Abstract
The mechanisms that coordinate the three-dimensional shape of the vertebrate brain during development are largely unknown. We have found that sonic hedgehog (Shh) is crucial in driving the rapid, extensive expansion of the early vesicles of the developing midbrain and forebrain. Transient displacement of the notochord from the midbrain floor plate resulted in abnormal folding and overall collapse of the vesicles, accompanied by reduced cell proliferation and increased cell death in the midbrain. Simultaneously, expression of Shh decreased locally in the notochord and floor plate, whereas overt patterning and differentiation proceeded normally. Normal midbrain expansion was restored by implantation of Shh-secreting cells in a dose-dependent manner; conversely, expansion was retarded following antagonism of the Shh signaling pathway by cyclopamine. Our results indicate that Shh signaling from the ventral midline is essential for regulating brain morphogenesis during early development.
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Acknowledgements
This work was supported by a Cambridge Australia Scholarship, the Cambridge Commonwealth Trust and a Peter Doherty Fellowship (J.B.), a Royal Society University Research Fellowship (D.T.), an International Research Scholars award from the Howard Hughes Medical Institute (R.K.), and by grants from the Medical Research Council and Wellcome Trust. We thank A. Fleming for comments on the manuscript.
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Britto, J., Tannahill, D. & Keynes, R. A critical role for sonic hedgehog signaling in the early expansion of the developing brain. Nat Neurosci 5, 103–110 (2002). https://doi.org/10.1038/nn797
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DOI: https://doi.org/10.1038/nn797
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