Publications by year
In Press
Gardilla AC, Sanchez D, Brunt L, Scholpp S (In Press). From top to bottom: Cell polarity in Hedgehog and Wnt trafficking. BMC Biology
Liu T-L, Upadhyayula S, Milkie D, Singh V, Wang K, Swineburn I, Scholpp S, Megason S, Kirchhausen T, Betzig E, et al (In Press). Observing the cell in its native state: Imaging subcellular dynamics in multicellular organisms. Science
Routledge D, Rogers S, Ashktorab H, Phesse TJ, Scholpp S (In Press). The scaffolding protein Flot2 regulates cytoneme-based transport of Wnt3 in gastric cancer.
Abstract:
The scaffolding protein Flot2 regulates cytoneme-based transport of Wnt3 in gastric cancer
AbstractThe Wnt/β-catenin signalling pathway regulates multiple cellular processes during development and many diseases, including cell proliferation, migration, and differentiation. Despite their hydrophobic nature, Wnt proteins exert their function over long distances to induce paracrine signalling. Recent studies have identified several factors involved in Wnt secretion, however, our understanding of how Wnt ligands are transported between cells to interact with their cognate receptors is still debated. Here, we demonstrate that gastric cancer cells utilise cytonemes to transport Wnt3 intercellularly to promote proliferation. Furthermore, we identify the membrane-bound scaffolding protein Flotillin-2 (Flot2), frequently overexpressed in gastric cancer, as a regulator of these cytonemes. Together with the Wnt co-receptor and cytoneme initiator Ror2, Flot2 determines the number and length of Wnt3 cytonemes in gastric cancer. Finally, we show that Flot2 is necessary for Wnt8a cytonemes during zebrafish embryogenesis, suggesting a conserved mechanism for Flot2-mediated Wnt transport on cytonemes in development and disease.
Abstract.
Brunt L, Greicius G, Evans BD, Virshup DM, Wedgwood KCA, Scholpp S (In Press). Vangl2 regulates the dynamics of Wnt cytonemes in vertebrates.
Abstract:
Vangl2 regulates the dynamics of Wnt cytonemes in vertebrates
AbstractThe Wnt signalling network regulates cell proliferation and cell differentiation as well as migration and polarity in development of multicellular organisms. However, it is still unclear how distribution of Wnt ligands is precisely controlled to fulfil all of these different functions. Here, we show that the four-pass transmembrane protein Vangl2 occupies a central role in determining the distribution of Wnt by cytonemes in vertebrate tissue. In zebrafish epiblast cells, mouse intestinal telocytes and human gastric cancer cells, activation of Vangl2 leads to the generation of fewer but extremely long cytonemes, which start to branch and deliver Wnt protein to multiple cells. The Vangl2-activated cytonemes increase Wnt/β-catenin signalling in the surrounding cells. Concordantly, inhibition of Vangl2 function leads to the formation of shorter cytonemes and reduced paracrine Wnt/β-catenin signal activation. A mathematical model simulating the observed Vangl2 functions on cytonemes in zebrafish gastrulation predicts an anterior shift of the morphogenetic signalling gradient, altered tissue patterning, and a loss of the sharpness of tissue domains. We confirmed these predictions during anteroposterior patterning in the zebrafish neural plate. In summary, we show that Vangl2 - a core member of the PCP signalling component - is fundamental to paracrine Wnt/β-catenin signalling by controlling cytoneme behaviour in vertebrate development and tissue homeostasis.
Abstract.
Piers TM, Namboori SC, Bhinge A, Killick R, Scholpp S (In Press). Wnt-7a-positive dendritic cytonemes induce synaptogenesis in cortical neurons.
Abstract:
Wnt-7a-positive dendritic cytonemes induce synaptogenesis in cortical neurons
SummaryNeuronal circuits evolve as a precisely patterned network. In this context, a growing neuron must locate the appropriate target area on a neurite of a neighbouring cell with which to connect. Controlled target selection involves dendritic filopodial contacts and requires the exact apposition of synaptic components. Calcium signalling has been postulated to trigger the transformation from dendritic filopodia into functional synapses. However, calcium is a rather unspecific signalling system, and it needs to be clarified how the exact development of synaptic connections is controlled. Similarly, Wnt/β-catenin signalling promotes synapse formation; however, how secreted Wnts induce and maintain synapses on neuronal dendrites is not well understood. Here, we show that Wnt-7a is tethered to the tips of dynamic dendritic filopodia during spine formation in human cortical neurons. These filopodia can activate Wnt signalling precisely at the contact sites on the dendrites of an adjacent neuron. Subsequently, local calcium transients can be observed at these Wnt-positive contact sites. Depleting either the filopodial-loaded Wnt or the extracellular calcium pool blocks the clustering of pre- and post-synaptic markers, hence the establishment of stable connections. Therefore, we postulate that local Wnt-7a signalling from the tip of the dendritic filopodia, verified by simultaneous calcium signalling, provides an elegant mechanism for orchestrating focal synapse maturation.
Abstract.
2022
Winter MJ, Ono Y, Ball JS, Walentinsson A, Michaelsson E, Tochwin A, Scholpp S, Tyler CR, Rees S, Hetheridge MJ, et al (2022). A Combined Human in Silico and CRISPR/Cas9-Mediated in Vivo Zebrafish Based Approach to Provide Phenotypic Data for Supporting Early Target Validation. Frontiers in Pharmacology, 13
Rogers S, Zhang C, Anagnostidis V, Fishel M, Gielen F, Scholpp S (2022). Cancer-associated fibroblast-derived ROR2 induces WNT/PCP activation and polarized migration in receiving gastric cancer cells.
Zhang C, Brunt L, Rogers S, Scholpp S (2022). Cytoneme-mediated transport of active Wnt5b/Ror2 complexes in zebrafish gastrulation.
Scholpp S, Brunt L (2022). PCP/VANGL2 SIGNALLING REGULATES WNT CYTONEMES.
Author URL.
Routledge D, Rogers S, Ono Y, Brunt L, Meniel V, Tornillo G, Ashktorab H, Phesse TJ, Scholpp S (2022). The scaffolding protein flot2 promotes cytoneme-based transport of wnt3 in gastric cancer.
eLife,
11Abstract:
The scaffolding protein flot2 promotes cytoneme-based transport of wnt3 in gastric cancer
The Wnt/β-catenin signalling pathway regulates multiple cellular processes during development and many diseases, including cell proliferation, migration, and differentiation. Despite their hydrophobic nature, Wnt proteins exert their function over long distances to induce paracrine signalling. Recent studies have identified several factors involved in Wnt secretion; however, our understanding of how Wnt ligands are transported between cells to interact with their cognate receptors is still debated. Here, we demonstrate that gastric cancer cells utilise cytonemes to transport Wnt3 intercellularly to promote proliferation and cell survival. Furthermore, we identify the membrane-bound scaffolding protein Flotillin-2 (Flot2), frequently overexpressed in gastric cancer, as a modulator of these cytonemes. Together with the Wnt co-receptor and cytoneme initiator Ror2, Flot2 determines the number and length of Wnt3 cytonemes in gastric cancer. Finally, we show that Flotillins are also necessary for Wnt8a cytonemes during zebrafish embryogenesis, suggesting a conserved mechanism for Flotillin-mediated Wnt transport on cytonemes in development and disease.
Abstract.
Rogers S, Scholpp S (2022). Vertebrate Wnt5a – at the crossroads of cellular signalling. Seminars in Cell & Developmental Biology, 125, 3-10.
2021
Rogers S, Scholpp S (2021). Preserving Cytonemes for Immunocytochemistry of Cultured Adherent Cells. In (Ed)
, 183-190.
Abstract:
Preserving Cytonemes for Immunocytochemistry of Cultured Adherent Cells.
Abstract.
Author URL.
Sutton G, Kelsh RN, Scholpp S (2021). Review: the Role of Wnt/β-Catenin Signalling in Neural Crest Development in Zebrafish.
Frontiers in Cell and Developmental Biology,
9Abstract:
Review: the Role of Wnt/β-Catenin Signalling in Neural Crest Development in Zebrafish
The neural crest (NC) is a multipotent cell population in vertebrate embryos with extraordinary migratory capacity. The NC is crucial for vertebrate development and forms a myriad of cell derivatives throughout the body, including pigment cells, neuronal cells of the peripheral nervous system, cardiomyocytes and skeletogenic cells in craniofacial tissue. NC induction occurs at the end of gastrulation when the multipotent population of NC progenitors emerges in the ectodermal germ layer in the neural plate border region. In the process of NC fate specification, fate-specific markers are expressed in multipotent progenitors, which subsequently adopt a specific fate. Thus, NC cells delaminate from the neural plate border and migrate extensively throughout the embryo until they differentiate into various cell derivatives. Multiple signalling pathways regulate the processes of NC induction and specification. This review explores the ongoing role of the Wnt/β-catenin signalling pathway during NC development, focusing on research undertaken in the Teleost model organism, zebrafish (Danio rerio). We discuss the function of the Wnt/β-catenin signalling pathway in inducing the NC within the neural plate border and the specification of melanocytes from the NC. The current understanding of NC development suggests a continual role of Wnt/β-catenin signalling in activating and maintaining the gene regulatory network during NC induction and pigment cell specification. We relate this to emerging models and hypotheses on NC fate restriction. Finally, we highlight the ongoing challenges facing NC research, current gaps in knowledge, and this field’s potential future directions.
Abstract.
Brunt L, Greicius G, Rogers S, Evans BD, Virshup DM, Wedgwood KCA, Scholpp S (2021). Vangl2 promotes the formation of long cytonemes to enable distant Wnt/β-catenin signaling.
Nat Commun,
12(1).
Abstract:
Vangl2 promotes the formation of long cytonemes to enable distant Wnt/β-catenin signaling.
Wnt signaling regulates cell proliferation and cell differentiation as well as migration and polarity during development. However, it is still unclear how the Wnt ligand distribution is precisely controlled to fulfil these functions. Here, we show that the planar cell polarity protein Vangl2 regulates the distribution of Wnt by cytonemes. In zebrafish epiblast cells, mouse intestinal telocytes and human gastric cancer cells, Vangl2 activation generates extremely long cytonemes, which branch and deliver Wnt protein to multiple cells. The Vangl2-activated cytonemes increase Wnt/β-catenin signaling in the surrounding cells. Concordantly, Vangl2 inhibition causes fewer and shorter cytonemes to be formed and reduces paracrine Wnt/β-catenin signaling. A mathematical model simulating these Vangl2 functions on cytonemes in zebrafish gastrulation predicts a shift of the signaling gradient, altered tissue patterning, and a loss of tissue domain sharpness. We confirmed these predictions during anteroposterior patterning in the zebrafish neural plate. In summary, we demonstrate that Vangl2 is fundamental to paracrine Wnt/β-catenin signaling by controlling cytoneme behaviour.
Abstract.
Author URL.
2020
Cavallo JC, Scholpp S, Flegg MB (2020). Delay-driven oscillations via Axin2 feedback in the Wnt/β-catenin signalling pathway.
J Theor Biol,
507Abstract:
Delay-driven oscillations via Axin2 feedback in the Wnt/β-catenin signalling pathway.
The Wnt signalling pathway plays an important role in development, disease, and normal tissue function. Mathematical models for Wnt signalling have predominantly focused on quantitatively predicting changes in steady-state β-catenin concentrations (the main downstream protein regulated by canonical Wnt signalling). One of the genes targeted for expression by Wnt/β-catenin signalling is the negative Wnt regulator Axin2. Recently, a number of authors have indicated a potential theoretical role of Axin2 feedback to induce oscillatory behaviour in the pathway and this has been observed in a number of detailed mathematical models. Due to the complexity of these models, the investigations to date have been limited to numerical experiments and parameter sensitivity analyses. In this manuscript, we study the fundamental structure of the dynamical system underlying the Wnt signalling mechanism with Axin2 feedback to gain some insight into why and when oscillations occur in models with this structure. We semi-rigorously analyse three simple models and, for these models, gain deep understanding of the characteristic set of conditions that are necessary and sufficient for oscillations to be induced. We discuss the possible biological consequences of these findings for Wnt signalling pathway oscillations. They include; to promote oscillations (1) Keeping all other parameters constant, the Wnt signal strength should neither be too high or too low but within a single finite window of values, (2) Wnt receptor complexes should fully deactivate Axin rather than temporarily deconstruct it from other scaffold proteins, (3) in the absence of stochastic effects or more complicated mechanisms, a critical delay in Axin2 feedback in the system is necessary, (4) Deactivation of Axin by the Wnt receptor complex needs to be critically efficient relative to β-catenin removal by Axin, and (5) conditions necessary are less strict if Axin2 feedback occurs after a fixed time rather than a Poisson-distributed time with the same average.
Abstract.
Author URL.
Alshami IJJ, Ono Y, Correia A, Hacker C, Lange A, Scholpp S, Kawasaki M, Ingham PW, Kudoh T (2020). Development of the electric organ in embryos and larvae of the knifefish, Brachyhypopomus gauderio. Developmental Biology, 466(1-2), 99-108.
Scholpp S (2020). Introduction: in vivo cell biology in zebrafish.
Histochem Cell Biol,
154(5), 457-461.
Author URL.
Rosenbauer J, Zhang C, Mattes B, Reinartz I, Wedgwood K, Schindler S, Sinner C, Scholpp S, Schug A (2020). Modeling of Wnt-mediated tissue patterning in vertebrate embryogenesis. PLOS Computational Biology, 16(6), e1007417-e1007417.
Bosze B, Ono Y, Mattes B, Sinner C, Gourain V, Thumberger T, Tlili S, Wittbrodt J, Saunders TE, Strähle U, et al (2020). Pcdh18a regulates endocytosis of E-cadherin during axial mesoderm development in zebrafish.
Histochemistry and Cell Biology,
154(5), 463-480.
Abstract:
Pcdh18a regulates endocytosis of E-cadherin during axial mesoderm development in zebrafish
The notochord defines the axial structure of all vertebrates during development. Notogenesis is a result of major cell reorganization in the mesoderm, the convergence and the extension of the axial cells. However, it is currently not fully understood how these processes act together in a coordinated way during notochord formation. The prechordal plate is an actively migrating cell population in the central mesoderm anterior to the trailing notochordal plate cells. We show that prechordal plate cells express Protocadherin 18a (Pcdh18a), a member of the cadherin superfamily. We find that Pcdh18a-mediated recycling of E-cadherin adhesion complexes transforms prechordal plate cells into a cohesive and fast migrating cell group. In turn, the prechordal plate cells subsequently instruct the trailing mesoderm. We simulated cell migration during early mesoderm formation using a lattice-based mathematical framework and predicted that the requirement for an anterior, local motile cell cluster could guide the intercalation and extension of the posterior, axial cells. Indeed, a grafting experiment validated the prediction and local Pcdh18a expression induced an ectopic prechordal plate-like cell group migrating towards the animal pole. Our findings indicate that the Pcdh18a is important for prechordal plate formation, which influences the trailing mesodermal cell sheet by orchestrating the morphogenesis of the notochord.
Abstract.
Dawes ML, Soeller C, Scholpp S (2020). Studying molecular interactions in the intact organism: fluorescence correlation spectroscopy in the living zebrafish embryo.
HISTOCHEMISTRY AND CELL BIOLOGY,
154(5), 507-519.
Author URL.
Porter L (2020). Wnt signalling and peroxisome dynamics in the zebrafish (Danio rerio).
Abstract:
Wnt signalling and peroxisome dynamics in the zebrafish (Danio rerio)
Cell-cell or paracrine signalling is a form of cellular communication in which a cell produces a signal that influences the behaviour of neighbouring cells, which is important because it allows for the local coordination of the activities of groups of cells. This coordination is indispensable during development; for example, paracrine Wnt signalling is fundamental to body patterning in all metazoans where it helps to determine cell fate in a developing embryo. Wnt can regulate the transcription of target genes including cyclin and peroxisome-proliferator activated receptor-ẟ. The importance of Wnt signalling is not temporally limited, and Wnt has roles throughout the life of an organism such as the management of stem cells and the cellular abundance of mitochondria, the ‘sister organelle’ of the peroxisome. The peroxisome is a single membrane-bound organelle with diverse roles in healthy development and life, inclusive of the breakdown of very long chain fatty acids (VLCFAs) and the production of plasmalogens for efficient nervous conduction. The relationship between the Wnt signalling pathway and peroxisomes is unknown. Here I investigate the influence of Wnt signalling on peroxisome dynamics in zebrafish. To do so, canonical wnt8a was knocked out and knocked down using the genomic engineering tool CRISPR and Morpholino oligomers. The number and morphology of peroxisomes was observed in Wnt8a-deficient zebrafish embryos and appeared to be aggregated and less numerate than in wild type zebrafish. Consistently, in zebrafish embryos overexpressing wnt8a, peroxisomes were visualised as highly numerate singular puncta. I hypothesise that - in addition to a set of functions in development and tissue homeostasis - Wnt signalling has a novel role in regulating peroxisome proliferation in zebrafish.
Abstract.
2019
Zhang C, Scholpp S (2019). Cytonemes in development.
Current Opinion in Genetics and Development,
57, 25-30.
Abstract:
Cytonemes in development
Cell–cell communication is essential during the development of multicellular organisms. Specialized cell protrusions called cytonemes have been identified to exchange signals between cells that are vital for tissue development. Cytonemes can carry signalling components between distant cells and thus regulate the activity levels of the corresponding signalling pathways across entire tissues. This review summarizes the key findings on the formation and function of cytonemes in tissue development.
Abstract.
Routledge D, Scholpp S (2019). Mechanisms of intercellular Wnt transport.
Development,
146(10).
Abstract:
Mechanisms of intercellular Wnt transport.
Wnt proteins are secreted glycoproteins that regulate multiple processes crucial to the development and tissue homeostasis of multicellular organisms, including tissue patterning, proliferation, cell fate specification, cell polarity and migration. To elicit these effects, Wnts act as autocrine as well as paracrine signalling molecules between Wnt-producing and Wnt-receiving cells. More than 40â€
years after the discovery of the Wg/Wnt pathway, it is still unclear how they are transported to fulfil their paracrine signalling functions. Several mechanisms have been proposed to mediate intercellular Wnt transport, including Wnt-binding proteins, lipoproteins, exosomes and cytonemes. In this Review, we describe the evidence for each proposed mechanism, and discuss how they may contribute to Wnt dispersal in tissue-specific and context-dependent manners, to regulate embryonic development precisely and maintain the internal steady state within a defined tissue.
Abstract.
Author URL.
2018
Mattes B, Scholpp S (2018). Emerging role of contact-mediated cell communication in tissue development and diseases.
Histochemistry and Cell Biology,
150, 431-442.
Abstract:
Emerging role of contact-mediated cell communication in tissue development and diseases
© 2018, the Author(s). Cells of multicellular organisms are in continuous conversation with the neighbouring cells. The sender cells signal the receiver cells to influence their behaviour in transport, metabolism, motility, division, and growth. How cells communicate with each other can be categorized by biochemical signalling processes, which can be characterised by the distance between the sender cell and the receiver cell. Existing classifications describe autocrine signals as those where the sender cell is identical to the receiver cell. Complementary to this scenario, paracrine signalling describes signalling between a sender cell and a different receiver cell. Finally, juxtacrine signalling describes the exchange of information between adjacent cells by direct cell contact, whereas endocrine signalling describes the exchange of information, e.g. by hormones between distant cells or even organs through the bloodstream. In the last two decades, however, an unexpected communication mechanism has been identified which uses cell protrusions to exchange chemical signals by direct contact over long distances. These signalling protrusions can deliver signals in both ways, from sender to receiver and vice versa. We are starting to understand the morphology and function of these signalling protrusions in many tissues and this accumulation of findings forces us to revise our view of contact-dependent cell communication. In this review, we will focus on the two main categories of signalling protrusions, cytonemes and tunnelling nanotubes. These signalling protrusions emerge as essential structural components of a vibrant communication network in the development and tissue homeostasis of any multicellular organism.
Abstract.
Brunt L, Scholpp S (2018). The function of endocytosis in Wnt signaling.
Cellular and Molecular Life Sciences,
75(5), 785-795.
Abstract:
The function of endocytosis in Wnt signaling
Wnt growth factors regulate one of the most important signaling networks during development, tissue homeostasis and disease. Despite the biological importance of Wnt signaling, the mechanism of endocytosis during this process is ill described. Wnt molecules can act as paracrine signals, which are secreted from the producing cells and transported through neighboring tissue to activate signaling in target cells. Endocytosis of the ligand is important at several stages of action: One central function of endocytic trafficking in the Wnt pathway occurs in the source cell. Furthermore, the β-catenin-dependent Wnt ligands require endocytosis for signal activation and to regulate gene transcription in the responding cells. Alternatively, Wnt/β-catenin-independent signaling regulates endocytosis of cell adherence plaques to control cell migration. In this comparative review, we elucidate these three fundamental interconnected functions, which together regulate cellular fate and cellular behavior. Based on established hypotheses and recent findings, we develop a revised picture for the complex function of endocytosis in the Wnt signaling network.
Abstract.
Scholpp S (2018). Wnt/PCP controls spreading of Wnt/β-catenin signals by cytonemes in vertebrates. eLife
2017
Mattes B, Scholpp S (2017). Towards deciphering the molecular mechanism regulating Wnt ligand trafficking.
Author URL.
2016
Reinartz I, Sinner C, Stanganello E, Mattes B, Scholpp S, Schug A (2016). 3D Simulations of Morphogen Transport in an Early Fish Embryo.
Author URL.
Sinner C, Reinartz I, Boesze B, Scholpp S, Schug A (2016). Dynamic Simulations of Cell Migration with Applications to Brain Development.
Author URL.
Heeren-Hagemann A, Kurz J, Kauffeld S, Chen Q, Reeves P, Weber S, Schindler S, Davidson G, Kirchhausen T, Scholpp S, et al (2016). In vivo analysis of formation and endocytosis of the Wnt/beta-Catenin signaling complex in zebrafish embryos.
Author URL.
Stanganello E, Scholpp S (2016). Role of cytonemes in Wnt transport.
J Cell Sci,
129(4), 665-672.
Abstract:
Role of cytonemes in Wnt transport.
Wnt signaling regulates a broad variety of processes during embryonic development and disease. A hallmark of the Wnt signaling pathway is the formation of concentration gradients by Wnt proteins across responsive tissues, which determines cell fate in invertebrates and vertebrates. To fulfill its paracrine function, trafficking of the Wnt morphogen from an origin cell to a recipient cell must be tightly regulated. A variety of models have been proposed to explain the extracellular transport of these lipid-modified signaling proteins in the aqueous extracellular space; however, there is still considerable debate with regard to which mechanisms allow the precise distribution of ligand in order to generate a morphogenetic gradient within growing tissue. Recent evidence suggests that Wnt proteins are distributed along signaling filopodia during vertebrate and invertebrate embryogenesis. Cytoneme-mediated transport has profound impact on our understanding of how Wnt signaling propagates through tissues and allows the formation of a precise ligand distribution in the recipient tissue during embryonic growth. In this Commentary, we review extracellular trafficking mechanisms for Wnt proteins and discuss the growing evidence of cytoneme-based Wnt distribution in development and stem cell biology. We will also discuss their implication for Wnt signaling in the formation of the Wnt morphogenetic gradient during tissue patterning.
Abstract.
Author URL.
Brinkmann E-M, Mattes B, Kumar R, Hagemann AIH, Gradl D, Scholpp S, Steinbeisser H, Kaufmann LT, Özbek S (2016). Secreted Frizzled-related Protein 2 (sFRP2) Redirects Non-canonical Wnt Signaling from Fz7 to Ror2 during Vertebrate Gastrulation.
J Biol Chem,
291(26), 13730-13742.
Abstract:
Secreted Frizzled-related Protein 2 (sFRP2) Redirects Non-canonical Wnt Signaling from Fz7 to Ror2 during Vertebrate Gastrulation.
Convergent extension movements during vertebrate gastrulation require a balanced activity of non-canonical Wnt signaling pathways, but the factors regulating this interplay on the molecular level are poorly characterized. Here we show that sFRP2, a member of the secreted frizzled-related protein (sFRP) family, is required for morphogenesis and papc expression during Xenopus gastrulation. We further provide evidence that sFRP2 redirects non-canonical Wnt signaling from Frizzled 7 (Fz7) to the receptor tyrosine kinase-like orphan receptor 2 (Ror2). During this process, sFRP2 promotes Ror2 signal transduction by stabilizing Wnt5a-Ror2 complexes at the membrane, whereas it inhibits Fz7 signaling, probably by blocking Fz7 receptor endocytosis. The cysteine-rich domain of sFRP2 is sufficient for Ror2 activation, and related sFRPs can substitute for this function. Notably, direct interaction of the two receptors via their cysteine-rich domains also promotes Ror2-mediated papc expression but inhibits Fz7 signaling. We propose that sFRPs can act as a molecular switch, channeling the signal input for different non-canonical Wnt pathways during vertebrate gastrulation.
Abstract.
Author URL.
2015
Stanganello E, Hagemann AIH, Mattes B, Sinner C, Meyen D, Weber S, Schug A, Raz E, Scholpp S (2015). Filopodia-based Wnt transport during vertebrate tissue patterning.
Nat Commun,
6Abstract:
Filopodia-based Wnt transport during vertebrate tissue patterning.
Paracrine Wnt/β-catenin signalling is important during developmental processes, tissue regeneration and stem cell regulation. Wnt proteins are morphogens, which form concentration gradients across responsive tissues. Little is known about the transport mechanism for these lipid-modified signalling proteins in vertebrates. Here we show that Wnt8a is transported on actin-based filopodia to contact responding cells and activate signalling during neural plate formation in zebrafish. Cdc42/N-Wasp regulates the formation of these Wnt-positive filopodia. Enhanced formation of filopodia increases the effective signalling range of Wnt by facilitating spreading. Consistently, reduction in filopodia leads to a restricted distribution of the ligand and a limited signalling range. Using a simulation, we provide evidence that such a short-range transport system for Wnt has a long-range signalling function. Indeed, we show that a filopodia-based transport system for Wnt8a controls anteroposterior patterning of the neural plate during vertebrate gastrulation.
Abstract.
Author URL.
Sinner C, Stanganello E, Hagemann AIH, Mattes B, Meyen D, Weber S, Raz E, Scholpp S, Schug A (2015). Monte Carlo Simulation of Wnt Propagation by a Novel Transport Mechanism Complementing a Joint Experimental Study.
Author URL.
Hirschbiel AF, Geyer S, Yameen B, Welle A, Nikolov P, Giselbrecht S, Scholpp S, Delaittre G, Barner-Kowollik C (2015). Photolithographic patterning of 3D-formed polycarbonate films for targeted cell guiding.
Adv Mater,
27(16), 2621-2626.
Abstract:
Photolithographic patterning of 3D-formed polycarbonate films for targeted cell guiding.
A facile photolithographic platform for the design of cell-guiding polymeric substrates is introduced. Specific areas of the substrate are photo-deactivated for the subsequent growth of bioresistant polymer brushes, creating zones for cell proliferation, and protein adhesion.
Abstract.
Author URL.
2014
Hagemann AIH, Kurz J, Kauffeld S, Chen Q, Reeves PM, Weber S, Schindler S, Davidson G, Kirchhausen T, Scholpp S, et al (2014). Correction to in vivo analysis of formation and endocytosis of the Wnt/β-Catenin signaling complex in zebrafish embryos [J. Cell Sci. 127, (2014) 3970-3982]. Journal of Cell Science, 127(24).
Rengarajan C, Matzke A, Reiner L, Orian-Rousseau V, Scholpp S (2014). Endocytosis of Fgf8 is a double-stage process and regulates spreading and signaling.
PLoS One,
9(1).
Abstract:
Endocytosis of Fgf8 is a double-stage process and regulates spreading and signaling.
Tightly controlled concentration gradients of morphogens provide positional information and thus regulate tissue differentiation and morphogenesis in multicellular organisms. However, how such morphogenetic fields are formed and maintained remains debated. Here we show that fibroblast growth factor 8 (Fgf8) morphogen gradients in zebrafish embryos are established and maintained by two essential mechanisms. Firstly, Fgf8 is taken up into the cell by clathrin-mediated endocytosis. The speed of the uptake rate defines the range of the morphogenetic gradient of Fgf8. Secondly, our data demonstrate that after endocytosis the routing of Fgf8 from the early endosome to the late endosome shuts down signaling. Therefore, intracellular endocytic transport regulates the intensity and duration of Fgf8 signaling. We show that internalization of Fgf8 into the early endosome and subsequent transport towards the late endosome are two independent processes. Therefore, we hypothesize that Fgf8 receiving cells control both, the propagation width and the signal strength of the morphogen.
Abstract.
Author URL.
Hagemann AIH, Kurz J, Kauffeld S, Chen Q, Reeves PM, Weber S, Schindler S, Davidson G, Kirchhausen T, Scholpp S, et al (2014). In vivo analysis of formation and endocytosis of the Wnt/β-Catenin signaling complex in zebrafish embryos. Development, 141(19), e1907-e1907.
Hagemann AIH, Kurz J, Kauffeld S, Chen Q, Reeves PM, Weber S, Schindler S, Davidson G, Kirchhausen T, Scholpp S, et al (2014). In vivo analysis of formation and endocytosis of the Wnt/β-catenin signaling complex in zebrafish embryos.
J Cell Sci,
127(Pt 18), 3970-3982.
Abstract:
In vivo analysis of formation and endocytosis of the Wnt/β-catenin signaling complex in zebrafish embryos.
After activation by Wnt/β-Catenin ligands, a multi-protein complex assembles at the plasma membrane as membrane-bound receptors and intracellular signal transducers are clustered into the so-called Lrp6-signalosome [Corrected]. However, the mechanism of signalosome formation and dissolution is yet not clear. Our imaging studies of live zebrafish embryos show that the signalosome is a highly dynamic structure. It is continuously assembled by Dvl2-mediated recruitment of the transducer complex to the activated receptors and partially disassembled by endocytosis. We find that, after internalization, the ligand-receptor complex and the transducer complex take separate routes. The Wnt-Fz-Lrp6 complex follows a Rab-positive endocytic path. However, when still bound to the transducer complex, Dvl2 forms intracellular aggregates. We show that this endocytic process is not only essential for ligand-receptor internalization but also for signaling. The μ2-subunit of the endocytic Clathrin adaptor Ap2 interacts with Dvl2 to maintain its stability during endocytosis. Blockage of Ap2μ2 function leads to Dvl2 degradation, inhibiton of signalosome formation at the plasma membrane and, consequently, reduction of signaling. We conclude that Ap2μ2-mediated endocytosis is important to maintain Wnt/β-catenin signaling in vertebrates.
Abstract.
Author URL.
Hagemann A, Kurz J, Kauffeld S, Chen Q, Reeves P, Davidson G, Kirchhausen T, Scholpp S (2014). In-vivo analysis of formation and endocytosis of the Wnt/beta-catenin signaling complex in zebrafish embryos.
Author URL.
Chatterjee M, Guo Q, Weber S, Scholpp S, Li JY (2014). Pax6 regulates the formation of the habenular nuclei by controlling the temporospatial expression of Shh in the diencephalon in vertebrates.
BMC Biol,
12Abstract:
Pax6 regulates the formation of the habenular nuclei by controlling the temporospatial expression of Shh in the diencephalon in vertebrates.
BACKGROUND: the habenula and the thalamus are two critical nodes in the forebrain circuitry and they connect the midbrain and the cerebral cortex in vertebrates. The habenula is derived from the epithalamus and rests dorsally to the thalamus. Both epithalamus and thalamus arise from a single diencephalon segment called prosomere (p)2. Shh is expressed in the ventral midline of the neural tube and in the mid-diencephalic organizer (MDO) at the zona limitans intrathalamica between thalamus and prethalamus. Acting as a morphogen, Shh plays an important role in regulating cell proliferation and survival in the diencephalon and thalamic patterning. The molecular regulation of the MDO Shh expression and the potential role of Shh in development of the habenula remain largely unclear. RESULTS: We show that deleting paired-box and homeobox-containing gene Pax6 results in precocious and expanded expression of Shh in the prospective MDO in fish and mice, whereas gain-of-function of pax6 inhibits MDO shh expression in fish. Using gene expression and genetic fate mapping, we have characterized the expression of molecular markers that demarcate the progenitors and precursors of habenular neurons. We show that the thalamic domain is shifted dorsally and the epithalamus is missing in the alar plate of p2 in the Pax6 mutant mouse. Conversely, the epithalamus is expanded ventrally at the expense of the thalamus in mouse embryos with reduced Shh activity. Significantly, attenuating Shh signaling largely rescues the patterning of p2 and restores the epithalamus in Pax6 mouse mutants, suggesting that Shh acts downstream of Pax6 in controlling the formation of the habenula. Similar to that found in the mouse, we show that pax6 controls the formation of the epithalamus mostly via the regulation of MDO shh expression in zebrafish. CONCLUSIONS: Our findings demonstrate that Pax6 has an evolutionarily conserved function in establishing the temporospatial expression of Shh in the MDO in vertebrates. Furthermore, Shh mediates Pax6 function in regulating the partition of the p2 domain into the epithalamus and thalamus.
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Author URL.
Chen Q, Su Y, Wesslowski J, Hagemann AI, Ramialison M, Wittbrodt J, Scholpp S, Davidson G (2014). Tyrosine phosphorylation of LRP6 by Src and Fer inhibits Wnt/β-catenin signalling.
EMBO Rep,
15(12), 1254-1267.
Abstract:
Tyrosine phosphorylation of LRP6 by Src and Fer inhibits Wnt/β-catenin signalling.
Low-density lipoprotein receptor-related proteins 5 and 6 (LRP5/6) function as transmembrane receptors to transduce Wnt signals. A key mechanism for signalling is Wnt-induced serine/threonine phosphorylation at conserved PPPSPxS motifs in the LRP6 cytoplasmic domain, which promotes pathway activation. Conserved tyrosine residues are positioned close to all PPPSPxS motifs, which suggests they have a functional significance. Using a cell culture-based cDNA expression screen, we identified the non-receptor tyrosine kinases Src and Fer as novel LRP6 modifiers. Both Src and Fer associate with LRP6 and phosphorylate LRP6 directly. In contrast to the known PPPSPxS Ser/Thr kinases, tyrosine phosphorylation by Src and Fer negatively regulates LRP6-Wnt signalling. Epistatically, they function upstream of β-catenin to inhibit signalling and in agreement with a negative role in regulating LRP6, MEF cells lacking these kinases show enhanced Wnt signalling. Wnt3a treatment of cells enhances tyrosine phosphorylation of endogenous LRP6 and, mechanistically, Src reduces cell surface LRP6 levels and disrupts LRP6 signalosome formation. Interestingly, CK1γ inhibits Fer-induced LRP6 phosphorylation, suggesting a mechanism whereby CK1γ acts to de-represses inhibitory LRP6 tyrosine phosphorylation. We propose that LRP6 tyrosine phosphorylation by Src and Fer serves a negative regulatory function to prevent over-activation of Wnt signalling at the level of the Wnt receptor, LRP6.
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Author URL.
2013
Scholpp S, Poggi L, Zigman M (2013).
Brain on the stage - spotlight on nervous system development in zebrafish: EMBO practical course, KIT, Sept. 2013. Abstract:
Brain on the stage - spotlight on nervous system development in zebrafish: EMBO practical course, KIT, Sept. 2013.
Abstract.
Author URL.
Scholpp S, Shimogori T (2013). Building the gateway to consciousness-about the development of the thalamus. In (Ed)
.
Author URL.
Efremov AN, Stanganello E, Welle A, Scholpp S, Levkin PA (2013). Micropatterned superhydrophobic structures for the simultaneous culture of multiple cell types and the study of cell-cell communication.
Biomaterials,
34(7), 1757-1763.
Abstract:
Micropatterned superhydrophobic structures for the simultaneous culture of multiple cell types and the study of cell-cell communication.
The ability to control spatial arrangement and geometry of different cell types while keeping them separated and in close proximity for a long time is crucial to mimic and study variety of biological processes in vitro. Although the existing cell patterning technologies allow co-culturing of different cell types, they are usually limited to relatively simple geometry. The methods used for obtaining complex geometries are usually applicable for patterning only one or two cell types. Here we introduce a convenient method for creating patterns of multiple (up to twenty) different cell types on one substrate. The method virtually allows any complexity of cell pattern geometry. Cell positioning on the substrate is realized by a parallel formation of multiple cell-containing microreservoirs confined to the geometry of highly hydrophilic regions surrounded by superhydrophobic borders built-in a fine nanoporous polymer film. As a case study we showed the cross-talk between two cell populations via Wnt signaling molecules propagation during co-culture in a mutual culture medium.
Abstract.
Author URL.
Schmidt R, Strähle U, Scholpp S (2013). Neurogenesis in zebrafish - from embryo to adult.
Neural Dev,
8Abstract:
Neurogenesis in zebrafish - from embryo to adult.
Neurogenesis in the developing central nervous system consists of the induction and proliferation of neural progenitor cells and their subsequent differentiation into mature neurons. External as well as internal cues orchestrate neurogenesis in a precise temporal and spatial way. In the last 20 years, the zebrafish has proven to be an excellent model organism to study neurogenesis in the embryo. Recently, this vertebrate has also become a model for the investigation of adult neurogenesis and neural regeneration. Here, we summarize the contributions of zebrafish in neural development and adult neurogenesis.
Abstract.
Author URL.
2012
Hagemann AIH, Scholpp S (2012). The Tale of the Three Brothers - Shh, Wnt, and Fgf during Development of the Thalamus.
Front Neurosci,
6Abstract:
The Tale of the Three Brothers - Shh, Wnt, and Fgf during Development of the Thalamus.
The thalamic complex is an essential part of the brain that requires a combination of specialized activities to attain its final complexity. In the following review we will describe the induction process of the mid-diencephalic organizer (MDO) where three different signaling pathways merge: Wnt, Shh, and Fgf. Here, we dissect the function of each signaling pathway in the thalamus in chronological order of their appearance. First we describe the Wnt mediated induction of the MDO and compartition of the caudal forebrain, then the Shh mediated determination of proneural gene expression before discussing recent progress in characterizing Fgf function during thalamus development. Then, we focus on transcription factors, which are regulated by these pathways and which play a pivotal role in neurogenesis in the thalamus. The three signaling pathways act together in a strictly regulated chronology to orchestrate the development of the entire thalamus.
Abstract.
Author URL.
Mattes B, Weber S, Peres J, Chen Q, Davidson G, Houart C, Scholpp S (2012). Wnt3 and Wnt3a are required for induction of the mid-diencephalic organizer in the caudal forebrain.
Neural Dev,
7Abstract:
Wnt3 and Wnt3a are required for induction of the mid-diencephalic organizer in the caudal forebrain.
BACKGROUND: a fundamental requirement for development of diverse brain regions is the function of local organizers at morphological boundaries. These organizers are restricted groups of cells that secrete signaling molecules, which in turn regulate the fate of the adjacent neural tissue. The thalamus is located in the caudal diencephalon and is the central relay station between the sense organs and higher brain areas. The mid-diencephalic organizer (MDO) orchestrates the development of the thalamus by releasing secreted signaling molecules such as Shh. RESULTS: Here we show that canonical Wnt signaling in the caudal forebrain is required for the formation of the Shh-secreting MD organizer in zebrafish. Wnt signaling induces the MDO in a narrow time window of 4 hours - between 10 and 14 hours post fertilization. Loss of Wnt3 and Wnt3a prevents induction of the MDO, a phenotype also observed upon blockage of canonical Wnt signaling per se. Pharmaceutical activation of the canonical Wnt pathways in Wnt3/Wnt3a compound morphant embryos is able to restore the lack of the MDO. After blockage of Wnt signaling or knock-down of Wnt3/Wnt3a we find an increase of apoptotic cells specifically within the organizer primordium. Consistently, blockage of apoptosis restores the thalamus organizer MDO in Wnt deficient embryos. CONCLUSION: We have identified canonical Wnt signaling as a novel pathway, that is required for proper formation of the MDO and consequently for the development of the major relay station of the brain - the thalamus. We propose that Wnt ligands are necessary to maintain the primordial tissue of the organizer during somitogenesis by suppressing Tp53-mediated apoptosis.
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Author URL.
2011
Peukert D, Weber S, Lumsden A, Scholpp S (2011). Lhx2 and Lhx9 determine neuronal differentiation and compartition in the caudal forebrain by regulating Wnt signaling.
PLoS Biol,
9(12).
Abstract:
Lhx2 and Lhx9 determine neuronal differentiation and compartition in the caudal forebrain by regulating Wnt signaling.
Initial axial patterning of the neural tube into forebrain, midbrain, and hindbrain primordia occurs during gastrulation. After this patterning phase, further diversification within the brain is thought to proceed largely independently in the different primordia. However, mechanisms that maintain the demarcation of brain subdivisions at later stages are poorly understood. In the alar plate of the caudal forebrain there are two principal units, the thalamus and the pretectum, each of which is a developmental compartment. Here we show that proper neuronal differentiation of the thalamus requires Lhx2 and Lhx9 function. In Lhx2/Lhx9-deficient zebrafish embryos the differentiation process is blocked and the dorsally adjacent Wnt positive epithalamus expands into the thalamus. This leads to an upregulation of Wnt signaling in the caudal forebrain. Lack of Lhx2/Lhx9 function as well as increased Wnt signaling alter the expression of the thalamus specific cell adhesion factor pcdh10b and lead subsequently to a striking anterior-posterior disorganization of the caudal forebrain. We therefore suggest that after initial neural tube patterning, neurogenesis within a brain compartment influences the integrity of the neuronal progenitor pool and border formation of a neuromeric compartment.
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Author URL.
2010
Scholpp S, Lumsden A (2010). Building a bridal chamber: development of the thalamus.
Trends Neurosci,
33(8), 373-380.
Abstract:
Building a bridal chamber: development of the thalamus.
The thalamus is a central brain region that plays a crucial role in distributing incoming sensory information to appropriate regions of the cortex. The thalamus develops in the posterior part of the embryonic forebrain, where early cell fate decisions are controlled by a local signaling center - the mid-diencephalic organizer - which forms at the boundary between prospective prethalamus and thalamus. In this review we discuss recent observations of early thalamic development in zebrafish, chick, and mouse embryos, that reveal a conserved set of interactions between homeodomain transcription factors. These interactions position the organizer along the neuraxis. The most prominent of the organizer's signals, Sonic hedgehog, is necessary for conferring regional identity on the prethalamus and thalamus and for patterning their differentiation.
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Author URL.
Blackshaw S, Scholpp S, Placzek M, Ingraham H, Simerly R, Shimogori T (2010).
Molecular pathways controlling development of thalamus and hypothalamus: from neural specification to circuit formation. 5 pages.
Abstract:
Molecular pathways controlling development of thalamus and hypothalamus: from neural specification to circuit formation.
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Author URL.
Peukert D, Scholpp S (2010). Ontogenesis of the brain: the development of the thalamus - the gateway to consciousness.
BioSpektrum,
16(6), 639-643.
Abstract:
Ontogenesis of the brain: the development of the thalamus - the gateway to consciousness
The development mechanism leading to the thalamus formation is largely unknown. Here, we describe the function of the signalling factor Shh and the bHLH protein Hero orchestrating the thalamic regionalization process.
Abstract.
Hagemann AI, Schindler S, Scholpp S (2010). The clathrin adaptor-protein subunit ap2m1 regulates canonical Wnt signalling in early neural development of the zebrafish.
Author URL.
Fassier C, Hutt JA, Scholpp S, Lumsden A, Giros B, Nothias F, Schneider-Maunoury S, Houart C, Hazan J (2010). Zebrafish atlastin controls motility and spinal motor axon architecture via inhibition of the BMP pathway.
Nat Neurosci,
13(11), 1380-1387.
Abstract:
Zebrafish atlastin controls motility and spinal motor axon architecture via inhibition of the BMP pathway.
To better understand hereditary spastic paraplegia (HSP), we characterized the function of atlastin, a protein that is frequently involved in juvenile forms of HSP, by analyzing loss- and gain-of-function phenotypes in the developing zebrafish. We found that knockdown of the gene for atlastin (atl1) caused a severe decrease in larval mobility that was preceded by abnormal architecture of spinal motor axons and was associated with a substantial upregulation of the bone morphogenetic protein (BMP) signaling pathway. Overexpression analyses confirmed that atlastin inhibits BMP signaling. In primary cultures of zebrafish spinal neurons, Atlastin partially colocalized with type I BMP receptors in late endosomes distributed along neurites, which suggests that atlastin may regulate BMP receptor trafficking. Finally, genetic or pharmacological inhibition of BMP signaling was sufficient to rescue the loss of mobility and spinal motor axon defects of atl1 morphants, emphasizing the importance of fine-tuning the balance of BMP signaling for vertebrate motor axon architecture and stability.
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Author URL.
2009
Yu SR, Burkhardt M, Nowak M, Ries J, Petrásek Z, Scholpp S, Schwille P, Brand M (2009). Fgf8 morphogen gradient forms by a source-sink mechanism with freely diffusing molecules.
Nature,
461(7263), 533-536.
Abstract:
Fgf8 morphogen gradient forms by a source-sink mechanism with freely diffusing molecules.
It is widely accepted that tissue differentiation and morphogenesis in multicellular organisms are regulated by tightly controlled concentration gradients of morphogens. How exactly these gradients are formed, however, remains unclear. Here we show that Fgf8 morphogen gradients in living zebrafish embryos are established and maintained by two essential factors: fast, free diffusion of single molecules away from the source through extracellular space, and a sink function of the receiving cells, regulated by receptor-mediated endocytosis. Evidence is provided by directly examining single molecules of Fgf8 in living tissue by fluorescence correlation spectroscopy, quantifying their local mobility and concentration with high precision. By changing the degree of uptake of Fgf8 into its target cells, we are able to alter the shape of the Fgf8 gradient. Our results demonstrate that a freely diffusing morphogen can set up concentration gradients in a complex multicellular tissue by a simple source-sink mechanism.
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Author URL.
Scholpp S, Delogu A, Gilthorpe J, Peukert D, Schindler S, Lumsden A (2009). Her6 regulates the neurogenetic gradient and neuronal identity in the thalamus.
Proc Natl Acad Sci U S A,
106(47), 19895-19900.
Abstract:
Her6 regulates the neurogenetic gradient and neuronal identity in the thalamus.
During vertebrate brain development, the onset of neuronal differentiation is under strict temporal control. In the mammalian thalamus and other brain regions, neurogenesis is regulated also in a spatially progressive manner referred to as a neurogenetic gradient, the underlying mechanism of which is unknown. Here we describe the existence of a neurogenetic gradient in the zebrafish thalamus and show that the progression of neurogenesis is controlled by dynamic expression of the bHLH repressor her6. Members of the Hes/Her family are known to regulate proneural genes, such as Neurogenin and Ascl. Here we find that Her6 determines not only the onset of neurogenesis but also the identity of thalamic neurons, marked by proneural and neurotransmitter gene expression: loss of Her6 leads to premature Neurogenin1-mediated genesis of glutamatergic (excitatory) neurons, whereas maintenance of Her6 leads to Ascl1-mediated production of GABAergic (inhibitory) neurons. Thus, the presence or absence of a single upstream regulator of proneural gene expression, Her6, leads to the establishment of discrete neuronal domains in the thalamus.
Abstract.
Author URL.
Scholpp S, Brand M (2009). Neural Patterning: Midbrain-Hindbrain Boundary. In (Ed)
Encyclopedia of Neuroscience, 205-211.
Abstract:
Neural Patterning: Midbrain-Hindbrain Boundary
Abstract.
2007
Wendl T, Adzic D, Schoenebeck JJ, Scholpp S, Brand M, Yelon D, Rohr KB (2007). Early developmental specification of the thyroid gland depends on han-expressing surrounding tissue and on FGF signals.
Development,
134(15), 2871-2879.
Abstract:
Early developmental specification of the thyroid gland depends on han-expressing surrounding tissue and on FGF signals.
The thyroid is an endocrine gland in all vertebrates that develops from the ventral floor of the anterior pharyngeal endoderm. Unravelling the molecular mechanisms of thyroid development helps to understand congenital hypothyroidism caused by the absence or reduction of this gland in newborn humans. Severely reduced or absent thyroid-specific developmental genes concomitant with the complete loss of the functional gland in the zebrafish hands off (han, hand2) mutant reveals the han gene as playing a novel, crucial role in thyroid development. han-expressing tissues surround the thyroid primordium throughout development. Fate mapping reveals that, even before the onset of thyroid-specific developmental gene expression, thyroid precursor cells are in close contact with han-expressing cardiac lateral plate mesoderm. Grafting experiments show that han is required in surrounding tissue, and not in a cell-autonomous manner, for thyroid development. Loss of han expression in the branchial arches and arch-associated cells after morpholino knock-down of upstream regulator genes does not impair thyroid development, indicating that other han-expressing structures, most probably cardiac mesoderm, are responsible for the thyroid defects in han mutants. The zebrafish ace (fgf8) mutant has similar thyroid defects as han mutants, and chemical suppression of fibroblast growth factor (FGF) signalling confirms that this pathway is required for thyroid development. FGF-soaked beads can restore thyroid development in han mutants, showing that FGFs act downstream of or in parallel to han. These data suggest that loss of FGF-expressing tissue in han mutants is responsible for the thyroid defects.
Abstract.
Author URL.
Scholpp S (2007). Hedgehogs, Fluorescence Imaging & Brain Development. infocus Magazine, 66-75.
Scholpp S, Foucher I, Staudt N, Peukert D, Lumsden A, Houart C (2007). Otx1l, Otx2 and Irx1b establish and position the ZLI in the diencephalon.
Development,
134(17), 3167-3176.
Abstract:
Otx1l, Otx2 and Irx1b establish and position the ZLI in the diencephalon.
The thalamic complex is the major sensory relay station in the vertebrate brain and comprises three developmental subregions: the prethalamus, the thalamus and an intervening boundary region - the zona limitans intrathalamica (ZLI). Shh signalling from the ZLI confers regional identity of the flanking subregions of the ZLI, making it an important local signalling centre for regional differentiation of the diencephalon. However, our understanding of the mechanisms responsible for positioning the ZLI along the neural axis is poor. Here we show that, before ZLI formation, both Otx1l and Otx2 (collectively referred to as Otx1l/2) are expressed in spatially restricted domains. Formation of both the ZLI and the Irx1b-positive thalamus require Otx1l/2; embryos impaired in Otx1l/2 function fail to form these areas, and, instead, the adjacent pretectum and, to a lesser extent, the prethalamus expand into the mis-specified area. Conditional expression of Otx2 in these morphant embryos cell-autonomously rescues the formation of the ZLI at its correct location. Furthermore, absence of thalamic Irx1b expression, in the presence of normal Otx1l/2 function, leads to a substantial caudal broadening of the ZLI by transformation of thalamic precursors. We therefore propose that the ZLI is induced within the competence area established by Otx1l/2, and is posteriorly restricted by Irx1b.
Abstract.
Author URL.
Erickson T, Scholpp S, Brand M, Moens CB, Waskiewicz AJ (2007). Pbx proteins cooperate with Engrailed to pattern the midbrain-hindbrain and diencephalic-mesencephalic boundaries.
Dev Biol,
301(2), 504-517.
Abstract:
Pbx proteins cooperate with Engrailed to pattern the midbrain-hindbrain and diencephalic-mesencephalic boundaries.
Pbx proteins are a family of TALE-class transcription factors that are well characterized as Hox co-factors acting to impart segmental identity to the hindbrain rhombomeres. However, no role for Pbx in establishing more anterior neural compartments has been demonstrated. Studies done in Drosophila show that Engrailed requires Exd (Pbx orthologue) for its biological activity. Here, we present evidence that zebrafish Pbx proteins cooperate with Engrailed to compartmentalize the midbrain by regulating the maintenance of the midbrain-hindbrain boundary (MHB) and the diencephalic-mesencephalic boundary (DMB). Embryos lacking Pbx function correctly initiate midbrain patterning, but fail to maintain eng2a, pax2a, fgf8, gbx2, and wnt1 expression at the MHB. Formation of the DMB is also defective as shown by a caudal expansion of diencephalic epha4a and pax6a expression into midbrain territory. These phenotypes are similar to the phenotype of an Engrailed loss-of-function embryo, supporting the hypothesis that Pbx and Engrailed act together on a common genetic pathway. Consistent with this model, we demonstrate that zebrafish Engrailed and Pbx interact in vitro and that this interaction is required for both the eng2a overexpression phenotype and Engrailed's role in patterning the MHB. Our data support a novel model of midbrain development in which Pbx and Engrailed proteins cooperatively pattern the mesencephalic region of the neural tube.
Abstract.
Author URL.
2006
Scholpp S, Wolf O, Brand M, Lumsden A (2006). Hedgehog signalling from the zona limitans intrathalamica orchestrates patterning of the zebrafish diencephalon.
Development,
133(5), 855-864.
Abstract:
Hedgehog signalling from the zona limitans intrathalamica orchestrates patterning of the zebrafish diencephalon.
Midway between the anterior neural border and the midbrain-hindbrain boundary, two well-known local signalling centres in the early developing brain, is a further transverse boundary with putative signalling properties -- the zona limitans intrathalamica (ZLI). Here, we describe formation of the ZLI in zebrafish in relation to expression of sonic hedgehog (shh) and tiggy-winkle hedgehog (twhh), and to development of the forebrain regions that flank the ZLI: the prethalamus and thalamus. We find that enhanced Hh signalling increases the size of prethalamic and thalamic gene expression domains, whereas lack of Hh signalling leads to absence of these domains. In addition, we show that shh and twhh display both unique and redundant functions during diencephalic patterning. Genetic ablation of the basal plate shows that Hh expression in the ZLI alone is sufficient for diencephalic differentiation. Furthermore, acquisition of correct prethalamic and thalamic gene expression is dependent on direct Hh signalling. We conclude that proper maturation of the diencephalon requires ZLI-derived Hh signalling.
Abstract.
Author URL.
2004
Scholpp S, Brand M (2004). Endocytosis controls spreading and effective signaling range of Fgf8 protein.
Curr Biol,
14(20), 1834-1841.
Abstract:
Endocytosis controls spreading and effective signaling range of Fgf8 protein.
Secreted signaling molecules released from a restricted source are of great importance during embryonic development because they elicit induction, proliferation, differentiation, and patterning events in target cells. Fgf8 is a member of the fibroblast growth factor family with key inductive functions during vertebrate development of, for example, the forebrain , midbrain , cerebellum , heart , inner ear , and mesoderm. However, the mechanism by which the signaling range of Fgf8 is controlled in a field of target cells is unknown. We studied Fgf8 as a potential morphogen in the nascent neuroectoderm of living zebrafish embryos. We find that spreading of epitope-tagged Fgf8 through target tissue is carefully controlled by endocytosis and subsequent degradation in lysosomes, or "restrictive clearance," from extracellular spaces. If internalization is inhibited, Fgf8 protein accumulates extracellularly, spreads further, and activates target gene expression over a greater distance. Conversely, enhanced internalization increases Fgf8 uptake and shortens its effective signaling range. Our results suggest that Fgf8 spreads extracellularly by a diffusion-based mechanism and demonstrate that target cells can actively influence, through endocytosis and subsequent degradation, the availability of Fgf8 ligand to other target cells.
Abstract.
Author URL.
Heinze KG, Schlopp S, Brand M, Schwille P (2004). Probing intercellular pathways and propagation of Fgf8 signalling protein during embryogenesis by FCS.
Author URL.
Scholpp S, Groth C, Lohs C, Lardelli M, Brand M (2004). Zebrafish fgfr1 is a member of the fgf8 synexpression group and is required for fgf8 signalling at the midbrain-hindbrain boundary.
Dev Genes Evol,
214(6), 285-295.
Abstract:
Zebrafish fgfr1 is a member of the fgf8 synexpression group and is required for fgf8 signalling at the midbrain-hindbrain boundary.
FGFR1 is an important signalling molecule during embryogenesis and in adulthood. FGFR1 mutations in human may lead to developmental defects and pathological conditions, including cancer and Alzheimer's disease. Here, we describe cloning and expression analysis of the zebrafish fibroblast growth factor receptor 1 ( fgfr1). Initially, fgfr1 is expressed in the adaxial mesoderm with transcripts distinctly localised to the anterior portion of each half-somite. Hereupon, fgfr1 is also strongly expressed in the otic vesicles, branchial arches and the brain, especially at the midbrain-hindbrain boundary (MHB). The expression patterns of fgfr1 and fgf8 are strikingly similar and knock-down of fgfr1 phenocopies many aspects observed in the fgf8 mutant acerebellar, suggesting that Fgf8 exerts its function mainly by binding to FgfR1.
Abstract.
Author URL.
2003
Scholpp S, Brand M (2003). Endocytosis controls propagation of Fgf8 during zebrafish embryogenesis.
Author URL.
Scholpp S, Lohs C, Brand M (2003). Engrailed and Fgf8 act synergistically to maintain the boundary between diencephalon and mesencephalon.
Development,
130(20), 4881-4893.
Abstract:
Engrailed and Fgf8 act synergistically to maintain the boundary between diencephalon and mesencephalon.
Specification of the forebrain, midbrain and hindbrain primordia occurs during gastrulation in response to signals that pattern the gastrula embryo. Following establishment of the primordia, each brain part is thought to develop largely independently from the others under the influence of local organizing centers like the midbrain-hindbrain boundary (MHB, or isthmic) organizer. Mechanisms that maintain the integrity of brain subdivisions at later stages are not yet known. To examine such mechanisms in the anterior neural tube, we have studied the establishment and maintenance of the diencephalic-mesencephalic boundary (DMB). We show that maintenance of the DMB requires both the presence of a specified midbrain and a functional MHB organizer. Expression of pax6.1, a key regulator of forebrain development, is posteriorly suppressed by the Engrailed proteins, Eng2 and Eng3. Mis-expression of eng3 in the forebrain primordium causes downregulation of pax6.1, and forebrain cells correspondingly change their fate and acquire midbrain identity. Conversely, in embryos lacking both eng2 and eng3, the DMB shifts caudally into the midbrain territory. However, a patch of midbrain tissue remains between the forebrain and the hindbrain primordia in such embryos. This suggests that an additional factor maintains midbrain cell fate. We find that Fgf8 is a candidate for this signal, as it is both necessary and sufficient to repress pax6.1 and hence to shift the DMB anteriorly independently of the expression status of eng2/eng3. By examining small cell clones that are unable to receive an Fgf signal, we show that cells in the presumptive midbrain neural plate require an Fgf signal to keep them from following a forebrain fate. Combined loss of both Eng2/Eng3 and Fgf8 leads to complete loss of midbrain identity, resulting in fusion of the forebrain and the hindbrain primordia. Thus, Eng2/Eng3 and Fgf8 are necessary to maintain midbrain identity in the neural plate and thereby position the DMB. This provides an example of a mechanism needed to maintain the subdivision of the anterior neural plate into forebrain and midbrain.
Abstract.
Author URL.
Scholpp S, Lohs C, Brand M (2003). Erratum: Engrailed and Fgf8 act synergistically to maintain the boundary between diencephalon and mesencephalon (Development vol. 130 (4881-4893)). Development, 130(21).
Scholpp S, Brand M (2003). Integrity of the midbrain region is required to maintain the diencephalic-mesencephalic boundary in zebrafish no isthmus/pax2.1 mutants.
Dev Dyn,
228(3), 313-322.
Abstract:
Integrity of the midbrain region is required to maintain the diencephalic-mesencephalic boundary in zebrafish no isthmus/pax2.1 mutants.
Initial anterior-posterior patterning of the neural tube into forebrain, midbrain, and hindbrain primordia occurs already during gastrulation, in response to signals patterning the gastrula embryo. After the initial establishment, further development within each brain part is thought to proceed largely independently of the others. However, mechanisms should exist that ensure proper delineation of brain subdivisions also at later stages; such mechanisms are, however, poorly understood. In zebrafish no isthmus mutant embryos, inactivation of the pax2.1 gene leads to a failure of the midbrain and isthmus primordium to develop normally from the gastrula stage onward (Lun and Brand [1998] Development 125:3049-3062). Here, we report that, after the initially correct establishment during gastrulation stages, the neighbouring forebrain primordium and, partially, the hindbrain primordium expand into the misspecified midbrain territory in no isthmus mutant embryos. The expansion is particularly evident for the posterior part of the diencephalon and less so for the first rhombomeric segment, the territories immediately abutting the midbrain/isthmus primordium. The nucleus of the posterior commissure is expanded in size, and marker genes of the forebrain and rhombomere 1 expand progressively into the misspecified midbrain primordium, eventually resulting in respecification of the midbrain primordium. We therefore suggest that the genetic program controlled by Pax2.1 is not only involved in initiating but also in maintaining the identity of midbrain and isthmus cells to prevent them from assuming a forebrain or hindbrain fate.
Abstract.
Author URL.
2002
Picker A, Scholpp S, Böhli H, Takeda H, Brand M (2002). A novel positive transcriptional feedback loop in midbrain-hindbrain boundary development is revealed through analysis of the zebrafish pax2.1 promoter in transgenic lines.
Development,
129(13), 3227-3239.
Abstract:
A novel positive transcriptional feedback loop in midbrain-hindbrain boundary development is revealed through analysis of the zebrafish pax2.1 promoter in transgenic lines.
The pax2.1 gene encodes a paired-box transcription factor that is one of the earliest genes to be specifically activated in development of the midbrain and midbrain-hindbrain boundary (MHB), and is required for the development and organizer activity of this territory. To understand how this spatially restricted transcriptional activity of pax2.1 is achieved, we have isolated and characterized the pax2.1-promoter using a lacZ and a GFP reporter gene in transient injection assays and transgenic lines. Stable transgenic expression of this reporter gene shows that a 5.3-kb fragment of the 5' region contains most, but not all, elements required for driving pax2.1 expression. The expressing tissues include the MHB, hindbrain, spinal cord, ear and pronephros. Transgene activation in the pronephros and developing ear suggests that these pax2.1-expressing tissues are composed of independently regulated subdomains. In addition, ectopic but spatially restricted activation of the reporter genes in rhombomeres 3 and 5 and in the forebrain, which do not normally express endogenous pax2.1, demonstrates the importance of negative regulation of pax2.1. Comparison of transgene expression in wild-type and homozygous pax2.1 mutant no isthmus (noi) embryos reveals that the transgene contains control element(s) for a novel, positive transcriptional feedback loop in MHB development. Transcription of endogenous pax2.1 at the MHB is known to be initially Pax2.1 independent, during activation in late gastrulation. In contrast, transgene expression requires the endogenous Pax2.1 function. Transplantations, mRNA injections and morpholino knock-down experiments show that this feedback regulation of pax2.1 transcription occurs cell-autonomously, and that it requires eng2 and eng3 as known targets for Pax2.1 regulation. We suggest that this novel feedback loop may allow continuation of pax2.1 expression, and hence development of the MHB organizer, to become independent of the patterning machinery of the gastrula embryo.
Abstract.
Author URL.
2001
Scholpp S, Brand M (2001). Morpholino-induced knockdown of zebrafish engrailed genes eng2 and eng3 reveals redundant and unique functions in midbrain--hindbrain boundary development.
Genesis,
30(3), 129-133.
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