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A lateral belt of cortical LGN and NuMA guides mitotic spindle movements and planar division in neuroepithelial cells

Elise Peyre, Florence Jaouen, Mehdi Saadaoui, Laurence Haren, Andreas Merdes, Pascale Durbec, and Xavier Morin

The cell in the middle exhibits the normal biphasic pattern of spindle rotation (planar alignment/planar maintenance) regulated by the lateral belt of the LGN complex (green). In the absence of this complex (left cell) or when it is not restricted in a belt (right cell), spindle movements are respectively lost or randomized.

To maintain tissue architecture, epithelial cells divide in a planar fashion, perpendicular to their main polarity axis. As the centrosome resumes an apical localisation in interphase, planar spindle orientation is reset at each cell cycle. We used 3-dimensional live imaging of GFP-labelled centrosomes to investigate the dynamics of spindle orientation in chick neuroepithelial cells. The mitotic spindle displays stereotypic movements during metaphase, with an active phase of planar orientation and a subsequent phase of planar maintenance before anaphase. We describe the localisation of the NuMA and LGN proteins in a belt at the lateral cell cortex during spindle orientation. Finally, we show that the complex formed of LGN, NuMA, and of cortically located Gαi subunits is necessary for spindle movements and regulates the dynamics of spindle orientation. The restricted localization of LGN and NuMA in the lateral belt is instructive for the planar alignment of the mitotic spindle, and required for its planar maintenance.

J Cell Biol. 2011 Apr 4 ;193(1):141-54.