CT-ScarBip

Bipolar disorder (BD) is a frequent, severe and burdensome psychiatric disorder. The severity of BD mainly relies on the risk of mood recurrences that are major providers of suicidal risk, hospitalizations, cognitive decline and psychosocial consequences. Predicting mood recurrences is thus a challenge for targeting patients who would require a more intense care plan (patient stratification) and moving towards personalized medicine in BD (drug prioritization). We have demonstrated that Childhood Traumatic events (CT) dramatically increase the severity of the clinical expression of BD and decrease the response to lithium, the gold standard mood stabilizer used in BD. Importantly, CT have been repeatedly found to increase the frequency of mood recurrences, but only in retrospective studies. Altogether, these findings highlight that CT may act as an environmental “disease modifier” in BD. The biological consequences of CT are still poorly understood. As evidenced in preclinical models, CT in humans have long lasting effects, both in brain and in blood, on the expression of genes involved in multiple biological pathways, such as systems related to stress reactivity (cortisol/HPA axis), immunity/inflammation, neurotransmission or neuroplasticity. Within mechanisms implicated in the regulation of transcriptional processes, microRNAs (miRNAs) are proposed as key players in epigenetic regulation that might play a role in adaptive mechanisms linked to the response to stress. Integrating different levels of alterations in gene expression (mRNA) and transcriptional regulation (miRNA) might provide a more comprehensive physiopathological pathway leading from CT exposure to recurrences in BD. Finally, further characterization of genes whose expression is modified in association with the exposure to CT might open avenues in the identification of new therapeutic targets. Such integrative genomic approaches that combine high throughput sequencing of mRNAs and miRNAs represent unique tools for drug repurposing and prioritization. The first clinical objective of this project is a validation of CT as a disease modifier (prediction of mood recurrences) in a prospective sample of patients with BD, most previous studies using a retrospective design. The second molecular objective is to generate an integrated mRNA and miRNA blood signature that is associated with the exposure to CT in patients with BD. This signature will be validated in independent samples of patients and healthy controls according to their levels of CT. This signature will be functionally validated both in silico and in vitro (interactions between specific mRNAs and miRNAs). The third therapeutic objective is to use this signature for drug repurposing, meaning that the identified networks of co-expressed genes will serve to the identification and prioritization of already known drugs that would be able to modulate the gene expression modifications associated with CT. The effects of these drugs to restore the molecular scars associated with CT will be tested on patients’ cells and compared to the effects of gold standards mood stabilizers used in BD, such as lithium and valproate. The fourth pathophysiological objective is to use a cross-species approach to test for the overlap or congruence of early life stress signatures observed in patients (mRNA/miRNA modifications in blood) and mice (mRNA/miRNA modifications in blood and brain). This will serve to identify miRNAs whose expression will be down-regulated in specific brain regions in mice to characterize the behavioral consequences. The project will therefore help patients stratification, provide a mRNA and miRNA signature in the blood of patients that will be used for drug repurposing and prioritization (improving thus personalized medicine) and allow further understanding in the complex molecular abnormalities that represent scars of CT.