title: Bidirectional transcripts of the expanded C9orf72 hexanucleotide repeat are translated into aggregating dipeptide repeat proteins.
abstract: Massive GGGGCC repeat expansion in the first intron of the gene C9orf72 is the most common known cause of familial frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). Despite its intronic localization and lack of an ATG start codon, the repeat region is translated in all three reading frames into aggregating dipeptide-repeat (DPR) proteins, poly-(Gly-Ala), poly-(Gly-Pro) and poly-(Gly-Arg). We took an antibody-based approach to further validate the translation of DPR proteins. To test whether the antisense repeat RNA transcript is also translated, we raised antibodies against the predicted products, poly-(Ala-Pro) and poly-(Pro-Arg). Both antibodies stained p62-positive neuronal cytoplasmic inclusions throughout the cerebellum and hippocampus indicating that not only sense but also antisense strand repeats are translated into DPR proteins in the absence of ATG start codons. Protein products of both strands co-aggregate suggesting concurrent translation of both strands. Moreover, an antibody targeting the putative carboxyl terminus of DPR proteins can detect inclusion pathology in C9orf72 repeat expansion carriers suggesting that the non-ATG translation continues through the entire repeat and beyond. A highly sensitive monoclonal antibody against poly-(Gly-Arg), visualized abundant inclusion pathology in all cortical regions and some inclusions also in motoneurons. Together, our data show that the GGGGCC repeat is bidirectionally translated into five distinct DPR proteins that co-aggregate in the characteristic p62-positive TDP-43 negative inclusions found in FTLD/ALS cases with C9orf72 repeat expansion. Novel monoclonal antibodies against poly-(Gly-Arg) will facilitate pathological diagnosis of C9orf72 FTLD/ALS.
authors.affiliation: Adolf Butenandt Institute, Biochemistry, Ludwig-Maximilians University Munich, Schillerstr. 44, 80336, Munich, Germany.
authors.forename: Kohji
authors.initials: K
authors.lastname: Mori
authors.forename: Thomas
authors.initials: T
authors.lastname: Arzberger
authors.forename: Friedrich A
authors.initials: FA
authors.lastname: Grässer
authors.forename: Ilse
authors.initials: I
authors.lastname: Gijselinck
authors.forename: Stephanie
authors.initials: S
authors.lastname: May
authors.forename: Kristin
authors.initials: K
authors.lastname: Rentzsch
authors.forename: Shih-Ming
authors.initials: SM
authors.lastname: Weng
authors.forename: Martin H
authors.initials: MH
authors.lastname: Schludi
authors.forename: Julie
authors.initials: J
authors.lastname: van der Zee
authors.forename: Marc
authors.initials: M
authors.lastname: Cruts
authors.forename: Christine
authors.initials: C
authors.lastname: Van Broeckhoven
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Kremmer
authors.forename: Hans A
authors.initials: HA
authors.lastname: Kretzschmar
authors.forename: Christian
authors.initials: C
authors.lastname: Haass
authors.forename: Dieter
authors.initials: D
authors.lastname: Edbauer
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D000073885:C9orf72 Protein; D042622:DNA Repeat Expansion; D057174:Frontotemporal Lobar Degeneration / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D000073885:C9orf72 Protein; C568651:C9orf72 protein, human; D011506:Proteins