03-P061 Comprehensive analysis of the interkinetic nuclear migration in developing mouse brain

The control of cell morphology is important for shaping animals during development. Here we address the role of the Wnt/ Wingless signal transduction pathway and two of its target genes, vestigial and shotgun (encoding E-cadherin), in controlling the columnar shape of Drosophila wing disc cells. We show that clones of cells mutant for arrow (encoding an essential component of the Wingless signal transduction pathway), vestigial, or shotgun undergo profound cell shape changes and are lost from the epithelium by basal extrusion. Compartment-wide expression of TCF, which inhibits Wingless target gene expression, or double-stranded RNA targeting vestigial or shotgun, leads to abnormally short cells throughout this region, indicating that these genes act cell autonomously to maintain normal columnar cell shape. Conversely, overexpression of Wingless or an activated form of Armadillo, Arm, results in precocious cell elongation. Co-expression of Vestigial partially suppresses the abnormal cell shape induced by TCF. We conclude that Wingless signal transduction plays a cell autonomous role in promoting and maintaining the columnar shape of wing disc cells. Our data furthermore suggest that Wingless controls cell shape in part through inducing vestigial expression.