TET1 and brain ischemia: However, there are other reports that overall 5hmC abundance in the cortex was decreased significantly, and the reduced expression of Tet1 and Tet2 enzymes might be responsible for this change after hypoxic‐ischemic injury46; moreover, Kahlilia C et al.19thought that TET3 regulated 5hmC to provide endogenous neuroprotection against cerebral ischemia.