The Drosophila BMPRII, Wishful thinking, is required for eggshell patterning. Rob Marmion¹, Milica Jevtic², George Pyrowolakis², Nir Yakoby¹. 1) Department of Biology and Center for Computational and Integrative Biology, Rutgers University, Camden, NJ; 2) Institute for Biology I, Albert-Ludwigs-University of Freiburg, Freiburg, Germany.

   The Drosophila eggshell is an established model to study cell signaling, tissue patterning, and morphogenesis. The bone morphogenetic protein (BMP) signaling pathway is a crucial regulator of tissue growth during multiple stages of Drosophila development. During oogenesis, the role of the type I BMP receptor, thickveins (tkv), on spatial distribution of signaling and eggshell patterning, has been established. However, BMP signaling requires a heterocomplex of type I and type II receptors. We found the type II receptor, wishful thinking (wit), to be dynamically and non-uniformly expressed in the follicle cells, which are a mono-layer of epithelial cells engulfing the developing oocyte. We found wit to be transcriptionally regulated by BMP signaling and necessary for BMP signaling in the follicle cells. Of importance, we demonstrate that WIT is essential for proper eggshell morphology. Interestingly, we discovered two independent enhancers that combinatorially recapitulate the endogenous pattern of WIT. The first enhancer is expressed uniformly throughout the follicle cells, and the second is restricted to the anterior domain. The dynamics of the two enhancers suggest that they are regulated by the epidermal growth factor receptor and BMP signaling, respectively. Since this locus contains no traditional P-MAD/MED binding site, and the genetic evidence supports that the second enhancer is regulated by BMP signaling, we are in the process of discovering this novel regulatory sequence.