Neuroprotection of photoreceptor cells in rod-cone dystrophies: from cell therapy to cell signalling. Neuroprotection of photoreceptor cells in rod-cone degenerations is primarily targeted at preventing the loss of function. Strategies for protecting rod cells should therefore aim not only at structural preservation but also must be assessed using functional parameters (e.g., electroretinogram). Given the number of mutations leading to an impaired visual response of rods, the preservation of cones is a realistic approach since (1) numerous mutations do not affect proteins expressed by cones; (2) the secondary degeneration of cones is the main event leading to profound visual impairment; (3) even a small proportion of functional cones is sufficient for major visual functions. Our group has (1) established and confirmed the existence of non cell autonomous mechanisms promoting cone cell viability; (2) shown that rod cell protection or replacement provides a mean to extend the survival of cones; (3) demonstrated that rod-cone trophic interactions are mediated by diffusible proteins; (4) identified by expression cloning a protein mediating such interactions: RdCVF (Rod-derived Cone Viability Factor). These studies provide clues for broad neuroprotective therapies of rod-cone dystrophies.