MicroRNA-9 directs late organizer activity of the midbrain-hindbrain boundary

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The midbrain-hindbrain boundary (MHB) is a long-lasting organizing center in the vertebrate neural tube that is both necessary and sufficient for the ordered development of midbrain and anterior hindbrain (midbrain-hindbrain domain, MH). The MHB also coincides with a pool of progenitor cells that contributes neurons to the entire MH. Here we show that the organizing activity and progenitor state of the MHB are co-regulated by a single microRNA, miR-9, during late embryonic development in zebrafish. Endogenous miR-9 expression, initiated at late stages, selectively spares the MHB. Gain- and loss-of-function studies, in silico predictions and sensor assays in vivo demonstrate that miR-9 targets several components of the Fgf signaling pathway, thereby delimiting the organizing activity of the MHB. In addition, miR-9 promotes progression of neurogenesis in the MH, defining the MHB progenitor pool. Together, these findings highlight a previously unknown mechanism by which a single microRNA fine-tunes late MHB coherence via its co-regulation of patterning activities and neurogenesis.

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Figure 1: Gain of miR-9 function causes MHB loss.
Figure 2: Sensor assay to reveal direct interaction of miR-9 with predicted binding sites.
Figure 3: miR-9 overexpression downregulates Fgf signaling.
Figure 4: miR-9 overexpression causes premature neurogenesis across the MHB.
Figure 5: Endogenous miR-9 expression in the MH area avoids the MHB and postmitotic domains.
Figure 6: Morpholino knockdown of miR-9 affects Fgf signaling in a manner opposite to miR-9 gain of function.
Figure 7: Morpholino knockdown of miR-9 affects neurogenesis in a manner opposite to miR-9 gain of function.


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We are grateful to members of the L.B.-C. laboratory for discussions and to M. Götz, W. Norton and M. Wassef for their insightful ideas and critical reading of the manuscript. This work was funded by a junior group grant from the Volkswagen Association, the EU 6th framework integrated project ZF-Models (contract No. LSHC-CT-2003-503466), the Life Science Association (No. GSF 2005/01), a special research grant from the Institut du Cerveau et de la Moelle épinière, the Excellence Center for Protein Science, Munich, and the Helmholtz 'Impuls und Vernetzungsfond'.

Author information

C.L. and C.S. jointly conducted the experiments. A.W. and R.K. conducted parallel analyses in chicken to support the findings described here. A.F. provided technical assistance and L.B.-C. supervised the project. C.L. and L.B.-C. wrote the manuscript.

Correspondence to Christoph Leucht or Laure Bally-Cuif.

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Leucht, C., Stigloher, C., Wizenmann, A. et al. MicroRNA-9 directs late organizer activity of the midbrain-hindbrain boundary. Nat Neurosci 11, 641–648 (2008) doi:10.1038/nn.2115

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