Limits...
Drosha inclusions are new components of dipeptide-repeat protein aggregates in FTLD-TDP and ALS C9orf72 expansion cases.

Porta S, Kwong LK, Trojanowski JQ, Lee VM - J. Neuropathol. Exp. Neurol. (2015)

Bottom Line: Moreover, through a repeat-associated non-ATG translation mechanism, G4C2 repeats translation leads to dipeptide-repeat protein aggregation in the cytoplasm of neurons.Further characterization of Drosha-positive neuronal cytoplasmic inclusions in the hippocampus, frontal cortex, and cerebellum revealed colocalization with p62 and ubiquilin-2, 2 pathognomonic signatures of c9FTLD-TDP and c9ALS cases; however, Drosha inclusions rarely colocalized with TDP-43 pathology.We conclude that Drosha may play a unique pathogenic role in the onset or progression of FTLD-TDP/ALS in patients with the C9orf72 mutation.

View Article: PubMed Central - PubMed

Affiliation: From the Center for Neurodegenerative Disease Research, Department of Pathology and Laboratory Medicine, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania.

ABSTRACT
Frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS) are 2 neurodegenerative disorders that share clinical, genetic, and neuropathologic features. The presence of abnormal expansions of GGGGCC repeats (G4C2 repeats) in a noncoding region of the Chromosome 9 open reading frame 72 (C9orf72) gene is the major genetic cause of both FTLD and ALS. Transcribed G4C2 repeats can form nuclear RNA foci and recruit RNA-binding proteins, thereby inhibiting their normal function. Moreover, through a repeat-associated non-ATG translation mechanism, G4C2 repeats translation leads to dipeptide-repeat protein aggregation in the cytoplasm of neurons. Here, we identify Drosha protein as a new component of these dipeptide-repeat aggregates. In C9orf72 mutation cases of FTLD-TDP (c9FTLD-TDP) and ALS (c9ALS), but not in FTLD or ALS cases without C9orf72 mutation, Drosha is mislocalized to form neuronal cytoplasmic inclusions in the hippocampus, frontal cortex, and cerebellum. Further characterization of Drosha-positive neuronal cytoplasmic inclusions in the hippocampus, frontal cortex, and cerebellum revealed colocalization with p62 and ubiquilin-2, 2 pathognomonic signatures of c9FTLD-TDP and c9ALS cases; however, Drosha inclusions rarely colocalized with TDP-43 pathology. We conclude that Drosha may play a unique pathogenic role in the onset or progression of FTLD-TDP/ALS in patients with the C9orf72 mutation.

Show MeSH

Related in: MedlinePlus

Mislocalized Drosha in the hippocampus of c9FTLD-TDP and c9ALS patients. Drosha immunohistochemistry in the hippocampus of c9FTLD-TDP (A–D), c9ALS (E, F), FTLD-TDP (G), and ALS (H) cases. Drosha-positive neuronal cytoplasmic inclusions (NCIs) were exclusively observed in the dentate gyrus in C9orf72 mutation carriers (see arrows in A, C, E). Drosha NCIs show starlike (C, arrowhead and inset) or dotlike shapes (C, arrow and inset) in the cytoplasm of dentate granule neurons. Drosha accumulation into NCIs does not result in nuclear clearance of Drosha protein (D, arrowhead). Drosha-positive dystrophic neurites (DNs) also were frequently found in c9FTLD-TDP and c9ALS cases (B, F, arrowhead and insets), but, unlike the NCIs, Drosha-positive DNs were not exclusively associated with the presence of C9orf72 mutations. Nuclear Drosha was observed in dentate granular cells of FTLD-TDP (G) and ALS (H) cases, but no NCIs were seen. The insets are higher-magnification images of the boxed areas in (B), (C), and (F). Scale bars = (A, B) 100 μm; (C, E–H) 50 μm; (D) 10 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4362478&req=5

Figure 1: Mislocalized Drosha in the hippocampus of c9FTLD-TDP and c9ALS patients. Drosha immunohistochemistry in the hippocampus of c9FTLD-TDP (A–D), c9ALS (E, F), FTLD-TDP (G), and ALS (H) cases. Drosha-positive neuronal cytoplasmic inclusions (NCIs) were exclusively observed in the dentate gyrus in C9orf72 mutation carriers (see arrows in A, C, E). Drosha NCIs show starlike (C, arrowhead and inset) or dotlike shapes (C, arrow and inset) in the cytoplasm of dentate granule neurons. Drosha accumulation into NCIs does not result in nuclear clearance of Drosha protein (D, arrowhead). Drosha-positive dystrophic neurites (DNs) also were frequently found in c9FTLD-TDP and c9ALS cases (B, F, arrowhead and insets), but, unlike the NCIs, Drosha-positive DNs were not exclusively associated with the presence of C9orf72 mutations. Nuclear Drosha was observed in dentate granular cells of FTLD-TDP (G) and ALS (H) cases, but no NCIs were seen. The insets are higher-magnification images of the boxed areas in (B), (C), and (F). Scale bars = (A, B) 100 μm; (C, E–H) 50 μm; (D) 10 μm.

Mentions: To elucidate if the presence of aberrant G4C2 repeats could alter the normal nuclear distribution of the RNA-binding proteins Drosha and DGCR8, their subcellular localization was analyzed in postmortem brain samples of FTLD-TDP and ALS cases with and without C9orf72 mutations and in age-matched control individuals (Table, Supplemental Digital Content 1, http://links.lww.com/NEN/A714). Interestingly, IHC of Drosha in the hippocampus, frontal cortex, and cerebellum revealed the presence of frequent Drosha-positive NCIs in c9FTLD-TDP and c9ALS cases but not in FTLD and ALS cases without G4C2 repeats expansion or in control individuals (Figs. 1, 2). We confirmed Drosha antibody specificity by competition experiments with the immunizing peptide using Western blot (Figure, Supplemental Digital Content 2, part a, http://links.lww.com/NEN/A715), double IF (Figure, Supplemental Digital Content 2, part b, http://links.lww.com/NEN/A715), and IHC (Figure, Supplemental Digital Content 2, part c, http://links.lww.com/NEN/A715, Materials and Methods, Supplemental Digital Content 3, http://links.lww.com/NEN/A716).


Drosha inclusions are new components of dipeptide-repeat protein aggregates in FTLD-TDP and ALS C9orf72 expansion cases.

Porta S, Kwong LK, Trojanowski JQ, Lee VM - J. Neuropathol. Exp. Neurol. (2015)

Mislocalized Drosha in the hippocampus of c9FTLD-TDP and c9ALS patients. Drosha immunohistochemistry in the hippocampus of c9FTLD-TDP (A–D), c9ALS (E, F), FTLD-TDP (G), and ALS (H) cases. Drosha-positive neuronal cytoplasmic inclusions (NCIs) were exclusively observed in the dentate gyrus in C9orf72 mutation carriers (see arrows in A, C, E). Drosha NCIs show starlike (C, arrowhead and inset) or dotlike shapes (C, arrow and inset) in the cytoplasm of dentate granule neurons. Drosha accumulation into NCIs does not result in nuclear clearance of Drosha protein (D, arrowhead). Drosha-positive dystrophic neurites (DNs) also were frequently found in c9FTLD-TDP and c9ALS cases (B, F, arrowhead and insets), but, unlike the NCIs, Drosha-positive DNs were not exclusively associated with the presence of C9orf72 mutations. Nuclear Drosha was observed in dentate granular cells of FTLD-TDP (G) and ALS (H) cases, but no NCIs were seen. The insets are higher-magnification images of the boxed areas in (B), (C), and (F). Scale bars = (A, B) 100 μm; (C, E–H) 50 μm; (D) 10 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4362478&req=5

Figure 1: Mislocalized Drosha in the hippocampus of c9FTLD-TDP and c9ALS patients. Drosha immunohistochemistry in the hippocampus of c9FTLD-TDP (A–D), c9ALS (E, F), FTLD-TDP (G), and ALS (H) cases. Drosha-positive neuronal cytoplasmic inclusions (NCIs) were exclusively observed in the dentate gyrus in C9orf72 mutation carriers (see arrows in A, C, E). Drosha NCIs show starlike (C, arrowhead and inset) or dotlike shapes (C, arrow and inset) in the cytoplasm of dentate granule neurons. Drosha accumulation into NCIs does not result in nuclear clearance of Drosha protein (D, arrowhead). Drosha-positive dystrophic neurites (DNs) also were frequently found in c9FTLD-TDP and c9ALS cases (B, F, arrowhead and insets), but, unlike the NCIs, Drosha-positive DNs were not exclusively associated with the presence of C9orf72 mutations. Nuclear Drosha was observed in dentate granular cells of FTLD-TDP (G) and ALS (H) cases, but no NCIs were seen. The insets are higher-magnification images of the boxed areas in (B), (C), and (F). Scale bars = (A, B) 100 μm; (C, E–H) 50 μm; (D) 10 μm.
Mentions: To elucidate if the presence of aberrant G4C2 repeats could alter the normal nuclear distribution of the RNA-binding proteins Drosha and DGCR8, their subcellular localization was analyzed in postmortem brain samples of FTLD-TDP and ALS cases with and without C9orf72 mutations and in age-matched control individuals (Table, Supplemental Digital Content 1, http://links.lww.com/NEN/A714). Interestingly, IHC of Drosha in the hippocampus, frontal cortex, and cerebellum revealed the presence of frequent Drosha-positive NCIs in c9FTLD-TDP and c9ALS cases but not in FTLD and ALS cases without G4C2 repeats expansion or in control individuals (Figs. 1, 2). We confirmed Drosha antibody specificity by competition experiments with the immunizing peptide using Western blot (Figure, Supplemental Digital Content 2, part a, http://links.lww.com/NEN/A715), double IF (Figure, Supplemental Digital Content 2, part b, http://links.lww.com/NEN/A715), and IHC (Figure, Supplemental Digital Content 2, part c, http://links.lww.com/NEN/A715, Materials and Methods, Supplemental Digital Content 3, http://links.lww.com/NEN/A716).

Bottom Line: Moreover, through a repeat-associated non-ATG translation mechanism, G4C2 repeats translation leads to dipeptide-repeat protein aggregation in the cytoplasm of neurons.Further characterization of Drosha-positive neuronal cytoplasmic inclusions in the hippocampus, frontal cortex, and cerebellum revealed colocalization with p62 and ubiquilin-2, 2 pathognomonic signatures of c9FTLD-TDP and c9ALS cases; however, Drosha inclusions rarely colocalized with TDP-43 pathology.We conclude that Drosha may play a unique pathogenic role in the onset or progression of FTLD-TDP/ALS in patients with the C9orf72 mutation.

View Article: PubMed Central - PubMed

Affiliation: From the Center for Neurodegenerative Disease Research, Department of Pathology and Laboratory Medicine, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania.

ABSTRACT
Frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS) are 2 neurodegenerative disorders that share clinical, genetic, and neuropathologic features. The presence of abnormal expansions of GGGGCC repeats (G4C2 repeats) in a noncoding region of the Chromosome 9 open reading frame 72 (C9orf72) gene is the major genetic cause of both FTLD and ALS. Transcribed G4C2 repeats can form nuclear RNA foci and recruit RNA-binding proteins, thereby inhibiting their normal function. Moreover, through a repeat-associated non-ATG translation mechanism, G4C2 repeats translation leads to dipeptide-repeat protein aggregation in the cytoplasm of neurons. Here, we identify Drosha protein as a new component of these dipeptide-repeat aggregates. In C9orf72 mutation cases of FTLD-TDP (c9FTLD-TDP) and ALS (c9ALS), but not in FTLD or ALS cases without C9orf72 mutation, Drosha is mislocalized to form neuronal cytoplasmic inclusions in the hippocampus, frontal cortex, and cerebellum. Further characterization of Drosha-positive neuronal cytoplasmic inclusions in the hippocampus, frontal cortex, and cerebellum revealed colocalization with p62 and ubiquilin-2, 2 pathognomonic signatures of c9FTLD-TDP and c9ALS cases; however, Drosha inclusions rarely colocalized with TDP-43 pathology. We conclude that Drosha may play a unique pathogenic role in the onset or progression of FTLD-TDP/ALS in patients with the C9orf72 mutation.

Show MeSH
Related in: MedlinePlus