transcript repeat that results in long dipeptide repeats. This is termed RAN (Repeat Associated Non-ATG) translation initiation. Aberrant Pur-alpha association with its RNA sequence segment may also be a feature of ALS types that do not involve C9ORF72 expansion. Addition of Pur-alpha suppresses neurodegeneration in mouse neuronal cells and in Drosophila expressing the C9ORF72 HRE. Pur-alpha also reverses neuronal changes caused by defects in the gene, FUS, which can lead to ALS. The mechanism of action of Pur-alpha in ALS is not known. There is presently no evidence that the PURA sequence itself is mutated in the C9ORF72 form of ALS. Rather, it is a regulatory nucleic acid sequence to which Pur-alpha binds that is altered. Notes References Further reading