The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform
Salvador Martinez - One of the best experts on this subject based on the ideXlab platform.
-
Wnt1 signal determines the patterning of the diencephalic dorso-ventral axis.
Brain Structure & Function, 2015Co-Authors: Maria Navarro-garberi, Carlos Bueno, Salvador MartinezAbstract:The diencephalon is a complex brain area that derives from the caudal region of the Prosencephalon. This structure is divided into four longitudinal neuroepithelial zones: roof, alar, basal and floor plates, which constitute its dorso-ventral (DV) columnar domains. Morphogenetic differences between alar and basal plates in the Prosencephalon and mesencephalon contribute to the characteristic expansion of alar plate derivatives in the brain and the formation of the cephalic flexure. Although differential histogenesis among DV regions seems to be relevant in understanding structural and functional complexity of the brain, most of our knowledge about DV regionalization comes from the spinal cord development. Therefore, it seems of interest to study the molecular mechanisms that govern DV patterning in the diencephalon, the brain region where strong differences in size and complexity between alar and basal derivatives are evident in all vertebrates. Different morphogenetic signals, which induce specific progenitors fate to the neighboring epithelium, are involved in the spinal cord DV patterning. To study if Wnt1, one of these signaling molecules, has a role for the establishment of the diencephalic longitudinal domains, we carried out gain- and loss-of-function experiments, using mice and chick embryos. Our results demonstrated functional differences in the molecular mechanisms downstream of Wnt1 function in the diencephalon, in relation to the spinal cord. We further demonstrated that Bmp4 signal induces Wnt1 expression in the diencephalon, unraveling a new molecular regulatory code downstream of primary dorsalizing signals to control ventral regionalization in the diencephalon.
-
telencephalic morphogenesis during the process of neurulation an experimental study using quail chick chimeras
The Journal of Comparative Neurology, 2009Co-Authors: Ana Pombero, Salvador MartinezAbstract:After gastrulation, during the process of neurulation, the anterior neural region undergoes important morphological transformations. The almost flat epithelium of the rostral neural plate becomes transformed into a spherical region, the prosencephalic vesicle, in the neural tube. Later in development, two bilateral areas (the optic and telencephalic vesicles) progressively protrude from the Prosencephalon, generating the eyes and the cerebral hemispheres, respectively. Although the principal processes of neurulation have been well characterized, the growth patterns and evolution of topological relations between internal prosencephalic regions have not been experimentally analyzed. In order to better characterize morphogenetic transformations of the Prosencephalon, we have realized and comparatively analyzed neuroepithelial fate maps before and after neurulation using quail/chick chimerical experiments. Since we have previously reported the fate map of the Prosencephalon at the neural plate stage, in the present work we report the corresponding fate map at the neural tube stage. Comparative analysis of the two maps has allowed us to descriptively characterize the morphogenetic transformations of the alar prosencephalic regions during neurulation and to establish the topologic evolution of the principal areas of the vertebrate telencephalon. J. Comp. Neurol. 512:784–797, 2009. © 2008 Wiley-Liss, Inc.
-
Telencephalic morphogenesis during the process of neurulation: An experimental study using quail–chick chimeras
The Journal of Comparative Neurology, 2009Co-Authors: Ana Pombero, Salvador MartinezAbstract:After gastrulation, during the process of neurulation, the anterior neural region undergoes important morphological transformations. The almost flat epithelium of the rostral neural plate becomes transformed into a spherical region, the prosencephalic vesicle, in the neural tube. Later in development, two bilateral areas (the optic and telencephalic vesicles) progressively protrude from the Prosencephalon, generating the eyes and the cerebral hemispheres, respectively. Although the principal processes of neurulation have been well characterized, the growth patterns and evolution of topological relations between internal prosencephalic regions have not been experimentally analyzed. In order to better characterize morphogenetic transformations of the Prosencephalon, we have realized and comparatively analyzed neuroepithelial fate maps before and after neurulation using quail/chick chimerical experiments. Since we have previously reported the fate map of the Prosencephalon at the neural plate stage, in the present work we report the corresponding fate map at the neural tube stage. Comparative analysis of the two maps has allowed us to descriptively characterize the morphogenetic transformations of the alar prosencephalic regions during neurulation and to establish the topologic evolution of the principal areas of the vertebrate telencephalon. J. Comp. Neurol. 512:784–797, 2009. © 2008 Wiley-Liss, Inc.
-
coordinate expression of fgf8 otx2 bmp4 and shh in the rostral Prosencephalon during development of the telencephalic and optic vesicles
Neuroscience, 2001Co-Authors: Philip H Crossley, Salvador Martinez, Y Ohkubo, John L.r. RubensteinAbstract:Abstract Previous studies suggest that Fgf8 has a key role in regulating vertebrate development. In the rostral head of the embryonic chicken, there are increasing numbers of separate Fgf8 domains; these are present in tissues that appear to have previously expressed Otx2 . As Fgf8 expression becomes established, Otx2 expression weakens, but remains in cells abutting the Fgf8 expression domain. These Fgf8 expression domains are closely associated with tissues expressing Bmp4 and Shh . Based on analogy with the embryonic limb, we suggest that Fgf8 , Bmp4 and Shh function together in patterning regions of the embryonic head. Gene expression changes are particularly prominent in 14–21 somite stage embryos in the rostral forebrain, during early morphogenesis of the telencephalic and optic vesicles, when several new interfaces of Fgf8 , Bmp4 and Shh are generated. To gain insights into the functions of fibroblast growth factor 8 (FGF8) in the embryonic forebrain, we studied the effects of implanting beads containing this protein in the dorsal Prosencephalon of embryonic day 2 chicken embryos. Ectopic FGF8 had profound effects on morphogenesis of the telencephalic and optic vesicles. It disrupted formation of the optic stalk and caused a transformation of the pigment epithelium into neural retina. Within the telencephalon, FGF8 beads frequently induced a sulcus that had features of an ectopic rostral midline. The sulcus separated the telencephalon into rostral and caudal vesicles. Furthermore, we present evidence that FGF8 can regulate regionalization of the Prosencephalon through inhibition of Otx2 and Emx2 expression. Thus, these experiments provide evidence that FGF8 can regulate both morphogenesis and patterning of the rostral Prosencephalon (telencephalic and optic vesicles). FGF8 beads can induce midline properties (e.g. a sulcus) and can modulate the specification and differentiation of adjacent tissues. We suggest that some of these effects are through regulating the expression of homeobox genes ( Otx2 and Emx2 ) that are known to participate in forebrain patterning.
-
induction of a mesencephalic phenotype in the 2 day old chick Prosencephalon is preceded by the early expression of the homeobox gene en
Neuron, 1991Co-Authors: Salvador Martinez, Marion Wassef, Rosamagda AlvaradomallartAbstract:Abstract The homeobox gene en , homologous to the gene engrailed of Drosophila, is expressed in the metencephalic-mesencephalic segment of the vertebrate neural tube. Using quail-chick chimeras, an antibody against en proteins, and cytoarchitectonic techniques, we demonstrate that metencephalon transplanted to Prosencephalon, at E2, maintains a high level of en proteins and its presumptive cerebellar fate. The ectopic metencephalon induces in the contiguous host Prosencephalon the expression of en and, subsequently, a mesencephalic phenotype. These related genetic and phenotypic expressions indicate that the transcriptional regulatory en gene is involved in cerebellar and mesencephalic cytodifferentiation. The expression of en can also be induced in chick Prosencephalon by a mammalian metencephalic graft, indicating that the factors regulating the transcription of en are phylogenetically well conserved.
Rosamagda Alvaradomallart - One of the best experts on this subject based on the ideXlab platform.
-
temporal sequence of gene expression leading caudal Prosencephalon to develop a midbrain hindbrain phenotype
Developmental Dynamics, 2002Co-Authors: Matias Hidalgosanchez, Rosamagda AlvaradomallartAbstract:Transplantation of prosomeres 1-2 into the cerebellar plate were used, by using chick/quail chimeras, to analyse the temporal sequence of the genetic cascade leading the graft to develop a midbrain/hindbrain phenotype. Our results show that (1) at Hamburger and Hamilton (HH) stage 13, Pax2 and En2 are already induced within the graft, before all other genes of the cascade, whereas misexpression of Fgf8 is also observed within the contiguous host cerebellar plate; (2) within the graft, Otx2 repression and Gbx2 induction (see Hidalgo-Sanchez et al. [1999] Development 126:3191–3203) are secondary events that affect, from stages HH14–15, the areas in contact with the host Gbx2/Fgf8-expressing cerebellar plate; (3) at these stages, the repressed Otx2 territory extends beyond the areas induced to express Gbx2, with the two territories not abutting before HH17–18; (4) Fgf8 expression becomes progressively induced within the Otx2-repressed/Gbx2-induced territory, starting at HH15–16. Our results support the hypothesis that the host-Gbx2/graft-Otx2 interface could trigger the genetic cascade induced within the graft and that the Gbx2-induced domain could play a key role during the establishment of the induced intragraft midbrain/hindbrain boundary. © 2001 Wiley-Liss, Inc.
-
induction of a mesencephalic phenotype in the 2 day old chick Prosencephalon is preceded by the early expression of the homeobox gene en
Neuron, 1991Co-Authors: Salvador Martinez, Marion Wassef, Rosamagda AlvaradomallartAbstract:Abstract The homeobox gene en , homologous to the gene engrailed of Drosophila, is expressed in the metencephalic-mesencephalic segment of the vertebrate neural tube. Using quail-chick chimeras, an antibody against en proteins, and cytoarchitectonic techniques, we demonstrate that metencephalon transplanted to Prosencephalon, at E2, maintains a high level of en proteins and its presumptive cerebellar fate. The ectopic metencephalon induces in the contiguous host Prosencephalon the expression of en and, subsequently, a mesencephalic phenotype. These related genetic and phenotypic expressions indicate that the transcriptional regulatory en gene is involved in cerebellar and mesencephalic cytodifferentiation. The expression of en can also be induced in chick Prosencephalon by a mammalian metencephalic graft, indicating that the factors regulating the transcription of en are phylogenetically well conserved.
Ana Pombero - One of the best experts on this subject based on the ideXlab platform.
-
telencephalic morphogenesis during the process of neurulation an experimental study using quail chick chimeras
The Journal of Comparative Neurology, 2009Co-Authors: Ana Pombero, Salvador MartinezAbstract:After gastrulation, during the process of neurulation, the anterior neural region undergoes important morphological transformations. The almost flat epithelium of the rostral neural plate becomes transformed into a spherical region, the prosencephalic vesicle, in the neural tube. Later in development, two bilateral areas (the optic and telencephalic vesicles) progressively protrude from the Prosencephalon, generating the eyes and the cerebral hemispheres, respectively. Although the principal processes of neurulation have been well characterized, the growth patterns and evolution of topological relations between internal prosencephalic regions have not been experimentally analyzed. In order to better characterize morphogenetic transformations of the Prosencephalon, we have realized and comparatively analyzed neuroepithelial fate maps before and after neurulation using quail/chick chimerical experiments. Since we have previously reported the fate map of the Prosencephalon at the neural plate stage, in the present work we report the corresponding fate map at the neural tube stage. Comparative analysis of the two maps has allowed us to descriptively characterize the morphogenetic transformations of the alar prosencephalic regions during neurulation and to establish the topologic evolution of the principal areas of the vertebrate telencephalon. J. Comp. Neurol. 512:784–797, 2009. © 2008 Wiley-Liss, Inc.
-
Telencephalic morphogenesis during the process of neurulation: An experimental study using quail–chick chimeras
The Journal of Comparative Neurology, 2009Co-Authors: Ana Pombero, Salvador MartinezAbstract:After gastrulation, during the process of neurulation, the anterior neural region undergoes important morphological transformations. The almost flat epithelium of the rostral neural plate becomes transformed into a spherical region, the prosencephalic vesicle, in the neural tube. Later in development, two bilateral areas (the optic and telencephalic vesicles) progressively protrude from the Prosencephalon, generating the eyes and the cerebral hemispheres, respectively. Although the principal processes of neurulation have been well characterized, the growth patterns and evolution of topological relations between internal prosencephalic regions have not been experimentally analyzed. In order to better characterize morphogenetic transformations of the Prosencephalon, we have realized and comparatively analyzed neuroepithelial fate maps before and after neurulation using quail/chick chimerical experiments. Since we have previously reported the fate map of the Prosencephalon at the neural plate stage, in the present work we report the corresponding fate map at the neural tube stage. Comparative analysis of the two maps has allowed us to descriptively characterize the morphogenetic transformations of the alar prosencephalic regions during neurulation and to establish the topologic evolution of the principal areas of the vertebrate telencephalon. J. Comp. Neurol. 512:784–797, 2009. © 2008 Wiley-Liss, Inc.
David M Helfman - One of the best experts on this subject based on the ideXlab platform.
-
brain specific tropomyosins tmbr 1 and tmbr 3 have distinct patterns of expression during development and in adult brain
Proceedings of the National Academy of Sciences of the United States of America, 1993Co-Authors: Stefan Stamm, Diana Casper, James P Leesmiller, David M HelfmanAbstract:In this study we report on the developmental and regional expression of two brain-specific isoforms of tropomyosin, TMBr-1 and TMBr-3, that are generated from the rat alpha-tropomyosin gene via the use of alternative promoters and alternative RNA splicing. Western blot analysis using an exon-specific peptide polyclonal antibody revealed that the two isoforms are differentially expressed in development with TMBr-3 appearing in the embryonic brain at 16 days of gestation, followed by the expression of TMBr-1 at 20 days after birth. TMBr-3 was detected in all brain regions examined, whereas TMBr-1 was detected predominantly in brain areas that derived from the Prosencephalon. Immunocytochemical studies on mixed primary cultures made from rat embryonic midbrain indicate that expression of the brain-specific epitope is restricted to neurons. The developmental pattern and neuronal localization of these forms of tropomyosin suggest that these isoforms have a specialized role in the development and plasticity of the nervous system.
Harukazu Nakamura - One of the best experts on this subject based on the ideXlab platform.
-
Expression of en in the Prosencephalon Heterotopically Transplanted into the Mesencephalon
Development Growth & Differentiation, 1992Co-Authors: Harukazu Nakamura, Nobue ItasakiAbstract:The alar plate of the Prosencephalon differentiates into a tectum-like structure when transplanted and integrated into the mesencephalon around 10-somite stage. Homeobox containing gene, en, is expressed in the mesencephalon with caudorostral gradient from 7-somite stage. Here expression of en in the prosencephalic transplant in the mesencephalon was studied immunohistochemically with anti-en antibody. Transplantation was carried out between quail and chick. It was shown that the transplant was stained with anti-en antibody at the caudal part of the mesencephalon. At the rostral part, the transplant did not express en. When the transplant was not contiguous to the caudal part of the host mesencephalon, it did not express en. The present study suggests that the prosencephalic transplant differentiates into the tectum-like structure when it expresses en at the caudal part of the mesencephalon.
-
projection of the retinal ganglion cells to the tectum differentiated from the Prosencephalon
Neuroscience Research, 1991Co-Authors: Harukazu Nakamura, Kohji A. Matsui, Shin Takagi, Hajime FujisawaAbstract:Abstract The alar plate of the Prosencephalon differentiates into a tectum-like structure when transplanted into the mesencephalon around the 10-somite stage. Here, we report on the projection pattern of the retinal ganglion cells to the transplants. Optic nerve fibers were labeled with horseradish peroxidase (HRP) and 3 H-proline, and the innervation of the optic nerve fibers to the chimeric tectum was analyzed by HRP histochemistry on whole-mounted specimens, by autoradiography and by electron microscopy on embryonic day 16. In the chimeric tectum, the transplant was distinguished from the host by difference in nuclear structure between the quail and the chick cells. It was shown that the transplant had the laminar pattern of the optic tectum when the transplant was integrated into the host mesencephalon. The whole-mount HRP histochemistry showed that the optic nerve fibers extend to the transplants. Autoradiography showed that the distribution pattern of silver grains was similar in both the host and the transplant. These results may indicate that the optic nerve fibers turn to the transplant and terminate on the transplant. Electron microscopy further confirmed that optic nerve fibers ended by making synaptic contacts with the dendrites in the transplant region of the tectum. These results indicate that the transplant with the laminar pattern of the optic tectum is a true tectum receiving input from the eye.
-
Do CNS anlagen have plasticity in differentiation? Analysis in quail-chick chimera
Brain Research, 1990Co-Authors: Harukazu NakamuraAbstract:Abstract Heterotopic transplantations of brain vesicles of a quail embryo into a chick embryo were carried out in order to elucidate if CNS anlagen have plasticity in differentiation at the 7–10 somite stage. Quail cells are distinguished from chick cells due to the difference in nuclear morphology. The Prosencephalon did not differentiate into the cerebellum when transplanted into the metencephalon, although previous study showed that the Prosencephalon has the capacity to differentiate into the optic tectum. The mesencephalon differentiated as an optic tectum when transplanted into the Prosencephalon or into the rhombencephalon. The metencephalon differentiated as a cerebellum in the telencephalon. It is concluded that only the Prosencephalon has limited plasticity, but the mesencephalon and rhombencephalon are determined by the 7–10 somite stage.
