DNMT1 and diabetes mellitus: In diabetes, Rac1 is also transcriptionally activated in the retina and its vasculature, and its promoter undergoes active DNA methylation-hydroxymethylation; while DNA methyl transferase 1 (Dnmt1) methylates cytosine forming 5 methyl cytosine (5mC), concomitant activation of Tet2 hydroxymethylates 5mC, forming 5 hydroxymethyl cytosine (5hmC).