Expression of Sonic hedgehog and its putative role as a precursor cell mitogen in the developing mouse retina.

We show that Sonic hedgehog and patched are expressed in adjacent domains in the developing mouse retina. Treatment of cultures of perinatal mouse retinal cells with the amino-terminal fragment of Sonic hedgehog protein results in an increase in the proportion of cells that incorporate bromodeoxuridine, in total cell numbers, and in rod photoreceptors, amacrine cells and Muller glial cells, suggesting that Sonic hedgehog promotes the proliferation of retinal precursor cells. These findings suggest that hedgehog and patched are part of a conserved signalling pathway in retinal development in mammals and insects.