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Kristis Vevis, Michael Powner, Jenny Mckenzie, Meidong Zhu, Mark Gillies, Marcus Fruttiger; Gene expression profiling of the human macula. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1591.
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The human macula, which is located at the centre of the retina and has a diameter of approximately 3mm, is responsible for the central vision and any damage in that area is immediately obvious. Macular telangiectasia type 2 (MacTel) is an eye disease affecting specifically an area of 2mm by 3mm within the macula which is consistent from patient to patient and throughout the disease. This suggests some specific molecular and/or cellular properties exist in that area making susceptible to the disease. Therefore we aimed to identify differentially expressed genes in MacTel area, which might reveal mechanisms of the disease and unique properties of the macula in general.
Human retinas were isolated from fresh healthy human eyes (enucleated 3-7 hours after death) and stored in RNAlater. From the tissue five different areas were dissected; nasal to the optic nerve (1), in the macula (2), temporal to macula (3), inferior to the macula (4) and superior to macula (5, Figure 1). RNA isolation was followed using Trizol and cDNA was then used for qPCR analysis and differential display, aiming to identify differentially expressed genes in the macula and the other four areas.
Initially, primers for genes with known distributions were used in qPCR experiments to test the suitability of cDNA extracted from post-mortem tissue for gene expression analysis. As expected mlOpsin (cones) was highest in the MacTel area, while rhodopsin (rods) and synuclein gamma (ganglion cells) were reduced. We then tested some candidate genes implicated in biochemical pathways taking place in the retina such as visual cycle and retinoic acid metabolism. ALDH1A1, ALDH1A3, RDH5 and RDH10 were found to be reduced within the MacTel area while PPARG was increased. From differential display, after testing ‘’macula’’ compared to ‘’temporal to macula’’ areas, ADARB1 was found to be reduced in the macula.
Human retina up to 7 hours post mortem can be used for gene expression analysis experiments. Using qPCR and differential display techniques, genes differentially expressed between the macula and the peripheral retina were found. Confirmation of the differentially expressed genes needs to be done by immunohistochemistry.
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