How Do A-P Differences Drive D-V Cell Movement?
Eve and Runt are clearly required for cell rearrangement during germband extension, but these results present a paradox: these genes are present in A-P stripes, but germband cells move dorsoventrally — perpendicular to this spatial information. One potential explanation is that Eve and Runt stripes may act to establish key differences between neighboring cells along the A-P axis. These differences would then set in motion a massive cell sorting event, where cells try to maximize contact with cells of the same type and minimize contact with cells perceived as “different.” Cells of a common stripe would coalesce into a group, forcing the germband to elongate. We are now using microarray analysis to identify the transcriptional targets of Eve and Runt that contribute directly to these differences between cells. Functional analysis of such target genes will provide information about how populations of cells work together to produce a global change in tissue structure.
