Jun.-Prof. Dr. Helen May-Simera
In recent years, primary cilia have emerged as unique and multifunctional organelles as well as having been implicated in a variety of cellular and developmental processes. Primary cilia are components of virtually all vertebrate cell types, which explains why primary cilia defects cause a spectrum of clinical phenotypes. Many human diseases have been associated with primary cilia dysfunction, collectively termed 'ciliopathies'. Bardet-Biedl syndrome (BBS) is one of the first human syndromes to be identified as being caused by primary cilia dysfunction. One of the hallmark symptoms of BBS and other ciliopathies is retinal degeneration. Till now, elucidation of disease mechanisms have focused on trafficking across the photoreceptor connecting cilium, which corresponds to the transition zone of a modified primary cilium; however, defects in other ciliated cell types in the eye may also be contributing to disease manifestation.
One of the first signaling pathways shown to be associated with the primary cilium is the wingless (Wnt) signaling pathway, which is known to regulate diverse processes during development, including cell fate, structural remodeling and cell polarity. Wnt signaling has been shown to be crucial for the development and function of the retinal pigment epithelium (RPE), a monolayer epithelium tightly associated with photoreceptors and critical for photoreceptor function and survival. Despite the well known close association of these two cell types, the potential contribution of RPE disruption to retinal degeneration has not, to date, been extensively considered. Concomitantly, studies into the ciliary regulation of Wnt signaling are predominantly restricted to in vitro based model systems with limited understanding in mammalian systems.