GGGGCC repeat expansion in C9orf72 compromises nucleocytoplasmic transport

• Published in: Nature (London) 2015-09, Vol.525 (7567), p.129-133
• Main Authors: Freibaum, Brian D., Lu, Yubing, Lopez-Gonzalez, Rodrigo, Kim, Nam Chul, Almeida, Sandra, Lee, Kyung-Ha, Badders, Nisha, Valentine, Marc, Miller, Bruce L., Wong, Philip C., Petrucelli, Leonard, Kim, Hong Joo, Gao, Fen-Biao, Taylor, J. Paul
• Format: Article
• Language: English
• Subjects: 13; 13/100; 13/109; 13/44; 14/19; 14/32; 49/22; 49/88; 64/24; 692/699/375/1917; 692/699/375/365; 82/1; 82/51; 82/80; 96/63; Active Transport, Cell Nucleus - genetics; Amyotrophic lateral sclerosis; Amyotrophic Lateral Sclerosis - genetics; Amyotrophic Lateral Sclerosis - pathology; Animals; Animals, Genetically Modified; Biological transport; C9orf72 Protein; Chromosomes; Cytoplasm; Dementia; Dementia disorders; DNA Repeat Expansion - genetics; Drosophila melanogaster - cytology; Drosophila melanogaster - genetics; Drosophila melanogaster - metabolism; Eye - metabolism; Female; Frontotemporal Dementia - genetics; Frontotemporal Dementia - pathology; Genetic aspects; Genetic research; HeLa Cells; Humanities and Social Sciences; Humans; Induced Pluripotent Stem Cells - cytology; Induced Pluripotent Stem Cells - metabolism; Insects; letter; Male; multidisciplinary; Muscles - cytology; Muscles - metabolism; Neurons - cytology; Neurons - metabolism; Nuclear Pore - genetics; Nuclear Pore - metabolism; Nuclear Pore - pathology; Open Reading Frames - genetics; Pathogenesis; Phenotype; Protein Biosynthesis; Proteins; Proteins - genetics; RNA - genetics; RNA - metabolism; RNA Transport - genetics; Salivary Glands - cytology; Salivary Glands - metabolism; Salivary Glands - pathology; Science; Toxicity; Trinucleotide repeats
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature14974

An unbiased genetic screen in Drosophila expressing G 4 C 2 -repeat-containing transcripts (repeats that in human cause pathogenesis in C9orf72 -related neurological disease) finds genes that encode components of the nuclear pore and nucleocytoplasmic transport machinery, and reveals that G 4 C 2 expanded-repeat-induced alterations in nucleocytoplasmic transport contribute to C9orf72 pathology and neurodegeneration. A novel mechanism of neurodegeneration The most common cause of the debilitating disease amyotrophic lateral sclerosis (ALS) is a hexanucleotide repeat expansion GGGGCC (G4C2) in the C9orf72 gene. Two studies in this issue use contrasting methods to arrive at a molecular mechanism that may cause a familial form of the disease. Using a candidate-based genetic screen in Drosophila expressing 30 G 4 C 2 repeats (Ke Zhang et al .) or an unbiased genetic screen in Drosophila expressing 8, 28 or 58 G 4 C 2 repeat-containing transcripts (Brian Freibaum et al .), the two groups sought genes that enhance or suppress the disease phenotype. Zhang et al . identify the gene encoding RanGAP, a key regulator of nucleocytoplasmic transport, and Freibaum et al . identifies genes that encode components of the nuclear pore and the nucleocytoplasmic transport machinery. Both papers show deficits in nucleocytoplasmic transport in Drosophila cells expressing G 4 C 2 repeats and in iPSC-derived neurons from ALS patients. Zhang et al . show that these defects can be rescued with antisense oligonucleotides or small molecules targeting the G-quadruplexes. The GGGGCC (G 4 C 2 ) repeat expansion in a noncoding region of C9orf72 is the most common cause of sporadic and familial forms of amyotrophic lateral sclerosis and frontotemporal dementia 1 , 2 . The basis for pathogenesis is unknown. To elucidate the consequences of G 4 C 2 repeat expansion in a tractable genetic system, we generated transgenic fly lines expressing 8, 28 or 58 G 4 C 2 -repeat-containing transcripts that do not have a translation start site (AUG) but contain an open-reading frame for green fluorescent protein to detect repeat-associated non-AUG (RAN) translation. We show that these transgenic animals display dosage-dependent, repeat-length-dependent degeneration in neuronal tissues and RAN translation of dipeptide repeat (DPR) proteins, as observed in patients with C9orf72 -related disease. This model was used in a large-scale, unbiased genetic screen, ultimately leading to the identification of 18 ge