Higher Dnmt1 and hypermethylation of the promoters of both CBS and MTHFR in the retinal microvessels from donors with diabetic retinopathy suggest that decreased CBS and MTHFR, seen in diabetic retinopathy donors, could be due to increased methylated cytosine levels at their promoters, impeding the binding of the transcription factors, and suppressing their gene expressions. The gene discussed is DNMT1; the disease is diabetic retinopathy.