Fig. 4: Corpse-derived LPC and fatty acids work with HFSC-derived RA to regulate phagocytosis.
From: Stem cells tightly regulate dead cell clearance to maintain tissue fitness
a, Top, experiment interrogating response to corpse-secreted factors: BEL, calcium-independent phospholipase A2 inhibitor; PC, phosphatidylcholine; FAs, fatty acids; JTE, JTE013 (S1P-receptor antagonist); sphingo, sphingosine; Apyr, Apyrase (ATP hydrolysis). Bottom, quantification of HFSCs with nuclear RXRα+. n = 8 (medium), n = 7 (rest) experiments per condition. b, Top, experimental design interrogating response to corpses. Bottom, quantified data. RXRα+ HFSCs: n = 7 (medium), n = 6 (corpses plus Veh), n = 5 (corpses plus BEL, corpses plus JTE), n = 4 (corpses plus Apyr) experiments. RARγ+ HFSCs: n = 4 (medium), n = 9 (corpses plus Veh), n = 5 (corpses plus BEL), n = 3 (corpses plus JTE, corpses plus Apyr) experiments. TAM-family+;lysosomehigh (middle) and corpse-containing (bottom) HFSCs. n = 9 (corpses plus Veh), n = 12 (corpses plus BEL), n = 6 (medium, corpses plus JTE, corpses plus Apyr) experiments. c, Top, strategy to block LPC and fatty acids. Bottom, quantified data. RXRα+ (left), phagocytic (middle) HFSCs, unengulfed corpses (right). n = 51 hair follicles (Veh), n = 48 hair follicles (BEL) across 6 mice. d, RXRα+ response to recombinant factors. dNTP, 10 nM dUTP + dATP. n = 15 (medium), n = 6 (dNTP, S1P), n = 8 (arachidonic acid (AA), LPC, 9cRA), n = 3 (AA plus LPC), n = 11 (ATRA) experiments. e, AA, LPC and RA stimulate expression of TAM-family proteins. n = 4 (medium, 9cRA, LPC plus AA), n = 6 (LPC, AA), n = 3 (remaining conditions) experimental replicates. One representative experiment (of two) shown. f, RA is required for phagocytosis in vivo. Left, experimental design. Middle, hair cycle-dependent RXR–RAR-reporter activity. n = 23 (CatVI), n = 32 each (CatVII,Telo) hair follicles (2 mice per stage). Right, phagocytic sensitivity to RA degradation. Quantification of phagocytic HFSCs (n = 3 mice), TAM-family intensity per mouse (n = 6 mice). OE, overexpression. g,h, ATAC-seq (g) and RXRα CUT&RUN-seq (h) peak tracks (replicate-pooled) for phagocytic gene enhancers from Rxra wild-type or Rxra-cKO HFSCs treated as indicated. Recombinant (recomb) signals: RA + LPC + AA. Differentially accessible peaks are shown in light blue. No RXRα enrichment was detected in Rxra-cKO HFSCs. Pairwise independent two-sided Student’s t-tests, P values indicated. NS, not significant (P > 0.1). In box plots, the centre line is the median, box edges delineate first and third quartiles and whiskers extend to 1.5× the inter-quartile range. Further details on statistics and reproducibility in Methods. See also Extended Data Figs. 7–9 for additional supporting experiments.
