Tet2 facilitates the de-repression of myeloid target genes during C/EBPa induced transdifferentiation of pre-B cells

Tet2 is an enzyme that hydroxylates methylated cytosines and has been implicated in hematopoietic differentiation and the formation of myeloid malignancies when mutated. An ideal system to study the role of Tet2 in myelopoeisis is C/EBPa induced transdifferentiation of pre-B cells into macrophages, where many myeloid genes become rapidly upregulated. Here we found that C/EBPa binds to upstream regions of Tet2 and that the gene becomes activated. Tet2 knockdowns impaired the upregulation of macrophage markers as well as phagocytic capacity, suggesting that the enzyme is required for both early and late stages of myeloid differentiation. A slightly weaker effect was seen in primary cells with a Tet2 ablation. Expression arrays of transdifferentiating cells with Tet2 knockdowns permitted the identification of a small subset of myeloid genes whose upregulation was blunted. Activation of these target genes was accompanied by a rapid increase of promoter hydroxy-methylation. Our observations indicate that Tet2 helps C/EBPa to rapidly de-repress myeloid genes during the conversion of pre-B cells into macrophages. Gene expression was measured in a control and Tet2kd mouse preB cell line (called Haftl) harboring an inducible form of C/EBPa. Expression was measured in starting cells and cells induced to transdifferentiate into macrophage-like cells for 24 hours. Technical duplicates for each treatment and time were assayed.