Light-entrained and brain-tuned circadian circuits regulate ILC3 and gut homeostasis

Group 3 innate lymphoid cells (ILC3) are major regulators of inflammation, infection, microbiota composition and metabolism. ILC3 and neuronal cells were shown to interact at discrete mucosal locations to steer mucosal defence. Nevertheless, whether neuroimmune circuits operate at an organismal level, integrating extrinsic environmental signals to orchestrate ILC3 responses remains elusive. Here we show that light-entrained and brain-tuned circadian circuits regulate enteric ILC3, intestinal homeostasis and the host lipid metabolism. We found that enteric ILC3 display circadian expression of clock genes and ILC3-related transcription factors. ILC3-autonomous ablation of the circadian regulator Arntl led to disrupted gut ILC3 homeostasis, impaired epithelial reactivity, deregulated microbiome, increased susceptibility to bowel infection and disrupted lipid metabolism. Loss of ILC3-intrinsic Arntl shaped the gut postcode receptors of ILC3. Strikingly, light-dark cycles, feeding rhythms and microbial cues differentially regulated ILC3 clocks, with light signals as major entraining cues of ILC3. Accordingly, surgical- and genetically-induced deregulation of brain rhythmicity led to disrupted circadian ILC3 oscillations, deregulated microbiome and altered lipid metabolism. Our work reveals a circadian circuitry that translates environmental light cues into enteric ILC3, shaping intestinal health and organismal homeostasis. Small intestine lamina propria ILC3 (CD45.2+ Lin- Thy1.2hi KLRG1-) were sort-purified from the small intestine of 8-14 weeks old WT (Arntlwt/fl) and KO (Rorc-Cre.Arntlfl/fl) mice at two different timepoints: ZT05 (WT n=3; KO n=3) and ZT23 (WT n=3; KO n=3). Total RNA was extracted (Qiagen Micro Kit) and quality was assessed using an Agilent 2100 Bioanalyzer. SMART-SeqII (ultra-low input RNA) libraries were prepared using Nextera XT DNA sample preparation kit (Illumina). Sequencing was performed on an Illumina HiSeq4000 platform, PE100.