Faculty Opinions recommendation of Distinct Sonic Hedgehog signaling dynamics specify floor plate and ventral neuronal progenitors in the vertebrate neural tube.

Author(s):  
Jean-François Brunet
2010 ◽  
Vol 24 (11) ◽  
pp. 1186-1200 ◽  
Author(s):  
V. Ribes ◽  
N. Balaskas ◽  
N. Sasai ◽  
C. Cruz ◽  
E. Dessaud ◽  
...  

Development ◽  
1998 ◽  
Vol 125 (14) ◽  
pp. 2533-2543 ◽  
Author(s):  
Q. Ding ◽  
J. Motoyama ◽  
S. Gasca ◽  
R. Mo ◽  
H. Sasaki ◽  
...  

Floor plate cells at the midline of the neural tube are specified by high-level activity of Sonic hedgehog (Shh) secreted by notochord, whereas motor neurons are thought to be specified by a lower level activity of Shh secreted in turn by floor plate cells. In Drosophila, the Gli zinc finger protein Cubitus interruptus functions as a transcription factor activating Hedgehog-responsive genes. We report that the expression of known Shh-responsive genes such as Ptc and Gli1 is downregulated in mutant mice lacking Gli2 function. Gli2 mutants fail to develop a floor plate yet still develop motor neurons, which occupy the ventral midline of the neural tube. Our results imply that Gli2 is required to mediate high level but not low level Shh activity and show that the development of motor neurons can occur in the absence of floor plate induction.


Development ◽  
2000 ◽  
Vol 127 (15) ◽  
pp. 3283-3293 ◽  
Author(s):  
L. Gunhaga ◽  
T.M. Jessell ◽  
T. Edlund

A secreted signaling factor, Sonic hedgehog (Shh), has a crucial role in the generation of ventral cell types along the entire rostrocaudal axis of the neural tube. At caudal levels of the neuraxis, Shh is secreted by the notochord and floor plate during the period that ventral cell fates are specified. At anterior prosencephalic levels that give rise to the telencephalon, however, neither the prechordal mesoderm nor the ventral neural tube expresses Shh at the time that the overt ventral character of the telencephalon becomes evident. Thus, the precise role and timing of Shh signaling relevant to the specification of ventral telencephalic identity remains unclear. By analysing neural cell differentiation in chick neural plate explants we provide evidence that neural cells acquire molecular properties characteristic of the ventral telencephalon in response to Shh signals derived from the anterior primitive streak/Hensen's node region at gastrula stages. Exposure of prospective anterior prosencephalic cells to Shh at this early stage is sufficient to initiate a temporal program of differentiation that parallels that of neurons generated normally in the medial ganglionic eminence subdivision of the ventral telencephalon.


Development ◽  
2002 ◽  
Vol 129 (10) ◽  
pp. 2507-2517 ◽  
Author(s):  
Patricia Ybot-Gonzalez ◽  
Patricia Cogram ◽  
Dianne Gerrelli ◽  
Andrew J. Copp

Neural tube closure is a fundamental embryonic event whose molecular regulation is poorly understood. As mouse neurulation progresses along the spinal axis, there is a shift from midline neural plate bending to dorsolateral bending. Here, we show that midline bending is not essential for spinal closure since, in its absence, the neural tube can close by a ‘default’ mechanism involving dorsolateral bending, even at upper spinal levels. Midline and dorsolateral bending are regulated by mutually antagonistic signals from the notochord and surface ectoderm. Notochordal signaling induces midline bending and simultaneously inhibits dorsolateral bending. Sonic hedgehog is both necessary and sufficient to inhibit dorsolateral bending, but is neither necessary nor sufficient to induce midline bending, which seems likely to be regulated by another notochordal factor. Attachment of surface ectoderm cells to the neural plate is required for dorsolateral bending, which ensures neural tube closure in the absence of sonic hedgehog signaling.


Cell ◽  
2012 ◽  
Vol 148 (1-2) ◽  
pp. 273-284 ◽  
Author(s):  
Nikolaos Balaskas ◽  
Ana Ribeiro ◽  
Jasmina Panovska ◽  
Eric Dessaud ◽  
Noriaki Sasai ◽  
...  

Development ◽  
2001 ◽  
Vol 128 (18) ◽  
pp. 3497-3509 ◽  
Author(s):  
Zoltán M. Varga ◽  
Angel Amores ◽  
Katharine E. Lewis ◽  
Yi-Lin Yan ◽  
John H. Postlethwait ◽  
...  

Sonic hedgehog (Shh) signaling patterns many vertebrate tissues. shh mutations dramatically affect mouse ventral forebrain and floor plate but produce minor defects in zebrafish. Zebrafish have two mammalian Shh orthologs, sonic hedgehog and tiggy-winkle hedgehog, and another gene, echidna hedgehog, that could have overlapping functions. To examine the role of Hedgehog signaling in zebrafish, we have characterized slow muscle omitted (smu) mutants. We show that smu encodes a zebrafish ortholog of Smoothened that transduces Hedgehog signals. Zebrafish smoothened is expressed maternally and zygotically and supports specification of motoneurons, pituitary cells and ventral forebrain. We propose that smoothened is required for induction of lateral floor plate and a subpopulation of hypothalamic cells and for maintenance of medial floor plate and hypothalamic cells.


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