A PUTATIVE CELL SIGNAL ENCODED BY THE FOLDED GASTRULATION GENE COORDINATES CELL-SHAPE CHANGES DURING DROSOPHILA GASTRULATION

The folded gastrulation (fog) gene is required during Drosophila gastr ulation for two morphogenetic movements, formation of the ventral furr ow and invagination of the posterior midgut primordium. fog coordinate s cell shape changes during these invaginations by inducing apical con striction of cells in spatially and temporally defined manners. fog is expressed in the invagination primordia in a pattern that precisely p recedes the pattern of constrictions. Overexpression of fog in the dor soanterior region of the embryo induces ectopic constrictions, indicat ing localization of fog transcripts may define domains of cell shape c hanges. fog encodes a novel protein with a putative signal sequence bu t no potential transmembrane domains. We suggest fog functions as a se creted signal that activates the G protein alpha subunit encoded by co ncertina in neighboring cells. Our analyses indicate that cell-cell co mmunication ensures the rapid, orderly progression of constriction ini tiations from the middle of invagination primordia out toward the marg ins.