SummaryNeutrophils, eosinophils and “classical” monocytes collectively account for ~70% of human blood leukocytes and are among the shortest-lived cells in the body1,2. Precise regulation of the lifespan of these myeloid cells is critical to maintain protective immune responses while minimizing the deleterious consequences of prolonged inflammation1,2. However, how the lifespan of these cells is strictly controlled remains largely unknown. Here, we identify a novel long non-coding RNA (lncRNA) that we termed Morrbid, which tightly controls the survival of neutrophils, eosinophils and “classical” monocytes in response to pro-survival cytokines. To control the lifespan of these cells, Morrbid regulates the transcription of its neighboring pro-apoptotic gene, Bcl2l11 (Bim), by promoting the enrichment of the PRC2 complex at the Bcl2l11 promoter to maintain this gene in a poised state. Notably, Morrbid regulates this process in cis, enabling allele-specific control of Bcl2l11 transcription. Thus, in these highly inflammatory cells, changes in Morrbid levels provide a locus-specific regulatory mechanism that allows for rapid control of apoptosis in response to extracellular pro-survival signals. As MORRBID is present in humans and dysregulated in patients with hypereosinophilic syndrome, this lncRNA may represent a potential therapeutic target for inflammatory disorders characterized by aberrant short-lived myeloid cell lifespan.

Summary Commitment to the innate lymphoid cells (ILC) lineage is determined by Id2, a transcriptional regulator that antagonizes T and B cell-specific gene expression programs. Yet how Id2 expression is regulated in each ILC subset remains poorly understood. We identified a cis-regulatory element demarcated by a long non-coding RNA (lncRNA) that controls the function and lineage identity of group 1 ILCs, while being dispensable for early ILC development and homeostasis of ILC2s and ILC3s. The locus encoding this lncRNA, which we termed Rroid, directly interacted with the promoter of its neighboring gene, Id2, in group 1 ILCs. Moreover, the Rroid locus, but not the lncRNA itself, controlled the identity and function of ILC1s by promoting chromatin accessibility and deposition of STAT5 at the promoter of Id2 in response to interleukin (IL)-15. Thus, non-coding elements responsive to extracellular cues unique to each ILC subset represent a key regulatory layer for controlling the identity and function of ILCs.

1 and markedly augments VCAM-1 expression induced by TNF or IL-1 (1-6). These changes favor the binding of eosinophils and T cells to endothelial cells (ECs). In addition, IL-4-treated ECs secrete the chemokine MCP-1 (7) and selectively stimulate transendothelial migration of eosinophils in vitro (8). The effects of IL-4 on EC differ from those on hematopoietic cell types in that IL-4 is not an endothelial mitogen or survival factor.IL-13 is another pleiotropic immunoregulatory cytokine (9, 10) that shares a number of biological properties with IL-4 (11-16). IL-13, like IL-4, selectively induces VCAM-1 in cultured human ECs (17, 18). IL-13 has been shown recently to stimulate tyrosine phosphorylation of the IL-4-binding subunit of the 140-kD IL-4 receptor (IL-4R) in a number of hematopoietic cell types (19), suggesting that IL-4 and IL-13 may activate a common tyrosine kinase. Two recent findings further suggest that the IL-13-binding subunit of the IL-13 receptor (IL-13R) may share at least one subunit with the IL-4R: ( a ) the IL-4 mutant protein Y124D, which inhibits IL-4-dependent reactions (20) also inhibits effects of IL-13 (21, 22); and ( b ) IL-13 competes with radiolabeled IL-4 for binding to some cells (21-24).The IL-2 receptor (IL-2R) ␥ chain is a functional component of the IL-4R in lymphocytes, required for tyrosine phosphorylation of the insulin receptor substrate-1 in response to IL-4 (25) and for IL-4-induced cell proliferation (26). The (IL-2R) ␥ chain, recently renamed the common ␥ chain ( ␥ c chain), is also a common receptor component of many other members of the cytokine receptor superfamily including , [30][31][32]34). It is not known if IL-13 can signal through ␥ c , but some cell lines of hematopoietic origin are known to respond to IL-4 and IL-13 in the absence of ␥ c (24,35). This evidence suggests two distinct signaling pathways for IL-4, one involving ␥ c , and an alternate pathway, shared with IL-13, that does not use ␥ c .Previous work by our laboratory has shown that IL-4 activates a protein tyrosine kinase that phosphorylates the IL-4R binding subunit in cultured human ECs and that activation of this protein tyrosine kinase may play a part in the signaling pathway leading to increased VCAM-1 expression in response to . We now show that IL-13, like IL-4, causes the activation of a protein tyrosine kinase in ECs that phosphorylates IL-4R, that both cytokines activate JAK2 and the Stat6 transcription factor, and that these responses cannot involve ␥ c , since this protein is not expressed in ECs. MethodsCell isolation and culture. ECs were isolated and cultured as described previously (37,38). ECs used in these experiments were of passage levels 2 to 5 and were free of detectable CD45 ϩ leukocytes. PHA- 1. Abbreviations used in this paper: EC, endothelial cell; JAK, Janus kinase; RT, reverse transcription; Stat, signal transducer and activator of transcription; VCAM-1, vascular cell adhesion molecule-1.