Coaxing plastic, non-neuronal cells to transdifferentiate into a particular type of neurons might have clinical applications. Previously we reported that neuroD induces transdifferentiation of retinal pigment epithelium (RPE) cells derived from day-6 chick embryos into cells that resemble young photoreceptor cells. These cells also express visinin, a gene expressed early during cone photoreceptor differentiation. Further characterization showed that the transdifferentiated cells express a number of photoreceptor genes, including interphotoreceptor retinoid binding protein, the α-subunit of phosphodiesterase, and opsin genes encoding rhodopsin, the red, the green, and the blue visual pigments. Our data demonstrate that neuroD can reprogram RPE to become photoreceptor cells with substantial differentiation, and suggest the possibility of generating photoreceptor cells from RPE using neuroD as a molecular trigger. (C) 2000 Elsevier Science Ireland Ltd.