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Regional Identity (regional + identity)
Selected AbstractsExtracerebellar progenitors grafted to the neurogenic milieu of the postnatal rat cerebellum adapt to the host environment but fail to acquire cerebellar identitiesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2010Chiara Rolando Abstract Stem or progenitor cells acquire specific regional identities during early ontogenesis. Nonetheless, there is evidence that cells heterotopically transplanted to neurogenic regions of the developing or mature central nervous system may switch their fate to adopt host-specific phenotypes. Here, we isolated progenitor cells from different germinative sites along the neuraxis where GABAergic interneurons are produced (telencephalic subventricular zone, medial ganglionic eminence, ventral mesencephalon and dorsal spinal cord), and grafted them to the prospective white matter of the postnatal rat cerebellum, at the time when local interneurons are generated. The phenotype acquired by transplanted cells was assessed by different criteria, including expression of region-specific transcription factors, acquisition of morphological and neurochemical traits, and integration in the cerebellar cytoarchitecture. Regardless of their origin, all the different types of donor cells engrafted in the cerebellar parenchyma and developed mature neurons that shared some morphological and neurochemical features with local inhibitory interneurons, particularly in the deep nuclei. Nevertheless, transplanted cells failed to activate cerebellar-specific regulatory genes. In addition, their major structural features, the expression profiles of type-specific markers and the laminar placement in the recipient cortex did not match those of endogenous interneurons generated during the same developmental period. Therefore, although exogenous cells are influenced by the cerebellar milieu and show remarkable capabilities for adapting to the foreign environment, they essentially fail to switch their fate, integrate in the host neurogenic mechanisms and adopt clear-cut cerebellar identities. [source] Explaining the Enforcement of Democracy by Regional Organizations: Comparing EU, Mercosur and SADCJCMS: JOURNAL OF COMMON MARKET STUDIES, Issue 3 2010ANNA VAN DER VLEUTEN Regional organizations sometimes intervene to preserve democracy in one of their Member States. When a regional organization has developed a democratic identity, non-intervention in case of violation of democratic principles would damage its credibility domestically and internationally. Nonetheless, violations of democratic principles sometimes go unsanctioned. Building on case studies of (non-)interventions by the EU, Mercosur and SADC, we show that the ideational costs of pressure by third parties and the interests of the regional leading powers can explain the enforcement of democracy by regional organizations. Third party pressure remains ineffective, however, when there is a clash between regional identities. [source] Retinoic acid affects craniofacial patterning by changing Fgf8 expression in the pharyngeal ectodermDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 9 2008Makoto Abe Retinoic acid signaling plays important roles in establishing normal patterning and cellular differentiation during embryonic development. In this study, we show that single administration of retinoic acid at embryonic day 8.5 causes homeotic transformation of the lower jaw into upper jaw-like structures. This homeosis was preceded by downregulation of Fgf8 and Sprouty expression in the proximal domain of the first pharyngeal arch. Downregulation of mesenchymal genes such as Dlx5, Hand2, Tbx1 and Pitx2 was also observed. The oropharynx in retinoic acid-treated embryos was severely constricted. Consistent with this observation, Patched expression in the arch endoderm and mesenchyme was downregulated. Thus, retinoic acid affects the expression of subsets of epithelial and mesenchymal genes, possibly disrupting the regional identity of the pharyngeal arch. [source] The role of Pax7 in determining the cytoarchitecture of the superior colliculusDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 3 2004Jennifer Thompson Pax genes are a family of transcriptional regulators vital for embryonic development. One member of the family, Pax7, functions early in neural development to establish dorsal polarity of the neural tube, and continuous refinement of its expression affords regional identity to brain nuclei, in particular the superior colliculus. Pax7 expression within the superior colliculus is eventually restricted to the stratum griseum et fibrosum superficiale (SGFS), the retinorecipient layer to which the optic nerve projects. The key role of Pax7 in specification of the superior colliculus has been highlighted by misexpression studies which result in ectopic formation of superior collicular tissue with characteristic laminae innervated by retinal ganglion cell axons. Here we review the role of Pax7 in formation of the superior colliculus and discuss the possibility that Pax7 may also assist in refinement of correct topographic mapping. [source] Human fetal cortical and striatal neural stem cells generate region-specific neurons in vitro and differentiate extensively to neurons after intrastriatal transplantation in neonatal ratsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 8 2006Therése Kallur Abstract Human fetal brain is a potential source of neural stem cells (NSCs) for cell replacement therapy in neurodegenerative diseases. We explored whether NSCs isolated from cortex and striatum of human fetuses, aged 6,9 weeks post-conception, maintain their regional identity and differentiate into specific neuron types in culture and after intrastriatal transplantation in neonatal rats. We observed no differences between cortex- and striatum-derived NSCs expanded as neurospheres in proliferative capacity, growth rate, secondary sphere formation, and expression of neural markers. After 4 weeks of differentiation in vitro, cortical and striatal NSCs gave rise to similar numbers of GABAergic and VMAT2- and parvalbumin-containing neurons. However, whereas cortical NSCs produced higher number of glutamatergic and tyrosine hydroxylase- and calretinin-positive neurons, several-fold more neurons expressing the striatal projection neuron marker, DARPP-32, were observed in cultures of striatal NSCs. Human cortical and striatal NSCs survived and migrated equally well after transplantation. The two NSC types also generated similar numbers of mature NeuN-positive neurons, which were several-fold higher at 4 months as compared to at 1 month after grafting. At 4 months, the grafts contained cells with morphologic characteristics of neurons, astrocytes, and oligodendrocytes. Many of neurons were expressing parvalbumin. Our data show that NSCs derived from human fetal cortex and striatum exhibit region-specific differentiation in vitro, and survive, migrate, and form mature neurons to the same extent after intrastriatal transplantation in newborn rats. © 2006 Wiley-Liss, Inc. [source] | ||||||||||