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Salvador Martinez - One of the best experts on this subject based on the ideXlab platform.
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PATTERNS & PHENOTYPES Expression of Chick Fgf19 and Mouse Fgf15 Orthologs Is Regulated in the Developing
2015Co-Authors: Brain Fgf, Leticia Gimeno, Salvador MartinezAbstract:Fibroblast growth factors (Fgfs) constitute a family of signaling molecules that play essential roles in development. We have studied the expression pattern of mouse Fgf15 in the developing brain. Fgf19 is another member of the FGF family that has been suggested as the chick and human ortholog of mouse and rat Fgf15. Here, we compare the expression pattern during neural development of chick Fgf19 with mouse Fgf15. Unlike Fgf15, Fgf19 presents an expression in the isthmic alar plate, diencephalic and mesencephalic parabasal plates, hindbrain basal plate, as well as in the Zona Limitans Intrathalamica (zli). Moreover, we explored the regulation between Fgf19 and the signaling molecules of the isthmic and zli organizers: Fgf8 and Shh, respectively. Considering the possibility that Fgf19 plays a similar role in humans and chicks, this finding could explain the significant diencephalic phenotypic differences between humans and mice in models and diseases where the Shh pathway is affected. Developmental Dynamics 236:2285–2297, 2007
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Endogenous and ectopic expression of Mgn.
2015Co-Authors: Clara-zoe Wende, Diego Echevarria, Salvador Martinez, Saida Zoubaa, Alexandra Blak, François Guillemot, Wolfgang Wurst, Jordi GuimeraAbstract:(A) Relative expression levels of Mgn and Mash1 in mutant to wild-type mice. The bar height and error bars show the mean and standard deviation, respectively. (B)Mgn mRNA was expressed at high levels in the vlMB of E12.5 mouse embryos compared with the low level of expression in the dMB determined by ISH, LacZ staining of MgntLacZ mice, and IHC of wild-type embryos with the anti-MGN antibody on coronal sections. The lines indicated the borders of m3-m5 domains. MASH1 protein is also expressed at higher levels in the vlMB compared with its dorsal expression, as determined by IHC with anti-MASH1 antibody. (C) WISH was performed with Gad67 probe in ONTC of wild-type E11.5 embryos with Mgn cDNA electroporated in one of the sides (right side), whereas the other side served as a control (left side). The neural tube is opened along the ventral anterior-posterior axis. Lightning bolt icons point to the ectopic expression of Gad67 after Mgn electroporation. Subdomains are shown according to the prosomeric model [21]. (D) WISH was performed with a Gad67 probe in the ONTCs of E11.5 wild-type mouse embryos after 10 h of incubation. The red dashed line delineates the alar/basal (a/b) boundary. The black dashed lines delineate the transversal neural tube domain boundaries. (E and F) E11.5 Mash1−/− ONTCs 24 h after micro-electroporation in the mesencephalic alar plate with the Mgn-IRES-EGFP plasmid. (E) A fluorescence signal showing the electroporated location. (F) Induction of Gad67 expression after electroporation of Mgn cDNA in Mash1−/− background embryos. (F1) A merged profile of the fluorescence signal and Gad67 induction. Scale bars: 500 μm. Abbreviations: a/b, alar/basal plate boundary; d/m, diencephalic–mesencephalic boundary; Hy, hypothalamus; Is, isthmus; p1–p3, prosomeres 1 to 3 in diencephalon; PcP, precommissural domain in the pretectum (p1); rp, roof plate; Zli, Zona Limitans Intrathalamica.
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wnt signal specifies the intrathalamic limit and its organizer properties by regulating shh induction in the alar plate
The Journal of Neuroscience, 2013Co-Authors: Almudena Martinezferre, Maria Navarrogarberi, C G Bueno, Salvador MartinezAbstract:The structural complexity of the brain depends on precise molecular and cellular regulatory mechanisms orchestrated by regional morphogenetic organizers. The thalamic organizer is the Zona Limitans Intrathalamica (ZLI), a transverse linear neuroepithelial domain in the alar plate of the diencephalon. Because of its production of Sonic hedgehog, ZLI acts as a morphogenetic signaling center. Shh is expressed early on in the prosencephalic basal plate and is then gradually activated dorsally within the ZLI. The anteroposterior positioning and the mechanism inducing Shh expression in ZLI cells are still partly unknown, being a subject of controversial interpretations. For instance, separate experimental results have suggested that juxtaposition of prechordal (rostral) and epichordal (caudal) neuroepithelium, anteroposterior encroachment of alar lunatic fringe (L-fng) expression, and/or basal Shh signaling is required for ZLI specification. Here we investigated a key role of Wnt signaling in the molecular regulation of ZLI positioning and Shh expression, using experimental embryology in ovo in the chick. Early Wnt expression in the ZLI regulates Gli3 and L-fng to generate a permissive territory in which Shh is progressively induced by planar signals of the basal plate.
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patterning of the diencephalon
Patterning and Cell Type Specification in the Developing CNS and PNS#R##N#Comprehensive Developmental Neuroscience, 2013Co-Authors: Luis Puelles, Salvador MartinezAbstract:The anatomic complexity of the diencephalon (considered here as defined within the prosomeric model; Puelles L and Rubenstein JLR (2003) Forebrain gene expression domains and the evolving prosomeric model. Trends in Neurosciences 9: 469–476; Puelles L, Martinez-de-la-Torre M, Paxinos G, Watson C, and Martinez S (2007) The Chick Brain in Stereotaxic Coordinates: an Atlas featuring Neuromeric Subdivisions and Mammalian Homologies . San Diego: Elsevier/Academic Press; Puelles L, Martinez-de-la-Torre M, Bardet S, and Rubenstein JLR (2012) Hypothalamus. In: Watson C, Paxinos G, and Puelles L (eds.) The Mouse Nervous System , pp. 221–312. London: Academic Press (Elsevier); Puelles L, Martinez-de-la-Torre M, Bardet S, and Rubenstein JLR (2012) Diencephalon. In: Watson C, Paxinos G, and Puelles L (eds.) The Mouse Nervous System , pp. 313–336. London: Academic Press (Elsevier) is the result of various molecular and cellular regulative patterning mechanisms orchestrated by signaling from different morphogenetic organizers during early development, at both neural plate and neural tube stages ( Martinez S, Puelles E, Puelles L, and Echevarria D (2012) Molecular regionalization of the developing neural tube. In: Watson C, Paxinos G, and Puelles L (eds.) The Mouse Nervous System , pp. 2–18. London: Academic Press (Elsevier)). In the diencephalon, like that in the rest of the brain, a variety of graded signals modulate positional information along the dorsoventral and anteroposterior (AP) dimensions, leading to areal neuroepithelial regionalization, that is, emergence of a differential molecular identity of characteristic areal patches of progenitor cells. Dorsalizing molecular signals such as retinoic acid, Fgf8, bone morphogenetic proteins, and Wnts are postulated to diffuse ventralward from the diencephalic roof plate. They interact antagonistically with Shh protein and other ventralizing signals produced first at the notochord and later also at the floor and basal plates of the diencephalon, which diffuse upward across the alar–basal boundary. Both effects participate in alar–basal patterning, which includes formation of an intermediate liminal territory with peculiar characteristics. The diencephalon is also regionalized along the AP dimension, after separating from the hypothalamus and telencephalon, rostrally, and from the midbrain, caudally. An intrinsic diencephalic secondary organizer, the Zona Limitans Intrathalamica (ZLI), also known as mid-diencephalic organizer, develops transversally after neurulation in a central part of the diencephalic alar plate, and releases supplementary Shh along the AP axis. The consequent rostralward and caudalward signaling increases regional complexity by establishing added differential anteroposterior positional codes within the alar plate. ZLI signaling emerges as a singular mechanism that cooperates with earlier diencephalic conditions to pattern the three neuromeric developmental units of the diencephalon, defined as prosomeres 1–3 (p1–p3) in the prosomeric model ( Martinez S, Puelles E, Puelles L, and Echevarria D (2012) Molecular regionalization of the developing neural tube. In: Watson C, Paxinos G, and Puelles L (eds.) The Mouse Nervous System , pp. 2–18. London: Academic Press (Elsevier); Puelles L and Rubenstein JLR (2003) Forebrain gene expression domains and the evolving prosomeric model. Trends in Neurosciences 9: 469–476). These encompass alar pretectal, thalamic, and prethalamic territories, respectively, as well as corresponding basal (tegmental) territories.
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Fgf8-related secondary organizers exert different polarizing planar instructions along the mouse anterior neural tube.
PloS one, 2012Co-Authors: Ivan Crespo-enriquez, Juha Partanen, Salvador Martinez, Diego EchevarriaAbstract:Early brain patterning depends on proper arrangement of positional information. This information is given by gradients of secreted signaling molecules (morphogens) detected by individual cells within the responding tissue, leading to specific fate decisions. Here we report that the morphogen FGF8 exerts initially a differential signal activity along the E9.5 mouse neural tube. We demonstrate that this polarizing activity codes by RAS-regulated ERK1/2 signaling and depends on the topographical location of the secondary organizers: the isthmic organizer (IsO) and the anterior neural ridge (anr) but not on Zona Limitans Intrathalamica (zli). Our results suggest that Sprouty2, a negative modulator of RAS/ERK pathway, is important for regulating Fgf8 morphogenetic signal activity by controlling Fgf8-induced signaling pathways and positional information during early brain development.
Andrew Lumsden - One of the best experts on this subject based on the ideXlab platform.
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tissue interactions in the developing chick diencephalon
Neural Development, 2007Co-Authors: Maria Flavia Guinazu, Andrew Lumsden, David J Chambers, Clemens KieckerAbstract:Background The developing vertebrate brain is patterned first by global signalling gradients that define crude anteroposterior and dorsoventral coordinates, and subsequently by local signalling centres (organisers) that refine cell fate assignment within pre-patterned regions. The interface between the prethalamus and the thalamus, the Zona Limitans Intrathalamica (ZLI), is one such local signalling centre that is essential for the establishment of these major diencephalic subdivisions by secreting the signalling factor Sonic hedgehog. Various models for ZLI formation have been proposed, but a thorough understanding of how this important local organiser is established is lacking.
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Tissue interactions in the developing chick diencephalon
Neural Development, 2007Co-Authors: Maria Flavia Guinazu, Andrew Lumsden, David Chambers, Clemens KieckerAbstract:Background The developing vertebrate brain is patterned first by global signalling gradients that define crude anteroposterior and dorsoventral coordinates, and subsequently by local signalling centres (organisers) that refine cell fate assignment within pre-patterned regions. The interface between the prethalamus and the thalamus, the Zona Limitans Intrathalamica (ZLI), is one such local signalling centre that is essential for the establishment of these major diencephalic subdivisions by secreting the signalling factor Sonic hedgehog. Various models for ZLI formation have been proposed, but a thorough understanding of how this important local organiser is established is lacking. Results Here, we describe tissue explant experiments in chick embryos aimed at characterising the roles of different forebrain areas in ZLI formation. We found that: the ZLI becomes specified unexpectedly early; flanking regions are required for its characteristic morphogenesis; ZLI induction can occur independently from ventral tissues; interaction between any prechordal and epichordal neuroepithelial tissue anterior to the midbrain-hindbrain boundary is able to generate a ZLI; and signals from the dorsal diencephalon antagonise ZLI formation. We further show that a localised source of retinoic acid in the dorsal diencephalon is a likely candidate to mediate this inhibitory signal. Conclusion Our results are consistent with a model where planar, rather than vertical, signals position the ZLI at early stages of neural development and they implicate retinoic acid as a novel molecular cue that determines its dorsoventral extent.
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Analysis of Lrrn1 expression and its relationship to neuromeric boundaries during chick neural development
Neural Development, 2007Co-Authors: Laura C Andreae, Daniela Peukert, Andrew Lumsden, Jonathan D GilthorpeAbstract:Background The Drosophila leucine-rich repeat proteins Tartan (TRN) and Capricious (CAPS) mediate cell affinity differences during compartition of the wing imaginal disc. This study aims to identify and characterize the expression of a chick orthologue of TRN/CAPS and examine its potential function in relation to compartment boundaries in the vertebrate central nervous system. Results We identified a complementary DNA clone encoding Leucine-rich repeat neuronal 1 (Lrrn1), a single-pass transmembrane protein with 12 extracellular leucine-rich repeats most closely related to TRN/CAPS. Lrrn1 is dynamically expressed during chick development, being initially localized to the neural plate and tube, where it is restricted to the ventricular layer. It becomes downregulated in boundaries following their formation. In the mid-diencephalon, Lrrn1 expression prefigures the position of the anterior boundary of the Zona Limitans Intrathalamica (ZLI). It becomes progressively downregulated from the presumptive ZLI just before the onset of expression of the signalling molecule Sonic hedgehog (Shh) within the ZLI. In the hindbrain, downregulation at rhombomere boundaries correlates with the emergence of specialized boundary cell populations, in which it is subsequently reactivated. Immunocolocalization studies confirm that Lrrn1 protein is endocytosed from the plasma membrane and is a component of the endosomal system, being concentrated within the early endosomal compartment. Conclusion Chick Lrrn1 is expressed in ventricular layer neuroepithelial cells and is downregulated at boundary regions, where neurogenesis is known to be delayed, or inhibited. The timing of Lrrn1 downregulation correlates closely with the activation of signaling molecule expression at these boundaries. This expression is consistent with the emergence of secondary organizer properties at boundaries and its endosomal localisation suggests that Lrrn1 may regulate the subcellular localisation of specific components of signalling or cell-cell recognition pathways in neuroepithelial cells.
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otx1l otx2 and irx1b establish and position the zli in the diencephalon
Development, 2007Co-Authors: Steffen Scholpp, Daniela Peukert, Andrew Lumsden, Isabelle Foucher, Nicole Staudt, Corinne HouartAbstract: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.
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hedgehog signalling from the Zona Limitans Intrathalamica orchestrates patterning of the zebrafish diencephalon
Development, 2006Co-Authors: Steffen Scholpp, Olivia Wolf, Michael Brand, Andrew LumsdenAbstract: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.
Kerstin Feistel - One of the best experts on this subject based on the ideXlab platform.
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An Evolutionarily Conserved Network Mediates Development of the Zona Limitans Intrathalamica, a Sonic Hedgehog-Secreting Caudal Forebrain Signaling Center
Journal of Developmental Biology, 2016Co-Authors: Elena Sena, Kerstin Feistel, Béatrice DurandAbstract:Recent studies revealed new insights into the development of a unique caudal forebrain-signaling center: the Zona Limitans Intrathalamica (zli). The zli is the last brain signaling center to form and the first forebrain compartment to be established. It is the only part of the dorsal neural tube expressing the morphogen Sonic Hedgehog (Shh) whose activity participates in the survival, growth and patterning of neuronal progenitor subpopulations within the thalamic complex. Here, we review the gene regulatory network of transcription factors and cis-regulatory elements that underlies formation of a shh-expressing delimitated domain in the anterior brain. We discuss evidence that this network predates the origin of chordates. We highlight the contribution of Shh, Wnt and Notch signaling to zli development and discuss implications for the fact that the morphogen Shh relies on primary cilia for signal transduction. The network that underlies zli development also contributes to thalamus induction, and to its patterning once the zli has been set up. We present an overview of the brain malformations possibly associated with developmental defects in this gene regulatory network (GRN).
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ciliogenesis and cerebrospinal fluid flow in the developing xenopus brain are regulated by foxj1
Cilia, 2013Co-Authors: Cathrin Hagenlocher, Peter Walentek, Christina Muller, Thomas Thumberger, Kerstin FeistelAbstract:Circulation of cerebrospinal fluid (CSF) through the ventricular system is driven by motile cilia on ependymal cells of the brain. Disturbed ciliary motility induces the formation of hydrocephalus, a pathological accumulation of CSF resulting in ventricle dilatation and increased intracranial pressure. The mechanism by which loss of motile cilia causes hydrocephalus has not been elucidated. The aim of this study was: (1) to provide a detailed account of the development of ciliation in the brain of the African clawed frog Xenopus laevis; and (2) to analyze the relevance of ependymal cilia motility for CSF circulation and brain ventricle morphogenesis in Xenopus. Gene expression analysis of foxj1, the bona fide marker for motile cilia, was used to identify potentially ciliated regions in the developing central nervous system (CNS) of the tadpole. Scanning electron microscopy (SEM) was used to reveal the distribution of mono- and multiciliated cells during successive stages of brain morphogenesis, which was functionally assessed by bead injection and video microscopy of ventricular CSF flow. An antisense morpholino oligonucleotide (MO)-mediated gene knock-down that targeted foxj1 in the CNS was applied to assess the role of motile cilia in the ventricles. RNA transcripts of foxj1 in the CNS were found from neurula stages onwards. Following neural tube closure, foxj1 expression was seen in distinct ventricular regions such as the Zona Limitans Intrathalamica (ZLI), subcommissural organ (SCO), floor plate, choroid plexus (CP), and rhombomere boundaries. In all areas, expression of foxj1 preceded the outgrowth of monocilia and the subsequent switch to multiciliated ependymal cells. Cilia were absent in foxj1 morphants, causing impaired CSF flow and fourth ventricle hydrocephalus in tadpole-stage embryos. Motile ependymal cilia are important organelles in the Xenopus CNS, as they are essential for the circulation of CSF and maintenance of homeostatic fluid pressure. The Xenopus CNS ventricles might serve as a novel model system for the analysis of human ciliary genes whose deficiency cause hydrocephalus.
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Ciliogenesis and cerebrospinal fluid flow in the developing Xenopus brain are regulated by foxj1
Cilia, 2013Co-Authors: Cathrin Hagenlocher, Peter Walentek, Christina Muller, Thomas Thumberger, Kerstin FeistelAbstract:Background Circulation of cerebrospinal fluid (CSF) through the ventricular system is driven by motile cilia on ependymal cells of the brain. Disturbed ciliary motility induces the formation of hydrocephalus, a pathological accumulation of CSF resulting in ventricle dilatation and increased intracranial pressure. The mechanism by which loss of motile cilia causes hydrocephalus has not been elucidated. The aim of this study was: (1) to provide a detailed account of the development of ciliation in the brain of the African clawed frog Xenopus laevis ; and (2) to analyze the relevance of ependymal cilia motility for CSF circulation and brain ventricle morphogenesis in Xenopus . Methods Gene expression analysis of foxj1 , the bona fide marker for motile cilia, was used to identify potentially ciliated regions in the developing central nervous system (CNS) of the tadpole. Scanning electron microscopy (SEM) was used to reveal the distribution of mono- and multiciliated cells during successive stages of brain morphogenesis, which was functionally assessed by bead injection and video microscopy of ventricular CSF flow. An antisense morpholino oligonucleotide (MO)-mediated gene knock-down that targeted foxj1 in the CNS was applied to assess the role of motile cilia in the ventricles. Results RNA transcripts of foxj1 in the CNS were found from neurula stages onwards. Following neural tube closure, foxj1 expression was seen in distinct ventricular regions such as the Zona Limitans Intrathalamica (ZLI), subcommissural organ (SCO), floor plate, choroid plexus (CP), and rhombomere boundaries. In all areas, expression of foxj1 preceded the outgrowth of monocilia and the subsequent switch to multiciliated ependymal cells. Cilia were absent in foxj1 morphants, causing impaired CSF flow and fourth ventricle hydrocephalus in tadpole-stage embryos. Conclusions Motile ependymal cilia are important organelles in the Xenopus CNS, as they are essential for the circulation of CSF and maintenance of homeostatic fluid pressure. The Xenopus CNS ventricles might serve as a novel model system for the analysis of human ciliary genes whose deficiency cause hydrocephalus.
Claudia Vieira - One of the best experts on this subject based on the ideXlab platform.
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Sonic hedgehog from the basal plate and the Zona Limitans Intrathalamica exhibits differential activity on diencephalic molecular regionalization and nuclear structure
Neuroscience, 2006Co-Authors: Claudia Vieira, Salvador MartinezAbstract:The diencephalon is the most complex area of the vertebrate brain, being particularly complex in amniotes. It has been suggested that diencephalic regionalization partially depends on local signaling mediated by sonic hedgehog (Shh). However, since the Shh gene is expressed in both the diencephalic basal plate and the Zona Limitans Intrathalamica (ZLI), it is still unclear which of these tissues exerts morphogenetic influence on thalamic regionalization. In the present study using chick and quail embryos, we have found that although Shh from the ZLI and the basal plate induces ectopic expression of diencephalic genes in the posterior prosencephalic alar plate, only Shh originating from the ZLI can induce ectopic gene expression in the anterior alar plate, indicating that the ZLI exerts specific activity in the anterior epithelium. By introducing microbarriers between the diencephalic alar neuroepithelium and either the ZLI or the basal plate, we generated local loss of Shh expression in the ZLI, leading to alterations in molecular regionalization and subsequently, in the nuclear organization of the alar diencephalic derivatives on both sides of the ZLI. We thus demonstrate in vivo that basal signals are required to induce Shh expression in the ZLI and that Shh from the ZLI plays a pivotal role in regionalizing the alar diencephalon. The structural phenotype of Shh abolition in the ZLI consisted of a progressive pattern of alterations in diencephalic organization which were associated with the observed gradient effects in the molecular regionalization of the diencephalon. We conclude that the ZLI is a secondary organizer which exerts its morphogenetic activity through Shh.
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Thalamic development induced by Shh in the chick embryo.
Developmental Biology, 2005Co-Authors: Claudia Vieira, Ana Lila Garda, Kenji Shimamura, Salvador MartinezAbstract:Patterning of the early neural tube is achieved in part by the inductive signals, which arise from neuroepithelial signaling centers. The Zona Limitans Intrathalamica (ZLI) is a neuroepithelial domain in the alar plate of the diencephalon which separates the prethalamus from the thalamus. The ZLI has recently been considered to be a possible secondary organizer, effecting its inductions via sonic hedgehog (Shh), a signaling molecule which drives morphogenetic information for the thalamus. Using experimental embryological techniques involving the generation of chimeric embryos, we show that the formation of the ZLI in the diencephalic alar plate is due to an interaction between the prechordal and epichordal plate neuroepithelia. We also provide evidence that Shh expression in the ZLI underlies the morphogenetic activity of this putative diencephalic organizer. Ectopic Shh led to the auto-induction of its own gene expression in host cells, as well as to the expression of other genes involved in diencephalic regionalization and histogenesis. Analysis of long-term surviving embryos after Shh ectopic expression demonstrated that Shh was able to induce thalamic structures and local overgrowth. Overall, these results indicate that Shh expressed in the ZLI plays an important role in diencephalic growth and in the development of the thalamus.
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fate map of the diencephalon and the Zona Limitans at the 10 somites stage in chick embryos
Developmental Biology, 2004Co-Authors: Raquel Garcialopez, Claudia Vieira, Diego Echevarria, Salvador MartinezAbstract:Abstract The diencephalon is a central area of the vertebrate developing brain, where the thalamic nuclear complex, the pretectum and the anterior tegmental structures are generated. It has been subdivided into prosomeres, which are transversal domains defined by morphological and molecular criteria. The Zona Limitans Intrathalamica is a central boundary in the diencephalon that separates the posterior diencephalon (prosomeres 1 and 2), from the anterior diencephalon (prosomere 3). This intrathalamic limit appears early on in neural tube development, and the molecular pattern that it reveals suggests an important role in the diencephalic histogenesis. We hereby present a fate map of the presumptive territories in the diencephalon of a chick embryo at the 10–11 somite stages (HH9–10), by homotopic and isochronic quail–chick grafts. The anatomical interpretation of chimeric brains was aided by correlative whole-mount in situ hybridization with RNA probes for chicken genes expressed in specific diencephalic territories. The resulting fate map describes the distribution of the presumptive diencephalic prosomeres in the neural tube, and demonstrates their topologically conserved relationships throughout the neural development. Moreover, we show that the presumptive epithelium of ZLI can be localized at early developmental stages in the diencephalic alar plate at the anterior limit of the Wnt8b gene expression domain.
Diego Echevarria - One of the best experts on this subject based on the ideXlab platform.
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Endogenous and ectopic expression of Mgn.
2015Co-Authors: Clara-zoe Wende, Diego Echevarria, Salvador Martinez, Saida Zoubaa, Alexandra Blak, François Guillemot, Wolfgang Wurst, Jordi GuimeraAbstract:(A) Relative expression levels of Mgn and Mash1 in mutant to wild-type mice. The bar height and error bars show the mean and standard deviation, respectively. (B)Mgn mRNA was expressed at high levels in the vlMB of E12.5 mouse embryos compared with the low level of expression in the dMB determined by ISH, LacZ staining of MgntLacZ mice, and IHC of wild-type embryos with the anti-MGN antibody on coronal sections. The lines indicated the borders of m3-m5 domains. MASH1 protein is also expressed at higher levels in the vlMB compared with its dorsal expression, as determined by IHC with anti-MASH1 antibody. (C) WISH was performed with Gad67 probe in ONTC of wild-type E11.5 embryos with Mgn cDNA electroporated in one of the sides (right side), whereas the other side served as a control (left side). The neural tube is opened along the ventral anterior-posterior axis. Lightning bolt icons point to the ectopic expression of Gad67 after Mgn electroporation. Subdomains are shown according to the prosomeric model [21]. (D) WISH was performed with a Gad67 probe in the ONTCs of E11.5 wild-type mouse embryos after 10 h of incubation. The red dashed line delineates the alar/basal (a/b) boundary. The black dashed lines delineate the transversal neural tube domain boundaries. (E and F) E11.5 Mash1−/− ONTCs 24 h after micro-electroporation in the mesencephalic alar plate with the Mgn-IRES-EGFP plasmid. (E) A fluorescence signal showing the electroporated location. (F) Induction of Gad67 expression after electroporation of Mgn cDNA in Mash1−/− background embryos. (F1) A merged profile of the fluorescence signal and Gad67 induction. Scale bars: 500 μm. Abbreviations: a/b, alar/basal plate boundary; d/m, diencephalic–mesencephalic boundary; Hy, hypothalamus; Is, isthmus; p1–p3, prosomeres 1 to 3 in diencephalon; PcP, precommissural domain in the pretectum (p1); rp, roof plate; Zli, Zona Limitans Intrathalamica.
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Fgf8-related secondary organizers exert different polarizing planar instructions along the mouse anterior neural tube.
PloS one, 2012Co-Authors: Ivan Crespo-enriquez, Juha Partanen, Salvador Martinez, Diego EchevarriaAbstract:Early brain patterning depends on proper arrangement of positional information. This information is given by gradients of secreted signaling molecules (morphogens) detected by individual cells within the responding tissue, leading to specific fate decisions. Here we report that the morphogen FGF8 exerts initially a differential signal activity along the E9.5 mouse neural tube. We demonstrate that this polarizing activity codes by RAS-regulated ERK1/2 signaling and depends on the topographical location of the secondary organizers: the isthmic organizer (IsO) and the anterior neural ridge (anr) but not on Zona Limitans Intrathalamica (zli). Our results suggest that Sprouty2, a negative modulator of RAS/ERK pathway, is important for regulating Fgf8 morphogenetic signal activity by controlling Fgf8-induced signaling pathways and positional information during early brain development.
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Bafilomycin A1 (BAF) treatment demonstrates the polarization of ERK activity by FGF8 signal activity along the neural tube.
2012Co-Authors: Ivan Crespo-enriquez, Juha Partanen, Salvador Martinez, Diego EchevarriaAbstract:A-C) BAF amplifies ectopic ERK1/2 activity-related FGF8 induction revealing a clear polarized distribution of ERK1/2 activity around FGF8 soaked beads depending of the implanted bead; rostral to IsO (C,D,G), or caudal to IsO (C,E). Nonetheles, isthmic organizer morphogenetic activity seems unaffected for Fgf8 (A) and negative regulator Sprouty 2 (B) expressions. Note that PBS bead implantation in control side (blue asterisk in C and F) did not show any ectopic induction. Two hours after bead implantation a clear amplified and almost non-homogeneous ERK1/2 activity was detected rostrally in the mesencephalon (rostral to the IsO), which was detected caudally when bead was placed in hindbrain (caudal to the IsO) territories (E). In telencephalic vesicles, caudal to the anr (H) the polarity of ERK activation was reversed. This polarized dpERK detection around the bead is lost at the zli (Zona Limitans Intrathalamica) region (I). Similar symmetric ERK-related FGF8 signal found in zli was seen when placing a FGF8 bead in the midbrain of Fgf8 hypomorphic mice (J,K). Importantly FGF8b protein distribution (M) was observed apparently in equal intensity and range at rostral (N) and caudal (O) sides of the bead (for comparison with PBS bead in panel L). Scale bars are 0,5 mm in A, B, C, H, I, 200 µm in D, E, J, 100 µm in F, G, K, L, M, and 50 µm in N, O.
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fate map of the diencephalon and the Zona Limitans at the 10 somites stage in chick embryos
Developmental Biology, 2004Co-Authors: Raquel Garcialopez, Claudia Vieira, Diego Echevarria, Salvador MartinezAbstract:Abstract The diencephalon is a central area of the vertebrate developing brain, where the thalamic nuclear complex, the pretectum and the anterior tegmental structures are generated. It has been subdivided into prosomeres, which are transversal domains defined by morphological and molecular criteria. The Zona Limitans Intrathalamica is a central boundary in the diencephalon that separates the posterior diencephalon (prosomeres 1 and 2), from the anterior diencephalon (prosomere 3). This intrathalamic limit appears early on in neural tube development, and the molecular pattern that it reveals suggests an important role in the diencephalic histogenesis. We hereby present a fate map of the presumptive territories in the diencephalon of a chick embryo at the 10–11 somite stages (HH9–10), by homotopic and isochronic quail–chick grafts. The anatomical interpretation of chimeric brains was aided by correlative whole-mount in situ hybridization with RNA probes for chicken genes expressed in specific diencephalic territories. The resulting fate map describes the distribution of the presumptive diencephalic prosomeres in the neural tube, and demonstrates their topologically conserved relationships throughout the neural development. Moreover, we show that the presumptive epithelium of ZLI can be localized at early developmental stages in the diencephalic alar plate at the anterior limit of the Wnt8b gene expression domain.
