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Tangential Migration (tangential + migration)
Selected AbstractsSubventricular zone-derived neuroblast migration to the olfactory bulb is modulated by matrix remodellingEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2007Serena Bovetti Abstract In the rodent brain neural progenitor cells are born in the subventricular zone and migrate along a pathway called the rostral migratory stream (RMS) into the olfactory bulb where they differentiate into several classes of interneurones. In the adult, tangential migration in the RMS takes place in ,chains' of cells contained within glial tubes. In contrast, neonatal neuroblasts along the RMS lack these defined glial tubes and chains, migrating instead as individual cells. Time-lapse confocal microscopy of neuroblasts at each of these ages shows that individual cells migrate in a saltatory manner with bursts of high speed followed by periods of slower speed. Tangential migration within a glial tube is 20% faster than migration as individual cells. Neuroblasts may also interact and modify the extracellular matrix during migration through expression of a family of proteins, the matrix metalloproteinases (MMPs). MMPs are present and active along the subventricular zone,olfactory bulb pathway. In the presence of inhibitors of MMPs, neuroblast migration rates were reduced only when cells migrate individually. Chain migration in the adult was unaffected by MMP inhibitors. Taken together, these data suggest that MMPs only influence migration as individual cells and not as chains. [source] Folding of the tectal cortex by local remodeling of neural differentiationDEVELOPMENTAL DYNAMICS, Issue 3 2004Tatsuo Mima Abstract The folding pattern of the brain cortex is a precisely regulated process, but the mechanism involved during development remains unclear. A proposed theory predicts that the initiation of cortical folding depends, at least partly, on nonuniform distribution of neuronal differentiation and neurite growth. We tested this theory experimentally, by remodeling the normal pattern of neuronal cell differentiation within the embryonic optic tectum. Multiple foci of activated fibroblast growth factor signaling were created in the tectal cortex to locally change the neural differentiation and axonal growth patterns. At these foci, tectal cells remained undifferentiated and their radial and tangential migration was suppressed. These local changes in the neuronal cell differentiation resulted in a conversion of the tectal cortex from smoothly extended into precociously folded. The results provide in vivo experimental evidence that microscopic changes in the neuronal cell differentiation pattern can induce or remodel the folding pattern of the brain cortex. Developmental Dynamics 229:475,479, 2004. © 2004 Wiley-Liss, Inc. [source] Multiple mechanisms mediate motor neuron migration in the zebrafish hindbrainDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2010Stephanie M. Bingham Abstract The transmembrane protein Van gogh-like 2 (Vangl2) is a component of the noncanonical Wnt/Planar Cell Polarity (PCP) signaling pathway, and is required for tangential migration of facial branchiomotor neurons (FBMNs) from rhombomere 4 (r4) to r5-r7 in the vertebrate hindbrain. Since vangl2 is expressed throughout the zebrafish hindbrain, it might also regulate motor neuron migration in other rhombomeres. We tested this hypothesis by examining whether migration of motor neurons out of r2 following ectopic hoxb1b expression was affected in vangl2, (trilobite) mutants. Hoxb1b specifies r4 identity, and when ectopically expressed transforms r2 to an "r4-like" compartment. Using time-lapse imaging, we show that GFP-expressing motor neurons in the r2/r3 region of a hoxb1b -overexpressing wild-type embryo migrate along the anterior-posterior (AP) axis. Furthermore, these cells express prickle1b (pk1b), a Wnt/PCP gene that is specifically expressed in FBMNs and is essential for their migration. Importantly, GFP-expressing motor neurons in the r2/r3 region of hoxb1b -overexpressing trilobite mutants and pk1b morphants often migrate, even though FBMNs in r4 of the same embryos fail to migrate longitudinally (tangentially) into r6 and r7. These observations suggest that tangentially migrating motor neurons in the anterior hindbrain (r1-r3) can use mechanisms that are independent of vangl2 and pk1b functions. Interestingly, analysis of tri; val double mutants also suggests a role for vangl2 -independent factors in neuronal migration, since the valentino mutation partially suppresses the trilobite mutant migration defect. Together, the hoxb1b and val experiments suggest that multiple mechanisms regulate motor neuron migration along the AP axis of the zebrafish hindbrain. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2010 [source] Subventricular zone-derived neuroblast migration to the olfactory bulb is modulated by matrix remodellingEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2007Serena Bovetti Abstract In the rodent brain neural progenitor cells are born in the subventricular zone and migrate along a pathway called the rostral migratory stream (RMS) into the olfactory bulb where they differentiate into several classes of interneurones. In the adult, tangential migration in the RMS takes place in ,chains' of cells contained within glial tubes. In contrast, neonatal neuroblasts along the RMS lack these defined glial tubes and chains, migrating instead as individual cells. Time-lapse confocal microscopy of neuroblasts at each of these ages shows that individual cells migrate in a saltatory manner with bursts of high speed followed by periods of slower speed. Tangential migration within a glial tube is 20% faster than migration as individual cells. Neuroblasts may also interact and modify the extracellular matrix during migration through expression of a family of proteins, the matrix metalloproteinases (MMPs). MMPs are present and active along the subventricular zone,olfactory bulb pathway. In the presence of inhibitors of MMPs, neuroblast migration rates were reduced only when cells migrate individually. Chain migration in the adult was unaffected by MMP inhibitors. Taken together, these data suggest that MMPs only influence migration as individual cells and not as chains. [source] Transient maternal hypothyroxinemia at onset of corticogenesis alters tangential migration of medial ganglionic eminence-derived neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2005Estela Cuevas Abstract Correct positioning of cortical neurons during development depends on the radial migration of the projection neurons and on the coordinated tangential and radial migrations of the subcortically generated interneurons. As previously shown, a transient and moderate maternal deficiency in thyroxin during early corticogenesis alters the radial migration of projection neurons. To determine if a similar effect might also affect tangential migration of medial ganglionic eminence (MGE)-derived neurons at the origin of cortical interneurons, explants of MGE from green fluorescent protein (GFP)-transgenic embryos were implanted into flat cortical mounts from wild-type embryos. The distances covered and the preferential migration (medially) of GFP-MGE neurons from embryos of hypothyroxinemic dams are not affected in their tangential migration into wild-type control cortices. In contrast, when GFP-MGE neurons from embryos of control or hypothyroxinemic dams migrate within cortices from embryos of hypothyroxinemic dams, the GFP-MGE-derived neurons lose their preferential direction of migration, although they still migrate for long distances throughout the cortex. Our results show that maternal hypothyroxinemia alters the tangential migration of GFP-MGE-derived neurons in the neocortex of the progeny and suggest that this alteration is not derived from the migratory neurons themselves but through undefined short- and long-range cues responsible for the guidance of their migration. [source] Radial migration of developing microglial cells in quail retina: A confocal microscopy studyGLIA, Issue 3 2004Ana Sánchez-López Abstract Microglial cells spread within the nervous system by tangential and radial migration. The cellular mechanism of tangential migration of microglia has been described in the quail retina but the mechanism of their radial migration has not been studied. In this work, we clarify some aspects of this mechanism by analyzing morphological features of microglial cells at different steps of their radial migration in the quail retina. Microglial cells migrate in the vitreal half of the retina by successive jumps from the vitreal border to progressively more scleral levels located at the vitreal border, intermediate regions, and scleral border of the inner plexiform layer (IPL). The cellular mechanism used for each jump consists of the emission of a leading thin radial process that ramifies at a more scleral level before retraction of the rear of the cell. Hence, radial migration and ramification of microglial cells are simultaneous events. Once at the scleral border of the IPL, microglial cells migrate through the inner nuclear layer to the outer plexiform layer by another mechanism: they retract cell processes, become round, and squeeze through neuronal bodies. Microglial cells use radial processes of s-laminin-expressing Müller cells as substratum for radial migration. Levels where microglial cells stop and ramify at each jump are always interfaces between retinal strata with strong tenascin immunostaining and strata showing weak or no tenascin immunoreactivity. When microglial cell radial migration ends, tenascin immunostaining is no longer present in the retina. These findings suggest that tenascin plays a role in the stopping and ramification of radially migrating microglial cells. © 2004 Wiley-Liss, Inc. [source] Secondary neurogenesis and telencephalic organization in zebrafish and mice: a brief reviewINTEGRATIVE ZOOLOGY (ELECTRONIC), Issue 1 2009Mario F. WULLIMANN Abstract Most zebrafish neurodevelopmental studies have focused on the embryo, which is characterized by primary neurogenesis of mostly transient neurons. Secondary neurogenesis becomes dominant in the hatching larva, when major brain parts are established and begin to differentiate. This developmental period allows for a comparative analysis of zebrafish brain organization with amniotes at equivalent stages of neurogenesis. Within a particular time window, the early forebrains of mice (Embyronic stage [E] 12.5/13.5 days [d]) and zebrafish (3 d) reveal highly comparable expression patterns of genes involved in neurogenesis, for example proneural and other transcription factors (Neurogenin1, NeuroD, Mash1/Zashla and Pax6). Further topological correspondences are seen in the expression of LIM and homeobox genes, such as Lhx6/7, Tbr2 and Dlx2a. When this analysis is extended to gamma-aminobutyric acid/glutamic acid decarboxylase (GABA/GAD) cell patterns during this critical time window, an astonishing degree of similarity between the two species is again seen, for example regarding the presence of GABA/GAD cells in the subpallium, with the pallium only starting to be invaded by such cells from the subpallium. Furthermore, the expression of proneural and other genes correlates with GABA cell patterns (e.g. Mash1/Zash1a gene expression in GABA-positive and Neurogenin1/NeuroD in GABA-negative telencephalic regions) in mice and zebrafish. Data from additional vertebrates, such as Xenopus, are also highly consistent with this analysis. Therefore, the vertebrate forebrain appears to undergo a phylotypic stage of secondary neurogenesis, characterized by regionally separated GABAergic (inhibitory) versus glutamatergic (excitatory) cell production sites, which are obscured later in development by tangential migration. This period is highly advantageous for molecular neuroanatomical cross-species comparisons. [source] Renewed focus on the developing human neocortexJOURNAL OF ANATOMY, Issue 4 2010Gavin Clowry Abstract Many specifically human psychiatric and neurological conditions have developmental origins. Rodent models are extremely valuable for the investigation of brain development, but cannot provide insight into aspects that are specifically human. The human brain, and particularly the cerebral cortex, has some unique genetic, molecular, cellular and anatomical features, and these need to be further explored. Cortical expansion in human is not just quantitative; there are some novel types of neurons and cytoarchitectonic areas identified by their gene expression, connectivity and functions that do not exist in rodents. Recent research into human brain development has revealed more elaborated neurogenetic compartments, radial and tangential migration, transient cell layers in the subplate, and a greater diversity of early-generated neurons, including predecessor neurons. Recently there has been a renaissance of the study of human brain development because of these unique differences, made possible by the availability of new techniques. This review gives a flavour of the recent studies stemming from this renewed focus on the developing human brain. [source] | ||||||||||