Cutting edge: the Ets1 transcription factor is required for the development of NK T cells in mice.

Ets1-deficient mice develop B and T cells but display a severe defect in the development of the NK cell lineage. In this report, we demonstrate that Ets1 is also required for the development of NK1.1+ T (NK T) cells. We observed significantly decreased numbers of NK T cells in the thymus, spleen, and liver of Ets1-deficient mice. These organs also contained markedly decreased levels of the canonical Valpha14-Jalpha281 TCRalpha transcript seen in NK T cells. Unlike wild-type NK T cells, Ets1-deficient thymocytes failed to produce detectable levels of IL-4 following anti-CD3 stimulation. The absence of NK T cells in the Ets1-deficient mice was not associated with defective expression of CD1, an MHC class I molecule required for NK T cell development. We conclude that Ets1 defines a novel transcriptional regulatory pathway that is required for the development of both the NK and NK T cell lineages.