Abstract
Abstract: :
Purpose: To examine whether cultured RPE cells can be coaxed to differentiate towards retinal ganglion cells using chick ath5 (cath5), either alone or in combination with bFGF. Vertebrate ath5 is a homologue of the Drosophila proneural gene «atonal» and plays an important role in the production of retinal ganglion cells. Previously, we reported that bFGF induced RPE cells to express RA4 immunoreactivity. But bFGF alone did not induce the expression of additional markers or the development of a neural morphology typical of retinal ganglion cells. Methods: RPE was isolated from day 6 chick embryos, and cultured as dissociated cells in the presence of 10% fetal calf serum. RPE cell culture was infected with retrovirus RCAS-cath5 to achieve ectopic expression of cath5. RPE transdifferentiation was assayed using chick retinal ganglion cell markers, including monoclonal antibodies RA4, 4H6, 3A10, and MAP2. Results: Rather surprisingly, ectopic expression of cath5 in cultured RPE cells did not induce detectable neural transdifferentiation. There was no increase in the number of positive cells identified with the various antibodies that label retinal ganglion cells, compared with the control RPE cell culture. However, in the presence of bFGF, ectopic expression of cath5 increased the number RA4+ cells several fold over that of bFGF alone. The number of cells positive for 4H6, 3A10, or MAP2 increased 50 fold or more. Morphologically, the positive cells appeared more neuron-like in the presence of both bFGF and cath5 than bFGF alone. Conclusion: Our studies suggest that cath5 alone is not sufficient to induce RPE transdifferentiation into retinal ganglion cells under the experimental conditions, but cath5 may enhance molecular and cellular differentiation along a bFGF-induced retinal ganglion cell pathway.
Keywords: 553 regeneration • 564 retinal development • 557 retina: proximal(bipolar, amacrine, and ganglion cells)