Dissection and Staining of Drosophila Pupal Ovaries

The Drosophila ovary is an excellent model system for studying stem cell niche development. Though methods for dissecting larval and adult ovaries have been published, pupal ovary dissections require different techniques that have not been published in detail. Here we outline a protocol for dissecting, staining, and mounting pupal ovaries.

Unlike adult Drosophila ovaries, pupal ovaries are relatively difficult to access and examine due to their small size, translucence, and encasing within a pupal case. The challenge of dissecting pupal ovaries also lies in their physical location within the pupa: the ovaries are surrounded by fat body cells inside the pupal abdomen, and these fat cells must be removed to allow for proper antibody staining. To overcome these challenges, this protocol utilizes customized Pasteur pipets to extract fat body cells from the pupal abdomen. Moreover, a chambered coverglass is used in place of a microcentrifuge tube during the staining process to improve visibility of the pupae. However, despite these and other advantages of the tools used in this protocol, successful execution of these techniques may still involve several days of practice due to the small size of pupal ovaries. The techniques outlined in this protocol could be applied to time course experiments in which ovaries are analyzed at various stages of pupal development.

Stem cell research using Drosophila ovaries has widely expanded since the first documentation of a stem cell niche^1,2,3,4. Following the development of lineage tracing genetic tools, Drosophila ovary dissections have been commonly used to study stem cell lineages and signaling pathways that regulate stem cell maintenance, proliferation, and fate in the stem cell niche. Knowledge of these signaling pathways may yield insights into potential causes of cancers that originate from aberrant stem cell activity^5<....

1. EggLaying

1. Combine approximately ten male and fifteen female adult Drosophila flies of the desired genotype in a vial of normal rich fly food supplemented with yeast. To avoid overcrowding the vial, allow mated females to lay eggs for no longer than 2–4 h¹⁴.
2. Transfer the adults from the vial into a new vial by tapping the vial opening against a different vial with fly food. Allow the eggs to develop into larvae at room temperature for 3–4 days.

Successful execution of this procedure should result in clear antibody staining that reveals the structure and cellular organization of a Drosophila pupal ovary. Immunohistochemistry outlined in this protocol can be used to identify cell types commonly stained in larval and adult ovaries. Cells of the pupal stalk derived from swarm cells¹⁸ (outlined by Fasciclin III in white) are shown in Figure 3. In addition to highlighting .......

The most critical and difficult step of this protocol involves the preparation of pupal ovaries prior to fixation. To ensure that the ovaries, small and buried by fat body cells inside the pupal abdomen, are stained sufficiently with antibodies, it is important to not only tear a large opening in the abdominal sack with forceps, but also extract the fat body cells that obstruct the ovaries from the antibodies. Successful execution of this step requires application of subtle pressure on the Pasteur pipet bulb while washin.......

This research was supported by the National Institutes of Health (RO1 GM079351 to D.K.). We thank Dorothea Godt for her helpful advice on pupal ovary dissections based on her original protocol. We also thank Amy Reilein for her assistance and comments on the manuscript.