Abstract
Purpose: :
The overall goal of this research project is to determine whether there are specific sets of molecular changes of epigenetic postranslational modification of core histones H3 and H4 that occur in a mouse model of Type I diabetes.
Methods: :
Animal use was in accordance with ARVO / IACUC guidelines. C57BL/6J-Ins2 Akita/+ mice (Jackson Lab) were continuously maintained by crossing with C57BL/6j stock at each generation. We developed ChIP-Seq procedures for solid primary tissue and applied them to obtain comprehensive chromatin profiling to compare epigenetic marks in retina of Akita mice and wild type littermates. ChIP-Seq analysis of retinal chromatin was performed with antibodies against H3K4me2, H3K27ac, H3K27me3, H3K9me3, H3K9ac, H4K20me3 and H4K12ac. ChIP DNA libraries were sequenced on a SOLiDTM 3 system. Data were analyzed with NextGENe.
Results: :
Electron microscopy studies show no changes in nuclear morphology or distribution of heterochromatin in rod nuclei in Akita mice compared with healthy littermates. Immunohistochemical studies show different distributions of several epigenetic marks between the retinas of Akita mice and healthy littermates. Overall Chip-Seq analysis suggests that H3K27ac and H3K4me2, activation epigenetic markers are upregulated, while H3K27me3 and H3K9me3, inhibitory markers are downregulated in Akita mice retinas compared with wild type littermates. Detailed analysis of promoter region occupancy with different epigenetic markers was performed for one hundred genes. Immunohistochemistry shows increased staining in rod photoreceptor nuclei with anti-H3K27ac antibody in Akita mice, and ChIP-Seq with the same antibody demonstrated an increase in occupancy of the set of promoter mostly of non-rod specific genes, suggesting activation of these genes inside rod photoreceptor in diabetic mice.
Conclusions: :
We used Akita mice as model to study epigenetic changes in diabetic retinopathy. Our study suggests epigenetic dysregulation in the retina of diabetic mice with increase of activation epigenetic marks and decrease of inhibitory marks. While these changes affect many genes, it is clear that not all genes are affected equally. These studies will give fundamental information about the range of retinal changes seen in diabetes and will offer new insights into the treatment of the diabetes.
Keywords: diabetic retinopathy • gene/expression • photoreceptors