Unknown,Transcriptomics,Genomics,Proteomics

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[E-MEXP-3786] IGF-I-induced chronic gliosis and retinal stress lead to neurodegeneration in an animal model of retinopathy

ABSTRACT: Transcription profiling by array of mouse male retinas to investigate IGF-I-induced chronic gliosis and retinal stress IGF-I exert multiple effects in different retinal cell populations in both physiological and pathological conditions. Transgenic mice overexpressing IGF-I in the retina showed impaired electroretinographic responses at 6-7 months of age that worsen with age. This retinal neuronal dysfunction was correlated with the loss of rod photoreceptors, bipolar, ganglion and amacrines cells. Neuronal alterations were preceded by the overexpression of retinal stress markers, acute phase proteins and gliosis-related genes. IGF-I overexpression leads to chronic gliosis and microgliosis in TgIGF-I retinas, with mild oxidative stress, impaired recycling of glutamate and defective potassium buffering. These impaired supportive functions can contribute to neurodegeneration in TgIGF-I retinas, together with the increased production of pro-inflammatory cytokines, potential mediators of neuronal death. 3 transgenic and 3 wild type biological replicates examined.

ORGANISM(S): Mus musculus

SUBMITTER: Miquel Garcia

PROVIDER: E-GEOD-46246 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Photoreceptor disorders are collectively known as retinal degeneration (RD), and include retinitis pigmentosa (RP), cone-rod dystrophy and age related macular degeneration (AMD). These disorders are largely genetic in origin; individual mutations in any one of >200 genes cause RD, making mutation specific therapies prohibitively expensive. A better treatment plan, particularly for late stage disease, may involve stem cell transplants into the photoreceptor or ganglion cell layers of the retina. Stem cells from young mouse retinas can be transplanted, and can form photoreceptors in adult retinas. These cells can be grown in tissue culture, but can no longer form photoreceptors. We have used microarrays to investigate differences in gene expression between cultured retinal progenitor cells (RPCs) that have lost photoreceptor potential, postnatal day 1 (pn1) retinas and the postnatal day 5 (pn5) retinas that contain transplantable photoreceptors. We have also compared FACS sorted Rho-eGFP expressing rod photoreceptors from pn5 retinas with Rho-eGFP negative cells from the same retinas. We have identified over 300 genes upregulated in rod photoreceptor development in multiple comparisons, 37 of which have been previously identified as causative of retinal disease when mutated. It is anticipated that this research should bring us closer to growing photoreceptors in culture and therefore better treatments for RD. This dataset is also a resource for those seeking to identify novel retinopathy genes in RD patients. We extracted whole retinas from postnatal day 1 (Pn1) and postnatal day 5 (Pn5) mice, and compared them with cultured RPCs derived from pn5 retinas, using Affymetrix mouse 430A_2 arrays. We also extracted cells from Rho-eGFP Pn5 retinas and FACS sorted them. GFP+ve cells represent immature rod photoreceptors, as they express the Rho-eGFP fusion protein, which is only expressed in rods. GFP-ve cells represent all other retinal neurons. These samples were amplified and compared using Affymetrix mouse 430A_2arrays, by Source Biosciences GMBH, Berlin, Germany. Results from immature rods were then compared with those from other retinal neurons, while results from whole Pn5 retinas were compared with Pn1 retinas (which don't yet express rod specific genes), and RPCs, which are glial precursors. RPCs were also compared with Pn1 retinas. Genes which showed changed expression profiles in at least 3/4 of comparisons were prioritised for further investigation.

Project description:Background: Mutations in the cone-rod-homeobox protein CRX are typically associated with dominant blinding retinopathies with variable age of onset and severity. Five well-characterized mouse models carrying different Crx mutations show a wide range of disease phenotypes. To determine if the phenotype variability correlates with distinct changes in CRX target gene expression, we perform RNA-seq analyses on three of these models and compare the results with published data. Results: Despite dramatic phenotypic differences between the three models tested, graded expression changes in shared sets of genes are detected. Phenotype severity correlates with the down-regulation of genes encoding key rod and cone phototransduction proteins. Interestingly, in increasingly severe mouse models, the transcription of many rod-enriched genes decreases decrementally, whereas that of cone-enriched genes increases incrementally. Unlike down-regulated genes, which show a high degree of CRX binding and dynamic epigenetic profiles in normal retinas, the up-regulated cone-enriched genes do not correlate with direct activity of CRX, but instead likely reflect a change in rod cell-fate integrity. Furthermore, these analyses describe the impact of minor gene expression changes on the phenotype, as two mutants showed marginally distinguishable expression patterns but huge phenotypic differences, including distinct mechanisms of retinal degeneration. Conclusions: Our results implicate a threshold effect of gene expression level on photoreceptor function and survival, highlight the importance of CRX in photoreceptor subtype development and maintenance, and provide a molecular basis for phenotype variability in CRX-associated retinopathies. All genotypes were analyzed in triplicate. Heterozygous and homozygous mutants were all sequenced at P10, the control for which is the P10 C57BL6/J data. Heterozygous mutants were also analyzed at P21, the control for which is the P21 C57BL6/J data.

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[E-MEXP-3786] IGF-I-induced chronic gliosis and retinal stress lead to neurodegeneration in an animal model of retinopathy

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