Whole-genome expression analysis reveals genes associated with treatment response to escitalopram in major depression

The reasons for variability in treatment response in major depressive disorder (MDD) are not fully understood, but there is accumulating evidence suggesting that therapeutic outcomes of antidepressants can be influenced by genetic factors. In the present study we applied the microarray Illumina platform for whole genome expression profiling in depressive patients treated with escitalopram medication in order to identify genes underlying response to antidepressant treatment. The initial study sample consisted of 135 outpatients with major depressive disorder (mean age 31.1±11.6 years, 68% females) treated with escitalopram 10-20mg/day for 12 weeks, from which 87 patients (55 females) were included in gene expression analyzing. The gene expression profiles were measured on peripheral blood cells at baseline, at week 4 and at the end of treatment (week 12) using BeadChips Illumina. The fold change was used to demonstrate rate of changes in average gene expressions between studied groups. Statistical analyses were performed using the false discovery rate (FDR). The most interesting gene, which showed the predictive effect on treatment outcome by delineating low dose responders and treatment-resistant patients at the beginning of medication, was NLGN2, belonging to a family of neuronal cell surface proteins and involving in synapse formation. In addition, the several gene clusters, related to immune response, signal transduction and neurotrophin pathway, have distinguished responders from non-responders at the week 4 of treatment. After 4 weeks of escitalopram treatment (10mg/day), the YWHAZ gene has showed the highest transcriptional change in responders as compared with non-responders. Finally, at the end of the treatment we noticed that at least three genes (NR2C2, ZNF641, FKBP1A) have been strongly associated with resistance to escitalopram. Thus the results of this study support that exploration of peripheral gene expression is a useful tool in the further identification of novel genetic biomarkers for antidepressant treatment response.

Whole-exome sequencing identifies a polymorphism in the BMP5 gene associated with SSRI treatment response in major depression

Although antidepressants are widely used in the pharmacotherapy of major depressive disorder (MDD), their efficacy is still insufficient as approximately one-third of the patients do not fully recover even after several treatment trials. Inter-individual genetic differences are thought to contribute to the variability in antidepressant response; however, current findings from pharmacogenetic studies are uncertain or not clearly replicated. Here we report the first application of full exome sequencing for the analysis of pharmacogenomics on antidepressant treatment. After 12 weeks of treatment with the selective serotonin re-uptake inhibitor escitalopram, we selected five clear responders and five clear non-responders for exome sequencing. By comparing the allele counts of previously known single nucleotide polymorphisms and novel polymorphisms we selected 38 markers for further genotyping in two independent patient samples treated with escitalopram (n=116 and n=394). The A allele, carried by approximately 30% of the patients with MDD, of rs41271330 in the bone morphogenetic protein (BMP5) gene showed strong association with worse treatment response in both sample sets (p=0.001), indicating that this is an promising pharmacogenetic marker for prediction of antidepressant therapeutic outcome.

Human microRNAs miR-22, miR-138-2, miR-148a, and miR-488 are associated with panic disorder and regulate several anxiety candidate genes and related pathways

BACKGROUND

The involvement of microRNAs (miRNAs) in neuronal differentiation and synaptic plasticity suggests a role for miRNAs in psychiatric disorders; association analyses and functional approaches were used to evaluate the implication of miRNAs in the susceptibility for panic disorder.

METHODS

Case-control studies for 712 single-nucleotide polymorphisms (SNPs) tagging 325 human miRNA regions were performed in 203 Spanish patients with panic disorder and 341 control subjects. A sample of 321 anxiety patients and 642 control subjects from Finland and 102 panic disorder patients and 829 control subjects from Estonia was used as a replica. Reporter-gene assays and miRNA overexpression experiments in neuroblastoma cells were used to functionally evaluate the spectrum of genes regulated by the associated miRNAs.

RESULTS

Two SNPs associated with panic disorder: rs6502892 tagging miR-22 (p < .0002), and rs11763020 tagging miR-339 (p < .00008). Other SNPs tagging miR-138-2, miR-488, miR-491, and miR-148a regions associated with different panic disorder phenotypes. Replication in the north-European sample supported several of these associations, although they did not pass correction for multiple testing. Functional studies revealed that miR-138-2, miR-148a, and miR-488 repress (30%-60%) several candidate genes for panic disorder--GABRA6, CCKBR and POMC, respectively--and that miR-22 regulates four other candidate genes: BDNF, HTR2C, MAOA, and RGS2. Transcriptome analysis of neuroblastoma cells transfected with miR-22 and miR-488 showed altered expression of a subset of predicted target genes for these miRNAs and of genes that might be affecting physiological pathways related to anxiety.

CONCLUSIONS

This work represents the first report of a possible implication of miRNAs in the etiology of panic disorder.