During development in most animals, tubes form as precursors to complex organs such as the neural tube, digestive system, and vasculature. To create a tube, cells within a sheet, or epithelium, must coordinate specific shape changes and movements. This coordination requires each cell to establish and maintain directional identity, thereby distinguishing the ‘top’ of the sheet from the ‘bottom’. While extensive research on a group of proteins, called ‘polarity proteins’, has elucidated how cells establish directional identity, little is known about how they maintain that orientation during the shape changes and rearrangements that occur during tube formation. To address this gap in our understanding, I am studying how these polarity proteins contribute to proper tube morphogenesis during the formation of specialized structures on Drosophila melanogaster eggshells called dorsal appendages (DAs). These appendages, which provide the developing embryo with oxygen, are formed from an epithelium that wraps into a tube, elongates, and then fills with eggshell protein. The epithelium sloughs off when the egg is laid, leaving the appendages as a visualization of the earlier tube formation. I used RNA interference (RNAi) to assess the role of 24 candidate proteins in DA formation. My initial results led me to hypothesize that one protein, Crumbs (crb), regulates the tube’s directional elongation. To explore this role, I am studying crb protein localization during tube elongation, assaying DA defects after knocking down expression using RNAi in subsets of cells, and analyzing the distribution of adhesion, motor, and other polarity proteins when crb is completely absent in null clones. These analyses will add to our understanding of the role of polarity proteins in the conserved development of epithelial sheets into tubes.