Lineage-based scaling of germline intercellular bridges during oogenesis

The size of subcellular structures must be tightly controlled to maintain normal cell function. Despite its importance, few studies have determined how the size of organelles or other structures is maintained during development, when cells are growing, dividing and rearranging. The developing Drosophila egg chamber is a powerful model in which to study the relative growth rates of subcellular structures. The egg chamber contains a cluster of 16 germline cells, which are connected through intercellular bridges called ring canals. As the egg chamber grows, the germline cells and the ring canals that connect them increase in size. Here, we demonstrate that ring canal size scaling is related to lineage; the largest, 'first-born' ring canals increase in size at a relatively slower rate than ring canals derived from subsequent mitotic divisions. This lineage-based scaling relationship is maintained even if directed transport is reduced, ring canal size is altered, or in egg chambers with twice as many germline cells. Analysis of lines that produce larger or smaller mature eggs reveals that different strategies could be used to alter final egg size.