Retinal ganglion cells (RGCs) send visual information to the brain regarding the environmental lighting conditions that entrains central clocks to the ambient photoperiod. Our results are the first evidences demonstrating that RGCs are autonomous circadian oscillators displaying daily changes in the biosynthesis of: a) phospholipids (Guido et al., 2001) and b) the reliable circadian marker melatonin that exhibits a diurnal peak (Garbarino et al., 2003). These and other studies reporting the presence of novel photopigments postulate RGCs as essential circadian system components. Cultured fibroblasts also display a remarkable circadian oscillation in gene expression (Balsalobre et al., 1998) and in the biosynthesis of their phospholipids (Marquez et al., 2003). Further investigations will allow understanding how these cells function, the physiological activities that control and the clock mechanisms operating on them. The goals of this project are: a) to fully characterize RGCs as autonomous oscillators and potential circadian photoreceptors in the wild type and GUCY1* chicks carrying a retinal degeneration that causes blindness at hatch (Cheng et al., 1980); b) to extend the metabolic studies to cultures of RGCs, wild type and mutant CLOCK fibroblasts isolated from central influences and c) to elucidate the molecular mechanisms involved in such metabolic oscillations