmental histories of beta-cells generate functional and proliferative heterogeneity during islet growth.

Nat Commun 2017 09 22;8(1):664. Epub 2017 Sep 22.

DFG-Center for Regenerative Therapies Dresden, Cluster of Excellence, Technische Universität Dresden, Dresden, 01307, Germany.

The proliferative and functional heterogeneity among seemingly uniform cells is a universal phenomenon. Identifying the underlying factors requires single-cell analysis of function and proliferation. Here we show that the pancreatic beta-cells in zebrafish exhibit different growth-promoting and functional properties, which in part reflect differences in the time elapsed since birth of the cells. Calcium imaging shows that the beta-cells in the embryonic islet become functional during early zebrafish development. At later stages, younger beta-cells join the islet following differentiation from post-embryonic progenitors. Notably, the older and younger beta-cells occupy different regions within the islet, which generates topological asymmetries in glucose responsiveness and proliferation. Specifically, the older beta-cells exhibit robust glucose responsiveness, whereas younger beta-cells are more proliferative but less functional. As the islet approaches its mature state, heterogeneity diminishes and beta-cells synchronize function and proliferation. Our work illustrates a dynamic model of heterogeneity based on evolving proliferative and functional beta-cell states.Βeta-cells have recently been shown to be heterogeneous with regard to morphology and function. Here, the authors show that β-cells in zebrafish switch from proliferative to functional states with increasing time since β-cell birth, leading to functional and proliferative heterogeneity.
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http://dx.doi.org/10.1038/s41467-017-00461-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5610262PMC
September 2017

Distinct Levels of Reactive Oxygen Species Coordinate Metabolic Activity with Beta-cell Mass Plasticity.

Sci Rep 2017 06 26;7(1):3994. Epub 2017 Jun 26.

DFG Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany.

The pancreatic beta-cells control glucose homeostasis by secreting insulin in response to nutrient intake. The number of beta-cells is under tight metabolic control, as this number increases with higher nutrient intake. However, the signaling pathways matching nutrition with beta-cell mass plasticity remain poorly defined. By applying pharmacological and genetic manipulations, we show that reactive oxygen species (ROS) regulate dose-dependently beta-cell proliferation in vivo and in vitro. In particular, reducing ROS levels in beta-cells blocks their proliferation in response to nutrients. Using a non-invasive genetic sensor of intracellular hydrogen peroxide (HO), we reveal that glucose can directly increase the levels of HO. Furthermore, a moderate increase in HO levels can stimulate beta-cell proliferation. Interestingly, while high HO levels are inhibitory to beta-cell proliferation, they expand beta-cell mass in vivo by inducing rapid beta-cell neogenesis. Our study thus reveals a ROS-level-dependent mechanism linking nutrients with beta-cell mass plasticity. Hence, given the requirement of ROS for beta-cell mass expansion, antioxidant therapies should be applied with caution in diabetes.
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http://dx.doi.org/10.1038/s41598-017-03873-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5484671PMC
June 2017

Reverse genetic morpholino approach using cardiac ventricular injection to transfect multiple difficult-to-target tissues in the zebrafish larva.

J Vis Exp 2014 Jun 17(88). Epub 2014 Jun 17.

DFG-Center for Regenerative Therapies Dresden, Technische Universität Dresden;

The zebrafish is an important model to understand the cell and molecular biology of organ and appendage regeneration. However, molecular strategies to employ reverse genetics have not yet been adequately developed to assess gene function in regeneration or tissue homeostasis during larval stages after zebrafish embryogenesis, and several tissues within the zebrafish larva are difficult to target. Intraventricular injections of gene-specific morpholinos offer an alternative method for the current inability to genomically target zebrafish genes in a temporally controlled manner at these stages. This method allows for complete dispersion and subsequent incorporation of the morpholino into various tissues throughout the body, including structures that were formerly impossible to reach such as those in the larval caudal fin, a structure often used to noninvasively research tissue regeneration. Several genes activated during larval finfold regeneration are also present in regenerating adult vertebrate tissues, so the larva is a useful model to understand regeneration in adults. This morpholino dispersion method allows for the quick and easy identification of genes required for the regeneration of larval tissues as well as other physiological phenomena regulating tissue homeostasis after embryogenesis. Therefore, this delivery method provides a currently needed strategy for temporal control to the evaluation of gene function after embryogenesis. 
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http://dx.doi.org/10.3791/51595DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4195391PMC
June 2014

The zebrafish reference genome sequence and its relationship to the human genome.

Nature 2013 Apr 17;496(7446):498-503. Epub 2013 Apr 17.

Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK.

Zebrafish have become a popular organism for the study of vertebrate gene function. The virtually transparent embryos of this species, and the ability to accelerate genetic studies by gene knockdown or overexpression, have led to the widespread use of zebrafish in the detailed investigation of vertebrate gene function and increasingly, the study of human genetic disease. However, for effective modelling of human genetic disease it is important to understand the extent to which zebrafish genes and gene structures are related to orthologous human genes. To examine this, we generated a high-quality sequence assembly of the zebrafish genome, made up of an overlapping set of completely sequenced large-insert clones that were ordered and oriented using a high-resolution high-density meiotic map. Detailed automatic and manual annotation provides evidence of more than 26,000 protein-coding genes, the largest gene set of any vertebrate so far sequenced. Comparison to the human reference genome shows that approximately 70% of human genes have at least one obvious zebrafish orthologue. In addition, the high quality of this genome assembly provides a clearer understanding of key genomic features such as a unique repeat content, a scarcity of pseudogenes, an enrichment of zebrafish-specific genes on chromosome 4 and chromosomal regions that influence sex determination.
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http://dx.doi.org/10.1038/nature12111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3703927PMC
April 2013