The survival factor

Neutrophils, eosinophils and Ly6C^hi monocytes have a short lifespan. In Nature, Hernao-Mejia and colleagues show that these immune cells have high expression of the long noncoding RNA Morrbid and that it controls their survival. Morrbid-deficient mice have specific loss of eosinophils, neutrophils, Ly6C^hi and Ly6C^lo monocytes but not of other immune cells. The effect is cell intrinsic and is restricted to mature cells. Morrbid-deficient short-lived myeloid cells have greater apoptosis and higher expression of the gene encoding the pro-apoptotic molecule Bim. The cytokines IL-3, IL-5 and GM-CSF, which promote the survival of short-lived myeloid cells, induce Morrbid expression. Morrbid represses Bim through direct interaction with the Ezh2 subunit of the repressive complex PRC2 and recruitment of PRC2 to the Bim promoter through DNA looping in cis between the Morrbid and Bim loci. Inhibition of PCR2 induces apoptosis in wild-type eosinophils but not in Bim-deficient eosinophils.

Nature (15 August 2016) doi:10.1038/nature19346