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Gillian C. Shaw, Cynthia Berlinicke, Donald J. Zack; Synaptotagmin 11: A Model for the Study of Retinal Ganglion Cell (RGC) Transcriptional Regulation. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1533.
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© ARVO (1962-2015); The Authors (2016-present)
Cell- specific regulation of gene expression is key to cell function. Compared to other retinal cell types, relatively little is known about transcriptional regulation in RGCs. As a model for studying RGC transcriptional regulation, we have been analyzing the cis-elements and trans-factors that regulate the expression of the RGC-enriched gene synaptotagmin 11 (Syt11).
5’-upstream fragments from seven RGC enriched genes (Syt11, Slc17a6, Sema6b, Sncg, Prph1, Nefm and Nrn1), ranging in size from 450 to 720 base pairs (bp), were inserted into reporter plasmids and transfected into primary rat RGCs and dissociated whole retina. Syt11 was chosen for more detailed studies as it showed the highest preferential expression in RGCs. Todetermine regions of the Syt11 promoter important for RGC expression, a series of sequential deletions of the Syt11 promoter in the reporter constructs was created. Bioinformatic analysis of the active promoter regions was used to identify putative transcription factors (TF) binding sites. This set of TFs was cross-referenced to microarray data of isolated rodent RGCs to identify onesthat are expressed in RGCs. The predicted binding sites of two transcription factors (Deaf1 and Sp1) were mutated in the reporter constructs and reporter activity compared to wild-type constructs was measured.
Promoter reporters of seven RGC enriched genes show differential activity in whole retina compared to RGCs. Synaptotagmin 11 is expressed in RGCs at a level that is higher than both brain and whole retina. Promoter analysis showed that the regions between -205 to -114 and -114 to -54 bp contain sequences that are important for promoter activity in primary RGCs. The active regions contain two sites with overlapping predicted binding sites for the transcription factors Deaf1 and Sp1, both of which are expressed in RGCs.
As a step in understanding transcriptional regulation in RGCs, a system to analyze promoter reporters in cultured primary rat retinal ganglion cells was established. Using this system we determined regions of Syt11 that are important for its RGC expression. Bioinformatic analysis of these regions identified binding sites for Deaf1 and Sp1, and additional studies to analyze the activity of these TFs on the Syt11 promoter are underway.
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