Repeat-Associated Non-AUG Translation of AGAGGG Repeats that Cause X-Linked Dystonia-Parkinsonism

X-linked dystonia-parkinsonism (XDP) is a neurodegenerative disorder caused by the intronic insertion of a SINE-VNTR-Alu (SVA) retrotransposon carrying an (AGAGGG)_n repeat expansion in the TAF1 gene. The molecular mechanisms by which this mutation causes neurodegeneration remain elusive.

We investigated whether (AGAGGG)_n repeats undergo repeat-associated non-AUG (RAN) translation, a pathogenic mechanism common among repeat expansion diseases.

XDP-specific RAN translation reporter plasmids were generated, transfected in HEK293 cells, and putative dipeptide repeat proteins (DPRs) were detected by Western blotting. Immunocytochemistry was performed in COS-7 cells to determine the subcellular localization of one DPR.

We detected putative DPRs from two reading frames, supporting the translation of poly-(Glu-Gly) and poly-(Arg-Glu) species. XDP RAN translation initiates within the (AGAGGG)_n sequence and poly-(Glu-Gly) DPRs formed nuclear inclusions in transfected cells.

In summary, our work provides the first in-vitro proof of principle that the XDP-linked (AGAGGG)_n repeat expansions can undergo RAN translation. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.