Translation of the poly(GR) frame in C9ORF72-ALS/FTD is regulated by cis-elements involved in alternative splicing

•Poly(GR) frame translation in C9ORF72-ALS/FTD reporter does not depend on repeats.•Poly(GR) frame translation does not depend on CUG start codon required for poly(GA) synthesis.•Poly(GR) frame translation is regulated by 5′ cis elements involved in alternative splicing.