The long non-coding RNA <i>Dreg1</i> is required for optimal ILC2 development

Gata3 is an essential transcription factor for the development of several distinct immune cell lineages such as T cells, natural killer (NK) cells, and innate lymphoid cells (ILCs). As such, the levels and timing of <i>Gata3</i> expression are critical for directing lineage fate decisions. The <i>Gata3</i> locus has a complex and dynamic distal regulatory enhancer landscape. Recently, we identified a non-coding RNA, <i>Dreg1</i>, located immediately upstream of the classic +280 kb T/NK cell enhancer (Tce1). To test its function, we excised the <i>Dreg1</i> locus in mice and observed a selective reduction of group 2 ILCs (ILC2) across multiple tissues, but mature T, NK, and other ILC lineages remained unchanged. In bone marrow, common innate lymphoid cell progenitors (ILCPs) increased while ILC2 progenitors (ILC2P) decreased, with a modest reduction of <i>Gata3</i> in upstream progenitors consistent with an early developmental bottleneck. Chromatin profiling showed the Dreg1 locus is accessible in early lymphoid progenitors and became decorated with H3K27ac in ILCP in a Tcf1-dependent manner. Furthermore, Tcf1-deficient cells did not express <i>Dreg1</i> and showed alterations in the epigenetic landscape of the <i>Dreg1</i> locus. Finally, we discovered that potential homologues of <i>Dreg1</i> harboured in a syntenic enhancer of <i>GATA3</i> are also highly expressed in human ILC2. Taken together, we conclude that <i>Dreg1</i> is a Tcf1-dependent non-coding RNA critical for fine tuning the high level of <i>Gata3</i> required for the optimal development of the ILC2 lineage.