To determine if C9ORF72 iMNs recapitulate neurodegenerative ALS processes, we examined their survival by performing longitudinal tracking of Hb9::RFP+ iMNs (Fig. 1a). This approach enabled us to distinguish differences in neurogenesis from differences in survival, which could not be addressed using previously-reported cross-sectional analyses6,7,10,26. In basal neuronal medium supplemented with neurotrophic factors, control and C9ORF72 patient iMNs survived equally well (Fig. 1b, Supplementary Fig. 3a, Supplementary Tables 5, 6). As human C9ORF72 ALS patients have elevated glutamate levels in their cerebrospinal fluid (possibly triggered by DPR-mediated aberrant splicing of the astrocytic excitatory amino acid transporter 2 EAAT2 4,27) we stimulated iMN cultures with a high glutamate pulse (12-hour treatment, 10 μM glutamate). This initiated a robust degenerative response in patient, but not control, iMNs (Fig. 1c-e and Supplementary Videos 3, 4) that was consistent across lines from multiple patients (n=6 patients) and controls (n=4 controls)(Fig. 1c, d and Supplementary Fig. 3d, e). While iMN survival varied slightly between live imaging systems, or between independent experiments due to the lengthy time course of neurodegeneration, the relative difference between control and C9-ALS patient iMNs was consistent (Fig. 1c - Nikon Biostation CT and Supplementary Fig. 3b - Molecular Devices ImageExpress). Moreover, iMNs from different iPSC lines derived from the same donor behaved similarly, suggesting genotypic differences accounted for these effects (Supplementary Fig. 3c). Treatment with glutamate receptor antagonists during glutamate administration prevented patient iMN degeneration (Fig. 1f). Alternatively, withdrawal of neurotrophic factors without glutamate stimulation also caused rapid degeneration of patient iMNs (n=3 patients, (Fig. 1g and Supplementary Fig. 3f).
In advanced traditional Chinese kung fu (martial arts), Neijing (Traditional Chinese: 內勁; pinyin: nèijìng) refers to the conscious control of the practitioner's qi, or "life energy", to gain advantages in combat. Nèijìng is developed by using "Neigong" (Traditional Chinese: 內功; pinyin: nèigōng) (內功), or "internal exercises," as opposed to "wàigōng" (外功), "external exercises."
To determine if patient iMN degeneration resulted from bona fide ALS disease processes specific for motor neurons, we measured the survival of induced dopaminergic neurons (iDAs) generated by expression of FoxA2, Lmx1a, Brn2, Ascl1, and Myt1l 29. These neurons expressed high levels of tyrosine hydroxylase, indicating they had established a key aspect of the dopamine synthesis pathway and were distinct from iMNs, which do not express this enzyme 24 (Supplementary Fig. 3m, n). Unlike iMN cultures, iDA cultures from C9ORF72 patients (n=2 patients) did not show reduced survival compared to controls (n=2 controls) in either glutamate treatment and neurotrophic factor withdrawal conditions (Fig. 1h and Supplementary Fig. 3o), indicating that the in vitro neurodegenerative phenotype elicited by the C9ORF72 mutation is selective for motor neurons.
RNA sequencing output was aligned to the GRCh38 Reference Genome and quantified using the STAR aligner.65 Genes were annotated against the GENCODE version 23 Comprehensive Gene Annotation. Quality control was performed using Picard Tools AlignmentSummaryMetrics. Samples passing quality control and having RNA Integrity Number (RIN) > 5 were used in downstream analysis. To identify differentially expressed genes, the R package DESeq2 was used as previously described.66 The function DESeq was used to estimate size factors, estimate dispersion, fit the data to a negative binomial generalized linear model, and generate differential expression statistics using the Wald test. KEGG enrichment analysis was performed for internal analysis using the R package clusterProfiler.67
HEK 293T cells were used to produce retrovirus, lentivirus, and C9ORF72 protein. HEK cells were used for these purposes based on previous published studies using HEK cells in order to produce viral particles and mammalian proteins. HEK cells were obtained from American Type Culture Collection, catalog number CRL-11268. HEK and iPS cells were tested for mycoplasma before, during, and after the study and were negative.
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To verify that PIKFYVE is the functional target of the inhibitor, we first confirmed PIKFYVE expression by qPCR in control and patient (n=3 patients) iMNs (Supplementary Fig. 15b). Next, we verified that YM201636 rescued C9ORF72 patient iMN survival in a dose-dependent manner (Supplementary Fig. 15c). We then asked if Apilimod, a structurally distinct PIKFYVE inhibitor, could rescue patient iMN survival 51(Fig. 6b). To verify target engagement by Apilimod in iPSC-derived motor neurons, we administered Apilimod for three hours and measured EEA1+ early endosome size. PIKFYVE inhibition increases PI3P levels, leading to increased recruitment of EEA1 to early endosomes, more homotypic early endosomal fusion, and larger EEA1+ early endosomes 54. As expected, Apilimod treatment increased EEA1+ endosome size in a dose-dependent manner, verifying target engagement in motor neurons (Supplementary Fig. 15d, e).
A 241-bp digoxigenin (DIG)-labeled probe was generated from 100 ng control genomic DNA (gDNA) by PCR reaction using Q5® High-Fidelity DNA Polymerase (NEB) with primers shown in Supplementary Data Table 4. Genomic DNA was harvested from control and patient iPSCs using cell lysis buffer (100 mM Tris-HCl pH 8.0, 50 mM EDTA, 1% w/v sodium dodecyl sulfate (SDS)) at 55ºC overnight and performing phenol:chloroform extraction. A total of 25 µg of gDNA was digested with XbaI at 37 ºC overnight, run on a 0.8% agarose gel, then transferred to a positive charged nylon membrane (Roche) using suction by vacuum and UV-crosslinked at 120 mJ. The membrane was pre-hybridized in 25 ml DIG EasyHyb solution (Roche) for 3 h at 47 ºC then hybridized at 47 ºC overnight in a shaking incubator, followed by two 5-min washes each in 2X Standard Sodium Citrate (SSC) and in 0.1% SDS at room temperature, and two 15-min washes in 0.1x SSC and in 0.1% SDS at 68 ºC. Detection of the hybridized probe DNA was carried out as described in DIG System User’s Guide. CDP-Star® Chemilumnescent Substrate (Sigma-Aldrich) was used for detection and the signal was developed on X-ray film (Genesee Scientific) after 20 to 40 min.
On the other hand, the level of the Neijing force depends on the extent one can exercise over one's will power to release an inner qi energy. Within the framework of Chinese martial arts, every person is believed to possess the inborn energy of qi. Martial artists can harness the force of qi so that it is strong enough to be applied in combat. When qi is being directed by one's will, it is called Neijing.
We wondered if reduced C9ORF72 activity renders motor neurons vulnerable to other insults that might be exacerbated by impaired endosomal-lysosomal system function, such as DPR toxicity. Without excess glutamate treatment, C9ORF72+/−, C9ORF72−/−, and C9ORF72 patient iMN survival was similar to control iMNs (Fig. 5a-d and Supplementary Fig. 14a, b). Exogenous expression of PR50 or GR50 DPRs using cassettes that do not contain the GGGGCC repeat expansion induced control iMN degeneration (Fig. 5a, b). Interestingly, C9ORF72+/−, C9ORF72−/−, and C9ORF72 patient iMNs (n=2 patients) degenerated significantly faster than controls in response to PR50 or GR50 expression (Fig. 5a-d and Supplementary Fig. 14a, b).
All experiments involving live vertebrates (cortical glial isolation) performed at USC were done in compliance with ethical regulations approved by the USC IACUC committee. All animal use and care at the University Medical Center Utrecht were in accordance with local institution guidelines of the University Medical Center Utrecht (Utrecht, the Netherlands) and approved by the Dierexperimenten Ethische Commissie Utrecht with the protocol number DEC 2013.I.09.069.
International Advisory Board: James Archibald (Translation Studies) - Hugo de Burgh (Chinese Media Studies) - Kristen Brustad (Arabic Linguistics) - Daniel Coste (French Language) - Luciano Curreri (Italian Literature) - Claudio Di Meola (German Linguistics) - Donatella Dolcini (Hindi Studies) - Johann Drumbl (German Linguistics) - Denis Ferraris (Italian Literature) - Lawrence Grossberg (Cultural Studies) - Stephen Gundle (Film and Television Studies) - Tsuchiya Junji (Sociology) - John McLeod (Post-colonial Studies) - Estrella Montolío Durán (Spanish Language) - Silvia Morgana (Italian Linguistics) - Samir Marzouki (Translation, Cultural Relations) - Mbare Ngom (Post-Colonial Literatures) - Christiane Nord (Translation Studies) - Roberto Perin (History) - Giovanni Rovere (Italian Linguistics) - Lara Ryazanova-Clarke (Russian Studies) - Shi-Xu (Discourse and Cultural Studies) - Srikant Sarangi (Discourse analysis) - Françoise Sabban, Centre d'études sur la Chine moderne et contemporaine (Chinese Studies) - Itala Vivan (Cultural Studies, Museum Studies)
Postsynaptic density extraction was done following a protocol published previously 63. Briefly, mouse spinal cord tissue or human cortical tissue was homogenized in cold Sucrose Buffer (320 mM Sucrose, 10 mM HEPES pH 7.4, 2 mM EDTA, 30 mM NaF, 40 mM β-Glycerophosphate, 10 mM Na3VO4, and protease inhibitor cocktail (Roche)) using a tissue grinder and then spun down at 500 g for 6 min at 4℃. The supernatant was re-centrifuged at 10,000 g for 10 min at 4℃. The supernatant was collected as the “Total” fraction, and the pellet was resuspended in cold Triton buffer (50 mM HEPES pH 7.4, 2 mM EDTA, 50 mM NaF, 40 mM β-Glycerophosphate, 10 mM Na3VO4, 1% Triton X-100 and protease inhibitor cocktail (Roche)) and then spun down at 30,000 RPM using a Beckman rotor MLA-130 for 40 min at 4℃. The supernantant was collected as the “Triton” fraction and the pellet was resuspended in DOC buffer (50 mM HEPES pH 9.0, 50 mM NaF, 40 mM β-Glycerophosphate, 10 mM Na3VO4, 20 uM ZnCl2, 1% Sodium Deoxycholate and protease inhibitor cocktail (Roche)) and collected as the “DOC”, PSD-enriched fraction. Collected samples were boiled with SDS-PAGE sample buffer and analyzed by western blot. Purity of the PSD preps was analyzed by immunoblotting for PSD-95 (PSD), p53 (non-PSD), and synaptophysin (non-PSD).
Libraries were prepared from total RNA using Clontech SMARTer Stranded RNA-Seq kit, with Clonetech RiboGone ribodepletion performed ahead of cDNA generation. Amounts of input RNA were estimated using the Bioanalyzer and libraries produced according to Clontech’s protocol. Library generation and sequencing were performed at the Norris Cancer Center Sequencing Core at USC. All FASTQ files were analyzed using FastQC (version 0.10.1), trimmed using the FASTQ Toolkit (v 1.0), aligned to the GRCh37/hg19 reference genome using Tophat (version 2), and transcripts assembled and tested for differential expression using Cufflinks (version 2.1.1). Raw data is available for public download in the NCBI database under accession code PRJNA296854.
Whole cell membrane potential and current recordings in voltage- and current-clamp configurations were made using an EPC9 patch clamp amplifier controlled with PatchMaster software (HEKA Electronics). Voltage- and current-clamp data was acquired at 50 kHz and 20 kHz, respectively, with a 2.9 kHz low-pass Bessel filter, while spontaneous action potential recordings were acquired at 1 kHz sampling frequency. For experiments, culture media was exchanged with warm extracellular solution consisting of (in mM): 140 NaCl, 2.8 KCl, 10 HEPES, 1 MgCl2, 2 CaCl2, and 10 glucose, with pH adjusted to 7.3 and osmolarity adjusted to 305 mOsm. Glass patch pipettes were pulled on a Narishige PC-10 puller and polished to 5–7 MΩ resistance. Pipettes were also coated with Sylgard 184 (Dow Corning) to reduce pipette capacitance. The pipette solution consisted of (in mM): 130 K-gluconate, 2 KCl, 1CaCl2, 4 MgATP, 0.3 GTP, 8 phosphocreatine, 10 HEPES, 11 EGTA, adjusted to pH 7.25 and 290 mOsm. Pipettes were sealed to cells in GΩ-resistance whole cell configuration, with access resistances typically between 10–20 MΩ, and leakage currents less than 50 pA. Capacitance transients were compensated automatically through software control. For voltage clamp, cells were held at −70 mV. For Current-voltage traces, a P/4 algorithm was used to subtract leakage currents from the traces. Measurements were taken at room temperature (approximately 20–25 °C). Data was analyzed and plotted in Igor Pro 6 (WaveMetrics) using Patcher’s Power Tools plug-in and custom programmed routines. Current density was obtained by dividing the measured ion channel current by the cell capacitance. For control iMNs, 10/10 tested fired action potentials. For C9-ALS iMNs, 9/10 tested fired action potentials.