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C. Bowes Rickman, J. Ebright, S. Rho; Macular Transcription Profiles and Single Cell RT-PCR Evaluation of Candidate Genes for Inherited Macular- and Cone-Rod Dystrophies . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2257.
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Purpose: To develop a high-throughput means to prioritize candidate genes within disease and susceptibility loci for macula- and cone-rod dystrophies based on macula-enriched transcription and expression in cone photoreceptor cells. Methods: Human cDNA microarrays representing over 9,000 transcripts were differentially screened with two distinct neural retina cDNA probes derived from 4mm trephine punches of pooled (28-66 year old) human neural macula and 4mm trephine punches of pooled mid-peripheral retina from the same donors. Elevated expression of candidate disease genes in the macula that map to macular- or cone-rod dystrophy loci was confirmed by real-time quantitative RT-PCR. Localization of their corresponding transcripts within cones was detected by RT-PCR amplification in isolated human cone photoreceptors. Results: Macula-enriched candidate genes for 25 macular- and cone-rod dystrophy loci and age-related macular degeneration susceptibility loci were identified by their microarray profiles. Greater transcript abundance in the macula versus the mid peripheral retina was validated by quantitative RT-PCR for many of these candidate genes. Expression of several of these candidate genes was localized to cone photoreceptors when their transcripts were co-amplified from single photoreceptor cell cDNAs with cone-specific transcripts for PDE6C or x-arrestin but not with rod-specific PDE6A. Conclusions: Photoreceptors are susceptible to a wide variety of inherited dysfunctions often resulting initially in rod photoreceptor loss followed by cone loss. Many of these retinal degenerations are caused by mutations in genes that are either specifically expressed or highly enriched in rod photoreceptors. So high is the correlation between cell specificity of expression and clinical phenotype in rod-based degenerations that knowledge of macula and cone expression profiles should be an equally powerful tool for identification of genes causing cone-based degenerations. These profiles should vastly reduce the number of candidate genes from within any mapped macular- or cone-rod dystrophy disease region that will have to be screened before identifying the disease gene.
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