Analyzing mirna expression changes in bipolar disorder patientspecific induced pluripotent stem cells (İPSC).

Bipolar disorder (BD) is a neuropsychiatric disorder characterized by manic and depressive episodes with intermittent periods of euthymia. Traditionally, the research on BD has relied on the use of animal models, biological fluids, or post-mortem tissues to identify biological changes associated with BD. However, such approaches suffer from various technical and biological limitations. Patient-derived induced pluripotent stem cell (iPSC) technology, on the other hand, offers an opportunity to overcome these limitations. In the present study, we aimed to identify miRNAs associated with BD by Nanostring miRNA profiling. In this study, we used fibroblast cells obtained from three BD patients and three healthy controls. These fibroblasts were reprogrammed to IPSCs with messenger RNA-based transfection method by Cellular Reprogramming company. Then we further induced these IPSCs to establish neural progenitor cells (NPC). After characterization, we differentiated NPCs into neurons and collected RNA samples on for two, four, or six weeks of differentiation. Then, we performed Nanostring analysis to identify differentially expressed miRNAs between BD- and control-derived NPCs and neurons. Finally, we evaluated how lithium modulates expression levels of miR-34a and its selected targets, together with NPH viability and neurogenesis parameters. Due to time and financial constraints, IPSCs have been established from three BD patients and three healthy controls. Statistical analysis on differentially expressed genes was not possible due to small sample size; therefore, we listed miRNAs with a fold-change of 1.5 or higher between two groups. Among several deregulated miRNAs, we identified miR-34a as one of the most consistently upregulated miRNA during different periods of neuronal differentiation. Building on this observation, we focused on miR-34a for target gene and treatment-related pathway analyses. Lithium treatment caused a marked reduction miR-34a expression in responder cells, which was further reflected in statistically significant elevation of miR-34a target genes' expression levels. Lithium treatment induced proliferation of NPCs and neurogenesis of neurons. On the other hand, lithium treatment failed to produce similar effects on non-responder cells. To our knowledge, this is the first study to investigate the effects of lithium on miRNAs by using BD patient derived neurons. Due to limited sample size, only one of the three patients was lithium responder, and the findings of this study require validation in larger cohorts. Taken together, the main findings of this study are twofold: 1) The regulatory network modulated by miR-34a may provide clues to the molecular mechanisms underlying BD pathogenesis and 2) Lithium may exerts its effects, at least in part, through miR-34a and its target genes. Further studies on a larger patient cohort are needed to determine the generalizability of these findings around miR-34a, as well as, to obtain a more comprehensive picture of the biological basis of lithium response.