PIWIL4 and Parkinson disease: Owing to recent reports of potential involvement of piRNAs in the etiology of different neurological diseases, such as Rett syndrome, Alzheimer’s disease (AD), Parkinson’s disease (PD) [3], and brain aging [4], we focused on piRNA dysregulation in sALS samples to identify targets of those piRNAs and to determine whether PIWI protein/piRNAs might contribute to ALS pathology.