Differential gene expression profiles in neurons generated from lymphoblastoid B-cell line-derived iPS cells from monozygotic twin cases with treatment-resistant schizophrenia and discordant responses to clozapine

Abstract

Schizophrenia is a chronic psychiatric disorder with complex genetic and environmental origins. While many antipsychotics have been demonstrated as effective in the treatment of schizophrenia, a substantial number of schizophrenia patients are partially or fully unresponsive to the treatment. Clozapine is the most effective antipsychotic drug for treatment-resistant schizophrenia; however, clozapine has rare but serious side-effects. Furthermore, there is inter-individual variability in the drug response to clozapine treatment. Therefore, the identification of the molecular mechanisms underlying the action of clozapine and drug response predictors is imperative. In the present study, we focused on a pair of monozygotic twin cases with treatment-resistant schizophrenia, in which one twin responded well to clozapine treatment and the other twin did not. Using induced pluripotent stem (iPS) cell-based technology, we generated neurons from iPS cells derived from these patients and subsequently performed RNA-sequencing to compare the transcriptome profiles of the mock or clozapine-treated neurons. Although, these iPS cells similarly differentiated into neurons, several genes encoding homophilic cell adhesion molecules, such as protocadherin genes, showed differential expression patterns between these two patients. These results, which contribute to the current understanding of the molecular mechanisms of clozapine action, establish a new strategy for the use of monozygotic twin studies in schizophrenia research.

Effect of Clozapine on DNA Methylation in Peripheral Leukocytes from Patients with Treatment-Resistant Schizophrenia

“…Similarly, in a recent analysis of differential gene expression profiles in neurons from twins with treatment-resistant SCZ who had discordant responses to clozapine using pluripotent stem (iPS) cell based technology, we found that differentially expressed genes were enriched for “cell adhesion” and “biological adhesion” [6]. Cell adhesion is essential for forming tissue and neuronal connections crucial for nervous system development [31].…”

“…Approximately, 30% of SCZ patients are treatment-resistant [2], and the atypical antipsychotic clozapine has become the treatment of choice in this setting [3,4]. Recently, we have demonstrated that cell adhesion molecules, which play an important role in brain development including in axonal/dendrite growth, synapse formation and plasticity [5], were potential candidates for the molecular basis of clozapine response by conducting gene expression profiling using induced pluripotent stem (iPS) cell-based technology [6]. However, the molecular and epigenetic mechanisms underlying the therapeutic efficacy of clozapine have not yet been fully elucidated.…”

Regulation of neural circuit formation by protocadherins

“…Neurons were differentiated from each twin's iPSCs and exposed to clozapine. RNA-Seq analysis revealed that many clustered Pcdh genes were differentially regulated by clozapine in neurons derived from the clozapine-responding twin compared to those derived from the non-responding twin [181]. By comparing monozygotic twins with identical genomes, but distinct responses to clozapine, this study implicates Pcdhs in the molecular mechanisms through which neuropsychiatric drugs may act.…”

“…Considering the epigenetic control of clustered Pcdh isoform expression and its functional consequences on dendritic arborization [105,180] discussed above, olanzapine-induced methylation of some clustered (as well as non-clustered) Pcdh genes is worth noting. In a significant study by Nakazawa et al [181], induced pluripotent stem cells (iPSCs) were derived from monozygotic twins diagnosed with treatment-resistant schizophrenia. Each twin was differentially responsive to clozapine, a drug that is effective in 60-70% of treatment-resistant patients, but which is used only when other options have proven ineffective due to its rare but life-threatening side effects.…”

Prenatal exposure to valproic acid increases miR-132 levels in the mouse embryonic brain

“…RNA sequence analysis was carried out as previously described [34] with minor modifications. Total RNA, including microRNA, was isolated from the whole brain of each embryo of each pup using the miRNeasy Mini Kit (Qiagen) according to the manufacturer's instructions.…”