Table 1.

Summary of the literature on findings in reprogrammed neuron‐like cells derived from patients with schizophrenia and schizoaffective disorder

Publication	Culture model	Cases	Cells	Summary of findings
Chiang et al. (2011)	Fibroblasts → iPSCs Episomal vector (EBV based) Plasmids (pEP4 EO2S ET2K, pEP4 EO2S EN2L, pEP4 EO2S EM2K)	Two cases chronic SCZ, DISC1 mutation, siblings	No Differentiation past iPSC	Proof of concept, for iPSC generation from SCZ patients. First SCZ‐derived iPSC line
Brennand et al. (2011)	Fibroblasts → iPSCs Tetracycline induceable Lentiviral vector (OCT4, SOX2, KLF4, c‐MYC, LIN28) → NPCs → iNeurons	Five cases (three SCZ, one SZA and drug abuse, one Schizoid personality and anorexia nervosa): Four in high‐incidence families One childhood onset Coriell Cell Repository GM02038 GM01792 GM01835 GM02497 GM02503 Six age‐ and ancestry‐matched controls GM02937 GM03440 GM03651 GM04506 AG09319 AG09429	30% GAD65/67+ 10% TH+ 60% VGLUT1+	Cell‐connectivity ↓ in SCZ Neurite outgrowth ↓ in SCZ PSD‐95 ↓ in SCZ Altered cAMP/WNT signalling Loxapine rescues alterations 42 Genes affected by CNV of those only CSMD1, MYH1, MYH4 showed > 1.3 fold expression difference 596 Genes differently expressed (> 1.3 fold) 25% of those connected to SCZ
Pedrosa et al. (2011)	Fibroblasts → iPSC Retroviral vector driven by long terminal repeat (OCT4, SOX2, KLF4, c‐MYC) → NPCs → iNeurons Neuronal differentiation medium, WNT3A to support glutamatergic cell fate	Three cases: One del(22q11.2) SCZ One childhood onset One familial case Two latter cases Coriell Cell Repository GM02039 GM02497 Two healthy subjects	Most cells are glutamatergic and express VGLUT1, GRIK3, AMPA2, GRIA2 Weak expression of GAD1 and TH	In del(22q11.2), decline of OCT4 and NANOG expression was markedly delayed SMARCA2, JARID2, MYT1L and NPAS3 all of which have been related to SCZ are expressed > 2 fold differently > 2 fold differences in the expression in SCZ‐relevant genes CHGB, SLC25A27, C4A, CHL1 and CTNNA2. NRXN3 was expressed at > 3 fold difference 1207 Genes expr. diff. The most significant GO cluster comprised ‘neurogenesis’, ‘neuronal differentiation’, ‘axon guidance’, and ‘adhesion’
Paulsen Bda et al. (2012)	Fibroblasts → iPSCs pMX‐based retroviral vector (OCT4, SOX2, KLF4, c‐MYC) → NPCs Retinoic acid and FGF2	One case, clozapine‐resistant SCZ One age‐matched healthy control	Differentiation to NPCs AADC, DAT, TH, ChAT and LMX1B were detected	Extramitochondrial O2 consumption ↑ in SCZ‐derived NPCs but not in iPSC or fibroblasts Level of reactive oxygen species ↑ in SCZ‐derived NPCs Valproic acid reverts reactive oxygen species level No changes in ATP‐coupled respiration
Robicsek et al. (2013)	Hair follicle keratinocytes → iPSC STEMCCA Lentivirus reprogramming kit → NPCs → iNeurons Dual SMAD inhibition for DA neurons No use of WNT3A or retinoic acid for GLUT differentiation	Three cases paranoid SCZ, clozapine treated Two healthy subjects	Differentiation to DA and GLUT neurons	SCZ‐derived iDA NPCs show higher PAX6 and reduced Nestin staining. Larger cell area. Conversion to iDAs is incomplete in SCZ cells. None express DAT, little release of dopamine and very few b3‐Tubulin+/TH+ cells. Outgrowth ↓ In Glut differentiation SCZ‐derived cells express no Tbr1; synapsin1 and PSD‐95 ↓ indicative of fewer synaptic contacts. Mitochondiral dysfunction described in SCZ‐derived cells including keratinocytes
Hook et al. (2014)	Fibroblasts → iPSCs Tetracycline inducible lentiviral vector (OCT4, SOX2, KLF4, c‐MYC, LIN28) → NPCs → iNeurons BDNF, GDNF, dibutryl‐cAMP and ascorbic acid	Three cases, SCZ One childhood onset Coriell Cell Repository GM01792 GM02038 GM2497 Three controls American Type Culture Collection AG09429 Coriell Cell Repository GM04506 One neonatal foreskin	Mixed population	> 2 fold number TH+ neurons derived from SCZ than healthy subjects’ iPSCs Large differenced between patients No increased transcription of TH Elevated release of dopamine, norepinephrine and epinephrine in SCZ‐derived iPSC neurons
Yu et al. (2014)	Fibroblasts → iPSC Tetracycline induceable Lentiviral vector (OCT4, SOX2, KLF4, c‐MYC, LIN28) → NPCs DKK1 Cyclopamine, Noggin → iNeurons WNT3A, BDNF	Four SCZ cases, derived from Brennand et al. (2011) Coriell Cell Repository GM02038 GM01792 GM01835 GM02497	> 85% vGLUT+ < 15% GABA+ Hippocampal DG granule neurons	Lower fraction of active neurons in SCZ Delayed conversion of NPCs to DG granule neurons in SCZ Reduced spontaneous neurotransmitter release and spontaneous excitatory post‐synaptic currents in SCZ
Yoon et al. (2014)	Fibroblasts → iPSC Sendai virus or episomal vector in concordance with Chiang et al. (2011) → NPCs → iNeurons	Five cases Three del(15q11.2) no clinical information Two DISC1 chronic SCZ (identical Chiang et al. (2011)) Three healthy subjects	Differentiation to NPCs No information on dcell identity	CYFIP1 (a gene involved in 15q11.2 CNVs) and Wave signalling mediators ACTR2/Arp2 SNPs do while not causing risk for SCZ individually, interact epistatically confer significant risk for SCZ. This may be due to derogation of apical polarity and adherens junctions in affected neurons
Wen et al. (2014)	Fibroblasts → iPSCs Episomal vector (EBV based) Plasmids(pEP4 EO2S ET2K, pEP4 EO2S EN2L, pEP4 EO2S EM2K) → NPCs → iNeurons	Two cases from one family One SCZ One major depression Pedigree H, frameshift mutation in DISC1 Three healthy subjects (One neonatal foreskin, two not affected relatives)	Forebrain identity 90% of neurons expressed VGLUT1 or α‐GAMKII few GAD6+7, VGAT+ or TH+	Impaired synaptic transmission in DISC1 mutation carriers. Defect in depolarization induced vesicle release. 1–2 weeks post‐conversion DISC1 carriers display larger soma and dentritic length. A large number of genes is differentially expressed at 4 weeks. Those are linked to synaptic transmission, dentritic spines and CNS development. 89 genes linked to mental Disorders
Hashimoto‐Torii et al. (2014)	Fibroblasts → iPSCs Tetracycline induceable Lentiviral vector (OCT4, SOX2, KLF4, c‐MYC, LIN28) → NPCs → iNeurons	Four cases, No further characterization Five controls	No differentiation past NPCs No information on cell identity	Following environmental challenges with methyl mercury and ethanol, NPCs derived from patients display sig. larger variability in HSP70 expression than healthy subjects. Means of HSP70 expr. are unchanged. GAPDH expression shows no difference
Paulsen Bda et al. (2014)	Fibroblasts → iPSCs pMX‐based retroviral vector (OCT4, SOX2, KLF4, c‐MYC) → NPCs Retinoic acid and FGF2	One clozapine‐resistant patient SCZ Two healthy subjects	No differentiation past NPCs	Significantly more Zn+ and K+ in SCZ‐derived NPC (but not iPSC) clones. Valproate reduced Zn+ and K+ levels to normal without affecting other trace elements as measured by syncrotron radiation x‐ray microflurescence spectrometry
Topol et al. (2015)	Fibroblasts → iPSC Tetracycline induceable lentiviruse vectors (OCT4, SOX2, KLF4, c‐MYC, LIN28) → NPCs → iNeurons	Four cases with SCZ Coriell Cell Repository GM02038 GM01792 GM01835 GM02497 Six healthy subjects	Study in NPCs forebrain identity	Significant over‐expression of translation‐related proteins with globally increased protein levels. Overexpression of protein clusters related to ribosome/RNA binding, nucleosome, chromatin, nucleocytoplasmatic and transport. Increased Translation is observed in NPCs but not in iPSCs. Primary Fibroblasts show a trend towards increased synthesis. The findings cannot be explained by cell size. No link between aberrant migration and protein over expression could be established
Brennand et al. (2015)	Fibroblasts → iPSCs Tetracycline induceable Lentiviral vector (OCT4, SOX2, KLF4, c‐MYC, LIN28) → NPCs → iNeurons	Four cases with three SCZ 1 SZA Two patients are siblings Coriell Cell Repository GM02038 GM01792 GM01835 GM02497 Six healthy subjects Coriell Cell Repository GM03440 GM03651 GM04506 American Type Culture Collection AG09319 AG09329 One neonatal foreskin CRL‐2522	Forebrain NPCs and early neurons	NPC and early neuron gene expression resembles first trimester forebrain neurons. SCZ and healthy subjects display similar gene expression and spatial and temporal identity. NCAM1, NLG1, NRXN1 and NRXN3 ↓ in SCZ 481 genes expressed at > 1.3 fold difference between SCZ and healthy subjects in NPCs; differences are conserved in older stages. Aberrant cell migration in SCZ cells (no effect of loxapine or clozapine) Morphological difference in mitochondria Increased oxidative stress in SCZ
Passeri et al. (2015)	Fibroblast direct conversion to iNeurons Lentiviral vector (ASCL1, POU3F2, MYT1L) novel conversion media	Four cases, childhood onset 2 del(22q11.2) 1 del(16p11.2) 1del(16p11.2)dupl.(22q13.3) Five healthy subjects	Mostly glutamatergic	del(16p11.2) is associated with significantly higher rate of conversion to neuron‐like cells
D'Aiuto et al. (2015)	Fibroblasts → iPSC → NPCs → iNeurons	One case SCZ Line 5404 One control neonatal foreskin HFF1‐S	Differentiation to glutamatergic neurons	Herpes simplex virus I can establish quiescent infection in iPSC‐derived neurons and alters gene expression in cognition relevant pathways. No information provided on differences regarding diagnosis
Zhao et al. (2015)	Fibroblasts → iPSC Nucleofection plasmids (OCT4, SOX2, KLF4, L‐MYC, LIN28 and p53 shRNA) → NPCs → iNeurons	Six cases 4 del(22q11.2) (1 SCZ, 3 SZA) Two childhood onset SCZ Six healthy subjects	GABAergic glutamatergic mixed population	45 miRNAs expressed differently according to diagnosis. Of 6 miRNAs with genome wide sign. down regulated in del(22q11.2) cells; 4 map to affected region (miRNA‐1306‐3p, miR‐1286, miRNA‐1306‐5p and miRNA‐185‐5p) and 2 do not (miRNA‐3175, miRNA‐3158‐3p) miRNA‐34 family miRNAs showed marked increase but did not reach genome wide sign. miRNA‐4449, miRNA‐146b‐3p, and miRNA‐23a‐5p showed the greatest increase in expression. No upregulated miRNAs reached genome wide sign
Lee et al. (2015)	Cohort 2: Fibroblasts → iPSCs Sendai viral vector → NPCs → Neurons Dual SMAD inhibition Lentiviral vector (Ngn2 induction) to yield glutamatergic neurons	One case (offspring) SZA heterozygous CNTNAP2 deletion Seven healthy subjects (father) heterozygous CNTNAP2 deletion (mother) no mutation Five unrelated healthy subjects	Forebrain identity and glutamatergic neurons late oligodendrocyte precursor cells (15% O4+/MBP+ mature oligodendrocytes) as well as ~15% astrocytes and ~20% neurons	Increased expression of the full length transcript in a phenotype‐specific way. In the SZA patient in 6‐weeks old neurons. Not affected father displayed increased transcription only in NPCs. NPC migration was significantly reduced in the SZA case, but not in the healthy carrier (father). In SZA (offspring) oligodendrocyte precursor cells predominantly the mutated allele of CNTNAP2 was expressed, whereas the father primarily expressed the wild‐type allele
Murai et al. (2016)	Fibroblasts → iPSCs Lentiviral vector → NPCs	Two cases SCZ Both from pedigree H with DISC1 frameshift mutation Three healthy subjects	No differentiation past NSC	miR‐219 expression is elevated in DISC1 carrier NSCs. miR‐219 acts downstream of TLX and leads to reduced NSC proliferation
Topol et al. (2016)	Cohort 1: iPSCs → NPCs → Neurons Tetracycline induceable Lentiviral vector (OCT4, SOX2, KLF4, c‐MYC, LIN28) Cohort 2: Fibroblasts → iPSCs Sendai viral vector → NPCs → Neurons Dual SMAD inhibition	Cohort 1: Four SCZ cases, six controls Cohort 2: 10 childhood onset SCZ cases 10 not related healthy subjects	NPCs and early neurons, forebrain identity	SCZ NPCs display reduced miR‐9 levels. A subset (~50%) of SCZ are below 25% quantile of healthy subjects’ NPCs. Perturbed miRNA‐9 levels can be observed in NPCs and early neurons but not after prolonged (6 weeks) maturation miRNA‐9 is correlated with impaired radial migration of NPCs in SCZ. Overexpression of miRNA‐9 rescues migration phenotype. Non‐genomic as well as genomic causes might affect altered miRNA‐9 Altered miRNA‐9 expression affects multiple genes on transcript and protein level

iPSC, induced pluripotent stem cells; SCZ, schizophrenia; NPC, neuronal progenitor cell; SZA, schizoaffective disorder; CNV, copy number variation; iNeuron: induced neuron‐like cell; iDA, induced dopaminergic neuron.