Antibody Therapy Targeting RAN Proteins Rescues C9 ALS/FTD Phenotypes in C9orf72 Mouse Model
Lien Nguyen1, Fabio Montrasio2, Amrutha Pattamatta1
1Center for NeuroGenetics, Department of Molecular Genetics and Microbiology, Genetics Institute, McKnight Brain Institute, Norman Fixel Institute for Neurological Diseases, University of Florida, Gainesville, FL 32610, USA.
Abstract:
The intronic C9orf72 G4C2 expansion, the most common genetic cause of ALS and FTD, produces sense- and antisense-expansion RNAs and six dipeptide repeat-associated, non-ATG (RAN) proteins, but their roles in disease are unclear. We generated high-affinity human antibodies targeting GA or GP RAN proteins. These antibodies cross the blood-brain barrier and co-localize with intracellular RAN aggregates in C9-ALS/FTD BAC mice. In cells, α-GA1 interacts with TRIM21, and α-GA1 treatment reduced GA levels, increased GA turnover, and decreased RAN toxicity and co-aggregation of proteasome and autophagy proteins to GA aggregates. In C9-BAC mice, α-GA1 reduced GA as well as GP and GR proteins, improved behavioral deficits, decreased neuroinflammation and neurodegeneration, and increased survival. Glycosylation of the Fc region of α-GA1 is important for cell entry and efficacy. These data demonstrate that RAN proteins drive C9-ALS/FTD in C9-BAC transgenic mice and establish a novel therapeutic approach for C9orf72 ALS/FTD and other RAN-protein diseases.
Insights
New antibodies targeting dipeptide repeat proteins (RANs) effectively cross the blood-brain barrier. Treatment reduced RAN proteins, improved motor function, and increased survival in mouse models of C9orf72 ALS and FTD.
Area of Science:
- Neuroscience
- Genetics
- Immunology
Background:
- The C9orf72 G4C2 expansion is the leading genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD).
- This expansion produces pathogenic repeat-associated non-ATG (RAN) proteins, but their precise roles in disease pathogenesis remain poorly understood.
Purpose of the Study:
- To investigate the therapeutic potential of targeting RAN proteins in C9orf72-associated neurodegenerative diseases.
- To develop and characterize high-affinity antibodies against specific RAN proteins.
Main Methods:
- Generation of human antibodies targeting GA and GP RAN proteins.
- Assessment of antibody blood-brain barrier penetration and co-localization with intracellular RAN aggregates in C9orf72 BAC mice.
- In vitro studies on antibody interaction with TRIM21, RAN protein levels, turnover, and toxicity.
- In vivo evaluation of antibody efficacy in C9orf72 BAC mice, including behavioral analysis, neuroinflammation, neurodegeneration, and survival.
- Investigation of the role of antibody Fc region glycosylation in cell entry and efficacy.
Main Results:
- Antibodies successfully crossed the blood-brain barrier and targeted intracellular RAN aggregates in a mouse model.
- In vitro, the α-GA1 antibody reduced GA levels, enhanced GA turnover, and mitigated RAN toxicity.
- In vivo, α-GA1 treatment significantly reduced GA, GP, and GR proteins, improved behavioral deficits, decreased neuroinflammation and neurodegeneration, and prolonged survival in C9-BAC mice.
- Fc glycosylation of α-GA1 was crucial for its cellular uptake and therapeutic effectiveness.
Conclusions:
- RAN proteins are key drivers of C9orf72-associated ALS and FTD pathology in this model.
- Targeting RAN proteins with specific antibodies represents a promising novel therapeutic strategy for C9orf72 ALS/FTD and other RAN proteinopathies.
