Bipolar disorder is a complex neuropsychiatric disorder that is characterized by intermittent episodes of mania and depression; without treatment, 15% of patients commit suicide1. Hence, it has been ranked by the World Health Organization as a top disorder of morbidity and lost productivity2. Previous neuropathological studies have revealed a series of alterations in the brains of patients with bipolar disorder or animal models3, such as reduced glial cell number in the prefrontal cortex of patients4, upregulated activities of the protein kinase A and C pathways5, 6, 7 and changes in neurotransmission8, 9, 10, 11. However, the roles and causation of these changes in bipolar disorder have been too complex to exactly determine the pathology of the disease. Furthermore, although some patients show remarkable improvement with lithium treatment for yet unknown reasons, others are refractory to lithium treatment. Therefore, developing an accurate and powerful biological model for bipolar disorder has been a challenge. The introduction of induced pluripotent stem-cell (iPSC) technology has provided a new approach. Here we have developed an iPSC model for human bipolar disorder and investigated the cellular phenotypes of hippocampal dentate gyrus-like neurons derived from iPSCs of patients with bipolar disorder. Guided by RNA sequencing expression profiling, we have detected mitochondrial abnormalities in young neurons from patients with bipolar disorder by using mitochondrial assays; in addition, using both patch-clamp recording and somatic Ca2+ imaging, we have observed hyperactive action-potential firing. This hyperexcitability phenotype of young neurons in bipolar disorder was selectively reversed by lithium treatment only in neurons derived from patients who also responded to lithium treatment. Therefore, hyperexcitability is one early endophenotype of bipolar disorder, and our model of iPSCs in this disease might be useful in developing new therapies and drugs aimed at its clinical treatment.
At a glance
- Mortality in affective disorder. J. Affect. Disord. 31, 91–96 (1994) &
- Treatment use and costs among privately insured youths with diagnoses of bipolar disorder. Psychiatr. Serv. 63, 1019–1025 (2012) et al.
- Bipolar disorder: from genes to behavior pathways. J. Clin. Invest. 119, 726–736 (2009) , &
- The neurobiology of bipolar disorder: identifying targets for specific agents and synergies for combination treatment. Int. J. Neuropsychopharmacol. 17, 1039–1052 (2014) &
- cAMP-Dependent protein kinase (PKA) subunit mRNA levels in postmortem brain from patients with bipolar affective disorder (BD). Brain Res. Mol. Brain Res. 116, 27–37 (2003) , &
- The neurobiology of bipolar disorder: focus on signal transduction pathways and the regulation of gene expression. Can. J. Psychiatry 47, 135–148 (2002) &
- Increased association of brain protein kinase C with the receptor for activated C kinase-1 (RACK1) in bipolar affective disorder. Biol. Psychiatry 50, 364–370 (2001) &
- Dopamine dysregulation syndrome: implications for a dopamine hypothesis of bipolar disorder. Acta Psychiatr. Scand. Suppl. 434, 41–49 (2007) et al.
- Serotonin and bipolar disorder. J. Affect. Disord. 66, 1–11 (2001) &
- Decreased hippocampal NMDA, but not kainate or AMPA receptors in bipolar disorder. Bipolar Disord. 5, 257–264 (2003) , , , &
- Bipolar disorder: involvement of signaling cascades and AMPA receptor trafficking at synapses. Neuron Glia Biol. 1, 231–243 (2004) , , , &
- Induction of pluripotent stem cells from adult human fibroblasts by defined factors. Cell 131, 861–872 (2007) et al.
- Neuronal pathology in the hippocampal area of patients with bipolar disorder: a study with proton magnetic resonance spectroscopic imaging. Biol. Psychiatry 53, 906–913 (2003) et al.
- Lower concentration of hippocampal N-acetylaspartate in familial bipolar I disorder. Am. J. Psychiatry 160, 873–882 (2003) , , , &
- Modeling hippocampal neurogenesis using human pluripotent stem cells. Stem Cell Rep. 2, 295–310 (2014) et al.
- Psychiatric comorbidity in 36 adults with mitochondrial cytopathies. CNS Spectr. 12, 429–438 (2007) , , , &
- Psychiatric disorders and mitochondrial dysfunctions. Eur. Rev. Med. Pharmacol. Sci. 16, 270–275 (2012) et al.
- Mitochondrial dynamics–fusion, fission, movement, and mitophagy–in neurodegenerative diseases. Hum. Mol. Genet. 18 (Suppl. R2), R169–R176 (2009) &
- Motile axonal mitochondria contribute to the variability of presynaptic strength. Cell Reports 4, 413–419 (2013) , , , &
- Activation of α1-adrenoceptors increases firing frequency through protein kinase C in pyramidal neurons of rat visual cortex. Neurosci. Lett. 430, 175–180 (2008) , , &
- Effect of dopamine receptor stimulation on voltage-dependent fast-inactivating Na+ currents in medial prefrontal cortex (mPFC) pyramidal neurons in adult rats. Acta Neurobiol. Exp. (Warsz.) 72, 351–364 (2012) , , &
- Protein kinase modulation of dendritic K+ channels in hippocampus involves a mitogen-activated protein kinase pathway. J. Neurosci. 22, 4860–4868 (2002) , , , &
- A model for neural development and treatment of Rett syndrome using human induced pluripotent stem cells. Cell 143, 527–539 (2010) et al.
- Imaging action potentials with calcium indicators. Cold Spring Harb. Protoc. 2011, 985–989 (2011) , , &
- High-speed in vivo calcium imaging reveals neuronal network activity with near-millisecond precision. Nature Methods 7, 399–405 (2010) , , , &
- Specific role of VTA dopamine neuronal firing rates and morphology in the reversal of anxiety-related, but not depression-related behavior in the Clock∆19 mouse model of mania. Neuropsychopharmacology 36, 1478–1488 (2011) et al.
- Immature dentate gyrus: an endophenotype of neuropsychiatric disorders. Neural Plast. 2013, 318596 (2013) , , , &
- Modelling schizophrenia using human induced pluripotent stem cells. Nature 473, 221–225 (2011) et al.
- Phenotypic differences in hiPSC NPCs derived from patients with schizophrenia. Mol. Psychiatry 20, 361–368 (2015) et al.
- K. edgeR: a Bioconductor package for differential expression analysis of digital gene expression data. Bioinformatics 26, 139–140 (2010) , &
Extended data figures and tables
Extended Data Figures
- Extended Data Figure 1: Generation of iPSCs from patients with BD and healthy people. (858 KB)
a, Human fibroblasts generated from punch biopsy. b, The iPSC colonies appeared after fibroblasts were reprogrammed using the Sendai virus. c, Purified iPSC colonies were cultured in Matrigel-coated plate. d, Immunostaining of iPSCs with DAPI and pluripotency markers Nanog and TRA-1-60. e, RT–PCR results showing that the introduced Sendai virus genes were cleared from the generated iPSCs. f, RT–PCR results showing that the generated iPSCs expressed human pluripotency markers NANOG, LIN28, OCT4, TDGF and cMYC. g, Representative karyotyping image of generated iPSCs showing normal chromosomal structure. h–j, Bar graphs of quantitative RT–PCR showing that the iPSCs can randomly differentiate into cells expressing the markers for endoderm, mesoderm and ectoderm. Data are representative for a total of 20 iPS cell lines from 10 patients (2 clones per patient). Scale bar, 50 μm. Bars, mean ± s.e.m.
- Extended Data Figure 2: Lentiviral transduction of Prox1::eGFP efficiently labels Prox1-positive DG granule cell-like neurons. (346 KB)
a, Sample immunostaining images showing the expression of Prox1 and Prox1::eGFP in the normal and BD neurons. Scale bar, 100 μm. b, Bar graph showing that, both in the normal and in BD groups, more than 90% of Prox1::eGFP-positive neurons express nuclear Prox1 protein. Normal, 92.1 ± 2.4%, n = 4 lines; BD, 93.3 ± 1.2%, n = 12 lines. c, Bar graph showing that, both in the normal and in BD groups, approximately 90% of Prox1-positive DG-like neurons express Prox1::eGFP. Bars, mean ± s.e.m.
- Extended Data Figure 3: Bar graphs summarizing the similarity between different cell lines of the same subject and comparison of low and high passage cells. (202 KB)
a, b, Bar graph comparing the MMP (n = 20 lines) (a) and mitochondria size (n = 68 images from 20 lines) (b) of different cell lines of one subject. c–f, Electrophysiological recording experiments, including peak Na+ currents (n = 92 neurons from 20 lines) (c), AP threshold (94 neurons from 20 lines) (d), total evoked AP number (n = 97 neurons from 20 lines) (e) and maximal AP amplitude (n = 96 neurons from 20 lines) (f). g, Bar graph comparing the frequency of Ca2+ transient events. Black bar, cell line/clone 1; grey bar, cell line/clone 2 (178 videos from 20 lines). h, Bar graph showing the normalized peak Na+ current in normal (NM) and BD neurons derived from <P5 and >P9 cell lines (P5: normal, n = 40 neurons from 8 lines; BD, n = 52 from 12 lines. P9: normal, n = 11 from 2 lines; BD, n = 23 from 5 lines). Student’s t-test, *P < 0.05. Bars, mean ± s.e.m.
- Extended Data Figure 4: K+ currents in the BD neurons. (56 KB)
a, Average peak values of K+ currents in the BD and normal neurons. b, Normalized average K+ currents at different membrane potentials (normal, n = 35 neurons from 7 lines; BD, n = 41 from 10 lines). Student’s t-test. Bars, mean ± s.e.m.
- Extended Data Figure 5: Prox1:eGFP expression in the BD LR and NR neurons and AP amplitude and threshold of BD neurons. (373 KB)
a, Sample immunostaining images showing the expression of Prox1::eGFP in the BD LR and NR neurons. Scale bar, 50 μm. b, Quantitative analysis revealed a similar percentage of Prox1::eGFP-positive DG-like neurons in the LR and NR groups (n = 32 images from 4 lines). c, d, Bar graphs showing the Li-induced effects in the maximal amplitude of evoked APs (LR without Li treatment, n = 27 neurons from 5 lines; with Li treatment, n = 18 from 5 lines) (c) and mean amplitude of spontaneous APs (LR without Li, n = 11 neurons from 3 lines; with Li, n = 10 from 3 lines) (d) of the LR neurons. e, Bar graph showing that the threshold of AP firing was not changed by Li (LR without Li, n = 11 neurons from 3 lines; with Li, n = 10 from 3 lines). Bars, mean ± s.e.m.
- Extended Data Figure 6: AP firing in the BD NR neurons treated with lamotrigine (LTG). (71 KB)
a, Representative traces of APs evoked during 300 ms stepwise depolarization periods in the normal and NR neurons with and without 100 μm lamotrigine treatment. b, c, Bar graphs summarizing the effects of lamotrigine on the total number (b) and maximal amplitude (c) of evoked APs in the normal and BD NR neurons (normal: without lamotrigine, n = 7 neurons; with lamotrigine, n = 8. BD NR: without lamotrigine,n = 5; with lamotrigine, n = 6). Student’s t-test, *P < 0.05; **P < 0.001. Bars, mean ± s.e.m.
- Extended Data Figure 7: Effect of Li on the normal neurons. (108 KB)
a, Representative traces of Na+/K+ currents in the normal neurons treated with Li at different concentrations. b, Representative traces of APs evoked during 300 ms stepwise depolarization periods in the normal neurons treated with Li at different concentrations. c, d, Bar graphs summarizing the effects of different concentrations of Li on the total number (c) and maximal amplitude (d) of evoked APs in the normal neurons (n = 4 neurons). Student’s t-test. *P < 0.05. Bars, mean ± s.e.m.
- Extended Data Figure 8: Reversal of hyperexcitability in old BD neurons. (367 KB)
a, b, Sample traces (a) and scatter graph (b) showing that the 8-week-old BD neurons exhibited weaker Na+ currents than the normal neurons (normal, n = 28 neurons from 4 lines; BD, n = 37 from 6 lines). c, d, Sample traces (c) and scatter graph (d) showing that the 8-week-old BD neurons exhibited a lower frequency of Ca2+ transient events than the normal neurons (n = 30 videos from 10 patients). e, Scatter graphs showing the MMP of 6- and 8-week-old BD and normal neurons (normal, n = 3 lines; BD, n = 3 lines). Student’s t-test, *P < 0.05; **P < 0.001. Bars, mean ± s.e.m.
- Extended Data Figure 9: The Prox1::eGFP-positive BD cells have similar expression of differentially expressed genes to the whole differentiation culture. (173 KB)
a, Sorting of cells strongly expressing Prox1::eGFP using flow cytometry. b, Bar graph showing that Prox1::eGFP expression is enriched in the selected cells. c, Enrichment of differentially expressed genes in the Prox1 + DG-like neurons (c) and non-DG cells (d) (n = 6 patients). Bars, mean ± s.e.m.
- Extended Data Figure 10: Representative icons of the subjects in the figures. (187 KB)
a, Representative icons of the patients with BD and healthy people used in the experiments shown in the figures. Identical symbols indicate the same subject.
- Supplementary Information (1.3 MB)
This file contains Supplementary Tables 1-7 and full RT-PCR gels for Extended Data Figure 1.