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Salvador Martinez - One of the best experts on this subject based on the ideXlab platform.
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Expression of chick Fgf19 and mouse Fgf15 orthologs is regulated in the developing brain by Fgf8 and Shh
Developmental Dynamics, 2020Co-Authors: 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.
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Fgf15 regulates thalamic development by controlling the expression of proneural genes
Brain Structure and Function, 2016Co-Authors: Almudena Martinez-ferre, John L R Rubenstein, Cosme Lloret-quesada, Nilima Prakash, Wolfgang Wurst, Salvador MartinezAbstract:The establishment of the brain structural complexity requires a precisely orchestrated interplay between extrinsic and intrinsic signals modulating cellular mechanisms to guide neuronal differentiation. However, little is known about the nature of these signals in the diencephalon, a complex brain region that processes and relays sensory and motor information to and from the cerebral cortex and subcortical structures. Morphogenetic signals from brain organizers regulate histogenetic processes such as cellular proliferation, migration, and differentiation. Sonic hedgehog (Shh) in the key signal of the ZLI, identified as the diencephalic organizer. Fgf15 , the mouse gene orthologous of human, chick, and zebrafish Fgf19 , is induced by Shh signal and expressed in the diencephalic Alar Plate progenitors during histogenetic developmental stages. This work investigates the role of Fgf15 signal in diencephalic development. In the absence of Fgf15, the complementary expression pattern of proneural genes: Ascl1 and Nng2, is disrupted and the GABAergic thalamic cells do not differentiate; in addition dorsal thalamic progenitors failed to exit from the mitotic cycle and to differentiate into neurons. Therefore, our findings indicate that Fgf15 is the Shh downstream signal to control thalamic regionalization, neurogenesis, and neuronal differentiation by regulating the expression and mutual segregation of neurogenic and proneural regulatory genes.
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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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Molecular Regionalization of the Diencephalon
Frontiers in Neuroscience, 2012Co-Authors: Almudena Martinez-ferre, Salvador MartinezAbstract:The anatomic complexity of the diencephalon depends on precise molecular and cellular regulative mechanisms orchestrated by regional morphogenetic organizers at the neural tube stage. In the diencephalon, like in other neural tube regions, dorsal and ventral signals codify positional information to specify ventro-dorsal regionalization. Retinoic acid, Fgf8, BMPs, and Wnts signals are the molecular factors acting upon the diencephalic epithelium to specify dorsal structures, while Shh is the main ventralizing signal. A central diencephalic organizer, the zona limitans intrathalamica (ZLI), appears after neurulation in the central diencephalic Alar Plate, establishing additional antero-posterior positional information inside diencephalic Alar Plate. Based on Shh expression, the ZLI acts as a morphogenetic center, which cooperates with other signals in thalamic specification and pattering in the Alar Plate of diencephalon. Indeed, Shh is expressed first in the basal Plate extending dorsally through the ZLI epithelium as the development proceeds. Despite the importance of ZLI in diencephalic morphogenesis the mechanisms that regulate its development remain incompletely understood. Actually, controversial interpretations in different experimental models have been proposed. That is, experimental results have suggested that (i) the juxtaposition of the molecularly heterogeneous neuroepithelial areas, (ii) cell reorganization in the epithelium, and/or (iii) planar and vertical inductions in the neural epithelium, are required for ZLI specification and development. We will review some experimental data to approach the study of the molecular regulation of diencephalic regionalization, with special interest in the cellular mechanisms underlying planar inductions.
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expression of chick fgf19 and mouse fgf15 orthologs is regulated in the developing brain by fgf8 and shh
Developmental Dynamics, 2007Co-Authors: 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. © 2007 Wiley-Liss, Inc.
Luis Puelles - One of the best experts on this subject based on the ideXlab platform.
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Topography of Somatostatin Gene Expression Relative to Molecular Progenitor Domains during Ontogeny of the Mouse Hypothalamus
Frontiers in Neuroanatomy, 2011Co-Authors: Nicanor Morales-delgado, Luis Puelles, Sylvia M Bardet, Paloma Merchán, José Luis Ferran, Carmen DíazAbstract:The hypothalamus comprises Alar, basal, and floor Plate developmental compartments. Recent molecular data support a rostrocaudal subdivision into rostral (terminal) and caudal (peduncular) halves. In this context, the distribution of neuronal populations expressing somatostatin (Sst) mRNA was analyzed in the developing mouse hypothalamus, comparing with the expression pattern of the genes Orthopedia (Otp), Distal-less 5 (Dlx5), Sonic Hedgehog (Shh), and Nk2 homeobox 1 (Nkx2.1). At embryonic day 10.5 (E10.5), Sst mRNA was first detectable in the anterobasal nucleus, a Nkx2.1-, Shh-, and Otp-positive basal domain. By E13.5, nascent Sst expression was also related to two additional Otp-positive domains within the Alar Plate and one in the basal Plate. In the Alar Plate, Sst-positive cells were observed in rostral and caudal ventral subdomains of the Otp-positive paraventricular complex. An additional basal Sst-expressing cell group was found within a longitudinal Otp-positive periretromamillary band that separates the retromamillary area from tuberal areas. Apart of subsequent growth of these initial populations, at E13.5 and E15.5 some Sst-positive derivatives migrate tangentially into neighboring regions. A subset of cells produced at the anterobasal nucleus disperses ventralward into the shell of the ventromedial hypothalamic nucleus and the arcuate nucleus. Cells from the rostroventral paraventricular subdomain reach the suboptic nucleus, whereas a caudal contingent migrates radially into lateral paraventricular, perifornical, and entopeduncular nuclei. Our data provide a topologic map of molecularly defined progenitor areas originating a specific neuron type during early hypothalamic development. Identification of four main separate sources helps to understand causally its complex adult organization.
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Conserved pattern of OTP-positive cells in the paraventricular nucleus and other hypothalamic sites of tetrapods.
Brain research bulletin, 2007Co-Authors: Sylvia M Bardet, Margaret Martinez-de-la-torre, R Glenn Northcutt, John L R Rubenstein, Luis PuellesAbstract:The paraventricular nucleus complex (Pa) is a component of central neural circuitry that regulates several homeostatic variables. The paraventricular nucleus is composed of magnocellular neurons that project to the posterior pituitary and parvicellular neurons that project to numerous sites in the central nervous system. According to the revised prosomeric model, the paraventricular nucleus is located caudal to the eye stalk along the rostrocaudal dimension of the dorsal hypothalamic Alar Plate. Caudally, the paraventricular nucleus abuts the prethalamus (prosomere 3), and the entire complex is flanked ventrally and dorsally by Dlx5-expressing domains of the Alar Plate. The homeodomain transcription factor Orthopedia (Otp) is expressed in several separate hypothalamic sites: the paraventricular nucleus, perimammillary region and arcuate nucleus. In this study, we compared Otp expression in the hypothalamus of mouse (Mus musculus), chick (Gallus gallus), frog (Rana perezi) and axolotol (Ambystoma mexicanum), using immunohistochemical and in situ hybridization techniques. In all cases, Otp-positive cells in the paraventricular nucleus were excluded from Dlx5-expressing adjacent domains. Other positive neuronal populations were observed in the arcuate nucleus and oblique perimammillary band. Expression in the medial amygdala appears to be continuous with the Otp-expressing paraventricular nucleus complex. This area is relatively unevaginated in the amphibian brains, barely evaginated in the chick, and fully evaginated in the mouse. These data led us to conclude that the expression pattern of Otp is topologically highly conserved in tetrapods and is plesiomorphic among chordates.
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locus coeruleus neurons originate in Alar rhombomere 1 and migrate into the basal Plate studies in chick and mouse embryos
The Journal of Comparative Neurology, 2006Co-Authors: Pilar Aroca, Beatriz Lorentecanovas, Francisco R Mateos, Luis PuellesAbstract:We investigated in the mouse and chick the neuroepithelial origin and development of the locus coeruleus (LoC), the most important noradrenergic neuronal population in the brain. We first studied the topography of the developing LoC in the hindbrain, using as markers the key noradrenergic marker gene Dbh and the transcription factors Phox2a and Phox2b (upstream of Dbh). In both mouse and chicken, LoC neurons first appear arranged linearly along the middle one-third of the Alar Plate of rhombomere 1 (r1), collinear to a reference ventricular longitudinal band that early on expresses Phox2a and Phox2b in the Alar Plate of r2 and later expands to r1. Double-labeling experiments with LoC markers (Dbh or Phox2a) and either Alar (Pax7 and Rnx3) or basal (Otp) genetic markers suggested that LoC cells migrate from their origin in the Alar Plate to a final position in the lateral basal Plate. To corroborate these suggestions experimentally and determine the precise origin of the LoC, we fate mapped the LoC in the chick at stage HH11 by using quail-chick homotopic grafts. The experimental results confirmed that the LoC originates in the Alar Plate throughout the rostrocaudal extent of r1 and ruled out a rostrocaudal translocation. They also corroborated a ventralward tangential migration of LoC cells into the lateral basal Plate, where the postmigratory LoC primordium is located. Comparisons with neighboring Alar r1-derived cell populations established that LoC neurons originate outside the cerebellum, in a matrix area intercalated dorsoventrally between the sources of the prospective vestibular and trigeminal columns. J. Comp. Neurol. 496:802– 818, 2006. © 2006 Wiley-Liss, Inc.
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molecular profiling indicates avian branchiomotor nuclei invade the hindbrain Alar Plate
Neuroscience, 2004Co-Authors: Min Jeong Ju, Christoph Redies, Pilar Aroca, Luis PuellesAbstract:Abstract It is generally believed that the spinal cord and hindbrain consist of a motor basal Plate and a sensory Alar Plate. We now have molecular markers for these territories. The relationship of migrating branchiomotor neurons to molecularly defined Alar and basal domains was examined in the chicken embryo by mapping the expression of cadherin-7 and cadherin-6B, in comparison to genetic markers for ventrodorsal patterning (Otp, Pax6, Pax7, Nkx2.2, and Shh) and motoneuron subpopulations (Phox2b and Isl1). We show cadherin-7 is expressed in a complete radial domain occupying a lateral region of the hindbrain basal Plate. The cadherin-7 domain abuts the medial border of Pax7 expression; this common limit defines, or at least approximates, the basal/Alar boundary. The hindbrain branchiomotor neurons originate in the medial part of the basal Plate, close to the floor Plate. Their cadherin-7-positive axons grow into the Alar Plate and exit the hindbrain close to the corresponding afferent nerve root. The cadherin-7-positive neuronal cell bodies later translocate laterally, following this axonal trajectory, thereby passing through the cadherin-7-positive basal Plate domain. Finally, the cell bodies traverse the molecularly defined basal/Alar boundary and move into positions within the Alar Plate. After the migration has ended, the branchiomotor neurons switch expression from cadherin-7 to cadherin-6B. These findings demonstrate that a specific subset of primary motor neurons, the branchiomotor neurons, migrate into the Alar Plate of the chicken embryo. Consequently, the century-old concept that all primary motor neurons come to reside in the basal Plate should be revised.
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Expression of calcium-binding proteins in the diencephalon of the lizard Psammodromus algirus.
The Journal of Comparative Neurology, 2000Co-Authors: José Carlos Dávila, Salvador Guirado, Luis PuellesAbstract:This work is a study of the distribution pattern of calbindin–D28k, calretinin, and parvalbumin in the diencephalic Alar Plate of a reptile, the lizard Psammodromus algirus, by using the prosomeric model (Puelles [1995] Brain Behav Evol 46:319–337), which divides the Alar Plate of the diencephalon into the caudorostrally arranged pretectum (p1), dorsal thalamus plus epithalamus (p2), and ventral thalamus (p3). Calbindin and calretinin are more extensively expressed in the dorsal thalamus than in the neighboring Alar regions, and therefore these calcium–binding proteins are particularly suitable markers for delimiting the dorsal thalamus/epithalamus complex from the ventral thalamus and the pretectum. Conversely, parvalbumin is more intensely expressed in the pretectum and ventral thalamus than in the dorsal thalamus/epithalamus complex. Within the dorsal thalamus, calcium–binding protein immunoreactivity reveals a three–tiered division. The pretectum displays the most intense expression of parvalbumin within the diencephalon. Virtually all nuclei in the three sectors of the pretectum (commissural, juxtacommissural, and precommissural) present strong to moderate expression of parvalbumin. We compare the distribution of calcium–binding proteins in the diencephalon of Psammodromus with other vertebrates, with mammals in particular, and suggest that the middle and ventral tiers of the reptilian dorsal thalamus may be comparable to nonspecific or plurimodal posterior/intralaminar thalamic nuclei in mammals, on the basis of the calcium–binding protein expression patterns, as well as the hodological and embryological data in the literature. J. Comp. Neurol. 427:67–92, 2000. © 2000 Wiley-Liss, Inc.
Fujio Murakami - One of the best experts on this subject based on the ideXlab platform.
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crossing the ventral midline causes neurons to change their response to floor Plate and Alar Plate attractive cues during transmedian migration
Developmental Biology, 2002Co-Authors: Hiroki Taniguchi, Atsushi Tamada, Timothy E Kennedy, Fujio MurakamiAbstract:Neuronal migration is required for the establishment of specific neural structures, such as layers and nuclei. Neurons migrate along specific migratory routes toward their final destinations, sometimes across long distances. However, the cellular and molecular interactions that control neuronal migration are largely unknown. Here, we examined the mechanism underlying the transmedian migration of precerebellar neurons using a flat whole-mount preparation of the rat embryo. These neurons were initially attracted by the floor Plate (FP) at the ventral midline. However, after crossing the midline, they lost their responsiveness to the FP and became attracted by the Alar Plate (AP). Although the loss of responsiveness to FP cues was caused by an encounter of migrating cells with the FP, the gain of responsiveness to AP cues occurred irrespective of their encounter with the FP. These results identify a crucial change in the response of migrating cells to attractive guidance cues during the transmedian migration of precerebellar neurons.
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Guidance of Circumferentially Growing Axons by Netrin-Dependent and -Independent Floor Plate Chemotropism in the Vertebrate Brain
Neuron, 1996Co-Authors: Ryuichi Shirasaki, Christine Mirzayan, Marc Tessier-lavigne, Fujio MurakamiAbstract:Abstract Netrin-1, a diffusible signal secreted by floor Plate cells at the ventral midline of the vertebrate CNS, can attract ventrally migrating axons and repel a subset of dorsally migrating axons in the spinal cord and rostral hindbrain in vitro. Whether netrin-1 can act as a global cue to guide all circumferentially migrating axons is, however, unknown. Here, we show that netrin-1 can attract Alar Plate axons that cross the floor Plate along its entire rostrocaudal axis. Dorsally directed axons forming the posterior commissure are, however, repelled by the floor Plate by a netrin-independent mechanism. These results suggest that netrin-1 functions as a global guidance cue for attraction to the midline. Moreover, floor Plate–mediated chemorepulsion may also operate generally to direct dorsal migrations, but its molecular basis may involve both netrin-dependent and -independent mechanisms.
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Floor Plate chemoattracts crossed axons and chemorepels uncrossed axons in the vertebrate brain.
Neuron, 1995Co-Authors: Atsushi Tamada, Ryuichi Shirasaki, Fujio MurakamiAbstract:Abstract In the bilaterally symmetrical vertebrate CNS, all developing axons must choose between remaining on the same side of the midline or growing across it. The mechanism underlying this axonal pathfinding is, however, poorly understood. Here we demonstrate that the ventral midline floor Plate (FP) chemorepels two types of ipsilaterally projecting axons, one from the Alar Plate and another from the basal Plate in the mesencephalon. We further demonstrate that the FP chemoattracts contralaterally projecting myelencephalic as well as metencephalic axons. The FP at all axial levels displayed both chemoattractive and chemorepellent activities, suggesting that FP chemoattraction and chemorepulsion may be at work throughout the neuraxis. Chemotropic guidance by the FP may therefore play a key role in the establishment of neuronal projection laterality.
Agustin Gonzalez - One of the best experts on this subject based on the ideXlab platform.
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Conserved localization of Pax6 and Pax7 transcripts in the brain of representatives of sarcopterygian vertebrates during development supports homologous brain regionalization.
Frontiers in Neuroanatomy, 2014Co-Authors: Nerea Moreno, Sandra Bandín, Ruth Morona, Jesús M López, Alberto Joven, Agustin GonzalezAbstract:Many of the genes involved in brain patterning during development are highly conserved in vertebrates and similarities in their expression patterns help to recognize homologous cell types or brain regions. Among these genes, Pax6 and Pax7 are expressed in regionally restricted patterns in the brain and are essential for its development. In the present immunohistochemical study we analyzed the distribution of Pax6 and Pax7 cells in the brain of six representative species of tetrapods and lungfishes, the closest living relatives of tetrapods, at several developmental stages. The distribution patterns of these transcription factors were largely comparable across species. In all species only Pax6 was expressed in the telencephalon, including the olfactory bulbs, septum, striatum and amygdaloid complex. In the diencephalon, Pax6 and Pax7 were distinct in the Alar and basal parts, mainly in prosomeres 1 and 3. Pax7 specifically labeled cells in the optic tectum (superior colliculus) and Pax6, but not Pax7, cells were found in the tegmentum. Pax6 was found in most granule cells of the cerebellum and Pax7 labeling was detected in cells of the ventricular zone of the rostral Alar Plate and in migrated cells in the basal Plate, including the griseum centrale and the interpeduncular nucleus. Caudally, Pax6 cells formed a column, whereas the ventricular zone of the Alar Plate expressed Pax7. Since the observed Pax6 and Pax7 expression patterns are largely conserved they can be used to identify subdivisions in the brain across vertebrates that are not clearly discernible with classical techniques.
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Immunohistochemical analysis of Pax6 and Pax7 expression in the CNS of adult Xenopus laevis.
Journal of chemical neuroanatomy, 2014Co-Authors: Sandra Bandín, Ruth Morona, Jesús M López, Nerea Moreno, Agustin GonzalezAbstract:Pax6 and Pax7 are transcription factors essential for the development of the CNS. In addition, increasing data, mainly obtained in amniotes, support that they are expressed in subsets of neurons in the adult, likely playing a role in maintaining neuron type identity. In the present study we analyzed the detailed distribution of Pax6 and Pax7 cells in the adult CNS of Xenopus laevis. Immunohistochemistry with antibodies that are required for high-resolution analysis of Pax-expressing cells was conducted. A wide distribution of Pax6 and Pax7 cells throughout the CNS was detected, with distinct patterns that showed only slight overlapping. Only Pax6 was expressed in the telencephalon, including the olfactory bulbs, septum, striatum and amygdaloid complex. In the diencephalon, Pax6 and Pax7 were distinct in the Alar and basal parts, respectively, of prosomere 3. Large numbers of Pax6 and Pax7 cells were distributed in the pretectal region (Alar Plate of prosomere 1) but only Pax6 cells extended into basal Plate. Pax7 specifically labeled cells in the optic tectum, including the ventricular zone, and Pax6 cells were the only cells found in the tegmentum. Pax6 was found in most granule cells of the cerebellum and Pax7 expression was found only in the ventricular zone. In the rostral rhombomere 1, Pax7 labeling was detected in cells of the ventricular zone of the Alar Plate, but numerous migrated cells were located in the basal Plate, including the griseum centrale and the interpeduncular nucleus. Pax6 cells also formed a column of scattered neurons in the reticular formation and were found in the octavolateral area. The rhombencephalic ventricular zone of the Alar Plate expressed Pax7. Dorsal Pax7 cells and ventral Pax6 cells were found along the spinal cord separated from the ventricle, which did not show immunoreactivity. Our results show that the expression of Pax6 and Pax7 is widely maintained in the adult brain of Xenopus, like in urodele amphibians and in contrast to the situation described in amniotes. Therefore, in amphibians these transcription factors seem to be needed to maintain specific entities of subpopulations of neurons in the adult CNS.
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Regional expression of Pax7 in the brain of Xenopus laevis during embryonic and larval development.
Frontiers in Neuroanatomy, 2013Co-Authors: Sandra Bandín, Ruth Morona, Nerea Moreno, Agustin GonzalezAbstract:Pax7 is a member of the highly conserved Pax gene family that is expressed in restricted zones of the central nervous system during development, being involved in early brain regionalization and the maintenance of the regional identity. Using sensitive immunohistochemical techniques we have analyzed the spatiotemporal pattern of Pax7 expression in the brain of the anuran amphibian Xenopus laevis, during development. Pax7 expression was first detected in early embryos in the basal Plate of prosomere 3, roof and Alar Plates of prosomere 1 and mesencephalon, and the Alar Plate of rhombomere 1. As development proceeded, Pax7 cells were observed in the hypothalamus close to the catecholaminergic population of the mammillary region. In the diencephalon, Pax7 was intensely expressed in a portion of the basal Plate of prosomere 3, in the roof Plate and in scattered cells of the thalamus in prosomere 2, throughout the roof of prosomere 1, and in the commissural and juxtacommissural domains of the pretectum. In the mesencephalon, Pax7 cells were localized in the optic tectum and, to a lesser extent, in the torus semicircularis. The rostral portion of the Alar part of rhombomere 1, including the ventricular layer of the cerebellum, expressed Pax7 and, gradually, some of these dorsal cells were observed to populate ventrally the interpeduncular nucleus and the isthmus (rhombomere 0). Additionally, Pax7 positive cells were found in the ventricular zone of the ventral part of the Alar Plate along the rhombencephalon and the spinal cord. The findings show that the strongly conserved features of Pax7 expression through development shared by amniote vertebrates are also present in the anamniote amphibians as a common characteristic of the brain organization of tetrapods.
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organization of the caudal rhombencephalic Alar Plate of the ribbed newt pleurodeles waltl evidence for the presence of dorsal column and lateral cervical nuclei
Brain Behavior and Evolution, 1998Co-Authors: Alberto Munoz, M Munoz, Agustin Gonzalez, H Ten J DonkelaarAbstract:As part of a recent program on the evolution of somatosensory systems in vertebrates, the cytoarchitecture, chemoarchitecture, and fiber connections of the caudal rhombencephalic Alar Plate were studi
E. Puelles - One of the best experts on this subject based on the ideXlab platform.
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Role of Shh in the development of molecularly characterized tegmental nuclei in mouse rhombomere 1
Brain Structure and Function, 2014Co-Authors: J. A. Moreno-bravo, L Puelles, A. Perez-balaguer, J. E. Martinez-lopez, P. Aroca, S. Martinez, E. PuellesAbstract:Hindbrain rhombomeres in general are differentially specified molecularly by unique combinations of Hox genes with other developmental genes. Rhombomere 1 displays special features, including absence of Hox gene expression. It lies within the hindbrain range of the Engrailed genes ( En1 , En2 ), controlled by the isthmic organizer via diffusion of FGF8. It is limited rostrally by the isthmus territory, and caudally by rhombomere 2. It is double the normal size of any other rhombomere. Its dorsal part generates the cerebellar hemispheres and its ventral part gives rise to several populations, such as some raphe nuclei, the interpeduncular nucleus, the rhabdoid nucleus, anterior, dorsal, ventral and posterodorsal tegmental nuclei, the cholinergic pedunculopontine and laterodorsal tegmental nuclei, rostral parts of the hindbrain reticular formation, the locus coeruleus, and part of the lateral lemniscal and paralemniscal nuclei, among other formations. Some of these populations migrate tangentially before reaching their final positions. The morphogen Sonic Hedgehog ( Shh ) is normally released from the local floor Plate and underlying notochord. In the present report we explore, first, whether Shh is required in the specification of these r1 populations, and, second, its possible role in the guidance of tangentially migrating neurons that approach the midline. Our results indicate that when Shh function is altered selectively in a conditional mutant mouse strain, most populations normally generated in the medial basal Plate of r1 are completely absent. Moreover, the relocation of some neurons that normally originate in the Alar Plate and migrate tangentially into the medial basal Plate is variously altered. In contrast, neurons that migrate radially (or first tangentially and then radially) into the lateral basal Plate were not significantly affected.