Abstract
Abstract: :
Purpose: Our previous studies have suggested that bone morphogenetic protein 7 (BMP7) stimulates outer segment formation in chick photoreceptor cells. We have now further characterized BMP7 effects by comparing outer segment initiation/elongation in rods and cones,, and investigating whether cell survival, proliferation, and the differentiation of other cell types were also affected. Methods:Low density cultures of cells dissociated from E6 or E8 chick retinae were treated daily with vehicle or BMP7 for 6 days, and analyzed by immunocytochemistry (ICC), in situ hybridization (ISH), quantitative image analysis, and RT–PCR. Results: Similar numbers of cells expressed photoreceptor markers in vehicle– and BMP7– treated cultures, but the frequency of outer segments was significantly increased in BMP7–treated cultures. The effects were photoreceptor subtype–specific, being detectable in photoreceptors immunoreacted with Rho4D2 (which recognizes rods and green cones), but not in cells stained with other cone markers. Rhodopsin was undetectable by ISH or RT–PCR, suggesting that the Rho4D2 (+), BMP7– responsive photoreceptors were green cones. Increases in outer segment initiation were not accompanied by changes in outer segment length, or by detectable changes in the expression of genes encoding visual pigments, visinin or peripherin. BMP7 did not have detectable effects on mitosis, survival, or the frequency of photoreceptors or amacrine cells, but caused significant increases in cells expressing ganglion cell markers. Conclusions: Our results indicate that BMP7 exerts a fairly specific effect on the initiation of outer segment formation in green cones, and can also regulate ganglion cell survival and/or differentiation.
Keywords: microscopy: light/fluorescence/immunohistochemistry • photoreceptors • ganglion cells