Analysis of induced pluripotent stem cells carrying 22q11.2 deletion

Abstract

Given the complexity and heterogeneity of the genomic architecture underlying schizophrenia, molecular analyses of these patients with defined and large effect-size genomic defects could provide valuable clues. We established human-induced pluripotent stem cells from two schizophrenia patients with the 22q11.2 deletion (two cell lines from each subject, total of four cell lines) and three controls (total of four cell lines). Neurosphere size, neural differentiation efficiency, neurite outgrowth, cellular migration and the neurogenic-to-gliogenic competence ratio were significantly reduced in patient-derived cells. As an underlying mechanism, we focused on the role of DGCR8, a key gene for microRNA (miRNA) processing and mapped in the deleted region. In mice, Dgcr8 hetero-knockout is known to show a similar phenotype of reduced neurosphere size (Ouchi et al., 2013). The miRNA profiling detected reduced expression levels of miRNAs belonging to miR-17/92 cluster and miR-106a/b in the patient-derived neurospheres. Those miRNAs are reported to target p38α, and conformingly the levels of p38α were upregulated in the patient-derived cells. p38α is known to drive gliogenic differentiation. The inhibition of p38 activity by SB203580 in patient-derived neurospheres partially restored neurogenic competence. Furthermore, we detected elevated expression of GFAP, a gliogenic (astrocyte) marker, in postmortem brains from schizophrenia patients without the 22q11.2 deletion, whereas inflammation markers (IL1B and IL6) remained unchanged. In contrast, a neuronal marker, MAP2 expressions were decreased in schizophrenia brains. These results suggest that a dysregulated balance of neurogenic-to-gliogenic competence may underlie neurodevelopmental disorders such as schizophrenia.

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“…We also examined reprogrammed neuronal lineage cells from patients with schizophrenia. Neurospheres are composed of freefloating clusters of neural stem or progenitor cells, differentiated from induced pluripotent stem cells (iPSCs) (Maekawa et al, 2015;Toyoshima et al, 2016). iPSCs-derived neurospheres from schizophrenia patients carrying 22q11.2 micro-deletions ( Fig 6D) (Bundo et al, 2014;Maekawa et al, 2015;Toyoshima et al, 2016) showed a significant increase in CBS mRNA compared to those derived from control subjects ( Fig 6E).…”

Modeling schizophrenia pathogenesis using patient-derived induced pluripotent stem cells (iPSCs)

“…In addition, genes involved in cell cycle, apoptosis and MAPK pathway were affected [38]. Consistent with this finding, another group also observed disruption of the MAPK pathway in 22q11.2 deletion syndrome in mixed neuronal populations [39], though there was differences in miRNA findings between these two studies [39,40]. This discrepancy may have resulted from small sample size, heterogeneous differentiation or the influence of gene variants not within the CNV.…”

“…Controls that better match the genetic background (sibling or isogenic control) and more homogeneous differentiation could reduce such discrepancies. The disrupted neurogenesis presumably resulting from dysregulation of the MAPK pathway was partially reversed by treating with the p38 inhibitor, SB203580 [39]. …”

Application of induced pluripotent stem cells to understand neurobiological basis of bipolar disorder and schizophrenia

“…MicroRNA interact with mRNA to regulate the translation and degradation of target mRNA . Zhao et al and Toyoshima et al independently studied the iPSC‐differentiated neurons of patients with 22q11.2 microdeletion, which is another most common SCZD‐associated CNV, and detected a lot of differentially expressed miRNA in the patient iPSC‐derived cells. Differentially expressed miRNA are largely proposed to be involved in neurogenesis, axon guidance, and synaptic plasticity .…”

“…In Zhao et al several miRNA that were previously found to be differentially expressed in SCZD and ASD tissues, such as miR‐34, miR‐4449, miR‐146b‐3p, and miR‐23a‐5p, showed significantly increased expression in the patient iPSC‐derived neurons . In Toyoshima et al downregulated expression of miRNA belonging to the miR‐17/92 cluster and miR‐106a/b promoted gliogenic differentiation of iPSC through enhancing the expression of p38α . Recent research has suggested that microRNA are fundamental for neurodevelopmental deficits in SCZD.…”