Investigation of de novo mutations in a schizophrenia case-parent trio by induced pluripotent stem cell based in vitro disease-modeling: Convergence of schizophrenia and autism-related cellular phenotypes

Abstract

Background: De novo mutations (DNMs) have been implicated in the etiology of schizophrenia (SZ), a chronic debilitating psychiatric disorder characterized by hallucinations, delusions, cognitive dysfunction and decreased community functioning. Several DNMs have been identified by examining SZ cases and their unaffected parents, however in most cases the biological significance of these mutations remains elusive. To overcome this limitation, we have developed an approach of using induced pluripotent stem cell (iPSC) lines from each member of a SZ case-parent trio, in order to investigate the effects of DNMs in cellular progenies of interest, particularly in dentate gyrus neuronal progenitors. Methods: We identified a male SZ patient characterized by early disease onset and negative symptoms, who is a carrier of 3 non-synonymous DNMs in genes LRRC7, KHSRP, and KIR2DL1. iPSC lines were generated from his and his parents’ peripheral blood mononuclear cells using Sendai virus-based reprogramming and differentiated into neuronal progenitor cells (NPCs) and hippocampal dentate gyrus granule cells. We used RNASeq to explore transcriptomic differences, and calcium (Ca 2+ ) imaging, cell proliferation, migration, oxidative stress, and mitochondrial assays to characterize the investigated NPC lines. Results: NPCs derived from the SZ patient exhibited transcriptomic differences related to Wnt-signaling, neuronal differentiation, axonal guidance and synaptic function, and decreased Ca 2+ reactivity to glutamate. Moreover, we could observe increased cellular proliferation, and alterations in mitochondrial quantity and morphology. Conclusions: The approach of reprograming case-parent trios represents an opportunity for investigating the molecular effects of disease-causing mutations, and comparing these in cell lines with reduced variation in genetic background. Our results are indicative of a partial overlap between schizophrenia and autism-related phenotypes in the investigated family. Limitations: Our study investigated only one family, therefore the generalizability of findings is limited. We could not derive iPSCs from two other siblings to test for possible genetic effects in the family that are not driven by DNMs. The transcriptomic and functional assays were limited to the NPC stage, although these variables should also be investigated at the mature neuronal stage.

Current progress in understanding Schizophrenia using genomics and pluripotent stem cells: A Meta-analytical overview

“…Both transcriptomic and proteomic analyses have found dysregulation in receptor proteins as well as differential expression of glutamate and GABA signaling pathway genes (Brennand et al 2011; Brennand et al 2015; Kathuria et al 2019b; Kathuria et al 2020; Narla et al 2017; Tiihonen et al 2019). Calcium imaging and microelectrode array experiments have been used to measure the altered excitatory and inhibitory responses of SCZ patient-specific neurons in several studies (Tiihonen et al 2019; Kathuria et al 2019b; Kathuria et al 2020; Hathy et al 2020; Stern, Zhang, et al 2022; Sarkar et al 2018). Electrophysiological recordings have found reduced activity in iPSC-derived neurons from SCZ patients as well as changes in excitatory and inhibitory synaptic activity (Fig 2b).…”