CD9 and atherosclerosis: Examining the expression levels of 29 genes that were recently identified as being enriched in human foam cells in atherosclerosis [41] (Additional File 1) revealed a pronounced enrichment of foam cell genes within the DAM cluster (Fig. 1F-H) and reveal partial TREM2 dependence with CD9, APOC1, SPP1, CTSD and APOE being most highly expressed within the DAM cluster (Fig. 1H, I) and overall significantly, albeit subtly, downregulated in R47H cells when comparing all TREM2-R47H cells vs. TREM2-WT cells (Fig. 1E, I).