Cell type-specific, BMP-dependent regulation of growth and migration by the ecdysone receptor in secondary cells of the male accessory gland.

Cell type-specific, BMP-dependent regulation of growth and migration by the ecdysone receptor in secondary cells of the male accessory gland. Aaron Leiblich^1,2, Michael Williams¹, Luke Marsden², Carina Gandy¹, Laura Corrigan¹, Shih-Jung Fan¹, Freddie Hamdy², Clive Wilson¹. 1) Deparment of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom; 2) Nuffield Department of Surgical Sciences, University of Oxford, Oxford, United Kingdom.

The steroid hormone ecdysone plays several critical roles during development but its functions in adults are less well characterised. We previously showed that secondary cells, a subclass of secretory cells in the male accessory gland, grow selectively as males age. A subset of these cells delaminates apically in multiply-mated males and can be transferred to females upon mating. These processes are normally promoted by BMP signalling. Recent work in our lab has shown that secondary cells also secrete exosomes that can fuse to sperm in females, indicating a surprising parallel with the mammalian prostate, an organ whose growth and secretion is critically regulated by steroid hormone signalling through the androgen receptor (AR) in normal and tumorigenic cells. We now demonstrate that the ecdysone receptor isoform, EcR-B1, which shares structural similarities with the AR, is specifically expressed in secondary cells, where it promotes cell growth and suppresses BMP-dependent delamination. Remarkably, EcR activity is controlled in a novel cell-type-specific manner by BMP signalling via an interaction involving the N-terminal AF1 domain of the EcR protein. BMP signalling regulates EcR protein levels and the nucleocytoplasmic distribution of the receptor. Our data reveal that, as in mammals, steroid receptor and BMP signalling plays a sex- and cell-type-specific role in controlling the growth and secretory activity of cells in Drosophila, providing a new in vivo model to investigate the importance of the interplay between these two pathways in the male reproductive system.