CRISPR/Cas9-mediated genome editing was performed in human iPSCs as previously described, using Cas9 nuclease62. To generate loss-of-function alleles of C9ORF72, control iPSCs were transfected with a sgRNA targeting exon 2 of the C9ORF72 gene. Colonies were picked on day 7 after transfection and genotyped by PCR amplification and sequencing of exon 2. Colonies containing a frameshift mutation were clonally purified on MEF feeders and the resulting clones were re-sequenced to verify the loss-of-function mutation in C9ORF72.
(a-b) Survival of control and CRISPR-mutant iMNs without excess glutamate with overexpression of eGFP or PR(50)-eGFP (a) or GR(50)-eGFP (b). (c-d) Survival of control and C9-ALS iMNs without excess glutamate with overexpression of eGFP or PR(50)-eGFP (c) or GR(50)-eGFP (d). For (a), n=50 (CTRL1 + GFP AND CTRL1 + PR(50)), 49 (C9ORF72+/− + GFP), and 47 (C9ORF72+/− + PR(50)) iMNs per line, iMNs quantified from 3 biologically independent iMN conversions per line. For (b), n=50 (CTRL1 + GFP AND CTRL1 + GR(50)), 49 (C9ORF72+/− + GFP), and 40 (C9ORF72+/− + GR(50)) iMNs per line, iMNs quantified from 3 biologically independent iMN conversions per line. For (c), n=50 (CTRL1 + GFP AND CTRL1 + PR(50)), 50 (from each of two C9-ALS lines + GFP), and 41 (from each of two C9-ALS lines + PR(50)) iMNs per line, iMNs quantified from 3 biologically independent iMN conversions per line per condition. For (d), n=50 (CTRL1 + GFP AND CTRL1 + GR(50)), 50 (from each of two C9-ALS lines + GFP), and 46 and 47 (from two C9-ALS lines + GR(50)) iMNs per line, iMNs quantified from 3 biologically independent iMN conversions per line per condition. All iMN survival experiments in (a-d) were analyzed by two-sided log-rank test, and statistical significance was calculated using the entire survival time course. Survival curves for the “+GFP” condition were included as a reference, but were not used in statistical analyses. (e) Relative decay in Dendra2 fluorescence over 12 hours in iMNs of specified genotypes. Mean +/− s.e.m. n = 18 (control) and 24 (C9ORF72+/−) iMNs quantified from two biologically independent iMN conversions each, two-tailed t-test with Welch’s correction between data points at each time point, t-value: 2.739, degrees of freedom: 25.62). (f-h) Immunostaining to determine endogenous PR+ puncta in control or C9-ALS iMNs with or without overexpression of C9ORF72 isoform A or B. Scale bar = 2 μm. This experiment was repeated twice with similar results. (g) Mean +/− s.d. n= 4 biologically independent iMN conversions generated from two different iPSC lines per genotype. Quantified values represent the average number of PR+ puncta in 40 iMNs from a single iMN conversion. Two-tailed t-test, t-value: 5.908, degrees of freedom: 6. (h) Mean +/− s.e.m. n= 3 biologically independent iMN conversions per condition. Quantified values represent the average number of PR+ puncta in 40 iMNs from a single iMN conversion. One-way ANOVA with Tukey correction, F-value (DFn, DFd): (2, 6)=10.5. iMN survival experiments in (a-d) were performed in a Molecular Devices ImageExpress.
The key to unlock and nurture Neijing is said to be the practice of ‘song’ (Traditional Chinese: 鬆 ). The term ‘song’ can function as a verb which means to keep one's mind and body loose resilient and expanding like the consistency of cotton or clouds or relaxed yet concentrated like the sharp alertness of cats immediately before attack. The term can also be used as an adjective which has the same meaning as described above. The greater the extent one can achieve ‘song’ and minimize the use of Li, the greater the release of Neijing force.
An intronic GGGGCC repeat expansion in C9ORF72 is the most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), but its pathogenic mechanism remains unclear. Here we use human induced motor neurons (iMNs) to show that repeat-expanded C9ORF72 is haploinsufficient in ALS. We show that C9ORF72 interacts with endosomes and is required for normal vesicle trafficking and lysosomal biogenesis in motor neurons. Repeat expansion reduces C9ORF72 expression, triggering neurodegeneration through two mechanisms: accumulation of glutamate receptors leading to excitotoxicity, and impaired clearance of neurotoxic dipeptide repeat proteins derived from the repeat expansion. Thus, cooperativity between gain- and loss-of-function mechanisms leads to neurodegeneration. Restoring C9ORF72 levels or augmenting its function with constitutively active RAB5 or chemical modulators of RAB5 effectors rescues patient neuron survival and ameliorates neurodegenerative processes in both gain- and loss-of function C9ORF72 mouse models. Thus, modulating vesicle trafficking can rescue neurodegeneration caused by the C9ORF72 repeat expansion. Coupled with rare mutations in ALS2, FIG4, CHMP2B, OPTN, and SQSTM1, our results reveal mechanistic convergence on vesicle trafficking in ALS/FTD.
The repeat expansion suppresses the production of C9ORF72 protein by inhibiting transcription 3,4,6,7,9,17, raising the possibility that haploinsufficiency for C9ORF72 activity triggers disease pathogenesis. Consistent with this hypothesis, elimination of C9orf72 activity alters myeloid cell behavior in mice 14,18,19 and in vitro studies suggest that C9ORF72 activity may enhance autophagy 20,21.
Cells were fixed in 6-well culture plates in 2.5 % glutaraldehyde in 0.1M cacodylate buffer, post-fixed in 1% osmium tetroxide for 1 hour and block stained in 1% uranyl acetate in 0.1M acetate buffer pH 4.4 overnight at 4 ˚C. Dehydration was performed in increasing concentrations of ethanol (10%/25%/50%/75%/90%/100%/100%/100%) for 15 minutes each and infiltrated with increasing concentrations of Eponate12 (Ted Pella Inc., Redding, CA, USA), 25% Eponate12 (no catalyst) in ethanol for 3 hours, 50% overnight, 100% for 5 hours, 100% overnight, and polymerized in fresh Eponate12 with DMP-30 for 48 hours at 60 ˚C. Previously marked areas were sawed out, the tissue culture plastic was removed and the selected area sectioned parallel to the substrate at a thickness of 70 nm. Sections at a depth of 3–5 µm were collected on formvar-filmed 50 mesh copper grids and imaged at 80 kV in an FEI 208 Morgagni (FEI is in Hillsboro, OR, USA). Per micrograph, cytosol was used to quantify the number of electron dense spheres that were defined as lysosomes 40.
iMNs were fixed in 4% paraformaldehyde (PFA) for 1h at 4 ºC, permeabilized with 0.5% PBS-T overnight at 4 ºC, blocked with 10% FBS in 0.1% PBS-T at room temperature for 2 h, and incubated with primary antibodies at 4 ºC overnight. Cells were then washed with 0.1% PBS-T and incubated with Alexa Fluor® secondary antibodies (Life Technologies) in blocking buffer for 2 h at room temperature. To visualize nuclei, cells were stained with DAPI (Life Technologies) then mounted on slides with Vectashield® (Vector Labs). Images were acquired on an LSM 780 confocal microcope (Zeiss). The following primary antibodies were used: mouse anti-HB9 (Developmental Studies Hybridoma Bank); mouse anti-TUJ1 (EMD Millipore); rabbit anti-VACHT (Sigma); rabbit anti-C9ORF72 (Sigma-Aldrich); mouse anti-EEA1 (BD Biosciences); mouse anti-RAB5 (BD Biosciences); mouse anti-RAB7 (GeneTex); mouse anti-LAMP1 (Abcam); mouse anti-LAMP3 (DSHB, cat. no. H5C6); rabbit anti-LAMP3 (Proteintech, cat. no. 12632); mouse anti-LAMP2 (DSHB, cat. no. H4B4); mouse anti-M6PR (Abcam, cat. no. Ab2733); rabbit anti-GluR1 (EMD Millipore, cat. no. pc246); mouse anti-GluR1 (Santa Cruz); rabbit anti-NR1 (EMD Millipore); mouse anti-NR1 (EMD Millipore, cat. no. MAB363); chicken anti-GFP (GeneTex).
Human lymphocytes from healthy subjects and ALS patients were obtained from the NINDS Biorepository at the Coriell Institute for Medical Research and reprogrammed into iPSCs as previously described using episomal vectors61. Briefly, mammalian expression vectors containing Oct4, Sox2, Klf4, L-Myc, Lin28, and a p53 shRNA were introduced into the lymphocytes using the Adult Dermal Fibroblast Nucleofector™ Kit and Nucleofector™ 2b Device (Lonza) according to the manufacturer’s protocol. The cells were then cultured on mouse feeders until iPSC colonies appeared. The colonies were then expanded and maintained on Matrigel (BD) in mTeSR1 medium (Stem Cell Technologies).