C9orf72 and amyotrophic lateral sclerosis: To date, five genes linked to ALS have been identified to contain tandem repeat domains (C9orf72, ATXN1, ATXN2, NIPA1 and WDR7) demonstrating that VNTRs are a strong candidate for genetic risk for this disease (Sproviero et al., 2017; Iacoangeli et al., 2019; Tazelaar et al., 2019, 2020; Course et al., 2020).