The journal Development has published the latest work of the Development and Growth Control Laboratory, led by ICREA Professor Marco Milán at IRB Barcelona. In collaboration with Stephen Cohen at the National University of Singapore, the study reveals how the repression of a single microRNA (miRNA), bentam, by the Notch pathway contributes to boundary formation in the Drosophila wing primordial. Two working hypotheses, one proposing differences in the affinity by the different adhesion molecules expressed in each cell population, the other claiming that in border cells the differences in cell-bond tension are mediated by the cytoskeleton, have been proposed to explain boundary formation and maintenance.

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Physical boundaries prevent cell movements from adjacent populations, thereby restricting them to their cell compartments. In multi-cellular organisms, from the central nervous system in vertebrates to the Drosophila wing, cell compartmentalization is essential for development. But how can adjacent populations of thousands of cells remain stable at both sides of these borders?.

Two working hypotheses, one proposing differences in the affinity by the different adhesion molecules expressed in each cell population, the other claiming that in border cells the differences in cell-bond tension are mediated by the cytoskeleton, have been proposed to explain boundary formation and maintenance.

The Development and Growth Control Laboratory’s study has now reconciled these two working hypotheses by finding the missing link between the Notch pathway and the formation of the affinity DV boundary. The repression of bentam miRNA by Notch in the cell populations at both sides of the border allows the actin regulator Enabled to be expressed normally. In these cells, Enabled promotes the elongation of the cytoskeleton along the cell membrane facing the border, thus creating tension that contributes to the DV boundary formation. The supra-molecular function of the cytoskeleton is generated by cells at the border producing physical tension through polarization of the actin cables. The regulation of this function, by the Notch signalling pathway through bentam is the new molecular actor in Drosophila wing compartmentalization.

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