By utilizing scRNA-seq technology, Hill et al. identified three discrete ATM populations (CD11b+ Ly6c+; CD11b+ Ly6c− CD9+; CD11b+ Ly6c− CD9−), two of which (CD11b+ Ly6c+ and CD11b+ Ly6c− CD9+) are associated with obesity [17]. This evidence concerns the gene CD9 and obesity due to melanocortin 4 receptor deficiency.