Unraveling the genetic landscape of ALS in Greece: identification of known and novel causative variants in a 353-patient cohort.

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is an adult-onset, progressive, fatal neurodegenerative disorder characterized by progressive loss of motor neurons. Approximately 15% of individuals diagnosed with ALS have a known genetic variant that contributes to disease. Herein, we present clinical and genetic data of a large Greek ALS cohort.

PATIENTS AND

METHODS

The cohort consisted of 353 Greek consecutive index patients with ALS, including 16 patients with related motor neuron disease (MND) subtypes (nine with PLS, four with PBP, and three with PMA). Next generation sequencing raw data (obtained from the NYGC ALS Consortium) were further analyzed and used to screen for causative variants in known implicated genes. Repeat expansions in C9ORF72 and ATXN2 were investigated using ExpansionHunter software, repeat-primed PCR and fragment analysis.

RESULTS

Pathogenic repeat expansions in C9ORF72 were detected in 41 patients (11.6%). In addition, 30 patients (8.5%) carried a causative variant in one of the genes studied. Known causative variants were identified in 27 cases (nine in SQSTM1, seven in TARDBP, five in SOD1, three in NEK1 and one each in SETX, VCP, FUS), whereas novel causative variants were identified in three cases (SOD1, FIG4, TBK1). In total, 71 cases received a molecular genetic diagnosis (20.1%). Additionally, seven cases (2.0%) carried an intermediate repeat expansion (30-33 CAG) in ATXN2.

CONCLUSION

Our results reveal the distinct genetic profile of Greek ALS patients. These findings will have an impact on genetic counseling, the design of diagnostic gene panels for the Greek population and on genotype-specific therapeutic interventions. Understanding the genetic causes of ALS in different populations is becoming increasingly important, especially with the advent of personalized medicine.