Dnmt3a and Tet proteins act at the edges of Canyons. As long as both proteins are present, Canyon size is maintained in successive rounds of cell division. Canyon expansion is more frequently associated with high levels of H3K4me3 and the presence of expressed genes. In the absence of Dnmt3a, the presence of 5hmC (deposited by Tet proteins) results in edge erosion. In the absence of Tet proteins, the absence of eposition of 5-hydroxymethylation is predicted to result in Canyon contraction.