The function and integrity of photoreceptor cells are dependent upon the creation and maintenance of specialized apical structures–ciliary-based membrane discs/outer segments in vertebrates and rhabdomeres in insects. Our long-term goal is to understand how these two elementary photoreceptive organelles are structured, assembled, maintained, and evolved. Our work addresses two fundamental questions about all photoreceptor cells: 1. How do photoreceptor cells initiate and regulate the morphogenesis of the apical membrane? 2. Upon initiation of the process, what molecules are involved and how do they function to transform the apical membrane? Currently, we are focusing on two molecules and their role for mechanisms for creating, organizing, and maintaining of the extracellular matrix (ECM) that surrounds and shapes the photoreceptor cells. These molecules are essential for determining the structure of the photoreceptor cells and mutation of either will lead to retinal degeneration in humans. We expect our studies to provide significant insights into the regulatory mechanisms for the creation, assembly, and maintenance of a cellular microenvironment and its influence on cellular morphology in both normal and mutant tissue. Furthermore, our work will have direct therapeutic impact/value in the treatment of their respective human retinal disorders.