Stem cell niche signals Wnt, Hedgehog, and Notch distinctively regulate Drosophila follicle precursor cell differentiation

Abstract

Adult stem cells commonly give rise to transit-amplifying progenitors, whose progeny differentiate into distinct cell types. Signals within the stem cell niche maintain the undifferentiated state. However it is unclear whether or how niche signals might also coordinate fate decisions within the progenitor pool. Here we use quantitative microscopy to elucidate distinct roles for Wnt, Hedgehog (Hh), and Notch signalling in progenitor development in the Drosophila ovary. Follicle stem cells (FSCs) self-renew and produce precursors whose progeny adopt distinct polar, stalk, and main body cell fates. We show that a steep gradient of Wnt signalling maintains a multipotent state in proximally located progenitor cells by inhibiting expression of the cell fate determinant Eyes Absent (Eya). A shallower gradient of Hh signalling controls the proliferation to differentiation transition. The combination of Notch and Wnt signalling specifies polar cells. These findings reveal a mechanism by which multiple niche signals coordinate cell fate diversification of progenitor cells.