TET2 Regulates Mast Cell Differentiation and Proliferation through Catalytic and Non-catalytic Activities.

Dioxygenases of the TET family impact genome functions by converting 5-methylcytosine in DNA to 5-hydroxymethylcytosine (5hmC), but their contribution to differentiation and function of immune cells is still incompletely understood. Here, we identified TET2 as a crucial regulator of mast cell differentiation and proliferation. Specifically, mast cell differentiation was impaired in absence of TET2, a defect that could be however compensated or further exacerbated modulating the activity of other TET family members. Mechanistically, delayed mast cell differentiation was related to the dysregulated expression of C/EBP transcription factors. Vice versa, the marked increase in proliferation induced by the absence of TET2 could be rescued exclusively by the specific re-expression of TET2 itself, regardless of its enzymatic activity. Our data indicate that in absence of TET2, mast cell differentiation is largely under the control of compensatory mechanisms mediated by other TET family members, while proliferation is strictly dependent on TET2 expression. Genomic DNA of FACS-sorted Kit+ FcεRIα+ populations of primary bone marrow-derived mast cells (BMMCs) from Tet2-/- and Tet2+/+ animals was extracted. Changes in 5hmC deposition were assessed genome-wide by biotin-based enrichment of 5hmC (Hydroxymethylation Collector-seq Kit, Active Motif) and multiparallel sequencing.