Polarity protein distribution on the metaphase furrow regulates hexagon dominated plasma membrane organization in syncytial Drosophila embryos

Epithelial cells have a polarised distribution of protein complexes on the lateral membrane and are present as a polygonal array dominated by hexagons. Metazoan embryogenesis enables the study of temporal formation of the polygonal array and mechanisms that regulate its distribution. The plasma membrane of the syncytial Drosophila blastoderm embryo is organized as a polygonal array during cortical division cycles with an apical membrane and lateral furrow in between adjacent nuclei. We find that polygonal plasma membrane organization arises in syncytial division cycle 11 and hexagon dominance occurs with increase in furrow length in cycle 12. This is coincident with DE-cadherin and Bazooka enrichment at edges and the septin, Peanut enrichment at vertices of the base of the furrow. DE-cadherin depletion leads to loss of hexagon dominance. Bazooka and Peanut depletion leads to a delay in occurrence of hexagon dominance from nuclear cycle 12 to 13. Hexagon dominance in Bazooka and Peanut mutants occurs with furrow extension and correlates with increase in DE-cadherin in syncytial cycle 13. We conclude that a change in polarity complex distribution leads to loss of furrow stability thereby changing the polygonal organization of the blastoderm embryo.\n\nHighlight Summary for TOCMetazoan embryogenesis starts with the formation of polygonal epithelial-like cells. We show that hexagon dominance in polygonal epithelial-like plasma membrane organization occurs in nuclear cycle 12 in the syncytial blastoderm Drosophila embryo. DE-cadherin and Bazooka distribution along the lateral furrow regulates this hexagon dominance.