Publication Date



Open access

Embargo Period


Degree Type


Degree Name

Doctor of Philosophy (PHD)


Human Genetics and Genomics (Medicine)

Date of Defense


First Committee Member

Juan Young

Second Committee Member

Eden R. Martin

Third Committee Member

Rong Wen

Fourth Committee Member

Zane Zeier


Diabetic Retinopathy (DR) is a complication of both Type 1 and Type 2 diabetes mellitus (T1DM, T2DM), and is the leading cause of vision loss in working age adults around the world. DR is estimated to be present to some degree in 93 million individuals. Diabetes causes a local ascorbate deficiency in the eye. Importantly, the role of ascorbate in epigenetic regulation of the genome has been largely ignored until recently. Ascorbate serves as a cofactor for ten elven translocation (TET) methylcytosine dioxygenases, the enzymes that actively demethylate cytosines. Both hydroxymethylcytosine (5hmC) and methylcytosine (5mC) play a role in transcriptional regulation. In the absence of ascorbate, TET enzymes cannot work at full capacity and there is a global reduction of 5hmC in the genome. The known ascorbate deficiency in the eyes of diabetics integrated with the new knowledge of the role of ascorbate in epigenetics has led to the hypothesis that hyperglycemia-induced ascorbate deficiency in the eyes of diabetics contributes to epigenetic dysregulations in the retina that promote the development of diabetic retinopathy. In this work I present the results of an investigation of ascorbate deficiency in retinal pigment epithelial (RPE) cells, the predominant cell type in the outer blood retinal barrier. Specifically, I present the results of an investigation of the influence of restoration of ascorbate on the hydroxymethylome and transcriptome of RPE cells, followed by a functional validation of the role of ascorbate in helping to regulate the production of vascular endothelial growth factor in the RPE.


Diabetic Retinopathy; Vitamin C; Hydroxymethylcytosine; Epigenetics; Blood Retinal Barrier