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E.F. Moreira, R. Adler; Regulation of Amacrine Cell Differentiation in the Chick Embryo by Follistatin, an Activin and BMP-7 Inhibitor . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1665.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The signals that regulate progenitor cell differentiation into various retinal cell types are not yet fully understood. We are investigating the involvement in these phenomena of the activins and bone morphogenetic proteins (BMPs), which are expressed in the retina in topographically specific, developmentally regulated patterns. The present study tests the hypothesis that the differentiation of amacrine neurons is regulated in vivo by the activins and/or one of the BMPs (BMP7). We have used a loss-of-function approach through the overexpression of their binding protein and inhibitor, follistatin. Methods: RCAS retroviruses, encoding either follistatin or the green fluorescent protein (GFP), were injected intravitreally on embryonic day 3 (ED3; HH stages 15-19). After further development, retinas were processed for immunocytochemistry either on cryosections (for qualitative observations), or after retinal dissociation and plating (for quantitative analysis). Results: Qualitative analysis at ED8 showed a decrease in the abundance of amacrine cells in follistatin-infected retinas in preparations immunoreacted with antibodies against the amacrine "markers" CRABP, calbindin D and syntaxin, as well as with the 3B5 antibody, that recognizes both amacrine and horizontal cells. These decreases were quantitatively confirmed in dissociated retinas; their magnitude appeared to correlate with the degree of infection of each retina, analyzed with virus-specific antibodies. No significant changes were observed in cells immunoreactive for photoreceptor or ganglion cell "markers". While the overall structure and organization of the retina was fairly well preserved until ED 8, extensive rosette formation was observed in nearly 50% of the follistatin-treated embryos at later stages (ED 11-15). Conclusions: These results indicate that the activins and/or BMP-7 play an important role in the differentiation of amacrine (and perhaps also horizontal) cells in ovo, in agreement with previous in vitro studies from this laboratory. The involvement of transcriptional regulators in these effects, and the mechanisms of rosette formation in follistatin-treated embryos, are currently under investigation.
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