Background: Amyotrophic lateral sclerosis (ALS) is a multifactorial neurodegenerative disease characterised by the loss of upper and lower motor neurons. Increasing evidence indicates that neuroinflammation mediated by microglia contributes to ALS pathogenesis. This microglial activation is evident in post-mortem brain tissues and neuroimaging data from patients with ALS. However, the role of microglia in the pathogenesis and progression of amyotrophic lateral sclerosis remains unclear, partly due to the lack of a model system that is able to faithfully recapitulate the clinical pathology of ALS. To address this shortcoming, we describe an approach that generates monocyte-derived microglia-like cells that are capable of expressing molecular markers, and functional characteristics similar to in vivo human brain microglia. Methods: In this study, we have established monocyte-derived microglia-like cells from 30 sporadic patients with ALS, including 15 patients with slow disease progression, 6 with intermediate progression, and 9 with rapid progression, together with 20 non-affected healthy controls. Results: We demonstrate that patient monocyte-derived microglia-like cells recapitulate canonical pathological features of ALS including non-phosphorylated and phosphorylated-TDP-43-positive inclusions. Moreover, ALS microglia-like cells showed significantly impaired phagocytosis, altered cytokine profiles, and abnormal morphologies consistent with a neuroinflammatory phenotype. Interestingly, all ALS microglia-like cells showed abnormal phagocytosis consistent with the progression of the disease. In-depth analysis of ALS microglia-like cells from the rapid disease progression cohort revealed significantly altered cell-specific variation in phagocytic function. In addition, DNA damage and NOD-leucine rich repeat and pyrin containing protein 3 (NLRP3) inflammasome activity were also elevated in ALS patient monocyte-derived microglia-like cells, indicating a potential new pathway involved in driving disease progression. Conclusions: Taken together, our work demonstrates that the monocyte-derived microglia-like cell model recapitulates disease-specific hallmarks and characteristics that substantiate patient heterogeneity associated with disease subgroups. Thus, monocyte-derived microglia-like cells are highly applicable to monitor disease progression and can be applied as a functional readout in clinical trials for anti-neuroinflammatory agents, providing a basis for personalised treatment for patients with ALS.

Objective: Recent evidence suggests that intermediate-length polyglutamine (PolyQ) expansions in the ataxin-2 (ATXN-2) gene are a risk factor for amyotrophic lateral sclerosis (ALS). This work was undertaken with the aim to investigate the frequency of ataxin-1 (ATXN-1) and ATXN-2 PolyQ expansions in a cohort of patients with sporadic ALS (sALS) and patients with familial ALS (fALS) from southern Italy. Methods: We assessed the PolyQ lengths of ATXN-1 and ATXN-2 in 405 patients with sALS, 13 patients with fALS, and 296 unrelated controls without history of neurodegenerative disorders. Results: We found significantly higher intermediate PolyQ expansions ≥32 for ATXN-1 alleles and ≥28 for ATXN-2 alleles in the sALS cohort (ATXN-1: ALS, 7.07% vs controls, 2.38%; p = 0.0001; ATXN-2: ALS, 2.72% vs controls, 0.5%; p = 0.001). ATXN-1 CAT and ATXN-2 CAA interruptions were detected in patients with ALS only. Age at onset, site of onset, and sex were not significantly related to the ATXN-1 or ATXN-2 PolyQ repeat length expansions. Conclusions: Both ATXN-1 and ATXN-2 PolyQ intermediate expansions are independently associated with an increased risk for ALS.