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J. M. Nickerson, J. Wisard, C. J. Johnson, G. I. Liou, J. H. Boatright, C. M. Donmoyer; ONL Thickness, Apoptosis, and Gene Expression in the IRBP Knockout Mouse. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3252.
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© ARVO (1962-2015); The Authors (2016-present)
IRBP is thought to protect the retina from damaging levels of retinoids and fatty acids. IRBP knockout (KO) mice experience slow retinal degeneration that continues throughout life. We sought to identify potential early death of photoreceptor cells and to find early changes in the expression of genes in the KO mouse. These changes may illuminate a protective role for IRBP.
Nuclear layer thickness at a fixed distance from the optic nerve head was counted at numerous ages from birth to more than two years. TUNEL staining was performed on at least three different postnatal ages, p2, p4, p7 and p10 IRBP KO and C57LB/6 (WT) eyes. Retinas were dissected from KO and WT mice at the same ages. Retinas from individual litters were pooled and extracted in RNAsol. Three RNA pools at each age and genotype were analyzed on ABI microarray gene chips (24 separate chips) each having about 36,000 genes represented. Results were analyzed with Bioconductor, PantherDB, Expander, and DAVID, v2.1.
In KO retinas, ONL begins to thin abnormally at p10, decreasing to 6-7 nuclei at p30, remaining stable until p60, and gradually thinning to 2 nuclei at 2 years. TUNEL staining indicated more apoptosis in KO than WT in p7 mice. ABI gene chips showed differential expression of a limited number of genes at each age. A group of about 75 genes changes consistently, and these can be clustered.
Small numbers of genes were differentially expressed in the KO mouse and WT mouse, regardless of the age tested. That is, at p2, p4, p7, and p10, respectively, 152, 48, 134, and 76 genes were differentially expressed, p<0.01. Among these genes about 75 consistently changed at most ages. The small number of affected functional groupings suggests that IRBP is required in several pathways to permit proper development of the retina. Because there are 150 genes that are differentially expressed at p2, early expression of IRBP appears to affect retina development and limit apoptotic death of photoreceptor cells.
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