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. Author manuscript; available in PMC: 2021 Feb 1.
Published in final edited form as: Curr Opin Insect Sci. 2020 Jan 30;37:39–48. doi: 10.1016/j.cois.2019.11.005

Figure 1: The Drosophila Germarium.

Figure 1:

Diagram of the early stages of Drosophila oogenesis and overview of sources of selected signaling ligands implicated in follicle cell development. The Drosophila germarium is divided in four subregions (1, 2a, 2b and 3). The first budded cyst is referred to as stage 2. Anterior-most terminal filament (TF) and cap cells (CC) build the niche for germline stem cells (GSC). Together with the inner germarial sheath (IGS) cells TF and CC provide Hedgehog (Hh) ligand to follicle stem cells (FSC), which are located at the 2a/2b border. IGS cells further provide Wingless (Wg) to FSCs. In response, FSCs and pFCs produce Spitz (Spi). A subset of prefollicle cells (pFC) receives Delta (Dl) from germline cells (GC) and assumes polar cell fate. Polar fated cells produce the JAK-STAT ligand Unpaired (Upd), which specifies stalk cells. To date, no signaling pathways have been identified to induce the earliest steps towards main body (MB) cell fate.