| 1. |
- Coutinho, Ana P, et al.
(författare)
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Induction of a parafacial rhythm generator by rhombomere 3 in the chick embryo.
- 2004
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Ingår i: Journal of Neuroscience. - 0270-6474 .- 1529-2401. ; 24:42, s. 9383-9390
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Tidskriftsartikel (refereegranskat)abstract
- Observations of knock-out mice suggest that breathing at birth requires correct development of a specific hindbrain territory corresponding to rhombomeres (r) 3 and 4. Focusing on this territory, we examined the development of a neuronal rhythm generator in the chick embryo. We show that rhythmic activity in r4 is inducible after developmental stage 10 through interaction with r3. Although the nature of this interaction remains obscure, we find that the expression of Krox20, a segmentation gene responsible for specifying r3 and r5, is sufficient to endow other rhombomeres with the capacity to induce rhythmic activity in r4. Induction is robust, because it can be reproduced with r2 and r6 instead of r4 and with any hindbrain territory that normally expresses Krox20 (r3, r5) or can be forced to do so (r1, r4). Interestingly, the interaction between r4 and r3/r5 that results in rhythm production can only take place through the anterior border of r4, revealing a heretofore unsuspected polarity in individual rhombomeres. The r4 rhythm generator appears to be homologous to a murine respiratory parafacial neuronal system developing in r4 under the control of Krox20 and Hoxa1. These results identify a late role for Krox20 at the onset of neurogenesis.
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| 2. |
- Gilthorpe, Jonathan, et al.
(författare)
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The migration of cerebellar rhombic lip derivatives.
- 2002
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Ingår i: Development. - : F1000 Research Ltd. - 0950-1991 .- 1477-9129. ; 129:20, s. 4719-4728
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Tidskriftsartikel (refereegranskat)abstract
- We have used cell labelling, co-culture and time-lapse confocal microscopy to investigate tangential neuronal migration from the rhombic lip. Cerebellar rhombic lip derivatives demonstrate a temporal organisation with respect to their morphology and response to migration cues. Early born cells, which migrate into ventral rhombomere 1, have a single long leading process that turns at the midline and becomes an axon. Later born granule cell precursors also migrate ventrally but halt at the lateral edge of the cerebellum, correlating with a loss of sensitivity to netrin 1 and expression of Robo2. The rhombic lip and ventral midline express Slit2 and both early and late migrants are repelled by sources of Slit2 in co-culture. These studies reveal an intimate relationship between birthdate, response to migration cues and neuronal fate in an identified population of migratory cells. The use of axons in navigating cell movement suggests that tangential migration is an elaboration of the normal process of axon extension.
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| 3. |
- Lumsden, A, et al.
(författare)
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Neurobiology.
- 2001
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Ingår i: Current Opinion in Neurobiology. - 0959-4388 .- 1873-6882. ; 11:3, s. 259-66
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Forskningsöversikt (refereegranskat)
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| 4. |
- Yaneza, May, et al.
(författare)
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No evidence for ventrally migrating neural tube cells from the mid- and hindbrain.
- 2002
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Ingår i: Developmental Dynamics. - : Wiley. - 1058-8388 .- 1097-0177. ; 223:1, s. 163-7
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Tidskriftsartikel (refereegranskat)abstract
- Abstract The neural crest is a migratory population of cells that originates from the dorsal neural tube in vertebrates. Recently, the existence of a group of ventrally emigrating neural tube (VENT) cells has been proposed, based upon cell labelling studies in the hindbrain of avian embryos. Like crest cells, these VENT cells have been reported to give rise to numerous cell types. VENT cell emigration is thought to occur after embryonic day (E) 3, when neural crest cell production has ceased. Migration of cells from the ventral neural tube into the periphery was inferred retrospectively after examining numerous embryos harvested at different stages. We have attempted to label VENT cells in vivo by using a green fluorescent protein (GFP) expression vector, electroporated into the ventral neural tube after crest cell migration and before the putative migration of the ventrally localised cells. Because GFP can be visualised strongly in living tissue a few hours after electroporation, the migration of labelled cells within the same embryo can be followed. Fluorescent cells labelled in the mid-hindbrain region were examined in ovo and in explant culture. No GFP-expressing cells were detected emigrating from the ventral neural tube from E3 to E5. Our findings are, thus, in disagreement with those of previous studies, which have indicated the existence of VENT cells in the cranial region.
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