Genetic Landscape of Amyotrophic Lateral Sclerosis in Czech Patients

Abstract

Background: Genetic factors are involved in the pathogenesis of familial and sporadic amyotrophic lateral sclerosis (ALS) and constitute a link to its association with frontotemporal dementia (FTD). Gene-targeted therapies for some forms of ALS (C9orf72, SOD1) have recently gained momentum. Genetic architecture in Czech ALS patients has not been comprehensively assessed so far.

Objective: We aimed to deliver pilot data on the genetic landscape of ALS in our country.

Methods: A cohort of patients with ALS (n = 88), recruited from two Czech Neuromuscular Centers, was assessed for hexanucleotide repeat expansion (HRE) in C9orf72 and also for genetic variations in other 36 ALS-linked genes via next-generation sequencing (NGS). Nine patients (10.1%) had a familial ALS. Further, we analyzed two subgroups of sporadic patients - with concomitant FTD (n = 7) and with young-onset of the disease (n = 22).

Results: We detected the pathogenic HRE in C9orf72 in 12 patients (13.5%) and three other pathogenic variants in FUS, TARDBP and TBK1, each in one patient. Additional 7 novel and 9 rare known variants with uncertain causal significance have been detected in 15 patients. Three sporadic patients with FTD (42.9%) were harbouring a pathogenic variant (all HRE in C9orf72). Surprisingly, none of the young-onset sporadic patients harboured a pathogenic variant and we detected no pathogenic SOD1 variant in our cohort.

Conclusion: Our findings resemble those from other European populations, with the highest prevalence of HRE in the C9orf72 gene. Further, our findings suggest a possibility of a missing genetic variability among young-onset patients.

Keywords: Amyotrophic lateral sclerosis; C9orf72 repeat expansion; gene variants; mutation screening; neurogenetics; next-generation sequencing.

Fig. 1

Schematic of patient distribution and variant detection between and within two cohorts. Prospective cohort – longitudinal recruitment and sample analysis between 2015–2020 at the ERN-NMC and Department of Biology and Medical Genetics, both University Hospital Motol; Retrospective cohort – samples from patients, analyzed in a routine setting, all at the Centre of Molecular Biology and Genetics, University Hospital Brno; 1 – pathogenic mutations in other ALS-linked genes: FUS, TBK1; 2 –TARDBP; fALS – at least one first- or second degree relative with ALS and/-or FTD.