Intergenerational trauma is associated with expression alterations in glucocorticoid- and immune-related genes

Abstract

Offspring of trauma survivors are more likely to develop PTSD, mood, and anxiety disorders and demonstrate endocrine and molecular alterations compared to controls. This study reports the association between parental Holocaust exposure and genome-wide gene expression in peripheral blood mononuclear cells (PBMC) from 77 Holocaust survivor offspring and 15 comparison subjects. Forty-two differentially expressed genes (DEGs) were identified in association with parental Holocaust exposure (FDR-adjusted p < 0.05); most of these genes were downregulated and co-expressed in a gene network related to immune cell functions. When both parental Holocaust exposure and maternal age at Holocaust exposure shared DEGs, fold changes were in the opposite direction. Similarly, fold changes of shared DEGs associated with maternal PTSD and paternal PTSD were in opposite directions, while fold changes of shared DEGs associated with both maternal and paternal Holocaust exposure or associated with both maternal and paternal age at Holocaust exposure were in the same direction. Moreover, the DEGs associated with parental Holocaust exposure were enriched for glucocorticoid-regulated genes and immune pathways with some of these genes mediating the effects of parental Holocaust exposure on C-reactive protein. The top gene across all analyses was MMP8, encoding the matrix metalloproteinase 8, which is a regulator of innate immunity. To conclude, this study identified a set of glucocorticoid and immune-related genes in association with parental Holocaust exposure with differential effects based on parental exposure-related factors.

Fig. 1. Differential gene expression associated with parental Holocaust exposure.

A Volcano plot illustrating the relationship of p value with fold changes (log₂FC) of the differential expression results by parental Holocaust exposure. Blue indicates downregulation, while red indicates upregulation. Bright colors indicate genes with adjusted p value < 0.05. The top ten genes with the lowest p values have been named. B Spearman correlations and C rank-rank hypergeometric overlap (RRHO) of differential gene expression fold-changes (log₂FC) based on maternal and paternal Holocaust exposure (“M Hol” and “F Hol”, respectively), childhood trauma (“CTQ tot”), maternal and paternal PTSD (“M-PTSD” and “F-PTSD”, respectively), and maternal and paternal age at Holocaust exposure (“M Hol Age” and “F Hol Age”, respectively) with log₂FC based on parental Holocaust exposure (“Hol”). D Spearman correlation of log₂FC from the differential expression analyses based on Hol vs. M Hol Age for genes nominally significant genes in both analyses. Genes with log₂FC > 1 SD in both analyses are named.

Fig. 2. Significant relationships between additional differential gene expression analyses.

Spearman correlation and rank-rank hypergeometric overlap (as an insert) of fold-changes (log₂FC) from the differential expression analyses based on A maternal and paternal Holocaust exposure (“M Hol” and “F Hol”, respectively), B maternal and paternal PTSD (“M-PTSD” and “F-PTSD”, respectively) C maternal and paternal age at Holocaust exposure (“M Hol Age” and “F Hol Age”, respectively), and D F-PTSD and childhood trauma (“CTQ tot”). Only genes nominally significant in both analyses of each pair are depicted, and genes with log₂FC >1 SD in both analyses are named.

Fig. 3. Gene set enrichment analysis.

Buble plots depicting the Top-20 enriched gene-sets of expression signatures based on parental Holocaust exposure (A) and genes differentially expressed by both parental Holocaust exposure and maternal age at Holocaust exposure (C). GSEA plots and heatmaps of expression signatures by parental Holocaust exposure overlapping with gene set derived based on in vivo DEX stimulation (B) and GO Immune Response (D). The y-axis represents enrichment score (ES) and the x-axis (bar-code plot) indicates the position of the genes on the expression data rank-sorted (boxplot) by its association with parental Holocaust exposure (i.e., Holocaust offspring vs. controls), with red and blue colors indicating up- and downregulation of mRNA. ES is the maximum deviation from zero as calculated for each gene going down the ranked list and represents the degree of over-representation of a gene set at the top or the bottom of the ranked gene list.

Fig. 4. Mediation analysis and tope-genes.

A Mediation: GRIP2 gene mediated 73.1% of the effect of parental Holocaust exposure on CRP (p=2e−04). B Mediation: Chocolate co-expression network mediated 58.8% of the effect of parental Holocaust exposure on CRP (p = 0.0042). C Venn diagram depicts the overlap of (i) FDR-significant DEGs, (ii) genes that were members of the Chocolate module, (iii) DEGs that were in the opposite direction in the analysis based maternal age at Holocaust exposure; (iv) DEGs that regulated by DEX; and (v) mediating effects of parental Holocaust exposure on blood functional measures. D Validation: box plot of RT-PCR based MMP8 expression in 50 subjects: comparison subjects (n = 6 in red) compared to Holocaust offspring (n = 44 in green). P value of the group difference was estimated by a Wilcoxon signed rank test.