Small RNAs isolated from these specimens, when injected into the striatum of healthy mice, induce motor symptoms characteristic for the disorder.54 In addition, loss of RNA processing enzymes in patients with another CNS disorder, pontocerebellar hypoplasia, may lead to the accumulation of specific tsRNAs and subsequent neuronal death.55 Mutations in CLP1 (cleavage factor polyribonucleotide kinase subunit 1) and TSEN components (tRNA splicing endonuclease, formed by subunits TSEN2, TSEN15, TSEN34 and TSEN54)56 underlie many forms of pontocerebellar hypoplasia. Here, TSEN54 is linked to pontocerebellar hypoplasia.