Hippo pathway coactivator WWTR1 drives self-renewal in alveolar macrophages 2257963

Abstract Introduction It is well known that Alveolar macrophages (AMs) self-renew in the lung and do not depend on circulating monocytes to maintain their population, but the transcriptional mechanisms driving this process remain incompletely defined. We have investigated the role of WWTR1/TAZ, a Hippo pathway coactivator that regulates cell growth and organ size, in AMs self-renewal. Methods We generated inducible myeloid knockouts by crossing LysM-CreERT2 mice with Wwtr1^fl/fl mice to obtain LysM-CreERT2 Wwtr1^fl/fl (conditional KO) and littermate controls. Mice received tamoxifen diet for 14 days to induce recombination, then BrdU (2 mg/day, i.p.) for 5 consecutive days to assess AM proliferation. To profile chromatin accessibility, we performed ATAC-seq on AMs in bone-marrow chimeras (CD45.1↔CD45.2) generated after clodronate liposome depletion, comparing host-derived resident versus donor-derived recruited AMs. Results BrdU incorporation by AMs was significantly reduced in LysM-CreERT2 Wwtr1^fl/fl mice relative to wild-type/Cre-negative controls, indicating impaired self-renewal upon Wwtr1 loss in myeloid cells. ATAC-seq revealed that chromatin at the WWTR1/TAZ-associated regulatory region(s) was accessible in host-derived AMs but not accessible in donor-derived recruited AMs in chimeric lungs, consistent with a resident AM program linked to WWTR1 activity Conclusion These data identify WWTR1/TAZ as a key regulator for the long-term maintenance of the tissue-resident AM pool. Future studies are warranted to define WWTR1 target genes and test whether modulating this pathway can bolster AM-dependent lung immunity in disorders with defective AMs function. Funding Source R35 HL155458 (C.V.J.) Topic Categories Innate Immune Responses and Host Defense: Molecular Mechanisms (INM)