Repeat-associated non-AUG translation in neuromuscular diseases: mechanisms and therapeutic insights

Expanded short tandem repeats cause more than 50 monogenic diseases, which are mostly neuromuscular diseases. In the non-coding repeat expansion diseases, in which the expanded repeat sequence is located outside of the coding region, the toxicity of the transcribed repeat-containing RNAs had been the focus of research. However, recent studies have revealed that repeat RNAs can be translated into repeat polypeptides, despite the lack of an AUG initiation codon, by non-canonical repeat-associated non-AUG translation (RAN translation). RAN translated repeat polypeptides have actually been confirmed in patients' tissues. Moreover, various cellular and animal disease models have demonstrated the toxicity of these peptides, suggesting the pathogenic roles of RAN translation in the repeat expansion diseases. In this review, we will outline RAN translation, from the viewpoint of its molecular mechanisms to its potential as a therapeutic target for the repeat expansion diseases.