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Cellular basis of neuroepithelial bending during mouse spinal neural tube closure.

McShane SG, Molè MA, Savery D, Greene ND, Tam PP, Copp AJ - Dev. Biol. (2015)

Bottom Line: As the neural folds elevate, cell numbers increase to a greater extent in the dorsolateral neural plate that contacts the surface ectoderm, compared with the more ventromedial neural plate where cells contact paraxial mesoderm and notochord.We hypothesised that neuroepithelial cells may translocate in a ventral-to-dorsal direction as DLHP formation occurs, and this was confirmed by vital cell labelling in cultured embryos.These findings suggest a model in which DLHP formation may proceed through 'buckling' of the neuroepithelium at a dorso-ventral boundary marked by a change in cell-packing density.

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Affiliation: Newlife Birth Defects Research Centre, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK.

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A model of DLHP bending during neural fold elevation. Diagrammatic transverse sections of flat (A) and elevated (B) half-neural plate (np), juxtaposed surface ectoderm (se) and paraxial mesoderm (pm). As the neural fold elevates, neuroepithelial cells translocate ventro-dorsally (curved arrow in B) so that increasing numbers contact the surface ectoderm in the elevated neural fold. This results in increased cell density and diminished cell width within the dorsal neural fold region. Two cells originating ventrally (pink) are depicted translocating dorsally, as was observed in the DiI vital cell labelling study. Cells at the midline (MHP) exhibit basal nuclear localisation, whereas elsewhere in the neuroepithelium nuclei are observed at all apico-basal positions. DLHP formation is suggested to result from physical ‘buckling’ of the neural plate (red arrow) at the junction between the dorsal region of increased cell density and ventral region of lower cell density.
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f0040: A model of DLHP bending during neural fold elevation. Diagrammatic transverse sections of flat (A) and elevated (B) half-neural plate (np), juxtaposed surface ectoderm (se) and paraxial mesoderm (pm). As the neural fold elevates, neuroepithelial cells translocate ventro-dorsally (curved arrow in B) so that increasing numbers contact the surface ectoderm in the elevated neural fold. This results in increased cell density and diminished cell width within the dorsal neural fold region. Two cells originating ventrally (pink) are depicted translocating dorsally, as was observed in the DiI vital cell labelling study. Cells at the midline (MHP) exhibit basal nuclear localisation, whereas elsewhere in the neuroepithelium nuclei are observed at all apico-basal positions. DLHP formation is suggested to result from physical ‘buckling’ of the neural plate (red arrow) at the junction between the dorsal region of increased cell density and ventral region of lower cell density.

Mentions: It is striking that DLHPs form precisely at the dorso-ventral level where the neural plate transitions from basal contact with paraxial mesoderm to basal contact with surface ectoderm. We found that, during DLHP formation, both cell number and cell density increase markedly, while nominal cell width decreases, particularly in the dorsal neural fold component of the neuroepithelium. This might suggest a mechanism of neural plate bending (Fig. 8) in which the elevating neuroepithelium behaves biomechanically as a biphasic structure. That is, each half-neural plate comprises a dorsolateral component of increasing cell density in direct physical contiguity with a ventromedial component of relatively constant, lower cell density. We suggest, therefore, that DLHP formation could represent the inward (i.e. medially directed) ‘buckling’ of the neuroepithelium at the phase transition point (see red arrow: ‘basal contact transition point’ in Fig. 8). This represents a markedly different view of neuroepithelial morphogenesis from the rather uniform bending that is usually envisaged to result from generalised apical constriction of the neuroepithelium (Sawyer et al., 2010).


Cellular basis of neuroepithelial bending during mouse spinal neural tube closure.

McShane SG, Molè MA, Savery D, Greene ND, Tam PP, Copp AJ - Dev. Biol. (2015)

A model of DLHP bending during neural fold elevation. Diagrammatic transverse sections of flat (A) and elevated (B) half-neural plate (np), juxtaposed surface ectoderm (se) and paraxial mesoderm (pm). As the neural fold elevates, neuroepithelial cells translocate ventro-dorsally (curved arrow in B) so that increasing numbers contact the surface ectoderm in the elevated neural fold. This results in increased cell density and diminished cell width within the dorsal neural fold region. Two cells originating ventrally (pink) are depicted translocating dorsally, as was observed in the DiI vital cell labelling study. Cells at the midline (MHP) exhibit basal nuclear localisation, whereas elsewhere in the neuroepithelium nuclei are observed at all apico-basal positions. DLHP formation is suggested to result from physical ‘buckling’ of the neural plate (red arrow) at the junction between the dorsal region of increased cell density and ventral region of lower cell density.
© Copyright Policy - CC BY
Related In: Results  -  Collection

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f0040: A model of DLHP bending during neural fold elevation. Diagrammatic transverse sections of flat (A) and elevated (B) half-neural plate (np), juxtaposed surface ectoderm (se) and paraxial mesoderm (pm). As the neural fold elevates, neuroepithelial cells translocate ventro-dorsally (curved arrow in B) so that increasing numbers contact the surface ectoderm in the elevated neural fold. This results in increased cell density and diminished cell width within the dorsal neural fold region. Two cells originating ventrally (pink) are depicted translocating dorsally, as was observed in the DiI vital cell labelling study. Cells at the midline (MHP) exhibit basal nuclear localisation, whereas elsewhere in the neuroepithelium nuclei are observed at all apico-basal positions. DLHP formation is suggested to result from physical ‘buckling’ of the neural plate (red arrow) at the junction between the dorsal region of increased cell density and ventral region of lower cell density.
Mentions: It is striking that DLHPs form precisely at the dorso-ventral level where the neural plate transitions from basal contact with paraxial mesoderm to basal contact with surface ectoderm. We found that, during DLHP formation, both cell number and cell density increase markedly, while nominal cell width decreases, particularly in the dorsal neural fold component of the neuroepithelium. This might suggest a mechanism of neural plate bending (Fig. 8) in which the elevating neuroepithelium behaves biomechanically as a biphasic structure. That is, each half-neural plate comprises a dorsolateral component of increasing cell density in direct physical contiguity with a ventromedial component of relatively constant, lower cell density. We suggest, therefore, that DLHP formation could represent the inward (i.e. medially directed) ‘buckling’ of the neuroepithelium at the phase transition point (see red arrow: ‘basal contact transition point’ in Fig. 8). This represents a markedly different view of neuroepithelial morphogenesis from the rather uniform bending that is usually envisaged to result from generalised apical constriction of the neuroepithelium (Sawyer et al., 2010).

Bottom Line: As the neural folds elevate, cell numbers increase to a greater extent in the dorsolateral neural plate that contacts the surface ectoderm, compared with the more ventromedial neural plate where cells contact paraxial mesoderm and notochord.We hypothesised that neuroepithelial cells may translocate in a ventral-to-dorsal direction as DLHP formation occurs, and this was confirmed by vital cell labelling in cultured embryos.These findings suggest a model in which DLHP formation may proceed through 'buckling' of the neuroepithelium at a dorso-ventral boundary marked by a change in cell-packing density.

View Article: PubMed Central - PubMed

Affiliation: Newlife Birth Defects Research Centre, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK.

Show MeSH
Related in: MedlinePlus