The retina is a neuronal tissue lining the back of the eye containing rod and cone photoreceptors that make vision possible. Highly regulated transcriptional networks control differentiation and maintenance of photoreceptors in the retina. DNA methylation of cytosine bases in genomic DNA is an epigenetic modification correlated with repression of gene expression. Currently in our lab, the biochemical relationship between DNA methylation and the ability of retina-specific transcription factors to bind in the genome is being studied. These transcription factors, known as cone-rod homeobox (CRX) and neural leucine zipper (NRL), have been shown to act synergistically to control photoreceptor expression in the retina. Preliminary data has supported the hypothesis that DNA methylation is critical for modulating cell-specific binding of CRX to target recognition sites. DNA binding domain coding sequences of the human CRX and NRL proteins were cloned into bacterial expression vectors, and were expressed and purified for downstream biochemical analysis. In vitro gel shift assays are currently being used to determine the ability of CRX and NRL to bind unmethylated and methylated oligonucleotides. Collectively, these studies will contribute to a better understanding of how epigenetic modifications influence the development, homeostasis and pathology of human retinal neurons
