A Scube2-Shh feedback loop links morphogen release to morphogen signaling to enable scale invariant patterning of the ventral neural tube

AbstractTo enable robust patterning, morphogen systems should be resistant to variations in gene expression and tissue size. Here we explore how a Shh morphogen gradient in the ventral neural tube enables proportional patterning in embryos of varying sizes. Using a surgical technique to reduce the size of zebrafish embryos and quantitative confocal microscopy, we find that patterning of neural progenitors remains proportional after size reduction. Intriguingly, a protein necessary for Shh release, Scube2, is expressed far from the source of sonic hedgehog production. scube2 expression levels control Shh signaling extent during ventral neural patterning and conversely Shh signaling represses the expression of scube2, thereby restricting its own signaling. scube2 is disproportionately downregulated in size-reduced embryos, providing a potential mechanism for size-dependent regulation of Shh. This regulatory feedback is necessary for pattern scaling, as demonstrated by a loss of scaling in scube2 overexpressing embryos. In a manner akin to the expander-repressor model of morphogen scaling, we conclude that feedback between Shh signaling and scube2 expression enables proportional patterning in the ventral neural tube by encoding a tissue size dependent morphogen signaling gradient.Summary StatementThe Shh morphogen gradient can scale to different size tissues by feedback between Scube2 mediated release of Shh and Shh based inhibition of Scube2 expressionAuthor ContributionsZ.M.C. conducted experiments and data analysis. Z.M.C and S.G.M. conceived the study, designed the experiments, and wrote the paper. K.I and Z.M.C. developed the size reduction technique. T.Y.C.T helped develop the image analysis technique and generated the tg(shha:memCherry) reporter line. S.G.M. supervised the overall study.

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Myogenesis in paraxial mesoderm: preferential induction by dorsal neural tube and by cells expressing Wnt-1

Development ◽

10.1242/dev.121.11.3675 ◽

1995 ◽

Vol 121 (11) ◽

pp. 3675-3686 ◽

Cited By ~ 40

Author(s):

H.M. Stern ◽

A.M. Brown ◽

S.D. Hauschka

Keyword(s):

Neural Tube ◽

Muscle Development ◽

Paraxial Mesoderm ◽

Myogenic Response ◽

Dorsal Neural Tube ◽

Ventral Neural Tube ◽

Myogenic Induction ◽

Inductive Activity

Previous studies have demonstrated that the neural tube/notochord complex is required for skeletal muscle development within somites. In order to explore the localization of myogenic inducing signals within the neural tube, dorsal or ventral neural tube halves were cultured in contact with single somites or pieces of segmental plate mesoderm. Somites and segmental plates cultured with the dorsal half of the neural tube exhibited 70% and 85% myogenic response rates, as determined by immunostaining for myosin heavy chain. This response was slightly lower than the 100% response to whole neural tube/notochord, but was much greater than the 30% and 10% myogenic response to ventral neural tube with and without notochord. These results demonstrate that the dorsal neural tube emits a potent myogenic inducing signal which accounts for most of the inductive activity of whole neural tube/notochord. However, a role for ventral neural tube/notochord in somite myogenic induction was clearly evident from the larger number of myogenic cells induced when both dorsal neural tube and ventral neural tube/notochord were present. To address the role of a specific dorsal neural tube factor in somite myogenic induction, we tested the ability of Wnt-1-expressing fibroblasts to promote paraxial mesoderm myogenesis in vitro. We found that cells expressing Wnt-1 induced a small number of somite and segmental plate cells to undergo myogenesis. This finding is consistent with the localized dorsal neural tube inductive activity described above, but since the ventral neural tube/notochord also possesses myogenic inductive capacity yet does not express Wnt-1, additional inductive factors are likely involved.

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Cell-autonomous shift from axial to paraxial mesodermal development in zebrafish floating head mutants

Development ◽

10.1242/dev.121.12.4257 ◽

1995 ◽

Vol 121 (12) ◽

pp. 4257-4264 ◽

Cited By ~ 25

Author(s):

M.E. Halpern ◽

C. Thisse ◽

R.K. Ho ◽

B. Thisse ◽

B. Riggleman ◽

...

Keyword(s):

Neural Tube ◽

Single Cells ◽

Floor Plate ◽

Paraxial Mesoderm ◽

Wild Type ◽

Genetic Mosaics ◽

Essential Step ◽

Ventral Neural Tube ◽

Mesodermal Development

Zebrafish floating head mutant embryos lack notochord and develop somitic muscle in its place. This may result from incorrect specification of the notochord domain at gastrulation, or from respecification of notochord progenitors to form muscle. In genetic mosaics, floating head acts cell autonomously. Transplanted wild-type cells differentiate into notochord in mutant hosts; however, cells from floating head mutant donors produce muscle rather than notochord in wild-type hosts. Consistent with respecification, markers of axial mesoderm are initially expressed in floating head mutant gastrulas, but expression does not persist. Axial cells also inappropriately express markers of paraxial mesoderm. Thus, single cells in the mutant midline transiently co-express genes that are normally specific to either axial or paraxial mesoderm. Since floating head mutants produce some floor plate in the ventral neural tube, midline mesoderm may also retain early signaling capabilities. Our results suggest that wild-type floating head provides an essential step in maintaining, rather than initiating, development of notochord-forming axial mesoderm.

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The zebrafish T-box genesno tailandspadetailare required for development of trunk and tail mesoderm and medial floor plate

Development ◽

10.1242/dev.129.14.3311 ◽

2002 ◽

Vol 129 (14) ◽

pp. 3311-3323 ◽

Cited By ~ 6

Author(s):

Sharon L. Amacher ◽

Bruce W. Draper ◽

Brian R. Summers ◽

Charles B. Kimmel

Keyword(s):

Embryonic Development ◽

Neural Tube ◽

Transcriptional Regulators ◽

Floor Plate ◽

Wild Type ◽

T Box ◽

No Tail ◽

Ventral Neural Tube ◽

Plate Formation ◽

In Cells

T-box genes encode transcriptional regulators that control many aspects of embryonic development. Here, we demonstrate that the mesodermally expressed zebrafish spadetail (spt)/VegT and no tail (ntl)/Brachyury T-box genes are semi-redundantly and cell-autonomously required for formation of all trunk and tail mesoderm. Despite the lack of posterior mesoderm in spt–;ntl– embryos, dorsal-ventral neural tube patterning is relatively normal, with the notable exception that posterior medial floor plate is completely absent. This contrasts sharply with observations in single mutants, as mutations singly in ntl or spt enhance posterior medial floor plate development. We find that ntl function is required to repress medial floor plate and promote notochord fate in cells of the wild-type notochord domain and that spt and ntl together are required non cell-autonomously for medial floor plate formation, suggesting that an inducing signal present in wild-type mesoderm is lacking in spt–;ntl– embryos.

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Direct action of the nodal-related signal cyclops in induction of sonic hedgehog in the ventral midline of the CNS

Development ◽

10.1242/dev.127.18.3889 ◽

2000 ◽

Vol 127 (18) ◽

pp. 3889-3897 ◽

Cited By ~ 4

Author(s):

F. Muller ◽

S. Albert ◽

P. Blader ◽

N. Fischer ◽

M. Hallonet ◽

...

Keyword(s):

Sonic Hedgehog ◽

Neural Tube ◽

Direct Action ◽

Brain Regions ◽

Floor Plate ◽

Ventral Midline ◽

Signal Transducers ◽

Step Model ◽

Ventral Neural Tube ◽

Differential Responsiveness

The secreted molecule Sonic hedgehog (Shh) is crucial for floor plate and ventral brain development in amniote embryos. In zebrafish, mutations in cyclops (cyc), a gene that encodes a distinct signal related to the TGF(beta) family member Nodal, result in neural tube defects similar to those of shh null mice. cyc mutant embryos display cyclopia and lack floor plate and ventral brain regions, suggesting a role for Cyc in specification of these structures. cyc mutants express shh in the notochord but lack expression of shh in the ventral brain. Here we show that Cyc signalling can act directly on shh expression in neural tissue. Modulation of the Cyc signalling pathway by constitutive activation or inhibition of Smad2 leads to altered shh expression in zebrafish embryos. Ectopic activation of the shh promoter occurs in response to expression of Cyc signal transducers in the chick neural tube. Furthermore an enhancer of the shh gene, which controls ventral neural tube expression, is responsive to Cyc signal transducers. Our data imply that the Nodal related signal Cyc induces shh expression in the ventral neural tube. Based on the differential responsiveness of shh and other neural tube specific genes to Hedgehog and Cyc signalling, a two-step model for the establishment of the ventral midline of the CNS is proposed.

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Neurogenin 1 (Neurog1) expression in the ventral neural tube is mediated by a distinct enhancer and preferentially marks ventral interneuron lineages

Developmental Biology ◽

10.1016/j.ydbio.2010.02.012 ◽

2010 ◽

Vol 340 (2) ◽

pp. 283-292 ◽

Cited By ~ 25

Author(s):

Herson I. Quiñones ◽

Trisha K. Savage ◽

James Battiste ◽

Jane E. Johnson

Keyword(s):

Neural Tube ◽

Ventral Neural Tube

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The function of SMN in positioning motor neurons in the ventral neural tube

Developmental Biology ◽

10.1016/j.ydbio.2009.05.320 ◽

2009 ◽

Vol 331 (2) ◽

pp. 472

Author(s):

Catherine E. Krull ◽

Fengyun Su ◽

Mustafa Sahin

Keyword(s):

Motor Neurons ◽

Neural Tube ◽

Ventral Neural Tube

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DiI labeling and homeobox gene Islet-1 expression reveal the contribution of ventral neural tube cells to the formation of the avian trigeminal ganglion

International Journal of Developmental Neuroscience ◽

10.1016/0736-5748(96)00002-0 ◽

1996 ◽

Vol 14 (4) ◽

pp. 419-427 ◽

Cited By ~ 19

Author(s):

G.S. Sohal ◽

D.E. Bockman ◽

M.M. Ali ◽

N.T. Tsai

Keyword(s):

Trigeminal Ganglion ◽

Neural Tube ◽

Homeobox Gene ◽

Ventral Neural Tube ◽

Islet 1

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The regeneration of the cephalic neural crest, a problem revisited: the regenerating cells originate from the contralateral or from the anterior and posterior neural fold

Development ◽

10.1242/dev.122.11.3393 ◽

1996 ◽

Vol 122 (11) ◽

pp. 3393-3407 ◽

Cited By ~ 31

Author(s):

G. Couly ◽

A. Grapin-Botton ◽

P. Coltey ◽

N.M. Le Douarin

Keyword(s):

Neural Crest ◽

Neural Tube ◽

Hox Genes ◽

Experimental Situation ◽

Neural Crest Cells ◽

Fate Map ◽

Somite Stage ◽

Dorsal Neural Tube ◽

Ventral Neural Tube ◽

Branchial Arches

The mesencephalic and rhombencephalic levels of origin of the hypobranchial skeleton (lower jaw and hyoid bone) within the neural fold have been determined at the 5-somite stage with a resolution corresponding to each single rhombomere, by means of the quail-chick chimera technique. Expression of certain Hox genes (Hoxa-2, Hoxa-3 and Hoxb-4) was recorded in the branchial arches of chick and quail embryos at embryonic days 3 (E3) and E4. This was a prerequisite for studying the regeneration capacities of the neural crest, after the dorsal neural tube was resected at the mesencephalic and rhombencephalic level. We found first that excisions at the 5-somite stage extending from the midmesencephalon down to r8 are followed by the regeneration of neural crest cells able to compensate for the deficiencies so produced. This confirmed the results of previous authors who made similar excisions at comparable (or older) developmental stages. When a bilateral excision was followed by the unilateral homotopic graft of the dorsal neural tube from a quail embryo, thus mimicking the situation created by a unilateral excision, we found that the migration of the grafted unilateral neural crest (quail-labelled) is bilateral and compensates massively for the missing crest derivatives. The capacity of the intermediate and ventral neural tube to yield neural crest cells was tested by removing the chick rhombencephalic neural tube and replacing it either uni- or bilaterally with a ventral tube coming from a stage-matched quail. No neural crest cells exited from the ventral neural tube but no deficiency in neural crest derivatives was recorded. Crest cells were found to regenerate from the ends of the operated region. This was demonstrated by grafting fragments of quail neural fold at the extremities of the excised territory. Quail neural crest cells were seen migrating longitudinally from both the rostral and caudal ends of the operated region and filling the branchial arches located inbetween. Comparison of the behaviour of neural crest cells in this experimental situation with that showed by their normal fate map revealed that crest cells increase their proliferation rate and change their migratory behaviour without modifying their Hox code.

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