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TE Wattnem, AV Das, J James, X Zhao, I Ahmad; ATH3: A bHLH Protein Involved in the Specification of Bipolar Cells in the Mammalian Retina . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2697.
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Purpose: We have previously shown that bHLH protein, Ath3 may play an important role in the sublineage specification during the late retinal neurogenesis (Ahmad & Dooley, 1999, Soc. Neuroscience Abst, 523). Here we demonstrate that Ath3 participates in the specification of bipolar cells in the mammalian retina. Methods: Full length Ath3 cDNA was cloned from E18 rat retina by RT-PCR. Spatial distribution of Ath3 transcriptions in the developing retina was studied by non-radioactive in situ hybridization. Antisense oligonucleotide and CNTF treatments of PN2/PN3 retinal explants were used to achieve inhibition and stimulation of Ath3 expression, respectively. The effect of modulation of Ath3 expression levels on retinal differentiation was studied by immunocytochemical analysis of cell-specific markers. Results: Ath3 expression was restricted to late neurogenesis (E18 onward). Ath3 transcripts were detected in the outer neuroblastic layer of the developing retina. As the development progressed Ath3 expression was restricted to the inner nuclear layer where it was co-localized in cells with bipolar cell-specific markers, PKC and mGluR6. Antisense oligoneucleotide treatment caused a decrease in the proportion of PKC positive cells in the explant culture. Exposure of the explant culture to CNTF caused a dose-dependant increase in Ath3 transcript levels followed by an increase in the proportion of PKC positive cells. In both treatments, the proportions of cells expressing rhodopsin remained relatively unchanged. Conclusion: The temporal and spatial pattern of Ath3 expression and the effect of the modulation of its levels on retinal differentiation suggest that it is one of the key regulators of bipolar cell specification. Supported by NEI
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