| The fusome plays an essential role in prefollicular germ cell development within insects such as Drosophila melanogaster. Understanding the protein composition of the fusome is crucial for gaining insight into its function. By screening a library of Drosophila protein trap strains, we have identified 14 novel fusome-enriched proteins, including many associated with the poorly understood tubulovesicular component of the fusome. Our study of the expression patterns of these lines reveal that the fusome's composition changes during development, that it contains recycling endosomal and lysosomal compartments, and that its composition differs markedly between male and female germ cells. Genetic disruption of the novel fusome components tropomodulin, ferritin-1 heavy chain, and scribble, does not alter fusome structure or female fertility. Thus, a significant number of cellular components enriched within the fusome are not required for normal fusome structure or fertility. In contrast, the fusome-localized recycling endosome marker Rab11 is required for cyst formation, spectrosome vesicle organization, and germline stem cell maintenance, suggesting novel roles for the fusome in intracellular membrane dynamics and cell signaling. |
