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O. Goureau, V. Brajeul, S. Thomasseau, J.-A. Sahel, X. Guillonneau; Misexpression of Ptf1a Induced Profound Modifications of Retinal Structure and Cell Differentiation in Chick Embryonic Eye. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5707.
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© ARVO (1962-2015); The Authors (2016-present)
During development, retinal progenitor cells (RPC) give birth to the different cell subtypes of the adult neural retina. To understand the molecular mechanisms involved in retinal cell fate, a differential screen was used to isolate genes specifically expressed in embryonic neural retina. We have focused our study on PTF1a, a gene recently shown to be involved in determining horizontal and amacrine cell fates during mouse retinal development.
RPC specific genes were isolated by a differential screen combining suppression subtractive hybridization and DNAchip hybridization. PTF1a expression was analyzed by quantitative real-time PCR (qPCR). Its function was investigated by injection of a RCAS-PTF1a virus in chick optic vesicle at embryonic day 2 (E2) in order to misexpress PTF1a during retinal development. The fate of PTF1a-infected RPC was analyzed by immunohistochemistry using antibodies specific to each retinal cell type.
qPCR demonstrated that PTF1a is expressed transiently from E6 to E12. Misexpression of PTF1a by injection of RCAS-PTF1 virus resulted in moderate to severe eye size reduction at E16, while no modification of cell death or proliferation was observed during development of infected retina. PTF1a-expressed retina appeared greatly disorganized, with an absence of plexiform layers or mislocalized plexiform-like structures. In PTF1a infected retina, ganglion cells (GC) failed to differentiate from E6 to E16, whereas cone and rod photoreceptor (PR) cell numbers were found to be dramatically reduced at E12 and E16. PR cells were localized in the entire thickness of the retina. Similarly, rod bipolar and Muller cells localizations were also affected without any modification of their number at E16. In contrast, the staining of N-CAM (VC1 antibody) and syntaxin amacrine/horizontal markers, and AP2 alpha amacrine marker appeared to be greatly induced in RCAS-PTF1a E16 retina, and these positive cells spread throughout the entire thickness of the retina.
Our study demonstrates that in chick, misexpression of PTF1a alone during retinal development induced severe modifications of the retinal structure. Furthermore, PTF1a inhibited GC and PR differentiation while inducing amacrine/horizontal cell differentiation.
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