Publications by authors named "Iris Koch"

72 Publications

Development and validation of a method for the weathering and detachment of representative nanomaterials from conventional silver-containing textiles.

Chemosphere 2021 Jun 18;284:131269. Epub 2021 Jun 18.

Environmental Sciences Group, Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, ON, K7K 7B4, Canada. Electronic address:

Nanotoxicology research commonly utilizes pristine nanomaterials for toxicity assessment, which may not be perfectly representative of what is released into environmental systems. The goal of the present study was to develop a method to simulate human weathering of silver-containing textiles. To achieve this goal the roles of physical and chemical stress on X-Static® containing athletic textiles were investigated and compared to data collected from human weathering experiments and literature. Chemical weathering methods (artificial sweat) were used independently and alongside physical weathering methods (3D printed stretching and abrasion instruments). Non-weathered control textiles were found to release 29 ± 11 mg Ag/kg of textile into wash water effluent (ICP-MS), with 16% being released as ionic silver (ICP-MS) and the rest as metallic nanomaterials, nanosheets, and particulates of varying size (SEM/XANES). Real and simulated human weathered textiles released similar amounts of total silver (67 ± 11 mg Ag/kg, 84 ± 13 mg Ag/kg respectively) with the silver released being composed of ionic (1.5%, 2%) and a mixture of metallic and chlorinated nanomaterials, nanosheets, and particulates. The method was shown to effectively detach environmentally representative silver materials from silver-containing textiles and can provide such materials for future studies on the assessment of their fate, transport, and toxicity.
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http://dx.doi.org/10.1016/j.chemosphere.2021.131269DOI Listing
June 2021

Evaluating mercury concentrations in edible plant and fungi species in the Canadian Arctic environment.

J Environ Qual 2021 Jul 24;50(4):877-888. Epub 2021 Jun 24.

Dep. of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, ON, K7K 7B4, Canada.

Levels of environmental mercury (Hg) within the Canadian Arctic are a current area of concern. Although efforts have been made to reduce Hg released into the environment, levels remain elevated in flora and fauna. This study examined the concentrations of Hg in soil and naturally occurring edible plant and fungi species, identified by local Inuit residents, from eight locations in Iqaluit, Nunavut, and the surrounding area during the summers of 2018 and 2019. Total Hg concentrations were obtained in 24 soil samples, 112 flora samples from 23 plant and five lichen species, and 157 fungal samples from eight species. Median Hg concentrations in plant species ranged from 0.005 μg g Hg dry weight (dw) in Saxifraga cernua to 0.19 μg g Hg dw in Oxytropis maydelliana. Median concentrations in edible fungi species ranged from 0.084 μg g Hg dw in the Cortinarius croceus (non-puffball species) to 1.6 μg g Hg dw in Lycoperdon perlatum (a puffball mushroom). Additionally, median Hg concentration in puffball species (1.4 μg g ) were higher than non-puffball species (0.12 μg g ). Three puffball species were assessed for methylmercury (MeHg), with mean concentrations ranging from 0.013 to 0.085 μg g MeHg dw. Limited research has been conducted on Hg uptake in naturally occurring edible plant and fungi species of the Canadian Arctic. This study contributes important information on Hg accumulation and processes in edible plant and fungi Arctic species, is the first to focus on plants used by the local Indigenous community, and demonstrates a need for further studies to assess Hg in Arctic environments.
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http://dx.doi.org/10.1002/jeq2.20253DOI Listing
July 2021

Gauge invariant and gauge dependent aspects of topological walking colloidal bipeds.

Soft Matter 2021 Feb;17(6):1663-1674

University of Bayreuth, Physics, Universitätsstr. 30, 95447 Bayreuth, Germany.

Paramagnetic colloidal spheres assemble to colloidal bipeds of various length in an external magnetic field. When the bipeds reside above a magnetic pattern and we modulate the direction of the external magnetic field, the rods perform topologically distinct classes of protected motion above the pattern. The topological protection allows each class to be robust against small continuous deformations of the driving loop of the external field. We observe motion of the rod from a passive central sliding and rolling motion for short bipeds toward a walking motion with both ends of the rod alternately touching down on the pattern for long bipeds. The change of character of the motion occurs in form of discrete topological transitions. The topological protection makes walking a form of motion robust against the breaking of the non symmorphic symmetry. In patterns with non symmorphic symmetry walking is reversible. In symmorphic patterns lacking a glide plane the walking can be irreversible or reversible involving or not involving ratchet jumps. Using different gauges allows us to unravel the active and passive aspects of the topological walks.
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http://dx.doi.org/10.1039/d0sm01670eDOI Listing
February 2021

Identification of Arctic Food Fish Species for Anthropogenic Contaminant Testing Using Geography and Genetics.

Foods 2020 Dec 8;9(12). Epub 2020 Dec 8.

Department of Biology, Queen's University, Kingston, ON K7L 3N6, Canada.

The identification of food fish bearing anthropogenic contaminants is one of many priorities for Indigenous peoples living in the Arctic. Mercury (Hg), arsenic (As), and persistent organic pollutants including polychlorinated biphenyls (PCBs) are of concern, and these are reported, in some cases for the first time, for fish sampled in and around King William Island, located in Nunavut, Canada. More than 500 salmonids, comprising Arctic char, lake trout, lake whitefish, and ciscoes, were assayed for contaminants. The studied species are anadromous, migrating to the ocean to feed in the summers and returning to freshwater before sea ice formation in the autumn. Assessments of muscle Hg levels in salmonids from fishing sites on King William Island showed generally higher levels than from mainland sites, with mean concentrations generally below guidelines, except for lake trout. In contrast, mainland fish showed higher means for As, including non-toxic arsenobetaine, than island fish. Lake trout were highest in As and PCB levels, with salmonid PCB congener analysis showing signatures consistent with the legacy of cold-war distant early warning stations. After DNA-profiling, only 4-32 Arctic char single nucleotide polymorphisms were needed for successful population assignment. These results support our objective to demonstrate that genomic tools could facilitate efficient and cost-effective cluster assignment for contaminant analysis during ocean residency. We further suggest that routine pollutant testing during the current period of dramatic climate change would be helpful to safeguard the wellbeing of Inuit who depend on these fish as a staple input to their diet. Moreover, this strategy should be applicable elsewhere.
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http://dx.doi.org/10.3390/foods9121824DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7764770PMC
December 2020

Colloidal trains.

Soft Matter 2020 Feb 20;16(6):1594-1598. Epub 2020 Jan 20.

Experimentalphysik X, Physikalisches Institut, Universität Bayreuth, D-95440 Bayreuth, Germany.

Single and double paramagnetic colloidal particles are placed above a magnetic square pattern and are driven with an external magnetic field processing around a high symmetry direction of the pattern. The external magnetic field and that of the pattern confine the colloids into lanes parallel to a lattice vector of the pattern. The precession of the external field causes traveling minima of the magnetic potential along the direction of the lanes. At sufficiently high frequencies of modulation, only the doublets respond to the external field and move in direction of the traveling minima along the lanes, while the single colloids cannot follow and remain static. We show how the doublets can induce a coordinated motion of the single colloids building colloidal trains made of a chain of several single colloids transported by doublets.
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http://dx.doi.org/10.1039/c9sm02261aDOI Listing
February 2020

Arsenic speciation in the bracket fungus Fomitopsis betulina from contaminated and pristine sites.

Environ Geochem Health 2020 Sep 2;42(9):2723-2732. Epub 2020 Jan 2.

Environmental Sciences Group, Royal Military College of Canada, Kingston, ON, K7K 7B4, Canada.

Uptake, distribution and speciation of arsenic (As) were determined in the bracket fungus Fomitopsis betulina (previously Piptoporus betulinus), commonly known as the birch polypore, collected from a woodland adjacent to a highly contaminated former mine in the Southwest UK and at an uncontaminated site in Quebec, Canada, with no past or present mining activity. The fruiting body was divided into cap, centre and pores representing the top, middle and underside to identify trends in the distribution and transformation of As. Total As, determined by inductively coupled plasma-mass spectrometry (ICP-MS), was approximately tenfold higher in the mushroom from the contaminated compared to the uncontaminated site. Overall, accumulation of As was low relative to values reported for some soil-dwelling species, with maximum levels of 1.6 mg/kg at the contaminated site. Arsenic speciation was performed on aqueous extracts via both anion and cation high-performance liquid chromatography-ICP-MS (HPLC-ICP-MS) and on whole dried samples using X-ray absorption near edge structure (XANES) analysis. Seven As species were detected in F. betulina from the contaminated site by HPLC-ICP-MS: arsenite (As), arsenate (As), dimethylarsinate (DMA), methylarsonate (MA), trimethylarsine oxide (TMAO), tetramethylarsonium ion (Tetra) and trace levels of arsenobetaine (AB). The same As species were observed at the uncontaminated site with the exception of TMAO and Tetra. Arsenic species were localized throughout the fruiting body at the contaminated site, with the cap and pores containing a majority of As, only the cap containing TMAO, and the pores containing higher concentrations of DMA and MA as well as tetra and a trace of AB. XANES analysis demonstrated that the predominant form of As at the contaminated site was inorganic As coordinated with sulphur or oxygen and As coordinated with oxygen. This is the first account of arsenic speciation in F. betulina or any fungi of the family Fomitopsidaceae.
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http://dx.doi.org/10.1007/s10653-019-00506-0DOI Listing
September 2020

CRISPR/Cas9-mediated knockout enables neutrophilic maturation of primary hematopoietic stem and progenitor cells and induced pluripotent stem cells of severe congenital neutropenia patients.

Haematologica 2020 03 27;105(3):598-609. Epub 2019 Jun 27.

Department of Oncology, Hematology, Immunology, Rheumatology and Clinical Immunology, University Hospital Tübingen, Tübingen, Germany

A Autosomal-dominant mutations are the most common cause of severe congenital neutropenia. Although the majority of congenital neutropenia patients respond to daily granulocyte colony stimulating factor, approximately 15 % do not respond to this cytokine at doses up to 50 μg/kg/day and approximately 15 % of patients will develop myelodysplasia or acute myeloid leukemia. "Maturation arrest," the failure of the marrow myeloid progenitors to form mature neutrophils, is a consistent feature of associated congenital neutropenia. As mutant neutrophil elastase is the cause of this abnormality, we hypothesized that associated neutropenia could be treated and "maturation arrest" corrected by a CRISPR/Cas9-sgRNA ribonucleoprotein mediated knockout. To examine this hypothesis, we used induced pluripotent stem cells from two congenital neutropenia patients and primary hematopoietic stem and progenitor cells from four congenital neutropenia patients harboring mutations as well as HL60 cells expressing mutant We observed that granulocytic differentiation of knockout induced pluripotent stem cells and primary hematopoietic stem and progenitor cells were comparable to healthy individuals. Phagocytic functions, ROS production, and chemotaxis of the KO (knockout) neutrophils were also normal. Knockdown of in the mutant expressing HL60 cells also allowed full maturation and formation of abundant neutrophils. These observations suggest that CRISPR/Cas9 RNP based knockout of patients' primary hematopoietic stem and progenitor cells followed by autologous transplantation may be an alternative therapy for congenital neutropenia.
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http://dx.doi.org/10.3324/haematol.2019.221804DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7049355PMC
March 2020

Organic-free, versatile sessile droplet microfluidic device for chemical separation using an aqueous two-phase system.

Lab Chip 2019 02;19(4):654-664

Department of Chemistry, Queen's University, 90 Bader Lane, Kingston, Ontario K7L 3N6, Canada.

This work presents a novel portable, versatile sessile droplet microfluidic (SDMF) device to perform liquid manipulation operations such as confining, splitting and colorimetric detection. Furthermore, chemical isolations based on an aqueous two-phase system (ATPS) for separating an analyte of choice from a complicated sample matrix can be carried out. ATPS extractions can replace conventional liquid-liquid extractions and take away the need for harmful organic solvents. Superhydrophobic (SH) surfaces were fabricated from a commercially available material, Ultra-Ever Dry® (UED®). On these SH surfaces, surface energy traps (SETs) were produced either by air plasma treatment (simultaneously) or laser micromachining (sequentially) to dock/pin an ATPS containing droplet onto the surface. Splitting of droplets or removing a precise volume of the top phase from a pinned extraction system was achieved with a sandwich-chip approach. For this, an additional SET patterned substrate was placed on top of the droplet and subsequently lifted. This multipurpose platform was used to isolate Cd from a mixture of several other metal ions (i.e. Mn, Ni, Cu, Pb, Fe) for its subsequent interference-free detection. An ATPS consisting of sodium sulfate and polyethylene glycol (PEG) as phase forming components and potassium iodine as extractant allowed separation of cadmium with an extraction efficiency of q(Cd2+) = 98.5%. Using a portable, cost-effective, smartphone-based UV/vis spectrometer, Cd was detected with a LoD of 3.4 ppm. Alternatively, the multipurpose platform can also be used as sampling platform for a benchtop UV/vis spectrometer, where a LoD of 0.53 ppm was obtained. Potential applications of the presented platform include sample preparation and separation that can be achieved by aqueous two-phase extractions, such as proteins, antibodies, DNA, cells, organic molecules and metal ions.
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http://dx.doi.org/10.1039/c8lc01121dDOI Listing
February 2019

Edge transport at the boundary between topologically equivalent lattices.

Soft Matter 2019 Feb;15(7):1539-1550

Institute of Physics and Mathematics, Universität Bayreuth, 95440 Bayreuth, Germany.

Edge currents of paramagnetic colloidal particles propagate at the edge between two topologically equivalent magnetic lattices of different lattice constant when the system is driven with periodic modulation loops of an external magnetic field. The number of topologically protected particle edge transport modes is not determined by a bulk-boundary correspondence. Instead, we find a rich variety of edge transport modes that depend on the symmetry of both the edge and the modulation loop. The edge transport can be ratchet-like or adiabatic, time or non-time reversal symmetric. The topological nature of the edge transport is classified by a set of winding numbers around bulk fence points extended by winding numbers around edge specific bifurcation points that cannot be deduced from the two bulk lattices.
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http://dx.doi.org/10.1039/c8sm02005aDOI Listing
February 2019

Estimating the number of airports potentially contaminated with perfluoroalkyl and polyfluoroalkyl substances from aqueous film forming foam: A Canadian example.

J Environ Manage 2018 Sep 26;222:122-131. Epub 2018 May 26.

Environmental Sciences Group, Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, ON, K7K 7B4, Canada. Electronic address:

Assessing the extent to which emerging contaminants (ECs) such as perfluoroalkyl and polyfluoroalkyl substances (PFAS) have been released into the environment is one of the foundations for developing effective management and remediation strategies for impacted sites. PFAS are known to have caused the contamination of soil, groundwater, and surface water as a result of aqueous film forming foam (AFFF) being accidentally or intentionally released into the environment. To date, the scope of the issue has not been evaluated in Canada. In this study we developed a framework, in the form of a decision tree, to estimate the number of potentially PFAS impacted airport sites in Canada as a result of AFFF releases. The screening process was completed using publicly available resources including airport websites, the Canadian Owners and Pilots Association website, Sky Vector, Transport Safety Board of Canada aviation investigation reports, the Aviation Safety Network website, and Google maps. The methodology presented in this study could be used to identify additional PFAS impacted sites in Canada or other jurisdictions worldwide. 2071 airport/heliport sites in Canada were investigated with indications that 152 (7%) of these sites likely have PFAS contamination as a result of the use of AFFF at firefighter training areas (FFTAs) and/or accidents where fires occurred. In addition, another 268 sites (13%) were identified as possibly impacted with PFASs primarily as a result of the location having the ability to store and dispense petroleum products, and therefore having AFFF systems onsite. Surficial geology was also identified for all sites determined to likely have PFAS contamination. An estimated 42.8% had surficial geology composed of sand, 27% had clay, 19.7% organic-based, with the remaining sites found on cryosols or rock. Methodological validation was also completed. The procedure used in this study successfully predicted occurrences of PFAS contamination at 25 sites where contamination, as a result of AFFF use, was confirmed by Canadian governmental departments. For these 25 sites, the distance from potential release areas to the nearest surface water was calculated. Five of the sites were within 200 meters of surface water, 19 were within one kilometer, and all 25 were within 2.5 kilometers. This suggests that surface water may have been historically impacted by PFAS at as many as 152 to 420 different airport locations in Canada.
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http://dx.doi.org/10.1016/j.jenvman.2018.05.028DOI Listing
September 2018

Lattice symmetries and the topologically protected transport of colloidal particles.

Soft Matter 2017 Jul;13(29):5044-5075

Experimental Physics, Universität Bayreuth, 95440 Bayreuth, Germany.

The topologically protected transport of colloidal particles on top of periodic magnetic patterns is studied experimentally, theoretically, and with computer simulations. To uncover the interplay between topology and symmetry we use patterns of all possible two dimensional magnetic point group symmetries with equal lengths lattice vectors. Transport of colloids is achieved by modulating the potential with external, homogeneous but time dependent magnetic fields. The modulation loops can be classified into topologically distinct classes. All loops falling into the same class cause motion in the same direction, making the transport robust against internal and external perturbations. We show that the lattice symmetry has a profound influence on the transport modes, the accessibility of transport networks, and the individual transport directions of paramagnetic and diamagnetic colloidal particles. We show how the transport of colloidal particles above a two fold symmetric stripe pattern changes from universal adiabatic transport at large elevations via a topologically protected ratchet motion at intermediate elevations toward a non-transport regime at low elevations. Transport above four-fold symmetric patterns is closely related to the two-fold symmetric case. The three-fold symmetric case however consists of a whole family of patterns that continuously vary with a phase variable. We show how this family can be divided into two topologically distinct classes supporting different transport modes and being protected by proper and improper six fold symmetries. We discuss and experimentally demonstrate the topological transition between both classes. All three-fold symmetric patterns support independent transport directions of paramagnetic and diamagnetic particles. The similarities and the differences in the lattice symmetry protected transport of classical over-damped colloidal particles versus the topologically protected transport in quantum mechanical systems are emphasized.
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http://dx.doi.org/10.1039/c7sm00983fDOI Listing
July 2017

Uptake and transformation of arsenic during the reproductive life stage of Agaricus bisporus and Agaricus campestris.

J Environ Sci (China) 2016 Nov 30;49:140-149. Epub 2016 Jul 30.

Environmental Sciences Group, Royal Military College of Canada, P.O. Box 17000, Station Forces, Kingston, ON K7K 7B4, Canada. Electronic address:

Fruiting bodies from the Agaricus genus have been found to contain non-toxic arsenobetaine (AB) as a major compound. It is unknown whether AB is formed during the vegetative or reproductive life stages of the fungus, or by the surrounding microbial community, but AB's structural similarity to glycine betaine has led to the hypothesis that AB may be adventitiously accumulated as an osmolyte. To investigate the potential formation of AB during the reproductive life stage of Agaricus species, growth substrate and fungi were collected during the commercial growth of Agaricus bisporus and analyzed for arsenic speciation using HPLC-ICP-MS. AB was found to be the major arsenic compound in the fungus at the earliest growth stage of fruiting (the primordium). The growth substrate mainly contained arsenate (As(V)). The distribution of arsenic in an A. bisporus primordium grown on As(V) treated substrate, and in a mature Agaricus campestris fruiting body collected from arsenic contaminated mine tailings, was mapped using two dimensional XAS imaging. The primordium and stalk of the mature fruiting body were both found to be growing around pockets of substrate material containing higher As concentrations, and AB was found exclusively in the fungal tissues. In the mature A. campestris the highest proportion of AB was found in the cap, supporting the AB as an osmolyte hypothesis. The results have allowed us to pinpoint the fungus life stage at which AB formation takes place, namely reproduction, which provides a direction for further research.
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http://dx.doi.org/10.1016/j.jes.2016.06.021DOI Listing
November 2016

In Vitro Variant Surface Antigen Expression in Plasmodium falciparum Parasites from a Semi-Immune Individual Is Not Correlated with Var Gene Transcription.

PLoS One 2016 1;11(12):e0166135. Epub 2016 Dec 1.

Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany.

Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is considered to be the main variant surface antigen (VSA) of Plasmodium falciparum and is mainly localized on electron-dense knobs in the membrane of the infected erythrocyte. Switches in PfEMP1 expression provide the basis for antigenic variation and are thought to be critical for parasite persistence during chronic infections. Recently, strain transcending anti-PfEMP1 immunity has been shown to develop early in life, challenging the role of PfEMP1 in antigenic variation during chronic infections. In this work we investigate how P. falciparum achieves persistence during a chronic asymptomatic infection. The infected individual (MOA) was parasitemic for 42 days and multilocus var gene genotyping showed persistence of the same parasite population throughout the infection. Parasites from the beginning of the infection were adapted to tissue culture and cloned by limiting dilution. Flow cytometry using convalescent serum detected a variable surface recognition signal on isogenic clonal parasites. Quantitative real-time PCR with a field isolate specific var gene primer set showed that the surface recognition signal was not correlated with transcription of individual var genes. Strain transcending anti-PfEMP1 immunity of the convalescent serum was demonstrated with CD36 selected and PfEMP1 knock-down NF54 clones. In contrast, knock-down of PfEMP1 did not have an effect on the antibody recognition signal in MOA clones. Trypsinisation of the membrane surface proteins abolished the surface recognition signal and immune electron microscopy revealed that antibodies from the convalescent serum bound to membrane areas without knobs and with knobs. Together the data indicate that PfEMP1 is not the main variable surface antigen during a chronic infection and suggest a role for trypsin sensitive non-PfEMP1 VSAs for parasite persistence in chronic infections.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0166135PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5132323PMC
July 2017

Magnetically Patterned Rolled-Up Exchange Bias Tubes: A Paternoster for Superparamagnetic Beads.

ACS Nano 2016 09 22;10(9):8491-8. Epub 2016 Aug 22.

Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel , Heinrich-Plett-Strasse 40, 34132 Kassel, Germany.

We realized a deterministic transport system for superparamagnetic microbeads through micrometer-sized tubes acting as channels. Beads are moved stepwise in a paternoster-like manner through the tube and back on top of it by weak magnetic field pulses without changing the field pulse polarity and taking advantage of the magnetic stray field emerging from the tubular structures. The microtubes are engineered by rolling up exchange bias layer systems, magnetically patterned into parallel stripe magnetic domains. In this way, the tubes possess distinct azimuthally aligned magnetic domain patterns. This transport mechanism features high step velocities and remote control of not only the direction and trajectory but also the velocity of the transport without the need of fuel or catalytic material. Therefore, this approach has the potential to impact several fields of 3D applications in biotechnology, including particle transport related phenomena in lab-on-a-chip and lab-in-a-tube devices.
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http://dx.doi.org/10.1021/acsnano.6b03566DOI Listing
September 2016

Sporozoite Route of Infection Influences In Vitro var Gene Transcription of Plasmodium falciparum Parasites From Controlled Human Infections.

J Infect Dis 2016 09 7;214(6):884-94. Epub 2016 Jun 7.

Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen.

Background: Antigenic variation in Plasmodium falciparum is mediated by the multicopy var gene family. Each parasite possesses about 60 var genes, and switching between active var loci results in antigenic variation. In the current study, the effect of mosquito and host passage on in vitro var gene transcription was investigated.

Methods: Thirty malaria-naive individuals were inoculated by intradermal or intravenous injection with cryopreserved, isogenic NF54 P. falciparum sporozoites (PfSPZ) generated from 1 premosquito culture. Microscopic parasitemia developed in 22 individuals, and 21 in vitro cultures were established. The var gene transcript levels were determined in early and late postpatient cultures and in the premosquito culture.

Results: At the early time point, all cultures preferentially transcribed 8 subtelomeric var genes. Intradermal infections had higher var gene transcript levels than intravenous infections and a significantly longer intrahost replication time (P = .03). At the late time point, 9 subtelomeric and 8 central var genes were transcribed at the same levels in almost all cultures. Premosquito and late postpatient cultures transcribed the same subtelomeric and central var genes, except for var2csa

Conclusions: The duration of intrahost replication influences in vitro var gene transcript patterns. Differences between premosquito and postpatient cultures decrease with prolonged in vitro growth.
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http://dx.doi.org/10.1093/infdis/jiw225DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4996147PMC
September 2016

A barrier to metal movement: Synchrotron study of iron plaque on roots of wetland plants.

J Environ Sci (China) 2016 Jun 12;44:1-3. Epub 2016 May 12.

Royal Military College of Canada, Kingston, Ontario, Canada.

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http://dx.doi.org/10.1016/j.jes.2016.05.001DOI Listing
June 2016

Manipulation of Superparamagnetic Beads on Patterned Exchange-Bias Layer Systems for Biosensing Applications.

Sensors (Basel) 2015 Nov 13;15(11):28854-88. Epub 2015 Nov 13.

Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel, Heinrich-Plett-Str.40, Kassel D-34132, Germany.

A technology platform based on a remotely controlled and stepwise transport of an array arrangement of superparamagnetic beads (SPB) for efficient molecular uptake, delivery and accumulation in the context of highly specific and sensitive analyte molecule detection for the application in lab-on-a-chip devices is presented. The near-surface transport of SPBs is realized via the dynamic transformation of the SPBs' magnetic potential energy landscape above a magnetically stripe patterned Exchange-Bias (EB) thin film layer systems due to the application of sub-mT external magnetic field pulses. In this concept, the SPB velocity is dramatically influenced by the magnitude and gradient of the magnetic field landscape (MFL) above the magnetically stripe patterned EB substrate, the SPB to substrate distance, the magnetic properties of both the SPBs and the EB layer system, respectively, as well as by the properties of the external magnetic field pulses and the surrounding fluid. The focus of this review is laid on the specific MFL design in EB layer systems via light-ion bombardment induced magnetic patterning (IBMP). A numerical approach is introduced for the theoretical description of the MFL in comparison to experimental characterization via scanning Hall probe microscopy. The SPB transport mechanism will be outlined in terms of the dynamic interplay between the EB substrate's MFL and the pulse scheme of the external magnetic field.
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http://dx.doi.org/10.3390/s151128854DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4701312PMC
November 2015

The LRR receptor Islr2 is required for retinal axon routing at the vertebrate optic chiasm.

Neural Dev 2015 Oct 22;10:23. Epub 2015 Oct 22.

Max-Planck-Institut für Entwicklungsbiologie, Abteilung Genetik, Spemannstraße 35, 72076, Tübingen, Germany.

Background: In the visual system of most binocular vertebrates, the axons of retinal ganglion cells (RGCs) diverge at the diencephalic midline and extend to targets on both ipsi- and contralateral sides of the brain. While a molecular mechanism explaining ipsilateral guidance decisions has been characterized, less is known of how RGC axons cross the midline.

Results: Here, we took advantage of the zebrafish, in which all RGC axons project contralaterally at the optic chiasm, to characterize Islr2 as an RGC receptor required for complete retinal axon midline crossing. We used a systematic extracellular protein-protein interaction screening assay to identify two Vasorin paralogs, Vasna and Vasnb, as specific Islr2 ligands. Antibodies against Vasna and Vasnb reveal cellular populations surrounding the retinal axon pathway, suggesting the involvement of these proteins in guidance decisions made by axons of the optic nerve. Specifically, Vasnb marks the membranes of a cellular barricade located anteriorly to the optic chiasm, a structure termed the "glial knot" in higher vertebrates. Loss of function mutations in either vasorin paralog, individually or combined, however, do not exhibit an overt retinal axon projection phenotype, suggesting that additional midline factors, acting either independently or redundantly, compensate for their loss. Analysis of Islr2 knockout mice supports a scenario in which Islr2 controls the coherence of RGC axons through the ventral midline and optic tract.

Conclusions: Although stereotypic guidance of RGC axons at the vertebrate optic chiasm is controlled by multiple, redundant mechanisms, and despite the differences in ventral diencephalic tissue architecture, we identify a novel role for the LRR receptor Islr2 in ensuring proper axon navigation at the optic chiasm of both zebrafish and mouse.
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http://dx.doi.org/10.1186/s13064-015-0050-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4618557PMC
October 2015

Biochar Soil Amendment Effects on Arsenic Availability to Mountain Brome ().

J Environ Qual 2015 Jul;44(4):1315-20

Biochar is a renewable energy byproduct that shows promise for remediating contaminated mine sites. A common contaminant at mine sites is arsenic (As). In this study, the effects of biochar amendments to a mine-contaminated soil on As concentrations in mountain brome ( Nees ex Steud.) were investigated. In the biochar-amended soil, mountain brome had greater root biomass and decreased root and shoot As concentrations. X-ray absorption near-edge structure spectroscopy results showed that arsenate [As(V)] is the predominant species in both the nonamended and biochar-amended soils. Soil extraction tests that measure phosphate and arsenate availability to plants failed to accurately predict plant tissue As concentrations, suggesting the arsenate bioavailability behavior in the soils is distinct from phosphate. Results from this study indicate that biochar will be a beneficial amendment to As-contaminated mine sites for remediation.
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http://dx.doi.org/10.2134/jeq2014.11.0477DOI Listing
July 2015

Transcriptomic Responses During Early Development Following Arsenic Exposure in Western Clawed Frogs, Silurana tropicalis.

Toxicol Sci 2015 Dec 1;148(2):603-17. Epub 2015 Oct 1.

*Chemistry and Chemical Engineering Department, Royal Military College of Canada, Kingston, ON, Canada, K7K 7B4;

Arsenic compounds are widespread environmental contaminants and exposure elicits serious health issues, including early developmental anomalies. Depending on the oxidation state, the intermediates of arsenic metabolism interfere with a range of subcellular events, but the fundamental molecular events that lead to speciation-dependent arsenic toxicity are not fully elucidated. This study therefore assesses the impact of arsenic exposure on early development by measuring speciation and gene expression profiles in the developing Western clawed frog (Silurana tropicalis) larvae following the environmental relevant 0.5 and 1 ppm arsenate exposure. Using HPLC-ICP-MS, arsenate, dimethylarsenic acid, arsenobetaine, arsenocholine, and tetramethylarsonium ion were detected. Microarray and pathway analyses were utilized to characterize the comprehensive transcriptomic responses to arsenic exposure. Clustering analysis of expression data showed distinct gene expression patterns in arsenate treated groups when compared with the control. Pathway enrichment revealed common biological themes enriched in both treatments, including cell signal transduction, cell survival, and developmental pathways. Moreover, the 0.5 ppm exposure led to the enrichment of pathways and biological processes involved in arsenic intake or efflux, as well as histone remodeling. These compensatory responses are hypothesized to be responsible for maintaining an in-body arsenic level comparable to control animals. With no appreciable changes observed in malformation and mortality between control and exposed larvae, this is the first study to suggest that the underlying transcriptomic regulations related to signal transduction, cell survival, developmental pathways, and histone remodeling may contribute to maintaining ongoing development while coping with the potential arsenic toxicity in S. tropicalis during early development.
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http://dx.doi.org/10.1093/toxsci/kfv207DOI Listing
December 2015

Life cycle exposure of the frog Silurana tropicalis to arsenate: Steroid- and thyroid hormone-related genes are differently altered throughout development.

Gen Comp Endocrinol 2016 08 21;234:133-41. Epub 2015 Sep 21.

Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Canada. Electronic address:

Arsenic contaminates water surface and groundwater worldwide. Several studies have suggested that arsenic acts as an endocrine disruptor in mammalian and non-mammalian species, although its chronic effect during development remains largely unknown. To address this question, life cycle exposures to 0, 0.3 and 0.8ppm of arsenate (pentavalent arsenic; As(V)) were performed in the Western clawed frog (Silurana tropicalis) from the gastrulae stage (developmental stage Nieuwkoop-Faber; NF12) until metamorphosis (NF66). Tissue samples were collected at the beginning of feeding (NF46; whole body), sexual development (NF56; liver), and at metamorphosis completion (NF66; liver and gonadal mesonephros complex). Real-time RT-PCR analysis quantified decreases in mRNA levels of genes related to estrogen- (estrogen receptor alpha and aromatase), androgen- (androgen receptor and steroid 5-alpha-reductase type 2), and cholesterol metabolism- (steroidogenic acute regulatory protein) at stage NF46. Similarly, arsenate decreased steroid 5-alpha-reductase type 2 expression in stage NF56 livers, but transcript increases were observed for both estrogen receptor alpha and steroidogenic acute regulatory protein at this stage. Given the changes observed in the expression of genes essential for proper sexual development, gonadal histological analysis was carried out in stage NF66 animals. Arsenate treatments did not alter sex ratio or produce testicular oocytes. On the other hand, arsenate interfered with thyroid hormone-related transcripts at NF66. Specifically, thyroid hormone receptor beta and deiodinase type 2 mRNA levels were significantly reduced after arsenate treatment in the gonadal mesonephros complex. This reduction in thyroid hormone-related gene expression, however, was not accompanied by any morphological changes measured. In summary, environmentally relevant concentrations of As(V) altered steroidogenesis-, sex steroid signaling- and thyroid hormone-related gene expression, although transcriptional changes varied among tissues and developmental stages.
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http://dx.doi.org/10.1016/j.ygcen.2015.09.015DOI Listing
August 2016

Directed Magnetic Particle Transport above Artificial Magnetic Domains Due to Dynamic Magnetic Potential Energy Landscape Transformation.

ACS Nano 2015 Jul 8;9(7):7323-31. Epub 2015 Jul 8.

Institute of Physics and Centre for Interdisciplinary Nanostructure Science and Technology (CINSaT),University of Kassel, Heinrich-Plett-Strasse 40, D-34132 Kassel, Germany.

An approach for a remotely controllable transport of magnetic micro- and/or nanoparticles above a topographically flat exchange-bias (EB) thin film system, magnetically patterned into parallel stripe domains, is presented where the particle manipulation is achieved by sub-mT external magnetic field pulses. Superparamagnetic core-shell particles are moved stepwise by the dynamic transformation of the particles' magnetic potential energy landscape due to the external magnetic field pulses without affecting the magnetic state of the thin film system. The magnetic particle velocity is adjustable in the range of 1-100 μm/s by the design of the substrate's magnetic field landscape (MFL), the particle-substrate distance, and the magnitude of the applied external magnetic field pulses. The agglomeration of magnetic particles is avoided by the intrinsic magnetostatic repulsion of particles due to the parallel alignment of the particles' magnetic moments perpendicular to the transport direction and parallel to the surface normal of the substrate during the particle motion. The transport mechanism is modeled by a quantitative theory based on the precise knowledge of the sample's MFL and the particle-substrate distance.
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http://dx.doi.org/10.1021/acsnano.5b02283DOI Listing
July 2015

Adenylate cyclase 5 is required for melanophore and male pattern development in the guppy (Poecilia reticulata).

Pigment Cell Melanoma Res 2015 Sep 17;28(5):545-58. Epub 2015 Jul 17.

Max Planck Institute for Developmental Biology, Tübingen, Germany.

Guppies (Poecilia reticulata) are colorful fish that have attracted the attention of pigmentation researchers for almost a century. Here, we report that the blond phenotype of the guppy is caused by a spontaneous mutation in the guppy ortholog of adenylate cyclase 5 (adcy5). Using double digest restriction site-associated DNA sequencing (ddRADseq) and quantitative trait locus (QTL) mapping, we linked the blond phenotype to a candidate region of 118 kb, in which we subsequently identified a 2-bp deletion in adcy5 that alters splicing and leads to a premature stop codon. We show that adcy5, which affects life span and melanoma growth in mouse, is required for melanophore development and formation of male orange pigmentation traits in the guppy. We find that some components of the male orange pattern are particularly sensitive to loss of Adcy5 function. Our work thus reveals a function for Adcy5 in patterning of fish color ornaments.
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http://dx.doi.org/10.1111/pcmr.12386DOI Listing
September 2015

Strategies of Gammarus pulex L. to cope with arsenic--Results from speciation analyses by IC-ICP-MS and XAS micro-mapping.

Sci Total Environ 2015 Oct 8;530-531:430-433. Epub 2015 Jun 8.

Environmental Geochemistry, Bayreuth Center for Ecology and Environmental Research (BayCEER), University Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.

The invertebrate shredder Gammarus pulex L. is a key species for aquatic carbon turnover via litter decomposition and can thrive in high-arsenic (As) environments. To understand their strategies for coping with increased As concentrations while fulfilling their ecosystem functions, we analyzed the As concentration and speciation in their aquatic habitat and in leaves with heterotrophic biofilms as their natural food source. We also followed the As distribution and speciation on the cuticle and within the body of G. pulex by X-ray absorption spectroscopic imaging. Half of the total As on G. pulex was found to be associated with the cuticle but was not taken up. Removing this externally bound As yielded only arsenate in the wash solution which reflects the speciation of the surrounding aquatic phase and shows that this As does not undergo any biotransformation. The major pathway into the organism is suggested to be incorporation via food intake, but only very low amounts of As were taken up or translocated from the gut system to other tissues. In one of the main food sources, leaves, 68% arsenate and 29% monomethylarsenate were found. After ingestion into the gut system, up to 23% of the more toxic arsenite was seen, but a substantial share was methylated to dimethylarsenate (46-56%). Little arsenate and arsenite were found in the adjacent tissues. Besides 76-80% mono- and di-methylarsenate, 10-21% of the As was complexed as As(III)-S species. G. pulex plays an important role in As cycling and our results indicate that As translocation from the gut to other tissues is minimized, but a transformation to other As-species occurred.
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http://dx.doi.org/10.1016/j.scitotenv.2015.06.015DOI Listing
October 2015

Arsenic(+3) and DNA methyltransferases, and arsenic speciation in tadpole and frog life stages of western clawed frogs (Silurana tropicalis) exposed to arsenate.

Metallomics 2015 Aug 12;7(8):1274-84. Epub 2015 Jun 12.

Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Canada.

Western clawed frog (Silurana tropicalis) embryos were exposed to control, low (nominally 0.5 mg L(-1)) and high (nominally 1 mg L(-1)) arsenate (As(V)) culture water concentrations to investigate the effects of arsenic (As) on different life stages, namely tadpole (Nieuwkoop and Faber stage 56, NF56) and frog stages (NF66). The effects were assessed by measuring arsenic(+3) and DNA methyltransferases (AS3MT and DNMT1), as well as As speciation in the tissues. The As content in frog tissues increased with water As concentration. The As species observed by high performance liquid chromatography - inductively coupled plasma mass spectrometry (HPLC-ICPMS) were mostly inorganic, dimethylarsinic acid (DMA) and trimethylarsine oxide (TMAO). With solid state X-ray absorption near edge structure (XANES) analysis, arsenobetaine/tetramethylarsonium ion were also seen. AS3MT levels decreased upon low As exposure in NF56, rising again to control levels at the high As exposure. In NF66 tissues, on the other hand, AS3MT decreased only with NF66 high As exposure. DNMT1 increased with exposure, and this was statistically significant only for the high As exposure at both life stages. Thus these enzymes seem to be affected by the As exposure. Methylation of As to form monomethylarsonate (MMA), DMA and TMAO in the frogs appeared to be inversely related to AS3MT levels. A possible interpretation of this finding is that when AS3MT is higher, excretion of MMA + DMA + TMAO is more efficient, leaving lower concentrations in the tissues, with the opposite effect (less excretion) when AS3MT is lower; alternatively, other enzymes or linked genes may affect the methylation of As.
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http://dx.doi.org/10.1039/c5mt00078eDOI Listing
August 2015

Excretion of cytoplasmic proteins (ECP) in Staphylococcus aureus.

Mol Microbiol 2015 Aug 19;97(4):775-89. Epub 2015 Jun 19.

Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany.

Excretion of cytoplasmic proteins (ECP) is a common physiological feature in bacteria and eukaryotes. However, how these proteins without a typical signal peptide are excreted in bacteria is poorly understood. We studied the excretion pattern of cytoplasmic proteins using two glycolytic model enzymes, aldolase and enolase, and show that their excretion takes place mainly during the exponential growth phase in Staphylococcus aureus very similar to that of Sbi, an IgG-binding protein, which is secreted via the Sec-pathway. The amount of excreted enolase is substantial and is comparable with that of Sbi. For localization of the exit site, we fused aldolase and enolase with the peptidoglycan-binding motif, LysM, to trap the enzymes at the cell wall. With both immune fluorescence labeling and immunogold localization on electron microscopic thin sections aldolase and enolase were found apart from the cytoplasmic area particularly in the cross wall and at the septal cleft of dividing cells, whereas the non-excreted Ndh2, a soluble NADH:quinone oxidoreductase, is only seen attached to the inner side of the cytoplasmic membrane. The selectivity, the timing and the localization suggest that ECP is not a result of unspecific cell lysis but is mediated by an as yet unknown mechanism.
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http://dx.doi.org/10.1111/mmi.13065DOI Listing
August 2015

Uptake and transformation of arsenic during the vegetative life stage of terrestrial fungi.

Environ Pollut 2015 Feb 15;197:108-115. Epub 2014 Dec 15.

Environmental Sciences Group, Royal Military College of Canada, P.O. Box 17000 Station Forces, Kingston, ON K7K 7B4, Canada. Electronic address:

Many species of terrestrial fungi produce fruiting bodies that contain high proportions of arsenobetaine (AB), an arsenic compound of no known toxicity. It is unknown whether fungi produce or accumulate AB from the surrounding environment. The present study targets the vegetative life stage (mycelium) of fungi, to examine the role of this stage in arsenic transformations and potential formation of AB. The mycelia of three different fungi species were cultured axenically and exposed to AB, arsenate (As(V)) and dimethylarsinoyl acetic acid for 60 days. Agaricus bisporus was additionally exposed to hypothesized precursors for AB and the exposure time to As(V) and dimethlyarsinic acid was also extended to 120 days. The mycelia of all fungi species accumulated all arsenic compounds with two species accumulating significantly more AB than other compounds. Few biotransformations were observed in these experiments indicating that it is unlikely that the mycelium of the fungus is responsible for biosynthesizing AB.
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http://dx.doi.org/10.1016/j.envpol.2014.12.006DOI Listing
February 2015

Arsenic speciation in edible mushrooms.

Environ Sci Technol 2014 Dec 2;48(24):14203-10. Epub 2014 Dec 2.

Environmental Sciences Group, Royal Military College of Canada , P.O. Box 17000, Station Forces, Kingston, Ontario, Canada K7K 7B4.

The fruiting bodies, or mushrooms, of terrestrial fungi have been found to contain a high proportion of the nontoxic arsenic compound arsenobetaine (AB), but data gaps include a limited phylogenetic diversity of the fungi for which arsenic speciation is available, a focus on mushrooms with higher total arsenic concentrations, and the unknown formation and role of AB in mushrooms. To address these, the mushrooms of 46 different fungus species (73 samples) over a diverse range of phylogenetic groups were collected from Canadian grocery stores and background and arsenic-contaminated areas. Total arsenic was determined using ICP-MS, and arsenic speciation was determined using HPLC-ICP-MS and complementary X-ray absorption spectroscopy (XAS). The major arsenic compounds in mushrooms were found to be similar among phylogenetic groups, and AB was found to be the major compound in the Lycoperdaceae and Agaricaceae families but generally absent in log-growing mushrooms, suggesting the microbial community may influence arsenic speciation in mushrooms. The high proportion of AB in mushrooms with puffball or gilled morphologies may suggest that AB acts as an osmolyte in certain mushrooms to help maintain fruiting body structure. The presence of an As(III)-sulfur compound, for the first time in mushrooms, was identified in the XAS analysis. Except for Agaricus sp. (with predominantly AB), inorganic arsenic predominated in most of the store-bought mushrooms (albeit with low total arsenic concentrations). Should inorganic arsenic predominate in these mushrooms from contaminated areas, the risk to consumers under these circumstances should be considered.
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http://dx.doi.org/10.1021/es5038468DOI Listing
December 2014

Hazard detection in noise-related incidents - the role of driving experience with battery electric vehicles.

Accid Anal Prev 2014 Dec 8;73:380-91. Epub 2014 Oct 8.

Department of Psychology, Technische Universität Chemnitz, Chemnitz, Germany.

The low noise emission of battery electric vehicles (BEVs) has led to discussions about how to address potential safety issues for other road users. Legislative actions have already been undertaken to implement artificial sounds. In previous research, BEV drivers reported that due to low noise emission they paid particular attention to pedestrians and bicyclists. For the current research, we developed a hazard detection task to test whether drivers with BEV experience respond faster to incidents, which arise due to the low noise emission, than inexperienced drivers. The first study (N=65) revealed that BEV experience only played a minor role in drivers' response to hazards resulting from low BEV noise. The tendency to respond, reaction times and hazard evaluations were similar among experienced and inexperienced BEV drivers; only small trends in the assumed direction were observed. Still, both groups clearly differentiated between critical and non-critical scenarios and responded accordingly. In the second study (N=58), we investigated additionally if sensitization to low noise emission of BEVs had an effect on hazard perception in incidents where the noise difference is crucial. Again, participants in all groups differentiated between critical and non-critical scenarios. Even though trends in response rates and latencies occurred, experience and sensitization to low noise seemed to only play a minor role in detecting hazards due to low BEV noise. An additional global evaluation of BEV noise further suggests that even after a short test drive, the lack of noise is perceived more as a comfort feature than a safety threat.
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http://dx.doi.org/10.1016/j.aap.2014.09.016DOI Listing
December 2014

A dominant mutation in tyrp1A leads to melanophore death in zebrafish.

Pigment Cell Melanoma Res 2014 Sep 3;27(5):827-30. Epub 2014 Jul 3.

Max Planck Institute for Developmental Biology, Tübingen, Germany.

Melanin biosynthesis in vertebrates depends on the function of three enzymes of the tyrosinase family, tyrosinase (Tyr), tyrosinase-related protein 1 (Tyrp1), and dopachrome tautomerase (Dct or Tyrp2). Tyrp1 might play an additional role in the survival and proliferation of melanocytes. Here, we describe a mutation in tyrp1A, one of the two tyrp1 paralogs in zebrafish, which causes melanophore death leading to a semi-dominant phenotype. The mutation, an Arg->Cys change in the amino-terminal part of the protein, is similar to mutations in humans and mice where they lead to blond hair (in melanesians) or dark hair with white bases, respectively. We demonstrate that the phenotype in zebrafish depends on the presence of the mutant protein and on melanin synthesis. Ultrastructural analysis shows that the melanosome morphology and pigment content are altered in the mutants. These structural changes might be the underlying cause for the observed cell death, which, surprisingly, does not result in patterning defects.
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http://dx.doi.org/10.1111/pcmr.12272DOI Listing
September 2014
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