title: Bromodomain inhibitors regulate the C9ORF72 locus in ALS.
abstract: A hexanucleotide repeat expansion residing within the C9ORF72 gene represents the most common known cause of amyotrophic lateral sclerosis (ALS) and places the disease among a growing family of repeat expansion disorders. The presence of RNA foci, repeat-associated translation products, and sequestration of RNA binding proteins suggests that toxic RNA gain-of-function contributes to pathology while C9ORF72 haploinsufficiency may be an additional pathological factor. One viable therapeutic strategy for treating expansion diseases is the use of small molecule inhibitors of epigenetic modifier proteins to reactivate expanded genetic loci. Indeed, previous studies have established proof of this principle by increasing the drug-induced expression of expanded (and abnormally heterochromatinized) FMR1, FXN and C9ORF72 genes in respective patient cells. While epigenetic modifier proteins are increasingly recognized as druggable targets, there have been few screening strategies to address this avenue of drug discovery in the context of expansion diseases. Here we utilize a semi-high-throughput gene expression based screen to identify siRNAs and small molecule inhibitors of epigenetic modifier proteins that regulate C9ORF72 RNA in patient fibroblasts, lymphocytes and reprogrammed motor neurons. We found that several bromodomain small molecule inhibitors increase the expression of C9ORF72 mRNA and pre-mRNA without affecting repressive epigenetic signatures of expanded C9ORF72 alleles. These data suggest that bromodomain inhibition increases the expression of unexpanded C9ORF72 alleles and may therefore compensate for haploinsufficiency without increasing the production of toxic RNA and protein products, thereby conferring therapeutic value.
authors.affiliation: Center for Therapeutic Innovation and Department of Psychiatry & Behavioral Sciences, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Zane
authors.initials: Z
authors.lastname: Zeier
authors.affiliation: Center for Therapeutic Innovation and Department of Psychiatry & Behavioral Sciences, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Rustam
authors.initials: R
authors.lastname: Esanov
authors.affiliation: John P. Hussman Institute for Human Genomics and The Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, USA.
authors.forename: Kinsley C
authors.initials: KC
authors.lastname: Belle
authors.affiliation: Center for Therapeutic Innovation and Department of Psychiatry & Behavioral Sciences, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Claude-Henry
authors.initials: CH
authors.lastname: Volmar
authors.affiliation: Center for Therapeutic Innovation and Department of Psychiatry & Behavioral Sciences, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Johnstone
authors.affiliation: Center for Therapeutic Innovation and Department of Psychiatry & Behavioral Sciences, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Halley
authors.affiliation: John P. Hussman Institute for Human Genomics and The Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, USA.
authors.forename: Brooke A
authors.initials: BA
authors.lastname: DeRosa
authors.affiliation: Center for Therapeutic Innovation and Department of Psychiatry & Behavioral Sciences, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Khoury
authors.affiliation: Mayo Clinic, Jacksonville FL, USA.
authors.forename: Marka
authors.initials: M
authors.lastname: van Blitterswijk
authors.affiliation: Mayo Clinic, Jacksonville FL, USA.
authors.forename: Rosa
authors.initials: R
authors.lastname: Rademakers
authors.affiliation: IntelliSynRD, Montreal, Canada.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Albert
authors.affiliation: Center for Therapeutic Innovation and Department of Psychiatry & Behavioral Sciences, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Shaun P
authors.initials: SP
authors.lastname: Brothers
authors.affiliation: Department of Neurology, University of Miami Miller School of Medicine, USA.
authors.forename: Joanne
authors.initials: J
authors.lastname: Wuu
authors.affiliation: John P. Hussman Institute for Human Genomics and The Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, USA.
authors.forename: Derek M
authors.initials: DM
authors.lastname: Dykxhoorn
authors.affiliation: Department of Neurology, University of Miami Miller School of Medicine, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Benatar
authors.affiliation: Center for Therapeutic Innovation and Department of Psychiatry & Behavioral Sciences, University of Miami Miller School of Medicine, Miami, FL 33136, USA. Electronic address: cwahlestedt@med.miami.edu.
authors.forename: Claes
authors.initials: C
authors.lastname: Wahlestedt
mesh_terms: D000255:Adenosine Triphosphate; D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics* / Q000473:pathology*; D001569:Benzodiazepines / Q000494:pharmacology; D000073885:C9orf72 Protein; D002453:Cell Cycle / Q000187:drug effects; D002461:Cell Line, Transformed; D019175:DNA Methylation / Q000187:drug effects / Q000235:genetics; D003841:Deoxycytidine / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D015723:Gene Library; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D011506:Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D014162:Transfection
chemical_list: D000073885:C9orf72 Protein; C568651:C9orf72 protein, human; D004791:Enzyme Inhibitors; D011506:Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D003841:Deoxycytidine; D001569:Benzodiazepines; C554645:molibresib; D000255:Adenosine Triphosphate
keywords: Amyotrophic lateral sclerosis; BET; Bromodomain; C9ORF72; Repeat expansion