C9orf72 hexanucleotide repeat expansion in amyotrophic lateral sclerosis and frontotemporal dementia: Molecular pathogenesis and therapeutic implications

Abstract

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are neurodegenerative disorders that share clinical, pathological, and genetic overlap, most notably through mutations in the C9orf72 gene. Since its discovery in 2011, this mutation has emerged as a key driver of neurodegeneration through a complex interplay of toxic gain-of-function and loss-of-function mechanisms. The repeat expansion disrupts RNA metabolism, proteostasis, and nucleocytoplasmic transport, while impairing autophagy and endolysosomal trafficking due to reduced C9orf72 protein expression. Concurrently, bidirectional transcription of repeat-containing RNA generates RNA foci and dipeptide repeat proteins via repeat-associated non-AUG translation, sequestering RNA-binding proteins and inducing cellular stress. These processes converge on neuroinflammation, mitochondrial dysfunction, and TDP-43 proteinopathy-culminating in a rapidly progressive clinical phenotype with frequent cognitive involvement. This review synthesizes recent mechanistic, clinical, and therapeutic advances in C9orf72-associated ALS/FTD. It highlights the growing relevance of biomarkers such as neurofilament light chain and poly-GP, the failure of antisense oligonucleotide therapy (BIIB078) to modify TDP-43 pathology despite adequate CNS penetration, and the promise of emerging approaches, including allele-specific CRISPR-Cas9 editing, autophagy modulation, and inflammasome inhibition. Future research must integrate multi-omics datasets, patient-derived organoids, and advanced preclinical models to clarify the relative contributions of gain- and loss-of-function mechanisms. Bridging these insights with precision medicine frameworks offers the most compelling path toward mechanism-driven interventions capable of altering the natural course of C9orf72-related neurodegeneration.

Keywords

C9orf72 hexanucleotide repeat expansion / Amyotrophic lateral sclerosis / Frontotemporal dementia / Dipeptide repeat proteins / TDP-43 proteinopathy / CRISPR/Cas9 gene editing / Precision medicine / Multi-omics integration

References

[1] Lai JD, Ichida JK. C9ORF72 protein function and immune dysregulation in amyotrophic lateral sclerosis. Neurosci Lett. 2019; 713. doi: 10.1016/j.neulet.2019.134523

[2] Chiò A, Logroscino G, Hardiman O, et al. Prognostic factors in ALS: A critical review. Amyotroph Lateral Scler. 2009; 10(5-6): 310-23. doi: 10.3109/17482960802566824

[3] Barberio J, Lally C, Kupelian V, Hardiman O, Flanders WD. Estimated Familial Amyotrophic Lateral Sclerosis Proportion: A Literature Review and Meta-analysis. Neurol Genet. 2023; 9(6). doi: 10.1212/NXG.0000000000200109

[4] Gossye H, Engelborghs S, Broeckhoven C Van, Zee J van der. C9orf72 Frontotemporal Dementia and/or Amyotrophic Lateral Sclerosis. GeneReviews. 2020.

[5] Nguyen HP, Van Broeckhoven C, van der Zee J. ALS Genes in the Genomic Era and their Implications for FTD. Trends Genet. 2018; 34(6): 404-23. doi: 10.1016/j.tig.2018.03.001

[6] Majounie E, Renton AE, Mok K, et al. Frequency of the C9orf72 hexanucleotide repeat expansion in patients with amyotrophic lateral sclerosis and frontotemporal dementia: A cross-sectional study. Lancet Neurol. 2012; 11(4): 323-330. doi: 10.1016/S1474-4422(12)70043-1

[7] Cooper-Knock J, Kirby J, Highley R, Shaw PJ. The Spectrum of C9orf72-mediated Neurodegeneration and Amyotrophic Lateral Sclerosis. Neurotherapeutics. 2015; 12(2): 326-339. doi: 10.1007/s13311-015-0342-1

[8] Balendra R, Isaacs AM. C9orf72-mediated ALS and FTD: multiple pathways to disease. Nat Rev Neurol. 2018; 14(9): 544. doi: 10.1038/s41582-018-0047-2

[9] Glasmacher SA, Wong C, Pearson IE, Pal S. Survival and Prognostic Factors in C9orf72 Repeat Expansion Carriers: A Systematic Review and Meta-analysis. JAMA Neurol . 2019; 77(3): 367. doi: 10.1001/jamaneurol.2019.3924

[10] Wolfson C, Gauvin DE, Ishola F, Oskoui M. Global Prevalence and Incidence of Amyotrophic Lateral Sclerosis: A Systematic Review. Neurology. 2023; 101(6): E613-23. doi: 10.1212/WNL.0000000000207474

[11] Marin B, Boumédiene F, Logroscino G, et al. Variation in worldwide incidence of amyotrophic lateral sclerosis: a meta-analysis. Int J Epidemiol. 2016; 46(1): 57. doi: 10.1093/ije/dyw061

[12] Xu L, Liu T, Liu L, et al. Global variation in prevalence and incidence of amyotrophic lateral sclerosis: a systematic review and meta-analysis. J Neurol. 2019; 267(4): 944-953. doi: 10.1007/s00415-019-09652-y

[13] Vasta R, Callegaro S, Canosa A, et al. Amyotrophic Lateral Sclerosis Prevalence Projection in 2040: A Less Rare Disease. Ann Clin Transl Neurol. 2025; 13(2): 379. doi: 10.1002/acn3.70226

[14] Mehta P, Raymond J, Nair T, et al. Amyotrophic lateral sclerosis estimated prevalence cases from 2022 to 2030, data from the national ALS Registry. Amyotroph Lateral Scler Frontotemporal Degener. 2025; 26(3-4): 290-295. doi: 10.1080/21678421.2024.2447919

[15] Douglas AGL, Thompson AG, Turner MR, Talbot K. Personalised penetrance estimation for C9orf72-related amyotrophic lateral sclerosis and frontotemporal dementia. BMJ Neurol Open. 2024; 6(2). doi: 10.1136/bmjno-2024-000792

[16] Van Der Ende EL, Jackson JL, White A, Seelaar H, Van Blitterswijk M, Van Swieten JC. Unravelling the clinical spectrum and the role of repeat length in C9ORF72 repeat expansions. J Neurol Neurosurg Psychiatry. 2021; 92(5): 502-509. doi: 10.1136/jnnp-2020-325377

[17] Bram E, Javanmardi K, Nicholson K, et al. Comprehensive genotyping of the C9orf72 hexanucleotide repeat region in 2095 ALS samples from the NINDS collection using a two-mode, long-read PCR assay. Amyotroph Lateral Scler Frontotemporal Degener. 2018; 20(1-2): 107-114. doi: 10.1080/21678421.2018.1522353

[18] Yokoyama JS, Rosen HJ. Neuroimaging features of C9ORF72 expansion. Alzheimers Res Ther. 2012; 4(6). doi: 10.1186/alzrt148

[19] Meisler MH, Grant AE, Jones JM, et al. C9ORF72 expansion in a family with bipolar disorder. Bipolar Disord. 2013; 15(3): 326-332. doi: 10.1111/bdi.12063

[20] Nagy ZF, Pál M, Engelhardt JI, Molnár MJ, Klivényi P, Széll M. Beyond C9orf72: repeat expansions and copy number variations as risk factors of amyotrophic lateral sclerosis across various populations. BMC Med Genom. 2024; 17(1). doi: 10.1186/s12920-024-01807-9

[21] Benatar M, Staffaroni AM, Wuu J, et al. Design considerations for C9orf72 disease prevention trials. Brain. 2025. doi: 10.1093/brain/awaf290

[22] Kaivorinne AL, Bode MK, Paavola L, et al. Clinical Characteristics of C9ORF72-Linked Frontotemporal Lobar Degeneration. Dement Geriatr Cogn Dis Extra. 2013; 3(1): 251-262. doi: 10.1159/000351859

[23] Poeta L, Drongitis D, Verrillo L, Miano MG. DNA Hypermethylation and Unstable Repeat Diseases: A Paradigm of Transcriptional Silencing to Decipher the Basis of Pathogenic Mechanisms. Genes. 2020; 11(6): 1-18. doi: 10.3390/genes11060684

[24] Querin G, Biferi MG, Pradat PF. Biomarkers for C9orf7-ALS in Symptomatic and Pre-symptomatic Patients: State-of-the-art in the New Era of Clinical Trials. J Neuromuscul Dis. 2021; 9(1): 25-37. doi: 10.3233/JND-210754

[25] Gijselinck I, Van Langenhove T, van der Zee J, et al. A C9orf72 promoter repeat expansion in a Flanders-Belgian cohort with disorders of the frontotemporal lobar degeneration-amyotrophic lateral sclerosis spectrum: A gene identification study. Lancet Neurol. 2012; 11(1): 54-65. doi: 10.1016/S1474-4422(11)70261-7

[26] Ogaki K, Li Y, Atsuta N, et al. Analysis of C9orf72 repeat expansion in 563 Japanese patients with amyotrophic lateral sclerosis. Neurobiol Aging. 2012; 33(10): 2527.e11-2527.e16. doi: 10.1016/j.neurobiolaging.2012.05.011

[27] Liu X, He J, Gao FB, Gitler AD, Fan D. The epidemiology and genetics of Amyotrophic lateral sclerosis in China. Brain Res. 2018; 1693(8): 121-126. doi: 10.1016/j.brainres.2018.02.035

[28] Jiao B, Tang B, Liu X, et al. Identification of C9orf72 repeat expansions in patients with amyotrophic lateral sclerosis and frontotemporal dementia in mainland China. Neurobiol Aging. 2014; 35(4): 936.e19-936.e22. doi: 10.1016/j.neurobiolaging.2013.10.001

[29] Tsai CP, Soong BW, Tu PH, et al. A hexanucleotide repeat expansion in C9ORF72 causes familial and sporadic ALS in Taiwan. Neurobiol Aging. 2012; 33(9): 2232.e11-2232.e18. doi: 10.1016/j.neurobiolaging.2012.05.002

[30] Rainero I, Rubino E, Michelerio A, D’Agata F, Gentile S, Pinessi L. Recent advances in the molecular genetics of frontotemporal lobar degeneration. Funct Neurol. 20171; 32(1): 7-16. doi: 10.11138/FNeur/2017.32.1.007

[31] Ng ASL, Tan EK. Intermediate C9orf72 alleles in neurological disorders: does size really matter? J Med Genet. 2017; 54(9): 591-597. doi: 10.1136/jmedgenet-2017-104752

[32] Shu L, Sun Q, Zhang Y, et al. The Association between C9orf72 Repeats and Risk of Alzheimer’s Disease and Amyotrophic Lateral Sclerosis: A Meta-Analysis. Parkinsons Dis. 2016; 2016. doi: 10.1155/2016/5731734

[33] Ibañez K, Jadhav B, Zanovello M, et al. Increased frequency of repeat expansion mutations across different populations. medRxiv. 2023. doi: 10.1101/2023.07.03.23292162

[34] Duran-Aniotz C, Orellana P, Leon Rodriguez T, et al. Systematic Review: Genetic, Neuroimaging, and Fluids Biomarkers for Frontotemporal Dementia Across Latin America Countries. Front Neurol. 2021; 12. doi: 10.3389/fneur.2021.663407

[35] Sironi F, Parlanti P, Margotta C, et al. C9ORF72 Is Pivotal to Maintain a Proper Protein Homeostasis in Mouse Skeletal Muscle. Cells 2025; 14(22). doi: 10.3390/cells14221765

[36] Ke PY. Molecular Mechanism of Autophagosome-Lysosome Fusion in Mammalian Cells. Cells. 2024; 13(6): 500. doi: 10.3390/cells13060500

[37] Farg MA, Sundaramoorthy V, Sultana JM, et al. C9ORF72, implicated in amytrophic lateral sclerosis and frontotemporal dementia, regulates endosomal trafficking. Hum Mol Genet. 2014; 23(13): 3579. doi: 10.1093/hmg/ddu068

[38] Lall D, Lorenzini I, Mota TA, et al. C9orf72 deficiency promotes microglial-mediated synaptic loss in aging and amyloid accumulation. Neuron. 2021; 109(14): 2275-2291.e8. doi: 10.1016/j.neuron.2021.05.020

[39] Chong ZZ, Souayah N. Targeting Gene C9orf72 Pathogenesis for Amyotrophic Lateral Sclerosis. Int J Mol Sci. 2025; 26(9). doi: 10.3390/ijms26094276

[40] Baumgartner D, Mušová Z, Zídková J, et al. Genetic Landscape of Amyotrophic Lateral Sclerosis in Czech Patients. J Neuromuscul Dis. 2024; 11(5): 1035. doi: 10.3233/JND-230236

[41] Iacoangeli A, Al Khleifat A, Jones AR, et al. C9orf72 intermediate expansions of 24-30 repeats are associated with ALS. Acta Neuropathol Commun. 2019; 7(1): 115. doi: 10.1186/s40478-019-0724-4

[42] Van Blitterswijk M, Van Es MA, Hennekam EAM, et al. Evidence for an oligogenic basis of amyotrophic lateral sclerosis. Hum Mol Genet. 2012; 21(17): 3776-3784. doi: 10.1093/hmg/dds199

[43] Kaivola K, Kiviharju A, Jansson L, Rantalainen V, Eriksson JG, Strandberg TE, et al. C9orf72 hexanucleotide repeat length in older population: normal variation and effects on cognition. Neurobiol Aging. 2019; 84: 242.e7-242.e12. doi: 10.1016/j.neurobiolaging.2019.02.026

[44] Wen X, Westergard T, Pasinelli P, Trotti D. Pathogenic determinants and mechanisms of ALS/FTD linked to hexanucleotide repeat expansions in the C9orf72 gene. Neurosci Lett. 2017; 636: 16-26. doi: 10.1016/j.neulet.2016.09.007

[45] Sellier C, Corcia P, Vourc’h P, Dupuis L. C9ORF72 hexanucleotide repeat expansion: From ALS and FTD to a broader pathogenic role? Rev Neurol . 2024; 180(5): 417-428. doi: 10.1016/j.neurol.2024.03.008

[46] Jiang J, Ravits J. Pathogenic Mechanisms and Therapy Development for C9orf72 Amyotrophic Lateral Sclerosis/Frontotemporal Dementia. Neurotherapeutics. 2019; 16(4): 1115-1132. doi: 10.1007/s13311-019-00797-2

[47] Belzil VV., Bauer PO, Prudencio M, et al. Reduced C9orf72 gene expression in c9FTD/ALS is caused by histone trimethylation, an epigenetic event detectable in blood. Acta Neuropathol. 2013; 126(6): 895-905. doi: 10.1007/s00401-013-1199-1

[48] Webster CP, Smith EF, Bauer CS, et al. The C9orf72 protein interacts with Rab1a and the ULK1 complex to regulate initiation of autophagy. EMBO J. 2016; 35(15): 1656-1676. doi: 10.15252/embj.201694401

[49] Ramesh N, Daley EL, Gleixner AM, et al. RNA dependent suppression of C9orf72 ALS/FTD associated neurodegeneration by Matrin-3. Acta Neuropathol Commun. 2020; 8(1): 177. doi: 10.1186/s40478-020-01060-y

[50] Rainaldi J, Mali P, Nourreddine S. Emerging clinical applications of ADAR based RNA editing. Stem Cells Transl Med. 2025; 14(5). doi: 10.1093/stcltm/szaf016

[51] Jafarinia H, van der Giessen E, Onck PR. Phase Separation of Toxic Dipeptide Repeat Proteins Related to C9orf72 ALS/FTD. Biophys J. 2020; 119(4): 843-851. doi: 10.1016/j.bpj.2020.07.005

[52] Kanekura K, Harada Y, Fujimoto M, et al. Characterization of membrane penetration and cytotoxicity of C9orf72-encoding arginine-rich dipeptides. Sci Rep. 2018; 8: 1. doi: 10.1038/s41598-018-31096-z

[53] Cook CN, Wu Y, Odeh HM, et al. C9orf72 poly(GR) aggregation induces TDP-43 proteinopathy. Sci Transl Med. 2020; 12(559). doi: 10.1126/SCITRANSLMED.ABB3774

[54] Yang M, Chen L, Swaminathan K, et al. A C9ORF72/SMCR8-containing complex regulates ULK1 and plays a dual role in autophagy. Sci Adv. 2016; 2(9). doi: 10.1126/sciadv.1601167

[55] Chiarini A, Gui L, Viviani C, Armato U, Dal Prà I. NLRP3 Inflammasome’s Activation in Acute and Chronic Brain Diseases-An Update on Pathogenetic Mechanisms and Therapeutic Perspectives with Respect to Other Inflammasomes. Biomedicines. 2023; 11(4). doi: 10.3390/biomedicines11040999

[56] Vatsavayai SC, Nana AL, Yokoyama JS, Seeley WW. C9orf72-FTD/ALS pathogenesis: evidence from human neuropathological studies. Acta Neuropathol. 2019; 137(1). doi: 10.1007/s00401-018-1921-0

[57] Tondo G, Iaccarino L, Cerami C, et al. 11C-PK11195 PET-based molecular study of microglia activation in SOD1 amyotrophic lateral sclerosis. Ann Clin Transl Neurol. 2020; 7(9): 1513-1523. doi: 10.1002/acn3.51112

[58] Wilson KM, Katona E, Glaria I, et al. Development of a sensitive trial-ready poly(GP) CSF biomarker assay for C9orf72-associated frontotemporal dementia and amyotrophic lateral sclerosis. J Neurol Neurosurg Psychiatry. 2022; 93(7): 761-71. doi: 10.1136/jnnp-2021-328710

[59] Benatar M, Macklin EA, Malaspina A, et al. Prognostic clinical and biological markers for amyotrophic lateral sclerosis disease progression: validation and implications for clinical trial design and analysis. EBioMedicine. 2024; 108. doi: 10.1016/j.ebiom.2024.105323

[60] Gendron TF, Daughrity LM, Heckman MG, et al. Phosphorylated neurofilament heavy chain: A biomarker of survival for C9ORF72-associated amyotrophic lateral sclerosis. Ann Neurol. 2017; 82(1): 139-146. doi: 10.1002/ana.24980

[61] Meeter LHH, Gendron TF, Sias AC, et al. Poly(GP), neurofilament and grey matter deficits in C9orf72 expansion carriers. Ann Clin Transl Neurol. 2018; 5(5): 583-97. doi: 10.1002/acn3.559

[62] van den Berg LH, Rothstein JD, Shaw PJ, et al. Safety, tolerability, and pharmacokinetics of antisense oligonucleotide BIIB078 in adults with C9orf72-associated amyotrophic lateral sclerosis: a phase 1, randomised, double blinded, placebo-controlled, multiple ascending dose study. Lancet Neurol. 2024; 23(9): 901-912. doi: 10.1016/S1474-4422(24)00216-3

[63] Rothstein JD, Baskerville V, Rapuri S, et al. G2C4 targeting antisense oligonucleotides potently mitigate TDP-43 dysfunction in human C9orf72 ALS/FTD induced pluripotent stem cell derived neurons. Acta Neuropathol. 2023; 147(1). doi: 10.1007/s00401-023-02652-3

[64] Balendra R, Moens TG, Isaacs AM. Specific biomarkers for C9orf72 FTD/ALS could expedite the journey towards effective therapies. EMBO Mol Med. 2017; 9(7): 853-855. doi: 10.15252/emmm.201707848

[65] Mori K, Gotoh S, Uozumi R, Miyamoto T, Akamine S, Kawabe Y, et al. RNA Dysmetabolism and Repeat-Associated Non-AUG Translation in Frontotemporal Lobar Degeneration/Amyotrophic Lateral Sclerosis due to C9orf72 Hexanucleotide Repeat Expansion. JMA J. 2022; 6(1). doi: 10.31662/jmaj.2022-0160

[66] Irwin KE, Sheth U, Wong PC, Gendron TF. Fluid biomarkers for amyotrophic lateral sclerosis: a review. Mol Neurodegener. 2024; 19(1). doi: 10.1186/s13024-023-00685-6

[67] Lehmer C, Oeckl P, Weishaupt JH, et al. Poly‐GP in cerebrospinal fluid links C9orf72‐associated dipeptide repeat expression to the asymptomatic phase of ALS/FTD. EMBO Mol Med. 2017; 9(7): 859-868. doi: 10.15252/emmm.201607486

[68] Verber NS, Shepheard SR, Sassani M, et al. Biomarkers in motor neuron disease: A state of the art review. Front Neurol. 2019; 10(APR). doi: 10.3389/fneur.2019.00291

[69] Vidovic M, Müschen LH, Brakemeier S, Machetanz G, Naumann M, Castro-Gomez S. Current State and Future Directions in the Diagnosis of Amyotrophic Lateral Sclerosis. Cells. 2023; 12(5). doi: 10.3390/cells12050736

[70] Krishnan G, Raitcheva D, Bartlett D, et al. Poly(GR) and poly(GA) in cerebrospinal fluid as potential biomarkers for C9ORF72-ALS/FTD. Nat Commun. 2022; 13(1). doi: 10.1038/s41467-022-30387-4

[71] Salomonsson SE, Maltos AM, Gill K, et al. Validated assays for the quantification of C9orf72 human pathology. Sci Rep. 2024; 14(1). doi: 10.1038/s41598-023-50667-3

[72] Puentes F, Lombardi V, Lu CH, et al. Immune reactivity to neurofilaments and dipeptide repeats in ALS progression. bioRxiv. 2020. doi: 10.1101/2020.02.25.965236

[73] Verde F, Otto M, Silani V. Neurofilament Light Chain as Biomarker for Amyotrophic Lateral Sclerosis and Frontotemporal Dementia. Front Neurosci. 2021; 15. doi: 10.3389/fnins.2021.679199

[74] Verde F, Steinacker P, Weishaupt JH, et al. Neurofilament light chain in serum for the diagnosis of amyotrophic lateral sclerosis. J Neurol Neurosurg Psychiatry. 2018; 90(2): 157-164. doi: 10.1136/jnnp-2018-318704

[75] Gaiottino J, Norgren N, Dobson R, et al. Increased Neurofilament Light Chain Blood Levels in Neurodegenerative Neurological Diseases. PLoS ONE. 2013; 8(9). doi: 10.1371/journal.pone.0075091

[76] Morello G, Salomone S, D’Agata V, Conforti FL, Cavallaro S. From Multi-Omics Approaches to Precision Medicine in Amyotrophic Lateral Sclerosis. Front Neurosci. 2020; 14. doi: 10.3389/fnins.2020.577755

[77] Behzadi A, Pujol-Calderón F, Tjust AE, et al. Neurofilaments can differentiate ALS subgroups and ALS from common diagnostic mimics. Sci Rep. 2021; 11(1). doi: 10.1038/s41598-021-01499-6

[78] Sattler R, Traynor BJ, Robertson J, et al. Roadmap for C9ORF72 in Frontotemporal Dementia and Amyotrophic Lateral Sclerosis: Report on the C9ORF72 FTD/ALS Summit. Neurol Ther. 2023; 12(6): 1821-1843. doi: 10.1007/s40120-023-00548-8

[79] González-Sánchez M, Ramírez-Expósito MJ, Martínez-Martos JM. Pathophysiology, Clinical Heterogeneity, and Therapeutic Advances in Amyotrophic Lateral Sclerosis: A Comprehensive Review of Molecular Mechanisms, Diagnostic Challenges, and Multidisciplinary Management Strategies. Life. 2025; 15(4). doi: 10.3390/life15040647

[80] Floeter MK, Gendron TF. Biomarkers for Amyotrophic Lateral Sclerosis and Frontotemporal Dementia Associated With Hexanucleotide Expansion Mutations in C9orf72. Front Neurol . 2018; 9. doi: 10.3389/fneur.2018.01063

[81] Benatar M, Wuu J, Andersen PM, Lombardi V, Malaspina A. Neurofilament light: A candidate biomarker of presymptomatic amyotrophic lateral sclerosis and phenoconversion. Ann Neurol. 2018; 84(1): 130-139. doi: 10.1002/ana.25276

[82] Bjornevik K, O’Reilly EJ, Molsberry S, et al. Prediagnostic Neurofilament Light Chain Levels in Amyotrophic Lateral Sclerosis. Neurology. 2021; 97(15): E1466-E1474. doi: 10.1212/WNL.0000000000012632

[83] Șerban M, Toader C, Covache-Busuioc RA. Blueprint of Collapse: Precision Biomarkers, Molecular Cascades, and the Engineered Decline of Fast-Progressing ALS. Int J Mol Sci. 2025; 26(16). doi: 10.3390/ijms26168072

[84] Mondesert E, Delaby C, De La Cruz E, et al. Comparative Performances of 4 Serum NfL Assays, pTau181, and GFAP in Patients With Amyotrophic Lateral Sclerosis. Neurology. 2025; 104(6). doi: 10.1212/WNL.0000000000213400

[85] Benatar M, Zhang L, Wang L, et al. Validation of serum neurofilaments as prognostic and potential pharmacodynamic biomarkers for ALS. Neurology. 2020; 95(1): 59-69. doi: 10.1212/WNL.0000000000009559

[86] Irwin KE, Jasin P, Braunstein KE, et al. A fluid biomarker reveals loss of TDP-43 splicing repression in presymptomatic ALS-FTD. Nat Med. 2024; 30(2): 382-393. doi: 10.1038/s41591-023-02788-5

[87] Prudencio M, Humphrey J, Pickles S, et al. Truncated stathmin-2 is a marker of TDP-43 pathology in frontotemporal dementia. J Clin Investig. 2020; 130(11): 6080-6092. doi: 10.1172/JCI139741

[88] Klim JR, Williams LA, Limone F, et al. Als implicated protein tdp-43 sustains levels of stmn2 a mediator of motor neuron growth and repair. Nat Neurosci. 2019; 22(2): 167-179. doi: 10.1038/s41593-018-0300-4

[89] Melamed Z, López-Erauskin J, Baughn MW, et al. Premature polyadenylation-mediated loss of stathmin-2 is a hallmark of TDP-43-dependent neurodegeneration. Nat Neurosci. 2018; 22(2): 180-190. doi: 10.1038/s41593-018-0293-z

[90] Brown AL, Wilkins OG, Keuss MJ, et al. TDP-43 loss and ALS-risk SNPs drive mis-splicing and depletion of UNC13A. Nature. 2022; 603(7899): 131-137. doi: 10.1038/s41586-022-04436-3

[91] Ma XR, Prudencio M, Koike Y, et al. TDP-43 represses cryptic exon inclusion in the FTD-ALS gene UNC13A. Nature. 2021; 603(7899): 124-130. doi: 10.1038/s41586-022-04424-7

[92] Anjum F, Bakhuraysah M, Alsharif A, Mohammad T, Shamsi A, Hassan MI. Emerging biomarkers in amyotrophic lateral sclerosis: from pathogenesis to clinical applications. Front Mol Biosci. 2025; 12. doi: 10.3389/fmolb.2025.1608853

[93] Reilly L, Seddighi S, Singleton AB, Cookson MR, Ward ME, Qi YA. Variant biomarker discovery using mass spectrometry-based proteogenomics. Front Aging. 2023; 4. doi: 10.3389/fragi.2023.1191993

[94] Chatterjee M, Özdemir S, Fritz C, et al. Plasma extracellular vesicle tau and TDP-43 as diagnostic biomarkers in FTD and ALS. Nat Med. 2024; 30(6): 1771-1783. doi: 10.1038/s41591-024-02937-4

[95] Bonham LW, Geier EG, Sirkis DW, et al. Radiogenomics of C9orf72 Expansion Carriers Reveals Global Transposable Element Derepression and Enables Prediction of Thalamic Atrophy and Clinical Impairment. J Neurosci. 2022; 43(2): 333-345. doi: 10.1523/JNEUROSCI.1448-22.2022

[96] Viodé A, Fournier C, Camuzat A, et al. New Antibody-Free Mass Spectrometry-Based Quantification Reveals That C9ORF72 Long Protein Isoform Is Reduced in the Frontal Cortex of Hexanucleotide-Repeat Expansion Carriers. Front Neurosci. 2018; 12(AUG). doi: 10.3389/fnins.2018.00589

[97] Juengling FD, Wuest F, Kalra S, et al. Simultaneous PET/MRI: The future gold standard for characterizing motor neuron disease-A clinico-radiological and neuroscientific perspective. Front Neurol. 2022; 13. doi: 10.3389/fneur.2022.890425

[98] Bond S, Saxena S, Sierra-Delgado JA. Microglia in ALS: Insights into Mechanisms and Therapeutic Potential. Cells. 2025; 14(6). doi: 10.3390/cells14060421

[99] Ghasemi M, Keyhanian K, Douthwright C. Glial Cell Dysfunction in C9orf72-Related Amyotrophic Lateral Sclerosis and Frontotemporal Dementia. Cells. 2021; 10(2): 1-25. doi: 10.3390/cells10020249

[100] Gille B, De Schaepdryver M, Goossens J, et al. Serum neurofilament light chain levels as a marker of upper motor neuron degeneration in patients with Amyotrophic Lateral Sclerosis. Neuropathol Appl Neurobiol. 2018; 45(3): 291-304. doi: 10.1111/nan.12511

[101] Ooi S, Patel SK, Eratne D, et al. Plasma Neurofilament Light Chain and Clinical Diagnosis in Frontotemporal Dementia Syndromes. J. Alzheimer’s Dis. 2022; 89(4): 1221-1231. doi: 10.3233/JAD-220272

[102] Gao W, Jing S, He C, et al. Advancements in Neurodegenerative Diseases: Pathogenesis and Novel Neurorestorative Interventions. J Neurorestoratology 2024; 13(2). doi: 10.1016/j.jnrt.2024.100176

[103] Saloner R, Staffaroni A, Dammer E, et al. Large-scale network analysis of the cerebrospinal fluid proteome identifies molecular signatures of frontotemporal lobar degeneration. Res Sq. 2024. doi: 10.21203/rs.3.rs-4103685/v1

[104] Sha SJ, Boxer A. Treatment implications of C9ORF72. Alzheimers Res Ther . 2012; 4. doi: 10.1186/alzrt149

[105] Goutman SA, Hardiman O, Al-Chalabi A, et al. Emerging insights into the complex genetics and pathophysiology of amyotrophic lateral sclerosis. Lancet Neurol. 2022; 21(5): 465-479. doi: 10.1016/S1474-4422(21)00414-2

[106] Beckers J, Tharkeshwar AK, Fumagalli L, et al. A toxic gain-of-function mechanism in C9orf72 ALS impairs the autophagy-lysosome pathway in neurons. Acta Neuropathol Commun. 2023; 11(1). doi: 10.1186/s40478-023-01648-0

[107] Shi Y, Lin S, Staats KA, et al. Haploinsufficiency leads to neurodegeneration in C9ORF72 ALS/FTD human induced motor neurons. Nat Med. 2018; 24(3): 313-325. doi: 10.1038/nm.4490

[108] Bono N, Fruzzetti F, Farinazzo G, Candiani G, Marcuzzo S. Perspectives in Amyotrophic Lateral Sclerosis: Biomarkers, Omics, and Gene Therapy Informing Disease and Treatment. Int J Mol Sci. 2025; 26(12). doi: 10.3390/ijms26125671

[109] Jiang Z, Zhang H, Gao Y, Sun Y. Multi-omics strategies for biomarker discovery and application in personalized oncology. Mol Biomed. 2025; 6(1). doi: 10.1186/s43556-025-00340-0

[110] Gao Q, Wu Y, Mao Y, Chen X, Geng Z, Su J. Organoids: A new frontier in precision medicine and engineering. Precis Med Eng. 2025; 2(4): 100049. doi: 10.1016/j.preme.2025.100049

[111] Abbadessa G, Bombaci A, Gajofatto A, Bonavita S. Editorial: Bridging the gap between basic neurosciences and clinical neuroimmunology. Front Neurosci. 2023; 17. doi: 10.3389/fnins.2023.1285678