Crosstalk of EGFR signalling with Notch and Hippo pathways to regulate cell specification, migration and proliferation in cockroach panoistic ovaries.

BACKGROUND INFORMATION Epidermal growth factor receptor (EGFR) signalling is crucial for the regulation of multiple developmental processes. Its function in relation to insect oogenesis has been thoroughly studied in the fly Drosophila melanogaster, which possesses ovaries of the highly modified meroistic type. Conversely, studies in other insect species with different ovary types are scarce. We have studied EGFR functions in the oogenesis of the cockroach Blattella germanica, a phylogenetically basal insect with panoistic ovaries. RESULTS In this cockroach, depletion of EGFR expression aborts oocyte maturation and prevents oviposition, as affects the distribution of F-actins in the follicular cells of the basal ovarian follicle, which triggers premature apoptosis. In the younger ovarian follicles within the ovariole, depletion of EGFR expression reduces the number of follicular cells, possibly because the Hippo pathway is altered; moreover, the concomitant reduction of Notch expression results in the absence of stalk. Finally, depletion of EGFR determines an increase in the number of germinal cells. CONCLUSIONS In the panoistic ovary of B. germanica, EGFR plays a role in the control of cell proliferation through interaction with Hippo and Notch pathways.