The entry includes Guanine nucleotide exchange factor C9orf72 protein, a component of the C9orf72-SMCR8 complex, which has guanine nucleotide exchange factor activity [4] and regulates autophagy [2,3]. The C9orf72 protein is proposed to be a catalytic component for the exchange of GDP to GTP and promoting autophagosome maturation by converting inactive GDP-bound RAB8A and RAB39B into their active forms [5]. Defects in the gene, C9orf72, are the cause of frontotemporal dementia and/or amyotrophic lateral sclerosis (FTDALS) which is an autosomal dominant neurodegenerative disorder. The disorder is caused by a large expansion of a GGGGCC hexa-nucleotide within the first C9orf72 intron located between the first and the second non-coding exons. The expansion leads to the loss of transcription of one of the two transcripts encoding isoform 1 and to the formation of nuclear RNA foci [1].

1: Expanded GGGGCC hexanucleotide repeat in noncoding region of C9ORF72 causes chromosome 9p-linked FTD and ALS. DeJesus-Hernandez M, Mackenzie IR, Boeve BF, Boxer AL, Baker M, Rutherford NJ, Nicholson AM, Finch NA, Flynn H, Adamson J, Kouri N, Wojtas A, Sengdy P, Hsiung GY, Karydas A, Seeley WW, Josephs KA, Coppola G, Geschwind DH, Wszolek ZK, Feldman H, Knopman DS, Petersen RC, Miller BL, Dickson DW, Boylan KB, Graff-Radford NR, Rademakers R; Neuron. 2011;72:245-256. PMID:21944778

2: Cryo-EM structure of C9ORF72-SMCR8-WDR41 reveals the role as a GAP for Rab8a and Rab11a. Tang D, Sheng J, Xu L, Zhan X, Liu J, Jiang H, Shu X, Liu X, Zhang T, Jiang L, Zhou C, Li W, Cheng W, Li Z, Wang K, Lu K, Yan C, Qi S; Proc Natl Acad Sci U S A. 2020;117:9876-9883. PMID:32303654

3: Structure of the human C9orf72-SMCR8 complex reveals a multivalent protein interaction architecture. Norpel J, Cavadini S, Schenk AD, Graff-Meyer A, Hess D, Seebacher J, Chao JA, Bhaskar V; PLoS Biol. 2021;19:e3001344. PMID:34297726

4: Multiplex image-based autophagy RNAi screening identifies SMCR8 as ULK1 kinase activity and gene expression regulator. Jung J, Nayak A, Schaeffer V, Starzetz T, Kirsch AK, Muller S, Dikic I, Mittelbronn M, Behrends C; Elife. 2017; [Epub ahead of print] PMID:28195531

5: Loss of C9ORF72 impairs autophagy and synergizes with polyQ Ataxin-2 to induce motor neuron dysfunction and cell death. Sellier C, Campanari ML, Julie Corbier C, Gaucherot A, Kolb-Cheynel I, Oulad-Abdelghani M, Ruffenach F, Page A, Ciura S, Kabashi E, Charlet-Berguerand N; EMBO J. 2016;35:1276-1297. PMID:27103069