DICER1 and microRNA regulation in post-traumatic stress disorder with comorbid depression

Abstract

DICER1 is an enzyme that generates mature microRNAs (miRNAs), which regulate gene expression post-transcriptionally in brain and other tissues and is involved in synaptic maturation and plasticity. Here, through genome-wide differential gene expression survey of post-traumatic stress disorder (PTSD) with comorbid depression (PTSD&Dep), we find that blood DICER1 expression is significantly reduced in cases versus controls, and replicate this in two independent cohorts. Our follow-up studies find that lower blood DICER1 expression is significantly associated with increased amygdala activation to fearful stimuli, a neural correlate for PTSD. Additionally, a genetic variant in the 3' un-translated region of DICER1, rs10144436, is significantly associated with DICER1 expression and with PTSD&Dep, and the latter is replicated in an independent cohort. Furthermore, genome-wide differential expression survey of miRNAs in blood in PTSD&Dep reveals miRNAs to be significantly downregulated in cases versus controls. Together, our novel data suggest DICER1 plays a role in molecular mechanisms of PTSD&Dep through the DICER1 and the miRNA regulation pathway.

Figure 1. Genome-wide differential gene expression profiles in PTSD&Dep cases vs controls.

(a) Volcano plot for genome-wide differential gene expression profiles between cases of PTSD&Dep and controls, adjusting for sex, age and population substructure. The red line represents P value at FDR of 0.05 (−log₁₀p=4.729). The blue dots represent genes significantly differentially expressed between cases and controls. These genes are MRPS23, DICER1, CHST15, ZXDC, PDCD5 and LOC649548. Cases had reduced DICER1 expression compared with controls. (b) Box plot for DICER1 expression level in cases of PTSD&Dep and controls. The horizontal line represents the mean DICER1 level in the overall sample. These were derived from expression microarrays.

Figure 2. The SNP rs10144436, located in the 3′UTR of DICER1, is associated with DICER1 mRNA expression level and with PTSD&Dep.

(a) The minor allele of rs10144436 was associated with lower DICER1 expression level. (b) The minor allele of rs10144436 was associated with PTSD&Dep. Of note the minor allele was coded as 1 in the additive model. Bar graph shows mean±s.e.m.

Figure 3. miRNA levels in PTSD&Dep cases vs. controls in the discovery (n=24) and replication sample (n=54).

(a) MA plot for genome-wide differential expression of miRNAs in the discovery sample. The two points coloured in red are the two miRNAs with genome-wide adjusted P value<0.05 (miR-212-3p and miR-3130-5p). (b) miR-3130-5p expression was significantly lower in cases vs. controls in the discovery sample after sex, age and principal components were adjusted for. (c) miR-3130-5p expression was significantly downregulated in cases vs. controls in the replication sample after sex, age and genotypic principal components were adjusted for (P=0.030). Note, higher threshold cycle (C_T) indicates lower abundance level. Error bar represents one s.e.m.

Figure 4. Lower DICER1 expression in blood is significantly associated with more activation of the right amygdala in response to fearful faces, an intermediate phenotype for PTSD.

Regions in which the response to threat (fearful>neutral face stimuli) correlated negatively with expression, P<0.05, corrected. (a) Clusters showing a significant correlation with expression in whole-brain analysis. Correction for multiple comparisons used a combined height-extent threshold calculated using Alphasim Monte-Carlo simulation, with 1,000 iterations and a cluster-forming threshold of P<0.01. (b) A significant negative correlation with expression in the amygdala region of interest (ROI). Amygdala ROI analyses used a small-volume correction implemented in Alphasim, with 1,000 iterations and a cluster-forming threshold of P<0.05. Scatter plot shows the average contrast estimate for the fear>neutral contrast, from voxels in the activated cluster. Images are shown in neurological orientation, overlaid on a single-subject template in Montreal Neurological Institute (MNI) space.

Figure 5. Replication of reduced DICER1 expression level in.

(a) The Detroit Neighborhood Health Study (DNHS) and (b) The Caregivers of family member with aggressive brain cancer (data from the publicly available data set GSE7893). The black horizontal lines represent the means of the overall samples. (c) Replication of the association between the DICER1 eQTL rs10144436 and PTSD&Dep in the Drakenstein, South Africa cohort (minor allele was coded as 1 in the additive model).