A rapid and simple procedure for the isolation and cultivation of fibroblast-like cells from medaka and zebrafish embryos and fin clip biopsies

Beedgen L., Hullen A., Gücüm, S., Thumberger, T., Wittbrodt, J. and Thiel C. (2021)

Published: September 22, 2021    DOI: 10.1177/00236772211045483


In many human diseases, the molecular pathophysiological mechanisms are not understood, which makes the development and testing of new therapeutic approaches difficult. The generation and characterization of animal models such as mice, rats, fruit flies, worms or fish offers the possibility for in detail studies of a disease’s development, its course and potential therapies in an organismal context, which considerably minimizes the risk of therapeutic side effects for patients. Nevertheless, due to the high numbers of experimental animals used in research worldwide, attempts to develop alternative test systems will help in reducing their count. In this regard, the cell culture system displays a suitable option due to its potential of delivering nearly unlimited material and the good opportunities for high-throughput studies such as drug testing. Here, we describe a quick and simple method to isolate and cultivate vital fibroblast-like cells from embryos and adults of two popular teleost model organisms, the Japanese rice fish medaka (Oryzias latipes) and the zebrafish (Danio rerio).


A spoonful of L-fucose-an efficient therapy for GFUS-CDG, a new glycosylation disorder

Rene G Feichtinger, Andreas Hullen, Andreas Koller, Dieter Kotzot, Valerian Grote, Erdmann Rapp, Peter Hofbauer, Karin Brugger,  Johannes A Mayr & Saskia B Wortmann (2021)

Published: September 07, 2021    DOI: 10.15252/emmm.202114332


Congenital disorders of glycosylation are a genetically and phenotypically heterogeneous family of diseases affecting the co- and posttranslational modification of proteins. Using exome sequencing, we detected biallelic variants in GFUS (NM_003313.4) c.[632G>A];[659C>T] (p.[Gly211Glu];[Ser220Leu]) in a patient presenting with global developmental delay, mild coarse facial features and faltering growth. GFUS encodes GDP-L-fucose synthase, the terminal enzyme in de novo synthesis of GDP-L-fucose, required for fucosylation of N- and O-glycans. We found reduced GFUS protein and decreased GDP-L-fucose levels leading to a general hypofucosylation determined in patient’s glycoproteins in serum, leukocytes, thrombocytes and fibroblasts. Complementation of patient fibroblasts with wild-type GFUS cDNA restored fucosylation. Making use of the GDP-L-fucose salvage pathway, oral fucose supplementation normalized fucosylation of proteins within 4 weeks as measured in serum and leukocytes. During the follow-up of 19 months, a moderate improvement of growth was seen, as well as a clear improvement of cognitive skills as measured by the Kaufmann ABC and the Nijmegen Pediatric CDG Rating Scale. In conclusion, GFUS-CDG is a new glycosylation disorder for which oral L-fucose supplementation is promising.


Congenital disorders of glycosylation with defective fucosylation

Andreas Hüllen, Kristina Falkenstein, Corina Weigel, Hidde Huidekoper, Nora Naumann-Bartsch, Johannes Spenger, René G. Feichtinger, Jacqueline Schaefers, Stephanie Frenz, Daniel Kotlarz, Tooba Momen, Razieh Khoshnevisan, Korbinian M. Riedhammer, René Santer, Theresia Herget, Alexander Rennings, Dirk J. Lefeber, Johannes A. Mayr, Christian Thiel and Saskia B. Wortmann (2021)

Published: August 12, 2021    DOI: 10.1002/jimd.12426


Fucosylation is essential for intercellular and intracellular recognition, cell-cell interaction, fertilization, and inflammatory processes. Only five types of congenital disorders of glycosylation (CDG) related to an impaired fucosylation have been described to date: FUT8-CDG, FCSK-CDG, POFUT1-CDG SLC35C1-CDG, and the only recently described GFUS-CDG. This review summarizes the clinical findings of all hitherto known 25 patients affected with those defects with regard to their pathophysiology and genotype. In addition, we describe five new patients with novel variants in the SLC35C1 gene. Furthermore, we discuss the efficacy of fucose therapy approaches within the different defects.

Glycosyltransferase POMGNT1 deficiency strengthens N-cadherin-mediated cell-cell adhesion

Sina Ibne Noor, Marcus Hoffmann, Natalie Rinis, Markus F. Bartels, Patrick Winterhalter, Christina Hoelscher, René Hennig, Nastassja Himmelreich, Christian Thiel, Thomas Ruppert, Erdmann Rapp and Sabine Strahl (2021)

Published: February 18, 2021   DOI: 10.1016/j.jbc.2021.100433


Defects in protein O-mannosylation lead to severe congenital muscular dystrophies collectively known as α-dystroglycanopathy. A hallmark of these diseases is the loss of the O-mannose-bound matriglycan on α-dystroglycan, which reduces cell adhesion to the extracellular matrix. Mutations in protein O-mannose β1,2-N-acetylglucosaminyltransferase 1 (POMGNT1), which is crucial for the elongation of O-mannosyl glycans, have mainly been associated with muscle-eye-brain (MEB) disease. In addition to defects in cell-extracellular matrix adhesion, aberrant cell-cell adhesion has occasionally been observed in response to defects in POMGNT1. However, specific molecular consequences of POMGNT1 deficiency on cell-cell adhesion are largely unknown. We used POMGNT1 knockout HEK293T cells and fibroblasts from an MEB patient to gain deeper insight into the molecular changes in POMGNT1 deficiency. Biochemical and molecular biological techniques combined with proteomics, glycoproteomics, and glycomics revealed that a lack of POMGNT1 activity strengthens cell-cell adhesion. We demonstrate that the altered intrinsic adhesion properties are due to an increased abundance of N-cadherin (N-Cdh). In addition, site-specific changes in the N-glycan structures in the extracellular domain of N-Cdh were detected, which positively impact on homotypic interactions. Moreover, in POMGNT1-deficient cells, ERK1/2 and p38 signaling pathways are activated and transcriptional changes that are comparable with the epithelial-mesenchymal transition (EMT) are triggered, defining a possible molecular mechanism underlying the observed phenotype. Our study indicates that changes in cadherin-mediated cell-cell adhesion and other EMT-related processes may contribute to the complex clinical symptoms of MEB or α-dystroglycanopathy in general and suggests that the impact of changes in O-mannosylation on N-glycosylation has been underestimated.

A patient-based medaka alg2 mutant as a model for hypo-N-glycosylation

Gücüm, S., Sakson, R., Hoffmann, M., Grote, V., Becker, C., Pakari, K., Beedgen, L., Thiel, C., Rapp, E., Ruppert, T., Thumberger, T., Wittbrodt, J. (2021)

Published: June 09, 2021    doi: https://doi.org/10.1242/dev.199385


Defects in the evolutionarily conserved protein-glycosylation machinery during embryonic development are often fatal. Consequently, congenital disorders of glycosylation (CDG) in human are rare. We modelled a putative hypomorphic mutation described in an alpha-1,3/1,6-mannosyltransferase (ALG2) index patient (ALG2-CDG) to address the developmental consequences in the teleost medaka (Oryzias latipes). We observed specific, multisystemic, late-onset phenotypes, closely resembling the patient’s syndrome, prominently in the facial skeleton and in neuronal tissue. Molecularly, we detected reduced levels of N-glycans in medaka and in the patient’s fibroblasts. This hypo-N-glycosylation prominently affected protein abundance. Proteins of the basic glycosylation and glycoprotein-processing machinery were over-represented in a compensatory response, highlighting the regulatory topology of the network. Proteins of the retinal phototransduction machinery, conversely, were massively under-represented in the alg2 model. These deficiencies relate to a specific failure to maintain rod photoreceptors, resulting in retinitis pigmentosa characterized by the progressive loss of these photoreceptors. Our work has explored only the tip of the iceberg of N-glycosylation-sensitive proteins, the function of which specifically impacts on cells, tissues and organs. Taking advantage of the well-described human mutation has allowed the complex interplay of N-glycosylated proteins and their contribution to development and disease to be addressed.


The C-mannosylome of human induced pluripotent stem cells implies a role for ADAMTS16 C-mannosylation in eye development

Karsten Cirksena, Hermann J.Hütte, Aleksandra Shcherbakova, Thomas Thumberger, Roman Sakson, Stefan Weiss, Lars Riff Jensen, Alina Friedrich, Daniel Todt, Andreas W.Kuss, Thomas Ruppert, Joachim Wittbrodt, Hans Bakker and Falk F.R.Buettner

Published: May 08, 2021    doi: https://doi.org/10.1242/dev.199385

Molecular & Cellular Proteomics


C-mannosylation is a modification of tryptophan residues with a single mannose, and can affect protein folding, secretion and/or function. To date, only a few proteins have been demonstrated to be C-mannosylated, and studies that globally assess protein C-mannosylation are scarce. To interrogate the C-mannosylome of human induced pluripotent stem cells (hiPSCs), we compared the secretomes of CRISPR-Cas9 mutants lacking either the C-mannosyltransferase DPY19L1 or DPY19L3 to wild-type hiPSCs using mass spectrometry-based quantitative proteomics. The secretion of numerous proteins was reduced in these mutants, including that of ADAMTS16, an extracellular protease that was previously reported to be essential for optic fissure fusion in zebrafish eye development. To test the functional relevance of this observation, we targeted dpy19l1 or dpy19l3 in embryos of the Japanese rice fish medaka (Oryzias latipes) by CRISPR-Cas9. We observed that targeting of dpy19l3 partially caused defects in optic fissure fusion, called coloboma. We further showed in a cellular model that DPY19L1 and DPY19L3 mediate C-mannosylation of a recombinantly expressed thrombospondin type 1 repeat of ADAMTS16 and thereby support its secretion. Taken together, our findings imply that DPY19L3-mediated C-mannosylation is involved in eye development by assisting secretion of the extracellular protease ADAMTS16.


Functional implications of MIR domains in protein O-mannosylation

Antonella Chiapparino, Antonija Grbavac, Hendrik RA Jonker, Yvonne Hackmann, Sofia Mortensen, Ewa Zatorska, Andrea Schott, Gunter Stier, Krishna Saxena, Klemens Wild, Harald Schwalbe, Sabine Strahl, Irmgard Sinning

eLife logo

Published: December 24, 2020    doi: 10.7554/eLife.61189


Protein O-mannosyltransferases (PMTs) represent a conserved family of multispanning endoplasmic reticulum membrane proteins involved in glycosylation of S/T-rich protein substrates and unfolded proteins. PMTs work as dimers and contain a luminal MIR domain with a β-trefoil fold, which is susceptive for missense mutations causing α-dystroglycanopathies in humans. Here, we analyze PMT-MIR domains by an integrated structural biology approach using X-ray crystallography and NMR spectroscopy and evaluate their role in PMT function in vivo. We determine Pmt2- and Pmt3-MIR domain structures and identify two conserved mannose-binding sites, which are consistent with general β-trefoil carbohydrate-binding sites (α, β), and also a unique PMT2-subfamily exposed FKR motif. We show that conserved residues in site α influence enzyme processivity of the Pmt1-Pmt2 heterodimer in vivo. Integration of the data into the context of a Pmt1-Pmt2 structure and comparison with homologous β-trefoil – carbohydrate complexes allows for a functional description of MIR domains in protein O-mannosylation.


Fatal outcome after heart surgery in PMM2-CDG due to a rare homozygous gene variant with double effects

Marlen Görlacher, Eleftheria Panagiotou, Nastassja Himmelreich, Andreas Hüllen, Lars Beedgen, Bianca Dimitrov, Virginia Geiger, Matthias Zielonka, Verena Peters, Sabine Strahl, Jaime Vázquez-Jiménez, Gunter Kerst, ChristianThiel

Molecular Genetics and Metabolism Reports

Published: November 7, 2020     DOI: 10.1016/j.ymgmr.2020.100673


Variants in Phosphomannomutase 2 (PMM2) lead to PMM2-CDG, the most frequent congenital disorder of glycosylation (CDG). We here describe the disease course of a ten-month old patient who presented with the classical PMM2-CDG symptoms as cerebellar hypoplasia, retinitis pigmentosa, seizures, short stature, hepato- and splenomegaly, anaemia, recurrent vomiting and inverted mamillae. A severe form of tetralogy of Fallot was diagnosed and corrective surgery was performed at the age of 10 months. At the end of the cardiopulmonary bypass, a sudden oedematous reaction of the myocardium accompanied by biventricular pump failure was observed immediately after heparin antagonization with protamine sulfate. The patient died seven days after surgery, since myocardial function did not recover on ECMO support. We here describe the first patient carrying the homozygous variant g.18313A > T in the PMM2 gene (NG_009209.1) that either can lead to c.394A > T (p.I132F) or even loss of 100 bp due to exon 5 skipping (c.348_447del; p.G117Rfs*4) which is comparable to a null allele. Proliferation and doubling time of the patient’s fibroblasts were affected. In addition, we show that the induction of cellular stress by elevating the cell culture temperature to 40 °C led to a decrease of the patients‘ PMM2 transcript as well as PMM2 protein levels and subsequently to a significant loss of residual activity. We assume that metabolic stressful processes occurring after cardiac surgery led to the drop of the patient’s PMM activity below a life-sustaining niveau which paved the way for the fatal outcome.


NMR characterization of the C-mannose conformation in a thrombospondin repeat using a selective labeling approach

Hendrik RA Jonker, Krishna Saxena, Aleksandra ShcherbakovaHans Bakker, Harald Schwalbe

Angewandte Chemie International Edition

Published: August 3, 2020       DOI: 10.1002/anie.202009489


Despite the great interest in glycoproteins, structural information reporting on conformation and dynamics of the sugar moieties are limited. We present a new biochemical method to express proteins with glycans that are selectively labeled with NMR active nuclei. We report on the incorporation of 13C-labeled mannose in the C-mannosylated UNC-5 thrombospondin repeat. The conformational landscape of the C-mannose sugar puckers attached to tryptophan residues of UNC-5 is characterized by interconversion between the canonical 1C4 state and the B03 / 1S3 state. This flexibility may be essential for protein folding and stabilization. We foresee that this versatile tool to produce proteins with selective labeled C-mannose can be applied and adjusted to other systems and modifications and potentially paves a way to advance glycoprotein research by unravelling the dynamical and conformational properties of glycan structures and their interactions.


C-mannosylation supports folding and enhances stability of thrombospondin repeats

Aleksandra ShcherbakovaMatthias PrellerManuel H TaftJordi PujolsSalvador VenturaBirgit TiemannFalk FR BuettnerHans Bakker

eLife logo

Published: December 23, 2019       https://doi: 10.7554/eLife.52978


Previous studies demonstrated importance of C-mannosylation for efficient protein secretion. To study its impact on protein folding and stability, we analyzed both C-mannosylated and non-C-mannosylated thrombospondin type 1 repeats (TSRs) of netrin receptor UNC-5. In absence of C-mannosylation, UNC-5 TSRs could only be obtained at low temperature and a significant proportion displayed incorrect intermolecular disulfide bridging, which was hardly observed when C-mannosylated. Glycosylated TSRs exhibited higher resistance to thermal and reductive denaturation processes, and the presence of C-mannoses promoted the oxidative folding of a reduced and denatured TSR in vitro. Molecular dynamics simulations supported the experimental studies and showed that C-mannoses can be involved in intramolecular hydrogen bonding and limit the flexibility of the TSR tryptophan-arginine ladder. We propose that in the endoplasmic reticulum folding process, C-mannoses orient the underlying tryptophan residues and facilitate the formation of the tryptophan-arginine ladder, thereby influencing the positioning of cysteines and disulfide bridging.


Membrane Topological Model of Glycosyltransferases of the GT-C Superfamily

Andreia Albuquerque-Wendt, Hermann J. Hütte, Falk F. R. Buettner, Françoise H. Routier, Hans Bakker


Published: September 29, 2019      https://doi: 10.3390/ijms20194842


Glycosyltransferases that use polyisoprenol-linked donor substrates are categorized in the GT-C superfamily. In eukaryotes, they act in the endoplasmic reticulum (ER) lumen and are involved in N-glycosylation, glypiation, O-mannosylation, and C-mannosylation of proteins. We generated a membrane topology model of C-mannosyltransferases (DPY19 family) that concurred perfectly with the 13 transmembrane domains (TMDs) observed in oligosaccharyltransferases (STT3 family) structures. A multiple alignment of family members from diverse organisms highlighted the presence of only a few conserved amino acids between DPY19s and STT3s. Most of these residues were shown to be essential for DPY19 function and are positioned in luminal loops that showed high conservation within the DPY19 family. Multiple alignments of other eukaryotic GT-C families underlined the presence of similar conserved motifs in luminal loops, in all enzymes of the superfamily. Most GT-C enzymes are proposed to have an uneven number of TDMs with 11 (POMT, TMTC, ALG9, ALG12, PIGB, PIGV, and PIGZ) or 13 (DPY19, STT3, and ALG10) membrane-spanning helices. In contrast, PIGM, ALG3, ALG6, and ALG8 have 12 or 14 TMDs and display a C-terminal dilysine ER-retrieval motif oriented towards the cytoplasm. We propose that all members of the GT-C superfamily are evolutionary related enzymes with preserved membrane topology.


Swift Large-scale Examination of Directed Genome Editing

Omar T. Hammouda, Frank Böttger, Joachim Wittbrodt, Thomas Thumberger



Published: March 5, 2019



In the era of CRISPR gene editing and genetic screening, there is an increasing demand for quick and reliable nucleic acid extraction pipelines for rapid genotyping of large and diverse sample sets. Despite continuous improvements of current workflows, the handling-time and material costs per sample remain major limiting factors. Here we present a robust method for low-cost DIY-pipet tips addressing these needs; i.e. using a cellulose filter disc inserted into a regular pipet tip. These filter-in-tips allow for a rapid, stand-alone four-step genotyping workflow by simply binding the DNA contained in the primary lysate to the cellulose filter, washing it in water and eluting it directly into the buffer for the downstream application (e.g. PCR). This drastically cuts down processing time to maximum 30 seconds per sample, with the potential for parallelizing and automation. We show the ease and sensitivity of our procedure by genotyping genetically modified medaka (Oryzias latipes) and zebrafish (Danio rerio) embryos (targeted by CRISPR/Cas9 knock-out and knock-in) in a 96-well plate format. The robust isolation and detection of multiple alleles of various abundancies in a mosaic genetic background allows phenotype-genotype correlation already in the injected generation, demonstrating the reliability and sensitivity of the protocol. Our method is applicable across kingdoms to samples ranging from cells to tissues i. e. plant seedlings, adult flies, mouse cell culture and tissue as well as adult fish fin-clips.


Novel variants and clinical symptoms in four new ALG3‐CDG patients review of the literature, and identification of AAGRP‐ALG3 as a novel ALG3 variant with alanine and glycine‐rich N‐terminus

Human Mutation
Variation, Informatics and Disease
Published: May 8, 2019


ALG3‐CDG is one of the very rare types of congenital disorder of glycosylation (CDG) caused by variants in the ER‐mannosyltransferase ALG3. Here, we summarize the clinical, biochemical, and genetic data of four new ALG3‐CDG patients, who were identified by a type I pattern of serum transferrin and the accumulation of Man5GlcNAc2‐PP‐dolichol in LLO analysis. Additional clinical symptoms observed in our patients comprise sensorineural hearing loss, right‐descending aorta, obstructive cardiomyopathy, macroglossia, and muscular hypertonia. We add four new biochemically confirmed variants to the list of ALG3‐CDG inducing variants: c.350G>C (p.R117P), c.1263G>A (p.W421*), c.1037A>G (p.N346S), and the intron variant c.296+4A>G. Furthermore, in Patient 1 an additional open‐reading frame of 141 bp (AAGRP) in the coding region of ALG3 was identified. Additionally, we show that control cells synthesize, to a minor degree, a hybrid protein composed of the polypeptide AAGRP and ALG3 (AAGRP‐ALG3), while in Patient 1 expression of this hybrid protein is significantly increased due to the homozygous variant c.160_196del (g.165C>T). By reviewing the literature and combining our findings with previously published data, we further expand the knowledge of this rare glycosylation defect.


Cutis laxa, exocrine pancreatic insufficiency and altered cellular metabolomics as additional symptoms in a new patient with ATP6AP1-CDG.

Dimitrov B,  Himmelreich N, Hipgrave Ederveen AL, Lüchtenborg C, Okun JG, Breuer M, Hutter AM, Carl M, Guglielmi L, Hellwig A, Thiemann KC, Jost M, Peters V, Staufner C, Hoffmann GF, Hackenberg A, Paramasivam N, Wiemann S, Eils R, Schlesner M, Strahl S, Brügger B, Wuhrer M, Christoph Korenke G, Thiel C

Molecular Genetics and Metabolism
Published: March 31, 2018



A mutation in mannose‐phosphate‐dolichol utilization defect 1 reveals clinical symptoms of congenital disorders of glycosylation type I and dystroglycanopathy

Walinka van Tol, Angel Ashikov, Eckhard Korsch, Nurulamin Abu Bakar, Michèl A. Willemsen, Christian Thiel, Dirk J. Lefeber

Journal of Inherited Metabolic Disease

Published: September 30, 2019



Congenital disorders of glycosylation type I (CDG‐I) are inborn errors of metabolism, generally characterized by multisystem clinical manifestations, including developmental delay, hepatopathy, hypotonia, and skin, skeletal, and neurological abnormalities. Among others, dolichol‐phosphate‐mannose (DPM) is the mannose donor for N‐glycosylation as well as O‐mannosylation. DOLK‐CDG, DPM1‐CDG, DPM2‐CDG, and DPM3‐CDG are defects in the DPM synthesis showing both CDG‐I abnormalities and reduced O‐mannosylation of alpha‐dystroglycan (αDG), which leads to muscular dystrophy‐dystroglycanopathy. Mannose‐phosphate‐dolichol utilization defect 1 (MPDU1) plays a role in the utilization of DPM. Here, we report two MPDU1‐CDG patients without skin involvement, but with massive dilatation of the biliary duct system and dystroglycanopathy characteristics including hypotonia, elevated creatine kinase, dilated cardiomyopathy, buphthalmos, and congenital glaucoma. Biochemical analyses revealed elevated disialotransferrin in serum, and analyses in fibroblasts showed shortened lipid linked oligosaccharides and DPM, and reduced O‐mannosylation of αDG. Thus, MPDU1‐CDG can be added to the list of disorders with overlapping biochemical and clinical abnormalities of CDG‐I and dystroglycanopathy.


The Fine Art of Destruction: A Guide to In‐Depth Glycoproteomic Analyses—Exploiting the Diagnostic Potential of Fragment Ions