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G. Dvoriantchikova, D. V. Ivanov, L. Nathanson, E. Hernandez, V. I. Shestopalov; Molecular Profiling of Midget and Parasol Retinal Ganglion Cells. Invest. Ophthalmol. Vis. Sci. 2007;48(13):245.
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© ARVO (1962-2015); The Authors (2016-present)
Different sub-types of mammalian retinal ganglion cells (RGC) possess distinct functions in processing visual information. Most commonly, RGC are divided into midget cells, which have smaller soma size, and the larger sized parasol cells. Parasol RGCs exhibit differential resistance to degeneration in a number of pathologies including glaucoma. In this work, we compared gene expression profiles of rat parasol and midget RGCs to identify molecular determinants underlying differences in function and tolerance to stress.
We used fluorescent-activated cell sorting (FACS) to collect RGCs retrogradely labeled with 4DI-10ASP and to sort them into the two groups based on the size: large (15-30 µm, parasol) and small (6-12 µm, midget). Differences in gene expression between the parasol and midget RGCs were characterized using microarray profiling of mRNA from the isolated sub-types. We utilized two-color Agilent Genomic Oligo microarrays in a dye swap design experiment to eliminate dye bias effects. Differential expression was validated for a group of randomly selected genes using quantitative RT-PCR.
To extract statistically significant differences, ratiometric data were analyzed using the Significance Analysis of Microarrays with high statistical stringency (FDR<1%), we identified 145 genes that were preferentially expressed in the parasol RGCs and 312 genes that were preferentially expressed in the midget ones. We found 30 genes that showed more then 2-fold difference in either of the two types of neurons. Many differentially expressed genes are implicated in synaptic transmission, neurotransmitter secretion, axon guidance and ion transport. Genes representing the GO category "chemotaxis" were relatively upregulated in the parasol cells, while genes from GO category of "sodium ion transport" were more active in the midget ones. Using in silico functional reconstruction with the MetaCore software, we demonstrated that a network for IL1b-mediated chemokine signaling was relatively activated in the large rather then small RGCs.
In this work, we demonstrated the feasibility of genome-wide characterization of two major sub-types of mammalian RGCs. The group of genes differentially expressed in parasol RGCs were characterized. Future experiments will test their relevance to the differential tolerance to stress.
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