Affiliations: 1) Hilde-Mangold-Haus, University of Freiburg, Germany; 2) Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, Germany; 3) CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg; 4) BIOSS Centre for Biological Signalling Studies, University of Freiburg; 5) Department for Applied Mathematics, University of Freiburg, Germany
Keywords: r. cell-cell interactions; b. oogenesis
Germline-soma interactions are central to reproduction. In most vertebrate and invertebrate species, differentiating gametes are enveloped by a somatic epithelium, where the apical surface interacts with the germline cells. While signaling pathways acting on the two lineages have been described, little is known about how morphogenesis is coordinated between them. In the developing Drosophila egg chamber, the somatic follicle epithelium envelops germline-derived nurse cells and the growing oocyte to produce fertile eggs. We show that egg chamber morphogenesis can be divided into three major phases, that all require coordinated germline-soma morphogenesis. The expression of the transcriptional regulator Eya in follicle cells controls coordination between the germline and somatic follicle cells by differentially modulating affinity of the apical epithelial surface for nurse cells and oocytes. In all three phases, Eya expression patterns and levels are crucial to guarantee the right segregation of follicle cells over nurse cell and oocyte surfaces. Importantly, Eya-mediated affinity furthermore controls the spatial organization of nurse cells and the oocyte within the germline. Consequently, Eya is a master regulator of the soma-germline interface and through that controls all stages of egg chamber development.
Our work uncovers a new morphogenetic principle that enables the coordination of soma and germline and emphasizes the plasticity of epithelial behaviors during interactions with their adjoining tissues.