Publications by authors named "Jonas Zaugg"

8 Publications

  • Page 1 of 1

Counter-directed leucine gradient promotes amino acid transfer across the human placenta.

J Nutr Biochem 2021 May 6;96:108760. Epub 2021 May 6.

Institute of Biochemistry and Molecular Medicine, Faculty of Medicine, University of Bern, Switzerland; Swiss National Centre of Competence in Research (NCCR) TransCure, University of Bern, Switzerland. Electronic address:

The developing fetus is highly vulnerable to imbalances in the supply of essential amino acids (AA). Transplacental AA transfer depends on complex interactions between accumulative transporters, exchangers and facilitators, which maintain both intra-extracellular and materno-fetal substrate gradients. We determined physiological AA gradients between maternal and fetal blood and assessed their importance by studying maternal-fetal leucine transfer in human trophoblasts. Maternal-venous and corresponding fetal-arterial/fetal-venous sera were collected from 22 healthy patients at partum. The acquisition of the full AA spectra in serum was performed by ion exchange chromatography. Physiological materno-fetal AA levels were evaluated using paired two-way ANOVA with Tukey's correction. AA concentrations and gradients were tested for associations with anthropometric data by Spearman correlation analysis. Functional effects of a physiological leucine gradient versus equimolar concentrations were tested in BeWo cells using L-[H]-leucine in conventional and Transwell-based uptake and transfer experiments. The LAT1/SLC7A5-specific inhibitor JPH203 was used to evaluate LAT1-transporter-mediated leucine transport. Maternal AA concentrations correlated with preconceptional and maternal weights at partum. Interestingly, low materno-fetal AA gradients were associated with maternal weight, BMI and gestational weight gain. Leucine uptake was promoted by increased extracellular substrate concentrations. Materno-fetal leucine transfer was significantly increased against a 137µM leucine gradient demonstrating that transplacental leucine transport is stimulated by a counter-directed gradient. Moreover, leucine transfer was inhibited by 10µM JPH203 confirming that Leu transport across the trophoblast monolayer is LAT1-dependent. This study demonstrates a currently underestimated effect of transplacental AA gradients on efficient leucine transfer which could severely affect fetal development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jnutbio.2021.108760DOI Listing
May 2021

Dynamics of Tryptophan Metabolic Pathways in Human Placenta and Placental-Derived Cells: Effect of Gestation Age and Trophoblast Differentiation.

Front Cell Dev Biol 2020 18;8:574034. Epub 2020 Sep 18.

Department of Pharmacology and Toxicology, Faculty of Pharmacy in Hradec Kralove, Charles University, Hradec Kralove, Czechia.

L-Tryptophan is an essential amino acid and a precursor of several physiologically active metabolites. In the placenta, the serotonin and kynurenine metabolic pathways of tryptophan metabolism have been identified, giving rise to various molecules of neuroactive or immunoprotective properties, such as serotonin, melatonin, kynurenine, kynurenic acid, or quinolinic acid. Current literature suggests that optimal levels of these molecules in the fetoplacental unit are crucial for proper placenta functions, fetal development and programming. Placenta is a unique endocrine organ that, being equipped with a battery of biotransformation enzymes and transporters, precisely orchestrates homeostasis of tryptophan metabolic pathways. However, because pregnancy is a dynamic process and placental/fetal needs are continuously changing throughout gestation, placenta must adapt to these changes and ensure proper communication in the feto-placental unit. Therefore, in this study we investigated alterations of placental tryptophan metabolic pathways throughout gestation. Quantitative polymerase chain reaction (PCR) analysis of 21 selected genes was carried out in first trimester ( = 13) and term ( = 32) placentas. Heatmap analysis with hierarchical clustering revealed differential gene expression of serotonin and kynurenine pathways across gestation. Subsequently, digital droplet PCR, Western blot, and functional analyses of the rate-limiting enzymes suggest preferential serotonin synthesis early in pregnancy with a switch to kynurenine production toward term. Correspondingly, increased function and/or protein expression of serotonin degrading enzyme and transporters at term indicates efficient placental uptake and metabolic degradation of serotonin. Lastly, gene expression analysis in choriocarcinoma-derived cell lines (BeWo, BeWo b30, JEG-3) revealed dissimilar expression patterns and divergent effect of syncytialization compared to primary trophoblast cells isolated from human term placentas; these findings show that the commonly used placental models are not suitable to study placental handling of tryptophan. Altogether, our data provide the first comprehensive evidence of changes in placental homeostasis of tryptophan and its metabolites as a function of gestational age, which is critical for proper placental function and fetal development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fcell.2020.574034DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7530341PMC
September 2020

Small molecule inhibitors provide insights into the relevance of LAT1 and LAT2 in materno-foetal amino acid transport.

J Cell Mol Med 2020 11 1;24(21):12681-12693. Epub 2020 Oct 1.

Institute of Biochemistry and Molecular Medicine, Faculty of Medicine, University of Bern, Bern, Switzerland.

The placenta supplies the foetus with critical nutrients such as essential amino acids (AA, eg leucine) for development and growth. It also represents a cellular barrier which is formed by a polarized, differentiated syncytiotrophoblast (STB) monolayer. Active Na -independent leucine transport across the placenta is mainly attributed to the System L transporters LAT1/SLC7A5 and LAT2/SLC7A8. This study explored the influence of trophoblast differentiation on the activity of LAT1/LAT2 and the relevance of LAT1/LAT2 in leucine uptake and transfer in trophoblasts by applying specific small molecule inhibitors (JPH203/JG336/JX009). L-leucine uptake (total dose = 167 μmol/L) was sensitive to LAT1-specific inhibition by JPH203 (EC  = 2.55 µmol/L). The inhibition efficiency of JPH203 was increased by an additional methoxy group in the JPH203-derivate JG336 (EC  = 1.99 µmol/L). Interestingly, JX009 showed efficient System L inhibition (EC  = 2.35 µmol/L) and was the most potent inhibitor of leucine uptake in trophoblasts. The application of JPH203 and JX009 in Transwell -based leucine transfer revealed LAT1 as the major accumulative transporter at the apical membrane, but other System L transporters such as LAT2 as rate-limiting for leucine efflux across the basal membrane. Therefore, differential specificity of the applied inhibitors allowed for estimation of the contribution of LAT1 and LAT2 in materno-foetal AA transfer and their potential impact in pregnancy diseases associated with impaired foetal growth.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/jcmm.15840DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7687008PMC
November 2020

Cryo-EM structures and functional properties of CALHM channels of the human placenta.

Elife 2020 05 6;9. Epub 2020 May 6.

Department of Biochemistry, University of Zurich, Zurich, Switzerland.

The transport of substances across the placenta is essential for the development of the fetus. Here, we were interested in the role of channels of the calcium homeostasis modulator (CALHM) family in the human placenta. By transcript analysis, we found the paralogs CALHM2, 4, and 6 to be highly expressed in this organ and upregulated during trophoblast differentiation. Based on electrophysiology, we observed that activation of these paralogs differs from the voltage- and calcium-gated channel CALHM1. Cryo-EM structures of CALHM4 display decameric and undecameric assemblies with large cylindrical pore, while in CALHM6 a conformational change has converted the pore shape into a conus that narrows at the intracellular side, thus describing distinct functional states of the channel. The pore geometry alters the distribution of lipids, which occupy the cylindrical pore of CALHM4 in a bilayer-like arrangement whereas they have redistributed in the conical pore of CALHM6 with potential functional consequences.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.7554/eLife.55853DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7242029PMC
May 2020

Gestational diabetes mellitus affects placental iron homeostasis: Mechanism and clinical implications.

FASEB J 2020 06 14;34(6):7311-7329. Epub 2020 Apr 14.

Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.

Clinical studies suggest that pregnant women with elevated iron levels are more vulnerable to develop gestational diabetes mellitus (GDM), but the causes and underlying mechanisms are unknown. We hypothesized that hyperglycemia induces cellular stress responses leading to dysregulated placental iron homeostasis. Hence, we compared the expression of genes/proteins involved in iron homeostasis in placentae from GDM and healthy pregnancies (n = 11 each). RT-qPCR and LC-MS/MS analyses revealed differential regulation of iron transporters/receptors (DMT1/FPN1/ZIP8/TfR1), iron sensors (IRP1), iron regulators (HEPC), and iron oxidoreductases (HEPH/Zp). To identify the underlying mechanisms, we adapted BeWo trophoblast cells to normoglycemic (N), hyperglycemic (H), and hyperglycemic-hyperlipidemic (HL) conditions and assessed Fe -uptake, expression patterns, and cellular pathways involving oxidative stress (OS), ER-stress, and autophagy. H and HL induced alterations in cellular morphology, differential iron transporter expression, and reduced Fe -uptake confirming the impact of hyperglycemia on iron transport observed in GDM patients. Pathway analysis and rescue experiments indicated that dysregulated OS and disturbed autophagy processes contribute to the reduced placental iron transport under hyperglycemic conditions. These adaptations could represent a protective mechanism preventing the oxidative damage for both fetus and placenta caused by highly oxidative iron. In pregnancies with risk for GDM, antioxidant treatment, and controlled iron supplementation could help to balance placental OS levels protecting mother and fetus from impaired iron homeostasis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1096/fj.201903054RDOI Listing
June 2020

Placental miR-340 mediates vulnerability to activity based anorexia in mice.

Nat Commun 2018 04 23;9(1):1596. Epub 2018 Apr 23.

Department of Neurobiology, Weizmann Institute of Science, 7610001, Rehovot, Israel.

Anorexia nervosa (AN) is a devastating eating disorder characterized by self-starvation that mainly affects women. Its etiology is unknown, which impedes successful treatment options leading to a limited chance of full recovery. Here, we show that gestation is a vulnerable window that can influence the predisposition to AN. By screening placental microRNA expression of naive and prenatally stressed (PNS) fetuses and assessing vulnerability to activity-based anorexia (ABA), we identify miR-340 as a sexually dimorphic regulator involved in prenatal programming of ABA. PNS caused gene-body hypermethylation of placental miR-340, which is associated with reduced miR-340 expression and increased protein levels of several target transcripts, GR, Cry2 and H3F3b. MiR-340 is linked to the expression of several nutrient transporters both in mice and human placentas. Using placenta-specific lentiviral transgenes and embryo transfer, we demonstrate the key role miR-340 plays in the mechanism involved in early life programming of ABA.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-018-03836-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5913294PMC
April 2018

Maximizing mutagenesis with solubilized CRISPR-Cas9 ribonucleoprotein complexes.

Development 2016 06 29;143(11):2025-37. Epub 2016 Apr 29.

Institute of Molecular Life Sciences, University of Zürich, Zürich 8057, Switzerland

CRISPR-Cas9 enables efficient sequence-specific mutagenesis for creating somatic or germline mutants of model organisms. Key constraints in vivo remain the expression and delivery of active Cas9-sgRNA ribonucleoprotein complexes (RNPs) with minimal toxicity, variable mutagenesis efficiencies depending on targeting sequence, and high mutation mosaicism. Here, we apply in vitro assembled, fluorescent Cas9-sgRNA RNPs in solubilizing salt solution to achieve maximal mutagenesis efficiency in zebrafish embryos. MiSeq-based sequence analysis of targeted loci in individual embryos using CrispRVariants, a customized software tool for mutagenesis quantification and visualization, reveals efficient bi-allelic mutagenesis that reaches saturation at several tested gene loci. Such virtually complete mutagenesis exposes loss-of-function phenotypes for candidate genes in somatic mutant embryos for subsequent generation of stable germline mutants. We further show that targeting of non-coding elements in gene regulatory regions using saturating mutagenesis uncovers functional control elements in transgenic reporters and endogenous genes in injected embryos. Our results establish that optimally solubilized, in vitro assembled fluorescent Cas9-sgRNA RNPs provide a reproducible reagent for direct and scalable loss-of-function studies and applications beyond zebrafish experiments that require maximal DNA cutting efficiency in vivo.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1242/dev.134809DOI Listing
June 2016