Abstract

TDP-43 was recently identified as the major disease protein in neuronal inclusions in frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U). TDP-43 is not only linked to disease mechanisms in FTLD-U, but it is also the most robust marker for the specific detection of neuronal inclusions in FTLD-U. In this study, we describe additional TDP-43 pathology in the white matter as a characteristic feature in a series of 38 FTLD-U cases including 3 cases with mutations in the progranulin gene. White matter pathology was most abundant in frontal and temporal lobes, but it was also detectable in brainstem and spinal cord. Based on morphology and double-labeling experiments, white matter cells with TDP-43-positive inclusions most likely represent oligodendrocytes. Biochemically, hyperphosphorylated and truncated TDP-43 was detectable in insoluble brain extracts from affected white matter regions in FTLD-U, similar to the biochemical signature observed in FTLD-U gray matter. Taken together, these results expand the spectrum of TDP-43 pathology in FTLD-U, suggesting that white matter pathology might contribute to the neurodegenerative process and clinical symptoms in FTLD-U.

Introduction

Frontotemporal dementias (FTDs) are a clinically, genetically, and pathologically heterogeneous group of neurodegenerative disorders accounting for up to 20% of presenile dementia cases. The clinical presentation is characterized by progressive changes in social, behavioral, and/or language function (1-3). Additionally, patients may display movement abnormalities such as parkinsonism or motor neuron disease (4,5). Genetic, immunohistochemical, and biochemical data are incorporated into the current nosology of FTDs, which broadly divides cases into those with tau-positive inclusions (e.g. Pick disease, corticobasal degeneration [CBD], and progressive supranuclear palsy [PSP]) versus those with ubiquitin-positive and tau- and α-synuclein-negative inclusions, designated as frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U) (2), the most common form of FTDs (4,6-8). More than 30% of FTDs are familial, and mutations in the microtubule associated protein tau (MAPT) gene are pathogenic for hereditary FTD characterized by tau pathology (9,10), whereas mutations in the progranulin gene (GRN) are pathogenic for familial FTLD-U (11,12).

Recently, TDP-43, a widely expressed nuclear protein with presumed functions in transcription regulation and exon skipping (13-15), was identified as the major disease protein ubiquitinated in the inclusions in FTLD-U including familial FTLD-U cases with GRN mutations (16). After initial identification, TDP-43 was rapidly confirmed as a disease protein in FTLD-U (17). Thus, TDP-43 is implicated in FTLD-U pathogenesis and is the most sensitive and specific marker for FTLD-U pathology. Furthermore, based on morphology and laminar distribution of ubiquitin and TDP-43-positive cytoplasmic, nuclear, and neuritic inclusions in affected cortical brain regions, at least three pathologic subtypes of FTLD-U can be distinguished (16,18,19).

In the present study, immunohistochemical analysis for TDP-43 in a series of 38 FTLD-U cases, including 3 cases with GRN mutations, revealed that in addition to neuronal pathology, FTLD-U is also characterized by TDP-43 pathology in the white matter of affected brain regions. Pathologic accumulation was predominantly found in oligodendrocytes. Biochemically, TDP-43 in affected white matter regions becomes hyperphosphorylated and truncated, similar to pathologic alterations of TDP-43 in affected gray matter regions, thereby suggesting that glial pathology might contribute to the neurodegenerative processes involved in FTLD-U.

Materials and Methods

Brain Tissue Collection and Neuropathologic Assessment

Frozen brain tissues and fixed, paraffin-embedded tissue blocks were obtained from the Center for Neurodegenerative Disease Research Brain Bank at the University of Pennsylvania and the Center for Neuropathology and Prion Research Brain Bank at the University of Munich, Germany. Consent for autopsy was obtained from legal representatives for all subjects in accordance with local institutional review board requirements.

Antibodies

Antibodies used in this study included mouse monoclonal antibody (mAB) 1510 anti-ubiquitin (Chemicon, Temecula, CA), affinity-purified rabbit polyclonal anti-TDP-43 (ProteinTech Group, Chicago, IL), mouse mAB 2E2-D3 anti-TDP-43 (Abnova, Taipei, Taiwan), and mAB tau-2 anti-tau (Sigma-Aldrich, St. Louis, MO). For double-labeling experiments, mouse mAB anti-glial fibrillary acidic protein (GFAP) (Dako, Glostrup, Denmark) was used as a marker for astrocytes, mouse mAB anti-CD68 (Dako) as a marker for activated microglia, and mouse mAB anti-CD57 (Leu-7; Chemicon) and mouse mAB SMI91 anti-2‘,3’-cyclic nucleotide 3′-phosphodiesterase (CNPase; Sternberger Monoclonals, Lutherville, MD) as a marker for oligodendrocytes.

Immunohistochemistry

The harvesting, fixation, and further processing of the tissue specimens used in this study were conducted as described previously (18). Briefly, tissue blocks from representative brain regions were fixed with either 70% ethanol in 150 mmol/L NaCl or phosphate-buffered 3.65% formaldehyde and embedded in paraffin. Immunohistochemistry was carried out using the avidin-biotin complex detection system (Vector Laboratories, Burlingame, CA) and 3,3′-diaminobenzidine as chromogen. Antigen retrieval was done by boiling the sections in 10 mmol/L citrate buffer (pH 6.0) in a microwave oven (three times for 5 minutes). Double-labeling immunofluorescence was performed using Alexa Fluor 488 and 594 conjugated secondary antibodies (Molecular Probes, Eugene, OR).

Sequential Biochemical Fractionation and Immunoblot Analysis

Frozen tissues from frontal and temporal lobes as well as from cerebellum were used for the sequential extraction of TDP-43 with buffers of increasing stringency, as described (16). Gray and white matter were separated and processed individually. Briefly, gray and white matter was extracted at 5 mL/g (v/w) with low-salt buffer (10 mmol/L Tris, pH 7.5, 5 mmol/L EDTA, 1 mmol/L dithiothreitol, 10% sucrose, and a cocktail of protease inhibitors), high salt-Triton X buffer (low salt buffer + 1% Triton X-100 + 0.5 mol/L NaCl), myelin flotation buffer (Triton X buffer containing 30% sucrose), and Sarkosyl buffer (low salt buffer + 1% N-lauroyl-sarcosine + 0.5 mol/L NaCl). The detergent-insoluble materials were extracted in 0.25 mL/g of urea buffer (7 mol/L urea, 2 mol/L thiourea, 4% 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, 30 mmol/L Tris, pH 8.5). For Western blot analysis, equal volumes of urea fractions (10 μL, equivalent to 40 mg of starting material) from different samples were resolved by Tris-glycine 5% to 20% gradient sodium dodecyl sulfate-polyacrylamide gel electrophoresis, transferred to polyvinylidene difluoride membranes (Millipore, Billerica, MA), and probed with antibodies to TDP-43. Primary antibodies were detected with alkaline phosphatase-conjugated anti-mouse or anti-rabbit IgG (Dako) and visualized by incubation with nitro blue tetrazolium/5-bromo-4-chloro-3-indolyl phosphate (Roche Molecular Biochemicals, Mannheim, Germany).

Results

TDP-43-Positive White Matter Pathology in Frontotemporal Lobar Degeneration With Ubiquitin-Positive Inclusion Cases

Anti-TDP-43 immunohistochemistry was performed on frontal and temporal cortex as well as medulla or spinal cord, if available, from 38 FTLD-U cases, including 3 cases with GRN mutations (Table). In addition to the neuronal inclusions, TDP-43 staining allowed the detection of FTLD-U-specific TDP-43 accumulation in the cytoplasm of glial cells, predominantly located in the white matter (Fig. 1A, B) but also scattered in the cortex and motor nuclei in the medulla and anterior horn of the spinal cord (Fig. 1C, arrow). Glial inclusions were predominantly found in cells of oligodendroglial morphology with small, round nuclei. The shape of TDP-43-positive inclusions varied from round to triangular to comma-shaped, and they occasionally extended into processes (Fig. 1D-F). Moreover, few TDP-43-positive thread-like inclusions in cell processes were detectable (Fig. 1G), but no intranuclear inclusions were noted in glial cells. No pathologic TDP-43 staining was observed in the white matter of controls and subjects with other neurodegenerative disorders, such as Alzheimer disease (AD), PSP, CBD, and multiple system atrophy (MSA) (data not shown), arguing that the observed TDP-43-positive white matter pathology is FTLD-U specific. To further characterize the glial cells bearing TDP-43 inclusions, we performed double-labeling experiments. Anti-GFAP used as a marker for astrocytes and CD68 used as a marker for microglia showed no colocalization with TDP-43-positive glial cells (Fig. 2A-F), giving further support to the hypothesis that the predominantly affected cell type with TDP-43 inclusions in the white matter is oligodendrocytes. Markers used to label oligodendroglia, including CNPase and CD57 (Leu7), gave only weak immunoreactivity of some of the cells with inclusions due in part to the well-recognized lack of robust cellular markers for mature oligodendrocytes (20). Ubiquitin staining revealed numerous small, dot-like structures in the white matter in FTLD-U (Fig. 2H), control, and AD brains, a common finding described in normal aging (21). However, TDP-43-positive glial inclusions were not stained by ubiquitin (Fig. 2G-I), in contrast to TDP-43-positive neuronal inclusions (16), and there was no labeling of TDP-43-positive glial inclusions with tau-2 (data not shown).

TABLE 1.

Demographic Information of FTLD-U Patients and Semiquantitative Assessment of TDP-43 Pathology

FIGURE 1.

Spectrum of TDP-43-positive white matter pathology in frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U). Immunohistochemistry with antibodies to TDP-43 reveals robust staining of cytoplasmic inclusions in glial cells in frontal (A) and temporal (B) white matter of FTLD-U cases. (C) Occasionally, glial inclusions (arrow) are detectable in the spinal cord in addition to neuronal inclusions in motor neurons (arrowhead). Different morphologies of TDP-43-positive white matter inclusions are shown in high-power magnification: round inclusion (D), triangular, flame-shaped inclusion (E), coiled-body-like inclusions (F), and thread-like pathology (G). Scale bars = (A-C) 25 μm; (C-G) 10 μm.

FIGURE 1.

Spectrum of TDP-43-positive white matter pathology in frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U). Immunohistochemistry with antibodies to TDP-43 reveals robust staining of cytoplasmic inclusions in glial cells in frontal (A) and temporal (B) white matter of FTLD-U cases. (C) Occasionally, glial inclusions (arrow) are detectable in the spinal cord in addition to neuronal inclusions in motor neurons (arrowhead). Different morphologies of TDP-43-positive white matter inclusions are shown in high-power magnification: round inclusion (D), triangular, flame-shaped inclusion (E), coiled-body-like inclusions (F), and thread-like pathology (G). Scale bars = (A-C) 25 μm; (C-G) 10 μm.

FIGURE 2.

Double-labeling experiments of TDP-43-positive glial inclusions. Glial cells in the frontal white matter with TDP-43-positive glial inclusions are not labeled by GFAP used as an astrocyte marker (A-C) and CD68 used as a microglia marker (D-F). TDP-43-positive glial inclusions are also not labeled by ubiquitin (G-I). Scale bar = (A-I) 10 μm.

FIGURE 2.

Double-labeling experiments of TDP-43-positive glial inclusions. Glial cells in the frontal white matter with TDP-43-positive glial inclusions are not labeled by GFAP used as an astrocyte marker (A-C) and CD68 used as a microglia marker (D-F). TDP-43-positive glial inclusions are also not labeled by ubiquitin (G-I). Scale bar = (A-I) 10 μm.

Because the abundance of glial inclusions varied from case to case, we asked whether the extent of TDP-43 white matter pathology correlated with the severity of TDP-43 gray matter pathology and whether there are differences among the three subtypes of FTLD-U described (16,18). Therefore, cases were separated into FTLD-U subtype 1 (cases 1-10), subtype 2 (cases 11-22), and subtype 3 (cases 23-35) according to Sampathu et al (18) on the basis of the morphology and laminar distribution of ubiquitin and TDP-43-positive neuronal inclusions. Briefly, subtype 1 was characterized by predominance of long neuritic profiles over cytoplasmic inclusions in superficial cortical layers, subtype 2 showed predominance of cytoplasmic inclusions in both superficial and deep cortical layers, and in subtype 3 ring-shaped cytoplasmic as well as short neuritic profiles were present predominantly in the superficial cortical layers. The amount of TDP-43 gray and white matter pathology in frontal and temporal cortex was assessed semiquantitatively (Table). Glial inclusions were most widespread and abundant in FTLD-U subtypes 2 and 3 and in familial FTLD-U with GRN mutations but were rare or absent in subtype 1. In subtype 2 and 3 cases, there was a slight correlation between severity of gray matter and white matter pathology. Glial inclusions in the medulla and spinal cord were only found in cases with motor neuron involvement as detected by TDP-43-positive inclusions in motor neurons of medulla and spinal cord (Fig. 1C).

Pathologic Alterations of TDP-43 in White Matter of Frontotemporal Lobar Degeneration With Ubiquitin-Positive Inclusion Cases

A disease-specific biochemical signature of pathologically altered TDP-43 was reported in detergent-insoluble, urea-soluble extracts of gray matter from sporadic and familial FTLD-U cases (16). To biochemically characterize TDP-43 in the white matter of FTLD-U, samples of frontal and temporal gray and white matter from FTLD-U cases were sequentially extracted with buffers of increasing strength and the proteins in these extracts were analyzed by TDP-43 immunoblot methods. Cerebellar gray and white matter from FTLD-U cases as well as frontal gray and white matter from AD brains were used as controls. Pathologic alterations of TDP-43 similar to those detected in frontal and temporal gray matter were observed in the urea extracts of affected frontal and temporal white matter from FTLD-U cases, namely additional bands of ~25 and 45 kDa as well as a high molecular weight protein smear (Fig. 3). Frontal gray and white matter from AD brains as well as cerebellar gray and white matter from FTLD-U brains only showed the full-length TDP-43, which migrated as an ~43-kDa band (Fig. 3), consistent with the lack of pathologically altered TDP-43 and inclusions formed by TDP-43.

FIGURE 3.

Biochemical analyses of TDP-43 in cortical gray and white matter of sporadic and familial frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U). Ten microliters of protein extracts in urea fractions isolated from gray and white matter of the frontal (Fg, Fw) and temporal (Tg, Tw) lobes as well as cerebellum (Cg, Cw) from FTLD-U subtypes 1, 2, and 3, familial FTLD-U with progranulin gene (GRN) mutation, and Alzheimer disease (AD) brains were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotted with antibodies to TDP-43. Variable presence of pathologic TDP-43 species were detected as ~25-kDa bands (*), 45-kDa bands (**), and high molecular weight smear (***) in affected gray and white matter regions from FTLD-U cases, but not in cerebellar gray and white matter and in urea extracts from AD brains.

FIGURE 3.

Biochemical analyses of TDP-43 in cortical gray and white matter of sporadic and familial frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U). Ten microliters of protein extracts in urea fractions isolated from gray and white matter of the frontal (Fg, Fw) and temporal (Tg, Tw) lobes as well as cerebellum (Cg, Cw) from FTLD-U subtypes 1, 2, and 3, familial FTLD-U with progranulin gene (GRN) mutation, and Alzheimer disease (AD) brains were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotted with antibodies to TDP-43. Variable presence of pathologic TDP-43 species were detected as ~25-kDa bands (*), 45-kDa bands (**), and high molecular weight smear (***) in affected gray and white matter regions from FTLD-U cases, but not in cerebellar gray and white matter and in urea extracts from AD brains.

The presence and amount of pathologic TDP-43 species obtained by immunoblot analyses varied among cases and regions. However, the intensity of the modified bands corresponded roughly with the density of TDP-43-positive inclusions demonstrated by immunohistochemistry. For example, case 15, with high density of inclusions in gray and white matter, showed strong pathologic TDP-43 bands by immunoblot in these regions, whereas in case 26 with only rare inclusions in the temporal white matter, no pathologic TDP-43 species were detectable by immunoblot in this region.

Discussion

TDP-43 is the major disease protein in FTLD-U that forms the signature intraneuronal cytoplasmic and intranuclear inclusions predominantly in the frontal and temporal cortex (16, 17) and therefore represents the most robust marker for the specific neuropathologic diagnosis of FTLD-U.

By immunohistochemical and biochemical approaches, we observed additional TDP-43 pathology in the white matter, composed of glial cytoplasmic inclusions and rare thread-like inclusions, as a characteristic feature in FTLD-U brains. TDP-43-positive glial inclusions could be found throughout the frontal and temporal lobes in most FTLD-U cases studied (n = 38), with the highest density in FTLD-U subtypes 2 and 3, providing further evidence for pathologic heterogeneity in FTLD-U (18,19). Moreover, scattered glial inclusions could be found in brainstem and spinal cord regions in FTLD-U cases with motor neuron involvement. These consistent findings of TDP-43-positive glial inclusions in areas with neurodegeneration suggests that glial abnormalities might be involved in the pathologic processes of FTLD-U.

On the basis of morphology and double-labeling experiments demonstrating a lack of colocalization of inclusion-bearing cells with markers for astrocytes and microglia, affected glial cells most likely represent oligodendrocytes. The morphology of TDP-43-positive glial inclusions varied from round or cap-shaped, resembling the α-synuclein-positive oligodendroglial cytoplasmic inclusions in MSA (22,23), to comma-like shapes resembling the tau-positive coiled bodies described in several neurodegenerative diseases, such as PSP, CBD, and familial forms of FTD with MAPT gene mutations (24, 25). A role of glial pathology in FTLD-U has been discussed previously by description of tau-2- or p62-positive glial inclusions (26,27). However, because cross-reactivity of tau-2 with proteins expressed in microglia has been described, and p62 also labels pathologic inclusions in other neurodegenerative disorders, the interpretation of these data with regard to etiology and pathogenesis of FTLD-U is unclear. Notably, the TDP-43-positive glial inclusions described in this study were not labeled by tau-2. Furthermore, α-synuclein- and tau-positive glial inclusions in MSA, PSP, and CBD were TDP-43-negative, and no TDP-43-positive inclusions were detectable in PSP, CBD, and MSA, thereby demonstrating specificity of the TDP-43 glial inclusions described in this study for FTLD-U. The fact that the TDP-43-positive glial inclusions are not immunoreactive for ubiquitin, in contrast to the neuronal TDP-43-positive inclusions in FTLD-U (16), might suggest that ubiquitination of TDP-43 is a later phenomenon in the disease course and is not necessary for TDP-43 accumulation.

By biochemical analyses of affected cortical brain regions in FTLD-U, we showed that hyperphosphorylated, ubiquitinated, and N-terminally truncated TDP-43 species are detected in the detergent-insoluble, urea-soluble protein extracts of these brain samples (16). In the current study, we demonstrated that an identical disease-specific biochemical signature of TDP-43, consisting of hyperphosphorylated, ubiquitinated, and truncated TDP-43, was also detectable in urea extracts from FTLD-U frontal and temporal white matter, arguing that similar pathomechanisms might be involved in neuronal and glial TDP-43 inclusion body formation.

TDP-43 is a highly conserved, ubiquitously expressed nuclear protein (28) that may act as a transcription repressor and activator of exon skipping (13-15) as well as a scaffold for nuclear bodies through interactions with survival motor neuron protein (29). Whereas physiologic TDP-43 is localized primarily to the nucleus of neuronal and glial cells, our data showed that under pathologic conditions immunodetection of nuclear TDP-43 was reduced in inclusion-bearing neuronal and glial cells and that TDP-43 is redistributed to accumulate in neuronal and glial cell bodies and processes, a consequence of which may be loss of TDP-43 nuclear function. Future studies will be needed to address these and other mechanistic aspects of the aggregation of pathologic TDP-43 in neuronal and glial cells and their role in the pathogenesis of neurodegeneration in FTDL-U.

In summary, this study expands the spectrum of TDP-43 pathology in FTLD-U by demonstrating widespread and abundant involvement of glial cells, especially oligodendroglia, in the white matter of FTLD-U brains. Thus, glial TDP-43 white matter pathology is a characteristic feature of FTDL-U in addition to neuronal TDP-43 gray matter pathology, thereby implying that glial TDP-43 pathology also contributes to the neurodegenerative process and the cognitive and motor impairments seen in patients affected by FTLD-U.

Acknowledgments

The authors thank the families of patients who made this research possible.

References

1.
Neary
D
Snowden
JS
Gustafson
L
et al
.
Frontotemporal lobar degeneration: A consensus on clinical diagnostic criteria
.
Neurology
 
1998
;
51
:
1546
54
2.
McKhann
GM
Albert
MS
Grossman
M
et al
.
Clinical and pathological diagnosis of frontotemporal dementia: Report of the Work Group on Frontotemporal Dementia and Pick's Disease
.
Arch Neurol
 
2001
;
58
:
1803
9
3.
Grossman
M
.
Frontotemporal dementia: A review
.
J Int Neuropsychol Soc
 
2002
;
8
:
566
83
4.
Hodges
JR
Davies
RR
Xuereb
JH
et al
.
Clinicopathological correlates in frontotemporal dementia
.
Ann Neurol
 
2004
;
56
:
399
406
5.
Lomen-Hoerth
C
Anderson
T
Miller
B
.
The overlap of amyotrophic lateral sclerosis and frontotemporal dementia
.
Neurology
 
2002
;
59
:
1077
79
6.
Lipton
AM
White
CL 3rd
Bigio
EH
.
Frontotemporal lobar degeneration with motor neuron disease-type inclusions predominate in 76 cases of frontotemporal degeneration
.
Acta Neuropathol (Berl)
 
2004
;
108
:
379
85
7.
Johnson
JK
Diehl
J
Mendez
MF
et al
.
Frontotemporal lobar degeneration: Demographic characteristics of 353 patients
.
Arch Neurol
 
2005
;
62
:
925
30
8.
Shi
J
Shaw
CL
Du Plessis
D
et al
.
Histopathological changes underlying frontotemporal lobar degeneration with clinicopathological correlation
.
Acta Neuropathol (Berl)
 
2005
;
110
:
501
12
9.
Hutton
M
Lendon
CL
Rizzu
P
et al
.
Association of missense and 5'-splice-site mutations in tau with the inherited dementia FTDP-17
.
Nature
 
1998
;
393
:
702
5
10.
Poorkaj
P
Bird
TD
Wijsman
E
et al
.
Tau is a candidate gene for chromosome 17 frontotemporal dementia
.
Ann Neurol
 
1998
;
43
:
815
25
11.
Cruts
M
Gijselinck
I
van der Zee
J
et al
.
Null mutations in progranulin cause ubiquitin-positive frontotemporal dementia linked to chromosome 17q21
.
Nature
 
2006
;
442
:
920
24
12.
Baker
M
Mackenzie
IR
Pickering-Brown
SM
et al
.
Mutations in progranulin cause tau-negative frontotemporal dementia linked to chromosome 17
.
Nature
 
2006
;
442
:
916
19
13.
Buratti
E
Brindisi
A
Pagani
F
et al
.
Nuclear factor TDP-43 binds to the polymorphic TG repeats in CFTR intron 8 and causes skipping of exon 9: A functional link with disease penetrance
.
Am J Hum Genet
 
2004
;
74
:
1322
25
14.
Buratti
E
Dork
T
Zuccato
E
et al
.
Nuclear factor TDP-43 and SR proteins promote in vitro and in vivo CFTR exon 9 skipping
.
EMBO J
 
2001
;
20
:
1774
84
15.
Mercado
PA
Ayala
YM
Romano
M
et al
.
Depletion of TDP-43 overrides the need for exonic and intronic splicing enhancers in the human apoA-II gene
.
Nucleic Acids Res
 
2005
;
33
:
6000
10
16.
Neumann
M
Sampathu
DM
Kwong
LK
et al
.
Ubiquitinated TDP-43 in frontotemporal lobar degeneration and amyotrophic lateral sclerosis
.
Science
 
2006
;
314
:
130
33
17.
Arai
T
Hasegawa
M
Akiyama
H
et al
.
TDP-43 is a component of ubiquitin-positive tau-negative inclusions in frontotemporal lobar degeneration and amyotrophic lateral sclerosis
.
Biochem Biophys Res Commun
 
2006
;
351
:
602
11
18.
Sampathu
DM
Neumann
M
Kwong
LK
et al
.
Pathological heterogeneity of frontotemporal lobar degeneration with ubiquitin-positive inclusions delineated by ubiquitin immunohistochemistry and novel monoclonal antibodies
.
Am J Pathol
 
2006
;
169
:
1343
52
19.
Mackenzie
IR
Baborie
A
Pickering-Brown
S
et al
.
Heterogeneity of ubiquitin pathology in frontotemporal lobar degeneration: Classification and relation to clinical phenotype
.
Acta Neuropathol (Berl)
 
2006
;
112
:
539
49
20.
Dickson
DW
Liu
WK
Hardy
J
et al
.
Widespread alterations of α-synuclein in multiple system atrophy
.
Am J Pathol
 
1999
;
155
:
1241
51
21.
Dickson
DW
Wertkin
A
Kress
Y
et al
.
Ubiquitin immunoreactive structures in normal human brainsDistribution and developmental aspects
.
Lab Invest
 
1990
;
63
:
87
99
22.
Tu
PH
Galvin
JE
Baba
M
et al
.
Glial cytoplasmic inclusions in white matter oligodendrocytes of multiple system atrophy brains contain insoluble α-synuclein
.
Ann Neurol
 
1998
;
44
:
415
22
23.
Lantos
PL
Papp
MI
.
Cellular pathology of multiple system atrophy: A review
.
J Neurol Neurosurg Psychiatry
 
1994
;
57
:
129
33
24.
Komori
T
.
Tau-positive glial inclusions in progressive supranuclear palsy, corticobasal degeneration and Pick's disease
.
Brain Pathol
 
1999
;
9
:
663
79
25.
Spillantini
MG
Bird
TD
Ghetti
B
.
Frontotemporal dementia and Parkinsonism linked to chromosome 17: A new group of tauopathies
.
Brain Pathol
 
1998
;
8
:
387
402
26.
Arai
T
Nonaka
T
Hasegawa
M
et al
.
Neuronal and glial inclusions in frontotemporal dementia with or without motor neuron disease are immunopositive for p62
.
Neurosci Lett
 
2003
;
342
:
41
44
27.
Forno
LS
Langston
JW
Herrick
MK
et al
.
Ubiquitin-positive neuronal and tau 2-positive glial inclusions in frontotemporal dementia of motor neuron type
.
Acta Neuropathol (Berl)
 
2002
;
103
:
599
606
28.
Ayala
YM
Pantano
S
D'Ambrogio
A
et al
.
Human, Drosophila, and C. elegans TDP43: Nucleic acid binding properties and splicing regulatory function
.
J Mol Biol
 
2005
;
348
:
575
88
29.
Wang
IF
Reddy
NM
Shen
CK
.
Higher order arrangement of the eukaryotic nuclear bodies
.
Proc Natl Acad Sci U S A
 
2002
;
99
:
13583
88

Author notes

This work was funded by the National Institutes of Health (AG10124 and AG17586) and the German Federal Ministry of Education and Research (01GI0299). VM-YL is the John H. Ware III Chair of Alzheimer's Research and JQT is the William Maul Measey-Truman G. Schnabel, Jr., MD, Professor of Geriatric Medicine and Gerontology.