scholarly journals Effect of G4C2-Repeat Expansions on the Motion of Lysosomes Inside Neurites.

2021 ◽  
Author(s):  
Maria Mytiliniou ◽  
Joeri A.J. Wondergem ◽  
Marleen Feliksik ◽  
Thomas Schmidt ◽  
Doris Heinrich
Keyword(s):  
Neuronal Cell ◽  
Repeat Expansion ◽  
Time Resolved ◽  
Lower Velocity ◽  
Hexanucleotide Repeat ◽  
Repeat Expansions ◽  
Local Mean ◽  
Hexanucleotide Repeat Expansion ◽  
Axonal Trafficking ◽  
Lateral Sclerosis

The G4C2 hexanucleotide repeat expansion in the c9orf72 locus is one among a plethora of mutations associated with amyotrophic lateral sclerosis. It accounts for the majority of disease cases. The exact processes underlying the pathology of this mutation remain elusive, yet recent evidence suggests a mechanism that disrupts axonal trafficking. Here, we used a neuronal cell line with and without the G4C2 repeats, and implemented time-resolved local mean squared displacement analysis to characterize the motion of lysosomes inside neurites. Neurites were either aligned along chemically patterned lines, or oriented randomly on the substrate. We confirmed that in the presence of the G4C2 repeats, lysosome motion was affected. Lysosomes had a smaller reach exhibited lower velocity, especially inside aligned neurites. At the same time they became more active with increasing length of the G4C2 repeats when the neurites were randomly oriented. The duration of diffusive and super-diffusive lysosome transport remained unaffected for both neurite geometries and for all lengths of the repeats, but the displacement and velocity was decreased on varying the repeat number and neurite geometry. Lastly, the ratio of anterograde/retrograde/neutral trajectories was affected disparately for the two neurite geometries. Our observations support the hypothesis that impaired axonal trafficking emerges in the presence of the G4C2 hexanucleotide repeat expansion.

scholarly journals Enhanced insulin signalling ameliorates C9orf72 hexanucleotide repeat expansion toxicity in Drosophila

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Magda L Atilano ◽  
Sebastian Grönke ◽  
Teresa Niccoli ◽  
Liam Kempthorne ◽  
Oliver Hahn ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Insulin Signalling ◽  
Repeat Expansion ◽  
Adult Brain ◽  
Systemic Injection ◽  
Hexanucleotide Repeat ◽  
Repeat Expansions ◽  
Hexanucleotide Repeat Expansion ◽  
Lateral Sclerosis ◽  
Dipeptide Repeat

G4C2 repeat expansions within the C9orf72 gene are the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The repeats undergo repeat-associated non-ATG translation to generate toxic dipeptide repeat proteins. Here, we show that insulin/IGF signalling is reduced in fly models of C9orf72 repeat expansion using RNA sequencing of adult brain. We further demonstrate that activation of insulin/IGF signalling can mitigate multiple neurodegenerative phenotypes in flies expressing either expanded G4C2 repeats or the toxic dipeptide repeat protein poly-GR. Levels of poly-GR are reduced when components of the insulin/IGF signalling pathway are genetically activated in the diseased flies, suggesting a mechanism of rescue. Modulating insulin signalling in mammalian cells also lowers poly-GR levels. Remarkably, systemic injection of insulin improves the survival of flies expressing G4C2 repeats. Overall, our data suggest that modulation of insulin/IGF signalling could be an effective therapeutic approach against C9orf72 ALS/FTD.

scholarly journals C9orf72-derived arginine-containing dipeptide repeats associate with axonal transport machinery and impede microtubule-based motility

2021 ◽  
Vol 7 (15) ◽  
pp. eabg3013
Author(s):  
Laura Fumagalli ◽  
Florence L. Young ◽  
Steven Boeynaems ◽  
Mathias De Decker ◽  
Arpan R. Mehta ◽  
...  
Keyword(s):  
Axonal Transport ◽  
Motor Neurons ◽  
Single Molecule ◽  
Repeat Expansion ◽  
Physical Interaction ◽  
Hexanucleotide Repeat ◽  
Hexanucleotide Repeat Expansion ◽  
Axonal Trafficking ◽  
Inhibitory Interactions

A hexanucleotide repeat expansion in the C9orf72 gene is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). How this mutation leads to these neurodegenerative diseases remains unclear. Here, we show using patient stem cell–derived motor neurons that the repeat expansion impairs microtubule-based transport, a process critical for neuronal survival. Cargo transport defects are recapitulated by treating neurons from healthy individuals with proline-arginine and glycine-arginine dipeptide repeats (DPRs) produced from the repeat expansion. Both arginine-rich DPRs similarly inhibit axonal trafficking in adult Drosophila neurons in vivo. Physical interaction studies demonstrate that arginine-rich DPRs associate with motor complexes and the unstructured tubulin tails of microtubules. Single-molecule imaging reveals that microtubule-bound arginine-rich DPRs directly impede translocation of purified dynein and kinesin-1 motor complexes. Collectively, our study implicates inhibitory interactions of arginine-rich DPRs with axonal transport machinery in C9orf72-associated ALS/FTD and thereby points to potential therapeutic strategies.

scholarly journals C9orf72 Hexanucleotide Repeat Expansion and Guam Amyotrophic Lateral Sclerosis–Parkinsonism-Dementia Complex

2013 ◽  
Vol 70 (6) ◽  
pp. 742 ◽  
Author(s):  
Beth A. Dombroski ◽  
Douglas R. Galasko ◽  
Ignacio F. Mata ◽  
Cyrus P. Zabetian ◽  
Ulla-Katrina Craig ◽  
...  
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Repeat Expansion ◽  
Hexanucleotide Repeat ◽  
Hexanucleotide Repeat Expansion ◽  
Lateral Sclerosis

scholarly journals TFEB/Mitf links impaired nuclear import to autophagolysosomal dysfunction in C9-ALS

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Kathleen M Cunningham ◽  
Kirstin Maulding ◽  
Kai Ruan ◽  
Mumine Senturk ◽  
Jonathan C Grima ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Amyotrophic Lateral Sclerosis ◽  
Nuclear Import ◽  
Transcriptional Regulator ◽  
Nucleocytoplasmic Transport ◽  
Repeat Expansion ◽  
Disease Pathogenesis ◽  
Hexanucleotide Repeat ◽  
Hexanucleotide Repeat Expansion ◽  
Lateral Sclerosis

Disrupted nucleocytoplasmic transport (NCT) has been implicated in neurodegenerative disease pathogenesis; however, the mechanisms by which disrupted NCT causes neurodegeneration remain unclear. In a Drosophila screen, we identified ref(2)P/p62, a key regulator of autophagy, as a potent suppressor of neurodegeneration caused by the GGGGCC hexanucleotide repeat expansion (G4C2 HRE) in C9orf72 that causes amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). We found that p62 is increased and forms ubiquitinated aggregates due to decreased autophagic cargo degradation. Immunofluorescence and electron microscopy of Drosophila tissues demonstrate an accumulation of lysosome-like organelles that precedes neurodegeneration. These phenotypes are partially caused by cytoplasmic mislocalization of Mitf/TFEB, a key transcriptional regulator of autophagolysosomal function. Additionally, TFEB is mislocalized and downregulated in human cells expressing GGGGCC repeats and in C9-ALS patient motor cortex. Our data suggest that the C9orf72-HRE impairs Mitf/TFEB nuclear import, thereby disrupting autophagy and exacerbating proteostasis defects in C9-ALS/FTD.

Different CSF protein profiles in amyotrophic lateral sclerosis and frontotemporal dementia with C9orf72 hexanucleotide repeat expansion

2020 ◽  
Vol 91 (5) ◽  
pp. 503-511 ◽  
Author(s):  
Peggy Barschke ◽  
Patrick Oeckl ◽  
Petra Steinacker ◽  
MHD Rami Al Shweiki ◽  
Jochen H Weishaupt ◽  
...  
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Frontotemporal Dementia ◽  
Multiple Reaction Monitoring ◽  
Repeat Expansion ◽  
Common Mutation ◽  
Hexanucleotide Repeat ◽  
Mutation Carriers ◽  
Csf Levels ◽  
Hexanucleotide Repeat Expansion ◽  
Lateral Sclerosis

ObjectivesThe hexanucleotide repeat expansion in the C9orf72 gene is the most common mutation associated with amyotrophic lateral sclerosis (C9-ALS) and frontotemporal dementia (C9-FTD). Until now, it is unknown which factors define whether C9orf72 mutation carriers develop ALS or FTD. Our aim was to identify protein biomarker candidates in the cerebrospinal fluid (CSF) which differentiate between C9-ALS and C9-FTD and might be indicative for the outcome of the mutation.MethodsWe compared the CSF proteome of 16 C9-ALS and 8 C9-FTD patients and 11 asymptomatic C9orf72 mutation carriers (CAR) by isobaric tags for relative and absolute quantitation. Eleven biomarker candidates were selected from the pool of differentially regulated proteins for further validation by multiple reaction monitoring and single-molecule array in a larger cohort (n=156).ResultsIn total, 2095 CSF proteins were identified and 236 proteins were significantly different in C9-ALS versus C9-FTD including neurofilament medium polypeptide (NEFM) and chitotriosidase-1 (CHIT1). Eight candidates were successfully validated including significantly increased ubiquitin carboxyl-terminal hydrolase isozyme L1 (UCHL1) levels in C9-ALS compared with C9-FTD and controls and decreased neuronal pentraxin receptor (NPTXR) levels in C9-FTD versus CAR.ConclusionsThis study presents a deep proteomic CSF analysis of C9-ALS versus C9-FTD patients. As a proof of concept, we observed higher NEFM and CHIT1 CSF levels in C9-ALS. In addition, we also show clear upregulation of UCHL1 in C9-ALS and downregulation of NPTXR in C9-FTD. Significant differences in UCHL1 CSF levels may explain diverging ubiquitination and autophagy processes and NPTXR levels might reflect different synapses organisation processes.

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