Altered calcium dynamics and glutamate receptor properties in iPSC-derived motor neurons from ALS patients with C9orf72, FUS, SOD1 or TDP43 mutations

Abstract

The fatal neurodegenerative disease amyotrophic lateral sclerosis (ALS) is characterized by a profound loss of motor neurons (MNs). Until now only riluzole minimally extends life expectancy in ALS, presumably by inhibiting glutamatergic neurotransmission and calcium overload of MNs. Therefore, the aim of this study was to investigate the glutamate receptor properties and key aspects of intracellular calcium dynamics in induced pluripotent stem cell (iPSC)-derived MNs from ALS patients with C9orf72 (n = 4 cell lines), fused in sarcoma (FUS) (n = 9), superoxide dismutase 1 (SOD1) (n = 3) or transactive response DNA-binding protein 43 (TDP43) (n = 3) mutations as well as healthy (n = 7 cell lines) and isogenic controls (n = 3). Using calcium imaging, we most frequently observed spontaneous transients in mutant C9orf72 MNs. Basal intracellular calcium levels and α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)-induced signal amplitudes were elevated in mutant TDP43 MNs. Besides, a majority of mutant TDP43 MNs responded to 3.5-dihydroxyphenylglycine as metabotropic glutamate receptor agonist. Quantitative real-time PCR demonstrated significantly increased expression levels of AMPA and kainate receptors in mutant FUS cells compared to healthy and isogenic controls. Furthermore, the expression of kainate receptors and voltage gated calcium channels in mutant C9orf72 MNs as well as metabotropic glutamate receptors in mutant SOD1 cells was markedly elevated compared to controls. Our data of iPSC-derived MNs from familial ALS patients revealed several mutation-specific alterations in glutamate receptor properties and calcium dynamics that could play a role in ALS pathogenesis and may lead to future translational strategies with individual stratification of neuroprotective ALS treatments.

Viral Infections Exacerbate FUS-ALS Phenotypes in iPSC-Derived Spinal Neurons in a Virus Species-Specific Manner

“…Eigengene classification identifies the cells in these cultures with whole spinal cord with 83% probability. All cell lines differentiated into Islet-1 positive MNs with a similar efficiency of approximately 50% (Figure 1F), and which we had previously demonstrated using this protocol as being electrophysiologically functional (Bursch et al, 2019). Since cultures expressed very high levels of spinal neuronal markers and were enriched with MNs, we hereafter refer to these cultures as iPSC-derived SNs.…”

Altered serum protein levels in frontotemporal dementia and amyotrophic lateral sclerosis indicate calcium and immunity dysregulation

“…The authors suggested that calcium homeostasis in addition to DNA damage and oxidative stress could be among major molecular underpinnings for a significant proportion of unexplained FTD etiology 36 . In separate studies, calcium dysregulation was reported to contribute to neurodegeneration in iPSC-derived neurons from FTD patients 38 and ALS patients 39 . In C9ORF72 iPSC-derived motor neurons from ALS and FTD patients, decreased cell survival correlated with calcium homeostasis, suggesting a novel pathogenic link between C9ORF72, dysregulated calcium signaling and altered proteostasis 40 .…”

Glial Cell Dysfunction in C9orf72-Related Amyotrophic Lateral Sclerosis and Frontotemporal Dementia

“…Nevertheless, in recent years, investigators have tried to elaborate a link between ALS/FTD gene mutations, including C9orf72 repeat expansions, and neuronal hyperexcitability/excitotoxicity mechanisms. The expression of kainate receptors and voltage-gated Ca 2+ channels in iPSC-derived motor neurons, cell surface levels of the NMDA receptor GluN1 and the AMPA receptor GluR1 on neurites, and dendritic spines of iMNs from C9orf72 ALS/FTD patients are found to be markedly elevated compared to controls [34,52,53]. Glutamate receptors also accumulate at postsynaptic densities in these neurons [34].…”