TET1 and thyroid tumor: Given that BrafV600E can drive dedifferentiation and poor iodine uptake of thyroid follicular epithelial cells [27, 28], we next tested the effect of Tet1 knockout on the uptake of radioiodine in these transgenic mice and found that Brafm/+; Tet1−/− mice exhibited stronger ability to take up radioiodine than Brafm/+; Tet1+/− and Brafm/+; Tet1+/+ mice, especially the latter (Fig. 2L), suggesting that the thyroid tumor was more differentiated (less aggressive) in Brafm/+; Tet1−/− mice.