RESUMEN

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative condition affecting upper and/or lower motor neurons and characterized neuropathologically by TDP-43 proteinopathy. Given its role in ALS pathobiology, it is currently under debate whether TDP-43 might represent a suitable ALS biomarker to be measured in patients' biofluids. The rs12608932 A > C single nucleotide polymorphism in the UNC13A gene is a risk factor for ALS and patients homozygous for the high-risk C allele display a higher burden of TDP-43 neuropathology than homozygotes for the low-risk A allele, although the association with TDP-43 levels in biofluids has never been evaluated. In this study, we measured serum levels of TDP-43 and neurofilament light chain (NFL) by Simoa technology in a cohort of 69 ALS patients stratified according to the UNC13A rs12608932 genotype compared to 43 neurologically healthy controls. By multiple linear regression analysis, serum TDP-43 was significantly elevated in ALS patients compared to controls, with UNC13A AA and AC, but not CC, ALS patients showing higher serum TDP-43 levels than controls. We also confirmed that serum NFL concentration was increased in ALS patients, without any correlation with the UNC13A genotype. Our results indicate that serum TDP-43 is higher in ALS patients compared to controls and that, in contrast to NFL, this increase is specifically associated with the UNC13A rs12608932 AA and AC genotypes, but not with the high-risk CC genotype. Studies in larger cohorts will be needed to confirm these findings and to elucidate the biological link between serum TDP-43 levels and UNC13A genotype.

RESUMEN

The hexanucleotide G4C2 repeat expansion (HRE) in C9ORF72 gene is the major cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), leading to both loss- and gain-of-function pathomechanisms. The wide clinical heterogeneity among C9ORF72 patients suggests potential modifying genetic and epigenetic factors. Notably, C9ORF72 HRE often co-occurs with other rare variants in ALS/FTD-associated genes, such as NEK1, which encodes for a kinase involved in multiple cell pathways, including DNA damage response and ciliogenesis. In this study, we generated induced pluripotent stem cells (iPSCs) and differentiated motoneurons (iPSC-MNs) from an ALS patient carrying both C9ORF72 HRE and a NEK1 loss-of-function mutation to investigate the biological effect of NEK1 haploinsufficiency on C9ORF72 pathology in a condition of oligogenicity. Double mutant C9ORF72/NEK1 cells showed increased pathological C9ORF72 RNA foci in iPSCs and higher DNA damage levels in iPSC-MNs compared to single mutant C9ORF72 cells, but no effect on DNA damage response. When we analysed the primary cilium, we observed a defective ciliogenesis in C9ORF72 iPSC-MNs which was not worsened by NEK1 haploinsufficiency in the double mutant iPSC-MNs. Altogether, our study shows that NEK1 haploinsufficiency influences differently DNA damage and cilia length, potentially acting as a modifier at biological level in an in vitro ALS patient-derived disease model of C9ORF72 pathology.

RESUMEN

The C9orf72 hexanucleotide repeat (HR) expansion is the main genetic cause of amyotrophic lateral sclerosis (ALS), with expansion size from 30 to >4000 units. Normal C9orf72 HR length is polymorphic (2-23 repeats) with alleles >8 units showing a low frequency in the general population. This study aimed to investigate if the normal C9orf72 HR length influences C9orf72 gene expression and acts as disease modifier in ALS patients negative for C9orf72 mutation (ALS-C9Neg). We found that the distribution of HR alleles was similar in 325 ALS-C9Neg and 303 healthy controls. Gene expression analysis in blood revealed a significant increase of total C9orf72 and V3 mRNA levels in ALS-C9Neg carrying two long alleles (L/L; ≥8 units) compared to patients homozygous for the 2-unit short allele (S/S). However, HR allele genotypes (L/L, S/L, S/S) correlated with no clinical parameters. Our data suggest that normal C9orf72 HR length does not act as disease modifier in ALS-C9Neg despite increasing gene expression.

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RESUMEN

During the last decades, our knowledge about the genetic architecture of sporadic amyotrophic lateral sclerosis (sALS) has significantly increased. However, besides the recognized genetic risk factors, also the environment is supposed to have a role in disease pathogenesis. Epigenetic modifications reflect the results of the interaction between environmental factors and genes and may play a role in the development and progression of ALS. A recent epigenome-wide association study (EWAS) in blood identified differentially methylated positions mapping to 42 genes involved in cholesterol biosynthesis and immune-related pathways. Here we performed a genome-wide DNA methylation analysis in the blood of an Italian cohort of 61 sALS patients and 61 healthy controls. Initially, a conventional genome-wide association analysis was performed, and results were subsequently integrated with the findings from the previous EWAS using a meta-analytical approach. To delve deeper into the significant outcomes, over-representation analysis (ORA) was employed. Moreover, the epigenetic signature obtained from the meta-analysis was examined to determine potential associations with chemical compounds, utilizing the Toxicogenomic Database. Expanding the scope of the epigenetic analysis, we explored both epigenetic drift and rare epivariations. Notably, we observed an elevated epigenetic drift in sALS patients compared to controls, both at a global and single gene level. Interestingly, epigenetic drift at a single gene level revealed an enrichment of genes related to the neurotrophin signaling pathway. Moreover, for the first time, we identified rare epivariations exclusively enriched in sALS cases associated with 153 genes, 88 of whom with a strong expression in cerebral areas. Overall, our study reinforces the evidence that epigenetics may contribute to the pathogenesis of ALS and that epigenetic drift may be a useful diagnostic marker. Moreover, this study suggests the potential role of epivariations in ALS.

RESUMEN

Background: The UNC13A gene is an established susceptibility locus for amyotrophic lateral sclerosis (ALS) and a determinant of shorter survival after disease onset, with up to 33.0 months difference in life expectancy for carriers of the rs12608932 risk genotype. However, its overall effect on other clinical features and ALS phenotypic variability is controversial. Methods: Genotype data of the UNC13A rs12608932 SNP (A-major allele; C-minor allele) was obtained from a cohort of 972 ALS patients. Demographic and clinical variables were collected, including cognitive and behavioral profiles, evaluated through the Edinburgh Cognitive and Behavioral ALS Screen (ECAS) - Italian version and the Frontal Behavioral Inventory (FBI); upper and lower motor neuron involvement, assessed by the Penn Upper Motor Neuron Score (PUMNS) and the Lower Motor Neuron Score (LMNS)/Medical Research Council (MRC) scores, respectively; the ALS Functional Rating Scale Revised (ALSFRS-R) score at evaluation and progression rate; age and site of onset; survival. The comparison between the three rs12608932 genotypes (AA, AC, and CC) was performed using the additive, dominant, and recessive genetic models. Results: The rs12608932 minor allele frequency was 0.31 in our ALS cohort, in comparison to 0.33-0.41 reported in other Caucasian ALS populations. Carriers of at least one minor C allele (AC + CC genotypes) had a shorter median survival than patients with the wild-type AA genotype (-11.7 months, p = 0.013), even after adjusting for age and site of onset, C9orf72 mutational status and gender. Patients harboring at least one major A allele (AA + AC genotypes) and particularly those with the wild-type AA genotype showed a significantly higher PUMNS compared to CC carriers (p = 0.015 and padj = 0.037, respectively), thus indicating a more severe upper motor neuron involvement. Our analysis did not detect significant associations with all the other clinical parameters considered. Conclusion: Overall, our findings confirm the role of UNC13A as a determinant of survival in ALS patients and show the association of this locus also with upper motor neuron involvement.