In VitroModeling of the Bipolar Disorder and Schizophrenia Using Patient-Derived Induced Pluripotent Stem Cells with Copy Number Variations ofPCDH15 andRELN

Abstract

Bipolar disorder (BP) and schizophrenia (SCZ) are major psychiatric disorders, but the molecular mechanisms underlying the complicated pathologies of these disorders remain unclear. It is difficult to establish adequate in vitro models for pathological analysis because of the heterogeneity of these disorders. In the present study, to recapitulate the pathologies of these disorders in vitro, we established in vitro models by differentiating mature neurons from human induced pluripotent stem cells (hiPSCs) derived from BP and SCZ patient with contributive copy number variations, as follows: two BP patients with PCDH15 deletion and one SCZ patient with RELN deletion. Glutamatergic neurons and GABAergic neurons were induced from hiPSCs under optimized conditions. Both types of induced neurons from both hiPSCs exhibited similar phenotypes of MAP2 (microtubule-associated protein 2)-positive dendrite shortening and decreasing synapse numbers. Additionally, we analyzed isogenic PCDH15-or RELN-deleted cells. The dendrite and synapse phenotypes of isogenic neurons were partially similar to those of patient-derived neurons. These results suggest that the observed phenotypes are general phenotypes of psychiatric disorders, and our in vitro models using hiPSC-based technology may be suitable for analysis of the pathologies of psychiatric disorders.

Focus on Causality in ESC/iPSC-Based Modeling of Psychiatric Disorders

“…This is of particular interest for the early detection of those carriers at risk which may develop full-blown symptomatology. In this context we note that isogenic modeling of private CNVs in PCDH15 and RELN1 in iPSCs from healthy donors recapitulated some, but not all, features of patient-specific iPSCs [33]. Although this may be explained by gene-dosage effects due to heterozygous deletions in patient-specific iPSCs versus homozygous deletions introduced into iPSCs derived from healthy donors, patient-specific iPSCs seemed to compensate to a significant degree for allelic loss by upregulation of the remaining wild-type allele during neural differentiation in vitro.…”

“…To investigate a causal role of PCDH15 and RELN haploinsufficiency in the pathogenesis of psychiatric disorders, Ishii et al [33] generated iPSCs from each two patients with BD and SCZ carrying heterozygous PCDH15 and RELN deletions, and from five healthy controls. Although embryoid body (EB) capacity of differentiation into the three germ layers was unaffected, neurite extension of the EB clusters was stunted in cases indicating an early differentiation deficit.…”

“…Having defined the phenotype of iPSC-derived neurons from patients with BD/SCZ carrying heterozygous PCDH15/RELN deletions, Ishii et al [33] applied targeted genome editing (CRISPR/CAS9) (clustered regulatory interspaced short palindromic repeats/CRISPR-associated protein 9) to introduce patient-like mutations in two healthy control iPSCs. EBs derived from isogenic homozygous gene-edited iPSCs showed for either mutation unaffected germ layer formation ruling out a general differentiation defect.…”

“…This finding suggests that very rare CNVs in PCDH15 or RELN1 contribute causally to brain pathology by affecting dendrite and synapse formation. A limitation of the present study [33] is the use of homozygous deletions in gene-edited control iPSCs raising the issue of gene dosage. Therefore, it would be interesting to know to what degree rescue of PCDH15 or RELN1 in patients' iPSCs would normalize structural abnormalities.…”

Transplanted Human Induced Pluripotent Stem Cell-Derived Neurons Wire and Fire with Balanced Excitation–Inhibition in Rat Cortex

“…The high failure of clinical trials investigating potential treatment options for Alzheimer's disease is one example. The significance of hiPSC lines continues to increase, as evidenced by the recent creation of hiPSC lines for other neurological disorders such as bipolar disorder and schizophrenia (Ishii et al, 2019).…”