Lineage-based scaling of germline intercellular bridges during oogenesis

Abstract

The size of subcellular structures must be tightly controlled to maintain normal cell function; this is especially important when cells are part of developing tissues or organs. Despite its importance, few studies have determined how the size of organelles or other structures is maintained during tissue growth, when cells are growing, dividing, and rearranging. The developing egg chamber is a powerful model in which to study the relative growth rates of subcellular structures. The egg chamber contains a cluster of sixteen germ cells, which are connected through intercellular bridges called ring canals. Ring canals are formed following incomplete cytokinesis after each of four germ cell divisions. As the egg chamber grows, the nurse cells and the ring canals that connect them increase in size. Here, we demonstrate that ring canal size scaling is related to their lineage; the largest, first born ring canals grow 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 if the germ cells go through an additional mitotic division. Further, we propose that changes in ring canal scaling could provide a mechanism to alter egg size.