[The Role of WNT Signaling During Ciliary-Dependent RPE Development]

The retinal pigment epithelium (RPE) is a highly polarized single layer of block-shaped epithelial cells that are densely packed with melanin. They lie between the light sensitive external segments of the photoreceptors and the choroid. They play an essential role in the development of photoreceptors and have important functions in nutrient supply and maintenance, in retinal metabolism and in shielding the blood supply of the choroid. The photoreceptors are subject to daily renewal, in which 10% of the external segments are phagocytosed by the retinal pigment epithelium. This requires close interactions between the retinal pigment epithelium and the retina. Thus, disturbance or delay of the maturation of the RPE can trigger pathogenic changes in the retina, leading to degeneration of the photoreceptors. The aging of the RPE can also impair underlying functions, which can lead to progressive loss of photoreceptors and visual acuity. Like many types of ocular cells, the RPE forms a primary cilium during its development, a protuberance of the cell membrane based on microtubuli. This is thought to be associated with some important cellular processes and various important signaling pathways. In particular, the WNT pathway (wingless-related integration site) is essential for the polarization and maturation of the RPE and therefore of decisive importance for the function of the epithelium.