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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.

Collins M, Riascos D, Kovalik T, An J, Krupa K, Krupa K, Hood BL, Conrads TP, Renton AE, Traynor BJ, Bowser R - Acta Neuropathol. (2012)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Departments of Neurobiology and Pathology, University of Pittsburgh, PA, USA.

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.

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RBM45 and tau pathology do not overlap in AD cases. a, b Hippocampal sections from two AD cases stained for RBM45 (green) and phosphorylated tau (red) with nuclei (DAPI-blue) in the merged image. Abundant pTau pathology is seen in both cases, as well as RBM45 inclusions marked with arrows. No overlap of pTau pathology with RBM45 inclusions or speckled RBM45 nuclear staining is seen. Scale bar 20 μm. Panels represent the following case numbers in Table 1: a 30, b 33
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Fig4: RBM45 and tau pathology do not overlap in AD cases. a, b Hippocampal sections from two AD cases stained for RBM45 (green) and phosphorylated tau (red) with nuclei (DAPI-blue) in the merged image. Abundant pTau pathology is seen in both cases, as well as RBM45 inclusions marked with arrows. No overlap of pTau pathology with RBM45 inclusions or speckled RBM45 nuclear staining is seen. Scale bar 20 μm. Panels represent the following case numbers in Table 1: a 30, b 33

Mentions: Since TDP-43 pathology is also evident in the dentate of FTLD-TDP cases, we next evaluated the distribution of RBM45 in the hippocampus from FTLD-TDP, ALS and control subjects. Control subjects, including both non-neurologic controls and Alzheimer’s disease, exhibited a punctate or speckled RBM45 pattern within the nucleus of dentate granule cells (Fig. 3a–c). In FTLD-TDP patients there were RBM45 positive cytoplasmic inclusions within dentate granule cells (Fig. 3d–f). A speckled RBM45 immunoreactivity was still evident in the nucleus of dentate granule cells in FTLD-TDP cases. RBM45 inclusions were also detected in dentate granule neurons of ALS cases (Fig. 3g), as well as some hippocampal pyramidal neurons in ALS and FTLD-TDP patients (Fig. 3h, i). RBM45 dystrophic neurites were not detected in the hippocampus. Of the available hippocampal tissue, we observed RBM45 neuronal inclusions in 63 % of ALS cases (n = 5 of 8), with no glial inclusions in any case. While only six FTLD-TDP cases were available for this study, RBM45 pathology occurred in the hippocampus and/or spinal cord of all cases. RBM45 inclusions were also observed in the dentate gyrus and pyramidal neurons for three of four AD cases (Table 2). We used confocal microscopy to determine association of RBM45 with tau pathology in AD cases. RBM45 did not co-localize with phosphorylated tau (pTau) in the hippocampus of AD cases (Fig. 4). A speckled RBM45 pattern was also detected within the nuclei of dentate cells in AD cases (Fig. 4a, b). Finally, we detected no RBM45 pathology in the hippocampus of any non-neurologic disease control case.Fig. 3


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.

Collins M, Riascos D, Kovalik T, An J, Krupa K, Krupa K, Hood BL, Conrads TP, Renton AE, Traynor BJ, Bowser R - Acta Neuropathol. (2012)

RBM45 and tau pathology do not overlap in AD cases. a, b Hippocampal sections from two AD cases stained for RBM45 (green) and phosphorylated tau (red) with nuclei (DAPI-blue) in the merged image. Abundant pTau pathology is seen in both cases, as well as RBM45 inclusions marked with arrows. No overlap of pTau pathology with RBM45 inclusions or speckled RBM45 nuclear staining is seen. Scale bar 20 μm. Panels represent the following case numbers in Table 1: a 30, b 33
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Related In: Results  -  Collection

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Fig4: RBM45 and tau pathology do not overlap in AD cases. a, b Hippocampal sections from two AD cases stained for RBM45 (green) and phosphorylated tau (red) with nuclei (DAPI-blue) in the merged image. Abundant pTau pathology is seen in both cases, as well as RBM45 inclusions marked with arrows. No overlap of pTau pathology with RBM45 inclusions or speckled RBM45 nuclear staining is seen. Scale bar 20 μm. Panels represent the following case numbers in Table 1: a 30, b 33
Mentions: Since TDP-43 pathology is also evident in the dentate of FTLD-TDP cases, we next evaluated the distribution of RBM45 in the hippocampus from FTLD-TDP, ALS and control subjects. Control subjects, including both non-neurologic controls and Alzheimer’s disease, exhibited a punctate or speckled RBM45 pattern within the nucleus of dentate granule cells (Fig. 3a–c). In FTLD-TDP patients there were RBM45 positive cytoplasmic inclusions within dentate granule cells (Fig. 3d–f). A speckled RBM45 immunoreactivity was still evident in the nucleus of dentate granule cells in FTLD-TDP cases. RBM45 inclusions were also detected in dentate granule neurons of ALS cases (Fig. 3g), as well as some hippocampal pyramidal neurons in ALS and FTLD-TDP patients (Fig. 3h, i). RBM45 dystrophic neurites were not detected in the hippocampus. Of the available hippocampal tissue, we observed RBM45 neuronal inclusions in 63 % of ALS cases (n = 5 of 8), with no glial inclusions in any case. While only six FTLD-TDP cases were available for this study, RBM45 pathology occurred in the hippocampus and/or spinal cord of all cases. RBM45 inclusions were also observed in the dentate gyrus and pyramidal neurons for three of four AD cases (Table 2). We used confocal microscopy to determine association of RBM45 with tau pathology in AD cases. RBM45 did not co-localize with phosphorylated tau (pTau) in the hippocampus of AD cases (Fig. 4). A speckled RBM45 pattern was also detected within the nuclei of dentate cells in AD cases (Fig. 4a, b). Finally, we detected no RBM45 pathology in the hippocampus of any non-neurologic disease control case.Fig. 3

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Departments of Neurobiology and Pathology, University of Pittsburgh, PA, USA.

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.

Show MeSH
Related in: MedlinePlus