Figure 2.

Trem2 Is a Master Genetic Regulator of Macrophage Multinucleation Network

(A) Heatmap of the correlations between macrophage mRNA levels of positional candidates (rows) and all trans-regulated genes of MMnet, showing that Trem2 was positively correlated with the majority (66%) of MMnet transcripts. Red indicates positive correlation and blue indicates negative correlations.

(B) Heatmap of the correlations between macrophage mRNA levels of positional candidates (rows) and ten trans-regulated genes representative of the larger MMnet selected for the siRNA knockdown experiments in rat BMDMs. Red indicates positive correlation and blue indicates negative correlations.

(C) siRNA against Trem2, Treml2, Treml1, D3ZDX3_Rat in rat macrophages followed by measurement of 10 transcripts belonging to the chromosome 9q11 trans cluster by quantitative real-time PCR. Cd68 and Cd11b expression levels were assessed as control transcripts that do not belong to MMnet. Given the correlation patterns shown in Figure 2B, a one-sample t test was used to test for directionality of the effect in the transcriptional response. Knockdown of Trem2 led to significant (∼50%, p < 0.001) downregulation of all genes tested, whereas knockdown of Treml2, Treml1, D3ZDX3_Rat did not result in a significant alteration in the expression levels of MMnet genes (p > 0.1 for all MMnet genes tested). At least n = 3 rats were used in each experiments. Error bars indicate SEM, ^∗p < 0.001.

(D) siRNA-mediated knockdown of TREM2 in human monocyte derived macrophages (MDMs) and the quantitative real-time PCR analysis of ten transcripts from the MMnet. MDMs are from buffy coats from four healthy donors. Error bars indicate SEM, ^∗p < 0.05 compared to control (scrambled).

(E) Knockdown of TREM2 in human MDMs resulted in transcriptional downregulation of MMnet genes, which significantly correlated with downregulation observed in rat BMDMs (R² = 0.69, p = 0.005).