BMP-induced reprogramming of the neural retina into retinal pigment epithelium requires Wnt signalling.

In vertebrates, the retinal pigment epithelium (RPE) and photoreceptors of the neural retina (NR) comprise a functional unit required for vision. During vertebrate eye development, a conversion of the RPE into NR can be induced by growth factors at optic cup stages, but the reverse process, the conversion of NR tissue into RPE, has not been reported. Here, we show that bone morphogenetic protein (BMP) signalling can reprogram the NR into RPE at optic cup stages in chick.

RPE specification in the chick is mediated by surface ectoderm-derived BMP and Wnt signalling.

The retinal pigment epithelium (RPE) is indispensable for vertebrate eye development and vision. In the classical model of optic vesicle patterning, the surface ectoderm produces fibroblast growth factors (FGFs) that specify the neural retina (NR) distally, whereas TGFβ family members released from the proximal mesenchyme are involved in RPE specification. However, we previously proposed that bone morphogenetic proteins (BMPs) released from the surface ectoderm are essential for RPE specification in chick.