Abnormal nucleotide insertions of C9orf72, which forms a complex with Smith–Magenis syndrome chromosomal region candidate gene 8 (SMCR8) protein and WD repeat-containing protein 41 (WDR41) protein, are associated with an autosomal-dominant neurodegenerative frontotemporal dementia and/or amyotrophic lateral sclerosis type 1 (FTDALS1). Here, WDR41 is linked to frontotemporal dementia and/or amyotrophic lateral sclerosis 1.