Twenty years of molecular analyses in amyotrophic lateral sclerosis: genetic landscape of Italian patients

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with a heterogeneous genetic back-ground. Because mutation analysis by Sanger sequencing is costly and time-consuming, in recent years,next-generation sequencing (NGS) techniques have become of much interest. This study analyses theresults of 20 years of molecular analyses in ALS patients in our laboratory using traditional methods andNGS. Almost 300 ALS patients underwent genetic analysis with Sanger sequencing of 7 genes or with anNGS panel of 23 genes. TheC9orf72expansion was tested by fragment size analysis. Sanger sequencingrevealed mutations in 23.8% of familial and 3.8% of sporadic cases, whereas NGS detected potentiallypathogenic variants in 45.5% of familial and 5.4% of sporadic cases and variants of unknown significancein 30.3% of patients. In 11.8% of patients, potentially causative mutations were found in 2 or more ALSgenes. Compared to traditional methods, NGS is more effective in revealing possibly causal variants, butcounseling patients becomes more complicated due to frequent variants of unknown significance andpotentially oligogenic cases