Figure 6. Evolutionary recent and human-specific genetic adaptation link IL6/IL6R/CEBP gene module with monocyte expansion and TB pathogenesis. ; (a) Heat map showing CEBPB network generated by STRING co-occurrence protein conservation scores across primates, mammals, birds and reptiles. Note only CEBPB and CEBPA differ strongly among hominids, while CEBPA/CEBPB/CEBPD vary significantly throughout primate and mammalian evolution, as compared to highly conserved STAT1/STAT3 (Figure 5—figure supplement 1d). (b) Top panel: Highly conserved type I IFN upregulation of ‘IFN/IL6-shared’ genes from humans to birds (derived from http://isg.data.cvr.ac.uk/) (Shaw et al., 2017), as compared to ‘IL6/STAT3’ and ‘CD34/myeloid differentiation’ genes. Bottom panel: CEBPB and CEBPD displays highest variation, and CXCL10 the lowest variation in type I IFN transcriptional regulation across human-mammalian-bird evolution. Inset, CEBPB and CEBPD selectively acquired type I IFN upregulation in humans (filled circles); ** p-value<0.01 and * p-value<0.05 represent CEBPB and CEBPD values, respectively for humans versus the other species. (c) ChipSeq analysis of STAT1-binding peaks in CEBPD (top panel), CEBPB (middle panel), CXCL9 and CXCL10 (bottom panel) in IFN-stimulated human monocytes, corresponding to regions with active chromatin (DNase Hypersensitivity Sites, DHS) and correlating with increased downstream transcription in CD14+ monocytes, as compared to purified CD34+ cells. Conservation analysis among >40 vertebrates (phyloP [Pollard et al., 2010], from chicken to human, analogous to Figure 5b) indicates STAT1 peaks are mostly conserved in CXCL9/CXCL10 (6/7) but not in CEBPD/CEBPB (3/11). (d) Top panel: overlap between human genes with significant Neanderthal introgression (Enard and Petrov, 2018; Quach et al., 2016), genes differentially expressed in Mtb-exposed CD34+ cells (CD34+ Mtb UP) and the ‘ML ratio’ gene set. Bottom left panel: OAS1, OAS2 and MT2A transcripts presented significantly higher effect sizes upon ML ratios, corresponding to monocyte expansion, as compared to other introgressed genes (p<0.05) and to all other genes shown to regulate ML ratio in vivo (p<0.001). Bottom right panel: normalized expression of introgressed genes found in CD34+Mtb UP (Venn diagram) in TLR1/2 agonist-treated monocytes from a cohort of matched Belgian individuals of European (EUB) vs. African (AFB) descendance, with documented presence or absence of Neanderthal introgression (Quach et al., 2016), respectively. p-value<0.05, ** p-value<0.01, *** p-value<0.001, **** p-value<0.0001.