title: The RNA-binding motif 45 (RBM45) protein accumulates in inclusion bodies in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with TDP-43 inclusions (FTLD-TDP) patients.
abstract: RNA-binding protein pathology now represents one of the best characterized pathologic features of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration patients with TDP-43 or FUS pathology (FTLD-TDP and FTLD-FUS). Using liquid chromatography tandem mass spectrometry, we identified altered levels of the RNA-binding motif 45 (RBM45) protein in the cerebrospinal fluid (CSF) of ALS patients. This protein contains sequence similarities to TAR DNA-binding protein 43 (TDP-43) and fused-in-sarcoma (FUS) that are contained in cytoplasmic inclusions of ALS and FTLD-TDP or FTLD-FUS patients. To further characterize RBM45, we first verified the presence of RBM45 in CSF and spinal cord tissue extracts of ALS patients by immunoblot. We next used immunohistochemistry to examine the subcellular distribution of RBM45 and observed in a punctate staining pattern within nuclei of neurons and glia in the brain and spinal cord. We also detected RBM45 cytoplasmic inclusions in 91 % of ALS, 100 % of FTLD-TDP and 75 % of Alzheimer's disease (AD) cases. The most extensive RBM45 pathology was observed in patients that harbor the C9ORF72 hexanucleotide repeat expansion. These RBM45 inclusions were observed in spinal cord motor neurons, glia and neurons of the dentate gyrus. By confocal microscopy, RBM45 co-localizes with ubiquitin and TDP-43 in inclusion bodies. In neurons containing RBM45 cytoplasmic inclusions we often detected the protein in a punctate pattern within the nucleus that lacked either TDP-43 or ubiquitin. We identified RBM45 using a proteomic screen of CSF from ALS and control subjects for candidate biomarkers, and link this RNA-binding protein to inclusion pathology in ALS, FTLD-TDP and AD.
authors.affiliation: Departments of Neurobiology and Pathology, University of Pittsburgh, PA, USA.
authors.forename: Mahlon
authors.initials: M
authors.lastname: Collins
authors.forename: David
authors.initials: D
authors.lastname: Riascos
authors.forename: Tina
authors.initials: T
authors.lastname: Kovalik
authors.forename: Jiyan
authors.initials: J
authors.lastname: An
authors.forename: Kelly
authors.initials: K
authors.lastname: Krupa
authors.forename: Kristin
authors.initials: K
authors.lastname: Krupa
authors.forename: Brian L
authors.initials: BL
authors.lastname: Hood
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Conrads
authors.forename: Alan E
authors.initials: AE
authors.lastname: Renton
authors.forename: Bryan J
authors.initials: BJ
authors.lastname: Traynor
authors.forename: Robert
authors.initials: R
authors.lastname: Bowser
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000690:Amyotrophic Lateral Sclerosis / Q000134:cerebrospinal fluid / Q000235:genetics / Q000473:pathology*; D001921:Brain / Q000473:pathology; D000073885:C9orf72 Protein; D002853:Chromatography, Liquid; D004268:DNA-Binding Proteins / Q000134:cerebrospinal fluid / Q000235:genetics / Q000378:metabolism*; D005260:Female; D057174:Frontotemporal Lobar Degeneration / Q000134:cerebrospinal fluid / Q000235:genetics / Q000473:pathology*; D005786:Gene Expression Regulation / Q000235:genetics; D006801:Humans; D002479:Inclusion Bodies / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000134:cerebrospinal fluid*; D009474:Neurons / Q000473:pathology* / Q000648:ultrastructure; D011506:Proteins / Q000235:genetics; D016601:RNA-Binding Proteins / Q000134:cerebrospinal fluid*; D013116:Spinal Cord / Q000378:metabolism / Q000473:pathology; D053719:Tandem Mass Spectrometry
chemical_list: D000073885:C9orf72 Protein; C568651:C9orf72 protein, human; D004268:DNA-Binding Proteins; D009419:Nerve Tissue Proteins; D011506:Proteins; C467044:RBM45 protein, human; D016601:RNA-Binding Proteins