Frontotemporal lobar degeneration with motor neuron disease-type inclusions predominates in 76 cases of frontotemporal degeneration

This report presents the largest series of consecutive, neuropathologically confirmed cases of frontotemporal degeneration (FTD). Prior studies have found dementia lacking distinctive histology (DLDH) to be the most common pathology underlying the clinical diagnosis of FTD. In this series of 76 cases, 29 (38%) were found to have frontotemporal lobar degeneration with motor neuron disease-type inclusions (FTLD-MND-type) or FTLD-MND (with ALS), the most common neuropathological classification in our series. Only eight (11%) were classified as Picks disease. Several cases originally designated as DLDH could be reclassified as FTLD-MND-type based on current recommendations for classification of FTD.     

ApoE and TDP-43 neuropathology in two siblings with familial FTLD-motor neuron disease

Frontotemporal lobar degeneration with motor neuron disease (FTLD-MND) is characterized by neuronal cytoplasmic inclusions containing TDP-43. Apolipoprotein E4 (apoE4), derived from the apoE ?4 allele, enhances brain atrophy in FTLD through unknown mechanisms. Here, we studied two siblings with C9ORF72-linked familial FTLD-MND, an apoE ?4 homozygote and an apoE ?3 homozygote. The apoE ?4 homozygote had more cognitive-behavioral symptoms, fronto-insulo-temporal atrophy, and apoE fragments and aggregates in the anterior cingulate cortex. ApoE formed complexes with TDP-43 that were more abundant in the apoE ?4 homozygote. Although differences seen in a sibling pair could arise due to chance, these findings raise the possibility that apoE4 exacerbates brain pathology in FTLD through formation of neurotoxic apoE fragments and interactions with TDP-43.     

Cortical ubiquitin-positive inclusions in frontotemporal dementia without motor neuron disease: a quantitative immunocytochemical study

Ubiquitin-positive tau-negative inclusions were initially described in the rare form of frontotemporal dementia (FTD) associated with motor neuron disease. However, recent studies have indicated that these inclusions are also present in typical FTD, which is usually characterized by nonspecific histological changes. To examine the contribution of these inclusions to neuronal loss and to explore their relationship with disease duration, we performed a quantitative immunocytochemical analysis of 38 typical FTD cases. Relationships between neuron and ubiquitin inclusion densities as well as between duration of illness and neuropathological parameters was studied using linear regression in both univariate and multivariate models. Ubiquitin-positive tau-negative intracytoplasmic inclusions were present in 65.8% of cases in the dentate gyrus, 57.9% in temporal cortex and 31.6% in frontal cortex. The highest densities of ubiquitin-positive inclusions were consistently observed in the dentate gyrus, followed by the temporal and frontal cortex. There was no statistically significant relationship between neuron and ubiquitin-positive inclusion densities in any of the areas studied. In contrast, ubiquitin-positive inclusion densities in the dentate gyrus were negatively related to the duration of illness. Our data suggest that the development of ubiquitin-related pathology is the rule and not the exception in typical FTD, yet is not causally related to neuronal loss. They also reveal that the development of ubiquitin-positive inclusion densities in the dentate gyrus may be associated with a more aggressive form of the disease.     

Coexisting adult polyglucosan body disease with frontotemporal lobar degeneration with transactivation response DNA-binding protein-43 (TDP-43)-positive neuronal inclusions

Almost one-third of the participants in a neuropsychological study signed the consent form below the given line. The relationship between a signature position on or below the line and participants’ cognitive function was investigated. Fifty drug-dependent individuals, 50 of their siblings, and 50 unrelated control participants completed a battery of neuropsychological tests using the Cambridge Neuropsychological Test Automated Battery (CANTAB). Individuals signing below, rather than on, the line performed more poorly on tests of visuospatial memory, but no differently on other cognitive tests. Signature positioning may be a soft sign for impairment of the mechanisms involved in visuospatial memory.     

Fine structural analysis of the neuronal inclusions of frontotemporal lobar degeneration with TDP-43 proteinopathy

TAR DNA-binding protein of 43 kDa (TDP-43) is a major component of the pathological inclusions of frontotemporal lobar degeneration with TDP-43 proteinopathy, also called FTLD with ubiquitin-positive, tau-negative inclusions (FTLD-U), and motor neuron disease (MND). TDP-43 is predominantly expressed in the nucleus and regulates gene expression and splicing. In FTLD with TDP-43 proteinopathy, neuronal inclusions present variably as cytoplasmic inclusions (NCIs), dystrophic neurites (DNs), and intranuclear inclusions (NIIs), leading to a fourfold neuropathological classification correlating with genotype. There have been few fine structural studies of these inclusions. Thus, we undertook an immunoelectron microscopic study of FTLD with TDP-43 proteinopathy, including sporadic and familial cases with progranulin (GRN) mutation. TDP-43-immunoreactive inclusions comprised two components: granular and filamentous. Filament widths, expressed as mean (range) were: NCI, 9 nm (4–16 nm); DN, 10 nm (5–16 nm); NII, 18 nm (9–50 nm). Morphologically distinct inclusion components may reflect the process of TDP-43 aggregation and interaction with other proteins: determining these latter may contribute towards understanding the heterogeneous pathogenesis of FTLD with TDP-43 proteinopathy. Supported by grants to JRT and NJC from the Wellcome Trust (GR066166AIA), and National Institute on Aging of the National Institutes of Health (P50 AG05681 and P01 AG03991) to NJC.     

Frontotemporal lobar degeneration with ubiquitin-positive, but TDP-43-negative inclusions

Frontotemporal lobar degeneration (FTLD) can be pathologically subdivided into tau-positive and tau-negative types. The most common tau-negative variant is FTLD with ubiquitin-immunoreactive lesions (FTLD-U). Recently, the TAR DNA binding protein 43 (TDP-43) was identified in neuronal inclusions in FTLD-U. After applying TDP-43 immunohistochemistry to a series of 44 cases of FTLD-U with no secondary pathology, three cases (7%) were identified with ubiquitin- and p62-positive neuronal cytoplasmic inclusions (NCI) that were negative for TDP-43. All the three cases had marked brain atrophy with striking atrophy of the striatum. Cases 1 and 2 presented at ages 43 and 38, respectively, as behavioral variant frontotemporal dementia (1 with positive family history) and had ubiquitin- and p62-positive NCI in frontotemporal neocortex and dentate granule cells of the hippocampus. Case 3 presented with the corticobasal syndrome. Unlike the other two cases, ubiquitin- and p62-positive NCI were also visible on hematoxylin and eosin stain. There were no neuronal intranuclear inclusions. Electron microscopic examination of the NCI in cases 2 and 3 revealed granulofilamentous inclusions. These cases confirm the existence of TDP-43-negative FTLD-U and extend the clinical and pathological spectrum of this disorder. The findings raise the possibly of an as yet identified protein that may play a pathogenic role in tau-negative FTLD.     

TDP-43 in differential diagnosis of motor neuron disorders

Motor neuron disorders are clinically and pathologically heterogeneous. They can be classified into those that affect primarily upper motor neurons, lower motor neurons or both. The most common disorder to affect both upper and lower motor neurons is amyotrophic lateral sclerosis (ALS). Some forms of motor neuron disease (MND) affect primarily motor neurons in the spinal cord or brainstem, while others affect motor neurons at all levels of the neuraxis. A number of genetic loci have been identified for the various motor neuron disorders. Several of the MND genes encode for proteins important for cytoskeletal stability and axoplasmic transport. Despite these genetic advances, the relationship of the various motor neuron disorders to each other is unclear. Except for rare familial forms of ALS associated with mutations in superoxide dismutase type 1 (SOD1), which are associated with neuronal inclusions that contain SOD1, specific molecular or cellular markers that differentiate ALS from other motor neuron disorders have not been available. Recently, the TAR DNA binding protein 43 (TDP-43) has been shown to be present in neuronal inclusions in ALS, and it has been suggested that TDP-43 may be a specific marker for ALS. This pilot study aimed to determine the value of TDP-43 in the differential diagnosis of MND. Immunohistochemistry for TDP-43 was used to detect neuronal inclusions in the medulla of disorders affecting upper motor neurons, lower motor neurons or both. Medullary motor neuron pathology also was assessed in frontotemporal lobar degeneration (FTLD) that had no evidence of MND. TDP-43 immunoreactivity was detected in the hypoglossal nucleus in all cases of ALS, all cases of FTLD-MND and some of cases of primary lateral sclerosis (PLS). It was not detected in FTLD-PLS. Surprisingly, sparse TDP-43 immunoreactivity was detected in motor neurons in about 10% of FTLD that did not have clinical or pathologic features of MND. The results suggest that TDP-43 immunoreactivity is useful in differentiating FTLD-MND and ALS from other disorders associated with upper or lower motor neuron pathology. It also reveals subclinical MND in a subset of cases of FTLD without clinical or pathologic evidence of MND.     

White matter lesions in the brain with frontotemporal lobar degeneration with motor neuron disease: TDP-43-immunopositive inclusions co-localize with p62, but not ubiquitin

Recently, TDP-43 was established as a major component of the ubiquitinated inclusions found in both amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with motor neuron disease (FTLD-MND). However, differences in the underlying pathogenesis between ALS and FTLD-MND remain yet to be elucidated. Originally, TDP-43-immunopositive inclusions were found in neuronal cells and reported to be ubiquitinated. This study shows that TDP-43-positive inclusions were distributed throughout the subcortical white matter except for the occipital lobe in the FTLD-MND brain, but not in the ALS brain. TDP-43-positive inclusions were also prominent features of pathologically proven FTLD-MND cases (p-FTLD-MND) without history of apparent clinical cognitive decline. A substantial fraction of these inclusions was also p62-immunoreactive, and another noteworthy feature was that those inclusions did not stain positively for ubiquitin. Significant correlations between immunoreactivity for TDP-43 and p62 were observed, particularly in p-FTLD-MND (Pearson correlation coefficient, 0.976). Furthermore, TDP-43 extracted from white matter appeared to be uncleaved. These results indicate that pathological changes might take place within the white matter also in the brain with FTLD-MND, but in a different manner than within the gray matter.     

Ultrastructural localization of TDP-43 in filamentous neuronal inclusions in various neurodegenerative diseases

Using post-embedding immunogold electron microscopy, TAR DNA-binding protein of 43 kDa (TDP-43) was localized to neuronal cytoplasmic (NCI) and intranuclear (NII) inclusions, as well as unmyelinated neurites, in frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-U), amyotrophic lateral sclerosis (ALS), Alzheimer's (AD), Pick's disease (PiD) and Lewy body disease (LBD). The TDP-43 immunoreactive structures were morphologically heterogeneous. The most common was characterized by bundles of 10-20 nm diameter straight filaments with electron dense granular material within NCI, NII and neurites. This type of pathology was found in FTLD-U, ALS and some cases of AD. Less often, inclusions in neuritic processes of FTLD-U and some cases of AD contained 10-17 nm diameter straight filaments without granular material. A final type of TDP-43 immunoreactivity was labeling of filaments and granular material associated with tau filaments in neurofibrillary tangles of AD and Pick bodies of PiD or alpha-synuclein filaments in Lewy bodies of LBD. The results suggest that TDP-43 is the primary component of the granulofilamentous inclusions in FTLD-U and ALS. Similar inclusions sometimes accompany filamentous aggregates composed of other abnormal proteins in AD, PiD and LBD.     

The molecular genetics and neuropathology of frontotemporal lobar degeneration: recent developments

The past year has seen a number of significant advances in our understanding of the neuropathological and molecular genetic basis of frontotemporal lobar degeneration (FTLD). Whereas, in the past, most attention focused on FTLD associated with tau-based pathology and microtubule associated protein tau gene (MAPT) mutations, there has recently been greater attention paid to non-tau FTLD. FTLD with tau-negative, ubiquitinated inclusions (FTLD-U) is now recognized as the most common pathology associated with clinical FTLD. Mutations in the progranulin gene (PGRN) have been identified as the cause of FTLD-U linked to chromosome 17. A rapidly growing number of PGRN mutations have been identified, and to date, all appear to cause FTLD by reducing the amount of functional PGRN protein (haploinsufficiency). The neuropathology associated with each of the known non-MAPT FTLD genes and loci (PGRN, valosin-containing protein gene, CHMP2B and 9p), has been shown to be a specific subtype of FTLD-U. The ubiquitinated pathological protein in FTLD-U has been identified as TAR deoxyribonucleic acid-binding protein with M _r 43 kDa (TDP-43). Immunohistochemical and biochemical studies of TDP-43 have helped to clarify the relationship between different sub-types of FTLD-U and related conditions. It is anticipated that these discoveries will facilitate the development of new diagnostic tests and therapeutics.     

Neuronal loss in familial frontotemporal dementia with ubiquitin-positive,tau-negative inclusions

The neuronal density in the frontal, temporal, and parietal lobes was determined in nine cases of familial frontotemporal dementia with ubiquitin-positive, tau-negative inclusions (FTDU). The mean age at onset was 56.9 +/- 2.2 years and the duration of disease was 6.7 +/- 0.5 years. The mean age at death was 63.6 +/- 2.2 years. There was substantial loss (34%) of brain weight (877 +/- 73 g) in the familial cases in comparison with 10 normal aged controls (1326 +/- 50 g, P < 0.001). All of the familial FTDU cases showed atrophy of the frontal, temporal, and parietal lobes; neuronal loss; vacuolation in superficial laminae; reactive astrocytosis; and ubiquitin-positive, tau-negative intracytoplasmic and intranuclear inclusions and dystrophic neurites in varying sites and numbers. Neuronal loss was estimated in nine cases of familial FTDU and in 10 aged controls using a stereological probe, the optical "disector," and a computerized stereology system (CAST-Grid, Olympus, Denmark). There was a significant reduction in neuronal density in the frontal lobe (22.3 +/- 3.8 x 10(3)/mm(3)) of familial FTDU in comparison to aged controls (33.1 +/- 1.7 x 10(3) per mm(3), P < 0.05). An estimate of the relative numbers of neurons was calculated by multiplying the numerical density by the cortical thickness, which showed a striking loss of neurons of 56% in the frontal lobe, 52% loss in the temporal lobe, and a 49% loss in the parietal lobe of familial FTDU when compared to controls. This study shows that familial FTDU has profound focal neuronal loss in multiple association areas that relate to the clinical symptoms characteristic of the disease.     

Spatial patterns of TDP-43 neuronal cytoplasmic inclusions (NCI) in fifteen cases of frontotemporal lobar degeneration with TDP-43 proteinopathy (FTLD-TDP)

Neuronal cytoplasmic inclusions (NCI) immunoreactive for transactive response DNA-binding protein (TDP-43) are the pathological hallmark of frontotemporal lobar degeneration with TDP-43 proteinopathy (FTLD-TDP). We studied the spatial patterns of the TDP-43 immunoreactive NCI in the frontal and temporal cortex of 15 cases of FTLD-TDP. The NCI were distributed parallel to the tissue boundary predominantly in regular clusters 50??00?μm in diameter. In five cortical areas, the size of the clusters approximated to the cells of the cortico-cortical pathways. In most regions, cluster size was smaller than 400?μm. There were no significant differences in spatial patterns between familial and sporadic cases. Cluster size of the NCI was not correlated with disease duration, brain weight, Braak stage, or disease subtype. The spatial pattern of the NCI was similar to that of neuronal inclusions in other neurodegenerative diseases and may reflect a common pattern of degeneration involving the cortico-cortical projections.     

Increased neuronal Rab5 immunoreactive endosomes do not colocalize with TDP-43 in motor neuron disease

Sporadic motor neuron disease (MND) is characterized by progressive degeneration of motor neurons and intraneuronal cytoplasmic translocation and deposition of the nuclear protein TDP-43. There is a paucity of data on the subcellular mechanisms of the nuclear-cytoplasmic trafficking of TDP-43, particularly about the precise role of the endosomal-lysosomal system (ELS). In the present study, using a neuron-specific morphometric approach, we examined the expression of the early endosomal marker Rab5 and lysosomal cathepsins B, D, F, and L as well as PAS-stained structures in the anterior horn cells in 11 individuals affected by sporadic MND and 5 age-matched controls. This was compared with the expression of ubiquitin, p62 and TDP-43 and its phosphorylated form. The principal finding was the increased expression of the endosomal marker Rab5 and lysosomal cathepsin D, and of PAS-positive structures in motor neurons of MND cases. Furthermore, the area-portion of Rab5 immunoreactivity correlated well with the intracellular accumulation of ubiquitin, p62 and (phosphorylated) TDP-43. However, double immunolabelling and immunogold electron microscopy excluded colocalization of phosphorylated TDP-43 with the ELS. These data contrast with observations on neuronal cytopathology in Alzheimer's or prion diseases where the disease-specific proteins are processed within endosomes, and suggest a distinct role of the ELS in MND.     

Basophilic inclusion body disease and neuronal intermediate filament inclusion disease: a comparative clinicopathological study

While both neuronal intermediate filament inclusion disease (NIFID) and basophilic inclusion body disease (BIBD) show frontotemporal lobar degeneration and/or motor neuron disease, it remains unclear whether, and how, these diseases differ from each other. Here, we compared the clinicopathological characteristics of four BIBD and two NIFID cases. Atypical initial symptoms included weakness, dysarthria, and memory impairment in BIBD, and dysarthria in NIFID. Dementia developed more than 1 year after the onset in some BIBD and NIFID cases. Upper and lower motor neuron signs, parkinsonism, and parietal symptoms were noted in both diseases, and involuntary movements in BIBD. Pathologically, severe caudate atrophy was consistently found in both diseases. Cerebral atrophy was distributed in the convexity of the fronto-parietal region in NIFID cases. In both BIBD and NIFID, the frontotemporal cortex including the precentral gyrus, caudate nucleus, putamen, globus pallidus, thalamus, amygdala, hippocampus including the dentate gyrus, substantia nigra, and pyramidal tract were severely affected, whereas lower motor neuron degeneration was minimal. While α-internexin-positive inclusions without cores were found in both NIFID cases, one NIFID case also had α-internexin- and neurofilament-negative, but p62-positive, cytoplasmic spherical inclusions with eosinophilic p62-negative cores. These two types of inclusions frequently coexisted in the same neuron. In three BIBD cases, inclusions were tau-, α-synuclein-, α-internexin-, and neurofilament-negative, but occasionally p62-positive. These findings suggest that: (1) the clinical features and distribution of neuronal loss are similar in BIBD and NIFID, and (2) an unknown protein besides α-internexin and neurofilament may play a pivotal pathogenetic role in at least some NIFID cases.     

Maturation process of TDP-43-positive neuronal cytoplasmic inclusions in amyotrophic lateral sclerosis with and without dementia

Parkinson’s disease (PD) is a neurodegenerative disease characterized by the selective loss of dopamine (DA) neurons and the presence of α-synuclein (AS) aggregates as Lewy bodies (LBs) in the remaining substantia nigra (SN) neurons. A continuing puzzle in studying PD pathogenesis is that although AS is expressed throughout the brain, LBs and selective dopaminergic cell loss lead to characteristic clinical signs of PD, suggesting that there is a link between AS aggregation and DA metabolism. One potential candidate for this link is the monoamine oxidase (MAO) metabolite of DA, 3,4-dihydroxyphenylacetaldehyde (DOPAL), as neither DA nor DA metabolites other than DOPAL are toxic to SN neurons at physiological concentrations. We tested DOPAL-induced AS aggregation in a cell-free system, in vitro in DA neuron cultures and in vivo with stereotactic injections into the SN of Sprague–Dawley rats by Western blots, fluorescent confocal microscopy and immunohistochemistry. We demonstrate that DOPAL in physiologically relevant concentrations, triggers AS aggregation in the cell-free system, and in cell cultures resulting in the formation of potentially toxic AS oligomers and aggregates. Furthermore, DOPAL injection into the SN of Sprague–Dawley rats resulted in DA neuron loss and the accumulation of high molecular weight oligomers of AS detected by Western blot. Our findings support the hypothesis that DA metabolism via DOPAL can cause both DA neuron loss and AS aggregation observed in PD. Supported by grants from Missouri ADRDA Program (WJB, NP), Nestle Foundation (VBK), St. Louis VAMC (WJB,VBK), NIH HL 64772 (WMP), NIH AG20764, AG 03991, AG 05681 (JEG), the American Federation on Aging Research (JEG), and generous gifts from the Alan A. and Edith L. Wolff Charitable Trust (JEG) and Blue Gator Foundation (JEG).     

TDP-43 proteinopathy: the neuropathology underlying major forms of sporadic and familial frontotemporal lobar degeneration and motor neuron disease

The rapid confirmation of the initial report by Neumann et al. (Science 314:130–133, 2006) that transactive response (TAR)-DNA-binding protein 43 (TDP-43) is the major disease protein linking frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U) with and without motor neuron disease (MND) as well as amyotrophic lateral sclerosis (ALS) implies that TDP-43 proteinopathy underlies major forms of sporadic as well as familial FTLD and ALS. Not only was the identity of the ubiquitinated proteins that accumulate in neurons and glia of these disorders finally resolved, but it also was shown that pathologic TDP-43 was hyperphosphorylated, ubiquitinated and cleaved to generate C-terminal fragments in affected brain and spinal cord of FTLD-U and ALS. This review summarizes the growing evidence that TDP-43 proteinopathy is the common pathologic substrate linking FTLD and ALS, and it considers the implications of these findings for developing better strategies to diagnose and treat these neurodegenerative disorders.     

TDP-43-negative FTLD-U is a significant new clinico-pathological subtype of FTLD

Frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U) is the most common neuropathological subtype of frontotemporal dementias. While TDP-43 is the pathologic protein in the majority of FTLD-U cases, small numbers of cases have recently been reported with TDP-43-negative FTLD-U pathology. To determine the frequency and to define the clinico-pathological spectrum of TDP-43-negative FTLD-U, we re-evaluated 44 cases with a previous diagnosis of FTLD-U or dementia lacking distinctive histopathology. We identified nine cases (20%) with TDP-43-negative FTLD-U pathology by immunohistochemistry and confirmed the absence of pathological TDP-43 by biochemical analysis. All patients presented with sporadic early-onset frontotemporal dementia with predominant behavioral and personality changes. Besides ubiquitin-positive neuronal cytoplasmic inclusions, the most intriguing neuropathological feature was the presence of ubiquitin-positive neuronal intranuclear inclusions (NIIs), often with curved or twisted morphology, in the neocortex, hippocampus, brainstem, and spinal cord. Double-label immunofluorescence revealed an unusual and distinct immunoreactivity profile for these NIIs, with ubiquitin-immunoreactivity, but absence of p62 labeling. The highly consistent clinical and neuropathological phenotype supports the concept that TDP-43-negative FTLD-U should be considered as a new clinicopathological FTLD entity.     

p62/sequestosome 1 binds to TDP-43 in brains with frontotemporal lobar degeneration with TDP-43 inclusions

Ubiquitin‐positive cytoplasmic inclusions are consistently found in various neurodegenerative diseases. As with ubiquitin, anti‐p62/SQSTM1 (referred to as p62) antibody clearly immunostains these inclusions. p62 has a ubiquitin‐associated domain at the carboxyl terminus and thereby interacts with ubiquitinated and misfolded proteins. Here we immunoprecipitated endogenous p62 in the cerebral cortex from patients with frontotemporal lobar degeneration with TDP‐43 inclusions (FTLD‐TDP) and found that p62 coimmunoprecipitated several proteins, including TDP‐43, which is a major disease protein in FTLD‐TDP. Unexpectedly, p62 immunoprecipitated a smaller amount of TDP‐43 in FTLD‐TDP compared with controls. Further analyses showed that p62 physiologically binds to TDP‐43 and likely is involved in degradation of TDP‐43 with 35‐kDa, but not full‐length TDP‐43. Our results suggest that the interaction of TDP‐43 and p62 is disrupted and may participate in the pathogenesis of TDP‐43 proteinopathy. © 2012 Wiley Periodicals, Inc.