Progressive supranuclear palsy (PSP) is a relatively common neurodegenerative tauopathy clinically characterized by parkinsonism, axial rigidity, and supranuclear gaze palsy. Pathologic findings of PSP are neuronal loss, gliosis, and neurofibrillary tangles in basal ganglia, diencephalon, and brainstem; there is increasing recognition of clinicopathologic variants of PSP.1
Mutations in ATP13A2 (PARK9), encoding a lysosomal P-type ATPase, are associated with both Kufor–Rakeb syndrome (KRS) and neuronal ceroid lipofuscinosis (NCL). KRS has recently been classified as a rare genetic form of Parkinson's disease (PD), whereas NCL is a lysosomal storage disorder. Although the transport activity of ATP13A2 has not been defined, in vitro studies show that its loss compromises lysosomal function, which in turn is thought to cause neuronal degeneration. To understand the role of ATP13A2 dysfunction in disease, we disrupted its gene in mice. Atp13a2−/− and Atp13a2+/+ mice were tested behaviorally to assess sensorimotor and cognitive function at multiple ages. In the brain, lipofuscin accumulation, α-synuclein aggregation and dopaminergic pathology were measured. Behaviorally, Atp13a2−/− mice displayed late-onset sensorimotor deficits. Accelerated deposition of autofluorescent storage material (lipofuscin) was observed in the cerebellum and in neurons of the hippocampus and the cortex of Atp13a2−/− mice. Immunoblot analysis showed increased insoluble α-synuclein in the hippocampus, but not in the cortex or cerebellum. There was no change in the number of dopaminergic neurons in the substantia nigra or in striatal dopamine levels in aged Atp13a2−/− mice. These results show that the loss of Atp13a2 causes sensorimotor impairments, α-synuclein accumulation as occurs in PD and related synucleinopathies, and accumulation of lipofuscin deposits characteristic of NCL, thus providing the first direct demonstration that null mutations in Atp13a2 can cause pathological features of both diseases in the same organism.
We examined the clinical and pathologic phenotypes of GRN mutation carriers with the pathogenic A9D (g.26C>A) missense mutation.
Three patients with GRN A9D mutations were evaluated clinically and came to autopsy with subsequent neuropathologic examination.
The clinical diagnoses of patients with GRN A9D mutations were amyotrophic lateral sclerosis, atypical extrapyramidal disorder, and behavioral variant frontotemporal dementia. Immunohistochemistry for TAR DNA-binding protein 43 (TDP-43) revealed variability in morphology and distribution of pathology. One patient had notable involvement of motor neurons in the spinal cord as well as type B TDP-43, whereas 2 other patients had type A TDP-43.
The clinical presentation of the GRN A9D missense mutation is not restricted to behavioral variant frontotemporal dementia and may include aphasia, extrapyramidal features, and, notably, amyotrophic lateral sclerosis.
Neuronal inclusions of α-synuclein (α-syn), termed Lewy bodies, are a hallmark of Parkinson disease (PD). Increased α-syn levels can occur in brains of aging human and neurotoxin treated mice. Since previous studies have shown increased brain lactate levels in aging brains, in PD affected subjects when compared to age-matched controls, and in mice treated with MPTP, we tested the effects of lactate exposure on α-syn in a cell based-study. We demonstrated that (i) lactate treatment led to α-syn accumulation and oligomerization in a time- and concentration-dependent manner, (ii) such alterations were mediated via adenosine-monophosphate activated protein kinase (AMPK) and associated with increasing cytoplasmic phosphorylated AMPK levels, (iii) AMPK activation facilitated α-syn accumulation and phosphorylation, (iv) lactate treatment or overexpression of active form of AMPK decreased α-syn turnover and neurite outgrowth and (v) Lewy body-bearing neurons displayed abnormal cytoplasmic distribution of phosphorylated AMPK, which normally is located in nuclei. Together, our results suggest that chronic neuronal accumulation of α-syn induced by lactate-triggered AMPK activation in aging brains may be a novel mechanism underlying α-synucleionpathies in PD and related disorders.
Alpha-synuclein; Parkinson’s disease; AMPK; lactate
CBD is a disorder affecting cognition and movement due to a progressive neurodegeneration associated with distinctive neuropathologic features, including abnormal phosphorylated tau protein in neurons and glia in cortex, basal ganglia, diencephalon and brainstem, as well as ballooned neurons and astrocytic plaques. We identified three cases of CBD with olivopontocerebellar atrophy (CBD-OPCA) that did not have α-synuclein-positive glial cytoplasmic inclusions of multiple system atrophy (MSA). Two patients had clinical features suggestive of progressive supranuclear palsy (PSP), and the third case had cerebellar ataxia thought to be due to idiopathic OPCA. Neuropathologic features of CBD-OPCA are compared to typical CBD, as well as MSA and PSP. CBD-OPCA and MSA had marked neuronal loss in pontine nuclei, inferior olivary nucleus, and Purkinje cell layer. Neuronal loss and grumose degeneration in the cerebellar dentate nucleus was comparable in CBD-OPCA and PSP. Image analysis of tau pathology showed greater infratentorial tau burden, especially in pontine base, in CBD-OPCA compared with typical CBD. Additionally, CBD-OPCA had TDP-43 immunoreactive neuronal and glial cytoplasmic inclusions and threads throughout the basal ganglia and in olivopontocerebellar system. CBD-OPCA met neuropathologic research diagnostic criteria for CBD and shared tau biochemical characteristics with typical CBD. These results suggest that CBD-OPCA is a distinct clinicopathologic variant of CBD with olivopontocerebellar TDP-43 pathology.
Corticobasal degeneration; olivopontocerebellar atrophy; tauopathy; multiple system atrophy; progressive supranuclear palsy; TDP-43
To reveal the underlying mechanisms responsible for the regional vulnerability to amyloid-β (Aβ) accumulation prior to the development of Alzheimer’s disease, we studied distribution of Aβ, apolipoprotein E (apoE), synaptic markers, and other molecules involved in Aβ metabolism in multiple brain areas of non-demented individuals. Twelve brain regions including neocortical, limbic, and subcortical areas were dissected from brains of non-demented individuals and extracted according to increasing insolubility by a sequential three-step method. The levels of Aβ40, Aβ42, apoE, APP, APP-CTFβ, BACE1, presenilin-1, neprilysin, insulysin, LRP1, LDLR, synaptophysin, PSD95, GFAP, and lactate were determined by ELISAs or enzymatic assays. The regional distribution of apoE showed moderate-to-strong inverse correlation with levels of Aβ, especially insoluble Aβ40. On the other hand, the regional distributions of synaptic markers, particularly PSD95, showed moderate-to-strong positive correlation with levels of Aβ, especially soluble Aβ40. The regional correlations between Aβ and LRP1, GFAP, or lactate were mild-to-moderate. Moderate-to-strong positive regional correlations were observed between apoE and GFAP or lactate and between PSD95 and LRP1. No significant regional correlations were detected between Aβ and APP, APP-CTFβ, BACE1, or presenilin-1, those involved in Aβ production. There were no significant negative regional correlations between Aβ and two major Aβ degrading enzymes, neprilysin and insulysin. These regional correlations remained consistent regardless of the degree of Aβ accumulation. The regional vulnerability to Aβ accumulation may be due to a net balance between two competing processes: (1) synapses involved in promoting the initial Aβ accumulation and (2) astrocyte-derived apoE involved in preventing Aβ accumulation.
Alzheimer’s disease; Amyloid-β; Regional vulnerability; Apolipoprotein E; Synapses
Pigmented orthochromatic leukodystrophy (POLD) and hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS) are rare neurodegenerative disorders characterized by cerebral white matter abnormalities, myelin loss, and axonal swellings. The striking overlap of clinical and pathologic features of these disorders suggested a common pathogenesis; however, no genetic or mechanistic link between POLD and HDLS has been established. Recently, we reported that mutations in the colony-stimulating factor 1 receptor (CSF1R) gene cause HDLS. In this study, we determined whether CSF1R mutations are also a cause of POLD.
We performed sequencing of CSF1R in 2 pathologically confirmed POLD families. For the largest family (FTD368), a detailed case report was provided and brain samples from 2 affected family members previously diagnosed with POLD were re-evaluated to determine whether they had HDLS features. In vitro functional characterization of wild-type and mutant CSF1R was also performed.
We identified CSF1R mutations in both POLD families: in family 5901, we found c.2297T>C (p.M766T), previously reported by us in HDLS family CA1, and in family FTD368, we identified c.2345G>A (p.R782H), recently reported in a biopsy-proven HDLS case. Immunohistochemical examination in family FTD368 showed the typical neuronal and glial findings of HDLS. Functional analyses of CSF1R mutant p.R782H (identified in this study) and p.M875T (previously observed in HDLS), showed a similar loss of CSF1R autophosphorylation of selected tyrosine residues in the kinase domain for both mutations when compared with wild-type CSF1R.
We provide the first genetic and mechanistic evidence that POLD and HDLS are a single clinicopathologic entity.
Recent genome-wide association studies (GWAS) of late-onset Alzheimer’s disease (LOAD) have identified single nucleotide polymorphisms (SNPs) which show significant association at the well-known APOE locus and at nineteen additional loci. Among the functional, disease-associated variants at these loci, missense variants are particularly important because they can be readily investigated in model systems to search for novel therapeutic targets. It is now possible to perform a low-cost search for these “actionable” variants by genotyping the missense variants at known LOAD loci already cataloged on the Exome Variant Server (EVS). In this proof-of-principle study designed to explore the efficacy of this approach, we analyzed three rare EVS variants in APOE, p.L28P, p.R145C and p.V236E, in our case control series of 9114 subjects. p.R145C proved to be too rare to analyze effectively. The minor allele of p.L28P, which was in complete linkage disequilibrium (D’ = 1) with the far more common APOE ϵ4 allele, showed no association with LOAD (P = 0.75) independent of the APOE ϵ4 allele. p.V236E was significantly associated with a marked reduction in risk of LOAD (P = 7.5×10−05; OR = 0.10, 0.03 to 0.45). The minor allele of p.V236E, which was in complete linkage disequilibrium (D’ = 1) with the common APOE ϵ3 allele, identifies a novel LOAD-associated haplotype (APOE ϵ3b) which is associated with decreased risk of LOAD independent of the more abundant APOE ϵ2, ϵ3 and ϵ4 haplotypes. Follow-up studies will be important to confirm the significance of this association and to better define its odds ratio. The ApoE p.V236E substitution is the first disease-associated change located in the lipid-binding, C-terminal domain of the protein. Thus our study (i) identifies a novel APOE missense variant which may profitably be studied to better understand how ApoE function may be modified to reduce risk of LOAD and (ii) indicates that analysis of protein-altering variants cataloged on the EVS can be a cost-effective way to identify actionable functional variants at recently discovered LOAD loci.
We recently reported a missense mutation and four variants in eukaryotic translation initiation factor 4-gamma (EIF4G1) associated with parkinsonism, dementia or both. In those with a positive family history, the mode of inheritance was autosomal dominant. Detailed neuropathologic descriptions of individuals with EIF4G1 genetic variants have not been reported. Herein, we report neuropathologic findings of three individuals from two American families with EIF4G1 variants. The patients had initial clinical presentations of dementia or parkinsonism and all had dementia at the time of autopsy. One family carried an EIF4G1 double variant, c.2056G>T (p.G686C) and c.3589C>T (p.R1197W), and one family carried variant c.1505C>T (p.A502V). All three patients also carried at least one ε4 allele of apolipoprotein E. One individual presented with cognitive impairment without significant parkinsonism; one presented with memory problems followed by bradykinesia; and the third presented with cardinal signs of Parkinson’s disease, followed more than a year later by cognitive dysfunction. Pathological examination showed diffuse cortical Lewy bodies and Lewy neurites in all patients. A small subset of Lewy bodies and Lewy neurites were immunopositive for eIF4G1. All patients had moderate to frequent non-neuritic, cortical amyloid plaques, mostly medial temporal neurofibrillary pathology (Braak neurofibrillary tangle stages of II to IV), and minimal or no TDP-43 pathology. The results suggest that in some patients variants in EIF4G1 can be associated with pathology that has a high likelihood of association with clinical features of dementia with Lewy bodies.
APOE; dementia with Lewy bodies; diffuse Lewy body disease; EIF4G1; parkinsonism; α-synuclein; tau
Mutations of the TARDBP gene encoding TDP-43 protein have been shown to cause amyotrophic lateral sclerosis and have been reported to present with clinical heterogeneity including parkinsonism. In addition, TDP-43 pathology has been observed across a spectrum of neurodegenerative disorders, including Alzheimer’s and Parkinson’s disease. Herein we report the presence of a TDP-43 mutation in a patient with a clinical diagnosis of Parkinson’s disease. The TDP-43 p.N267S substitution has been previously implicated in both amyotrophic lateral sclerosis and behavioral variant frontotemporal dementia. Our findings widen the phenotypic presentation for the TDP-43 p.N267S substitution and support a possible role for rare TDP-43 mutations presenting with Parkinson’s disease.
TDP-43; amyotrophic lateral sclerosis; Parkinson’s disease
Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) are devastating neurodegenerative disorders with clinical, genetic, and neuropathological overlap. Hexanucleotide (GGGGCC) repeat expansions in a non-coding region of C9ORF72 are the major genetic cause of FTD and ALS (c9FTD/ALS). The RNA structure of GGGGCC repeats renders these transcripts susceptible to an unconventional mechanism of translation – repeat-associated non-ATG (RAN) translation. Antibodies generated against putative GGGGCC repeat RAN translated peptides (anti-C9RANT) detected high molecular weight, insoluble material in brain homogenates, and neuronal inclusions throughout the central nervous system of c9FTD/ALS cases. C9RANT immunoreactivity was not found in other neurodegenerative diseases, including CAG repeat disorders, or in peripheral tissues of c9FTD/ALS. The specificity of C9RANT for c9FTD/ALS is a potential biomarker for this most common cause of FTD and ALS. These findings have significant implications for treatment strategies directed at RAN translated peptides and their aggregation, and the RNA structures necessary for their production.
Rrecent studies have highlighted a group of 4-repeat (4R) tauopathies that are characterised neuropathologically by widespread, globular glial inclusions (GGIs). Tau immunohistochemistry reveals 4R immunore-active globular oligodendroglial and astrocytic inclusions and the latter are predominantly negative for Gallyas silver staining. These cases are associated with a range of clinical presentations, which correlate with the severity and distribution of underlying tau pathology and neurodegeneration. Their heterogeneous clinicopathological features combined with their rarity and under-recognition have led to cases characterised by GGIs being described in the literature using various and redundant terminologies. In this report, a group of neuropathologists form a consensus on the terminology and classification of cases with GGIs. After studying microscopic images from previously reported cases with suspected GGIs (n = 22), this panel of neuropathologists with extensive experience in the diagnosis of neurodegenerative diseases and a documented record of previous experience with at least one case with GGIs, agreed that (1) GGIs were present in all the cases reviewed; (2) the morphology of globular astrocytic inclusions was different to tufted astrocytes and finally that (3) the cases represented a number of different neuropathological subtypes. They also agreed that the different morphological subtypes are likely to be part of a spectrum of a distinct disease entity, for which they recommend that the overarching term globular glial tauopathy (GGT) should be used. Type I cases typically present with frontotemporal dementia, which correlates with the fronto-temporal distribution of pathology. Type II cases are characterised by pyramidal features reflecting motor cortex involvement and corticospinal tract degeneration. Type III cases can present with a combination of frontotemporal dementia and motor neuron disease with fronto-temporal cortex, motor cortex and corticospinal tract being severely affected. extrapyramidal features can be present in Type II and III cases and significant degeneration of the white matter is a feature of all GGT subtypes. Improved detection and classification will be necessary for the establishment of neuropathological and clinical diagnostic research criteria in the future.
We aimed to assess associations between clinical, imaging, pathological and genetic features and frontal lobe asymmetry in behavioral variant frontotemporal dementia (bvFTD). Volumes of the left and right dorsolateral, medial and orbital frontal lobes were measured in 80 bvFTD subjects and subjects were classified into three groups according to the degree of asymmetry (asymmetric left, asymmetric right, symmetric) using cluster analysis. The majority of subjects were symmetric (65%), with 20% asymmetric left and 15% asymmetric right. There were no clinical differences across groups, although there was a trend for greater behavioral dyscontrol in right asymmetric compared to left asymmetric subjects. More widespread atrophy involving the parietal lobe was observed in the symmetric group. Genetic features differed across groups with symmetric frontal lobes associated with C9ORF72 and tau mutations, while asymmetric frontal lobes were associated with progranulin mutations. These findings therefore suggest that neuroanatomical patterns of frontal lobe atrophy in bvFTD are influenced by specific gene mutations.
Frontotemporal dementia; frontal lobes; MRI; asymmetry; microtubule associated protein tau; progranulin; C9ORF72; pathology
An expanded GGGGCC hexanucleotide repeat in C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration associated with TDP-43 pathology (FTLD-TDP). In addition to TDP-43-positive neuronal and glial inclusions, C9ORF72-linked FTLD-TDP has characteristic TDP-43-negative neuronal cytoplasmic and intranuclear inclusions as well as dystrophic neurites in the hippocampus and cerebellum. These lesions are immunopositive for ubiquitin and ubiquitin-binding proteins, such as sequestosome-1/p62 and ubiquilin-2. Studies examining the frequency of the C9ORF72 mutation in clinically probable Alzheimer’s disease (AD) have found a small proportion of AD cases with the mutation. This prompted us to systematically explore the frequency of Alzheimer type pathology in a series of 17 FTLD-TDP cases with mutations in C9ORF72 (FTLD-C9ORF72). We identified 4 cases with sufficient Alzheimer type pathology to meet criteria for intermediate-to-high likelihood AD. We compared AD pathology in the 17 FTLD-C9ORF72 to 13 cases of FTLD-TDP linked to mutations in the gene for progranulin (FTLD-GRN) and 36 cases of sporadic FTLD (sFTLD). FTLD-C9ORF72 cases had higher Braak neurofibrillary tangle stage than FTLD-GRN. Increased tau pathology in FTLD-C9ORF72 was assessed with thioflavin-S fluorescent microscopy-based neurofibrillary tangle counts and with image analysis of tau burden in temporal cortex and hippocampus. FTLD-C9ORF72 had significantly more neurofibrillary tangles and higher tau burden compared with FTLD-GRN. The differences were most marked in limbic regions. On the other hand, sFTLD and FTLD-C9ORF72 had a similar burden of tau pathology. These results suggest FTLD-C9ORF72 has increased propensity for tau pathology compared to FTLD-GRN, but not sFTLD. The accumulation of tau as well as lesions immunoreactive for ubiquitin and ubiquitin binding proteins (p62 and ubiquilin-2) suggests that mutations in C9ORF72 may involve disrupted protein degradation that favors accumulation of multiple different proteins.
frontotemporal lobar degeneration; C9ORF72; ubiquitin; p62; ubiquilin-2; tau
Four subtypes of frontotemporal lobar degeneration with TDP-43 immunoreactive inclusions have been described (types A–D). Of these four subtypes, motor neuron disease is more commonly associated with type B pathology, but has also been reported with type A pathology. We have noted, however, the unusual occurrence of cases of type C pathology having corticospinal tract degeneration. We aimed to assess the severity of corticospinal tract degeneration in a large cohort of cases with type C (n = 31). Pathological analysis included semi-quantitation of myelin loss of fibres of the corticospinal tract and associated macrophage burden, as well as axonal loss, at the level of the medullary pyramids. We also assessed for motor cortex degeneration and fibre loss of the medial lemniscus/olivocerebellar tract. All cases were subdivided into three groups based on the degree of corticospinal tract degeneration: (i) no corticospinal tract degeneration; (ii) equivocal corticospinal tract degeneration; and (iii) moderate to very severe corticospinal tract degeneration. Clinical, genetic, pathological and imaging comparisons were performed across groups. Eight cases had no corticospinal tract degeneration, and 14 cases had equivocal to mild corticospinal tract degeneration. Nine cases, however, had moderate to very severe corticospinal tract degeneration with myelin and axonal loss. In these nine cases, there was degeneration of the motor cortex without lower motor neuron degeneration or involvement of other brainstem tracts. These cases most commonly presented as semantic dementia, and they had longer disease duration (mean: 15.3 years) compared with the other two groups (10.8 and 9.9 years; P = 0.03). After adjusting for disease duration, severity of corticospinal tract degeneration remained significantly different across groups. Only one case, without corticospinal tract degeneration, was found to have a hexanucleotide repeat expansion in the C9ORF72 gene. All three groups were associated with anterior temporal lobe atrophy on MRI; however, the cases with moderate to severe corticospinal tract degeneration showed right-sided temporal lobe asymmetry and greater involvement of the right temporal lobe and superior motor cortices than the other groups. In contrast, the cases with no or equivocal corticospinal tract degeneration were more likely to show left-sided temporal lobe asymmetry. For comparison, the corticospinal tract was assessed in 86 type A and B cases, and only two cases showed evidence of corticospinal tract degeneration without lower motor neuron degeneration. These findings confirm that there exists a unique association between frontotemporal lobar degeneration with type C pathology and corticospinal tract degeneration, with this entity showing a predilection to involve the right temporal lobe.
TDP-43 type C; corticospinal tract; MRI; semantic dementia; right temporal lobe
Current criteria for the clinical diagnosis of pathologically confirmed corticobasal degeneration (CBD) no longer reflect the expanding understanding of this disease and its clinicopathologic correlations. An international consortium of behavioral neurology, neuropsychology, and movement disorders specialists developed new criteria based on consensus and a systematic literature review. Clinical diagnoses (early or late) were identified for 267 nonoverlapping pathologically confirmed CBD cases from published reports and brain banks. Combined with consensus, 4 CBD phenotypes emerged: corticobasal syndrome (CBS), frontal behavioral-spatial syndrome (FBS), nonfluent/agrammatic variant of primary progressive aphasia (naPPA), and progressive supranuclear palsy syndrome (PSPS). Clinical features of CBD cases were extracted from descriptions of 209 brain bank and published patients, providing a comprehensive description of CBD and correcting common misconceptions. Clinical CBD phenotypes and features were combined to create 2 sets of criteria: more specific clinical research criteria for probable CBD and broader criteria for possible CBD that are more inclusive but have a higher chance to detect other tau-based pathologies. Probable CBD criteria require insidious onset and gradual progression for at least 1 year, age at onset ≥50 years, no similar family history or known tau mutations, and a clinical phenotype of probable CBS or either FBS or naPPA with at least 1 CBS feature. The possible CBD category uses similar criteria but has no restrictions on age or family history, allows tau mutations, permits less rigorous phenotype fulfillment, and includes a PSPS phenotype. Future validation and refinement of the proposed criteria are needed.
Pallido-ponto-nigral degeneration (PPND), caused by an N279K mutation of the MAPT gene, is 1 of a family of disorders collectively referred to as frontotemporal dementia and parkinsonism linked to chromosome 17. This study aims to characterize the nature of the sleep disturbance in PPND and compare these findings to those in other progressive neurological illnesses. Pathological findings are also provided.
Ten subjects were recruited from the PPND kindred; 5 affected and 5 unaffected. The subjects underwent clinical assessment, polysomnography, and wrist actigraphy. Available sleep-relevant areas (pedunculopontine/laterodorsal tegmentum, nucleus basalis of Meynert, thalamus, and locus ceruleus) of affected subjects were analyzed postmortem.
The affected group's total sleep time was an average of 130.8 minutes compared to 403.6 minutes in the control group (p < 0.01). Initial sleep latency was significantly longer in affected subjects (range, 58–260 minutes vs 3–34 minutes). Affected subjects also had an increase in stage I sleep (8.5% vs 1%), and less stage III/IV sleep (8.5% vs 17%). At the time of autopsy, all cases had severe neuronal tau pathology in wake-promoting nuclei, as well as decreases in thalamic cholinergic innervations. There was no difference in orexinergic fiber density in nucleus basalis of Meynert or locus ceruleus compared to controls.
The PPND kindred showed severe sleep disturbance. Sleep abnormalities are common in neurodegenerative illnesses, but this is the first study of sleep disorders in PPND. Unlike most neurodegenerative conditions, PPND is characterized by decreased total sleep time, increased sleep latency, and decreased sleep efficiency, without daytime hypersomnolence.
The majority of cases of frontotemporal lobar degeneration and amyotrophic lateral sclerosis are pathologically defined by the cleavage, cytoplasmic redistribution and aggregation of TAR DNA binding protein of 43 kDa (TDP-43). To examine the contribution of these potentially toxic mechanisms in vivo, we generated transgenic mice expressing human TDP-43 containing the familial amyotrophic lateral sclerosis-linked M337V mutation and identified two lines that developed neurological phenotypes of differing severity and progression. The first developed a rapid cortical neurodegenerative phenotype in the early postnatal period, characterized by fragmentation of TDP-43 and loss of endogenous murine Tdp-43, but entirely lacking aggregates of ubiquitin or TDP-43. A second, low expressing line was aged to 25 months without a severe neurodegenerative phenotype, despite a 30% loss of mouse Tdp-43 and accumulation of lower molecular weight TDP-43 species. Furthermore, TDP-43 fragments generated during neurodegeneration were not C-terminal, but rather were derived from a central portion of human TDP-43. Thus we find that aggregation is not required for cell loss, loss of murine Tdp-43 is not necessarily sufficient in order to develop a severe neurodegenerative phenotype and lower molecular weight TDP-43 positive species in mouse models should not be inherently assumed to be representative of human disease. Our findings are significant for the interpretation of other transgenic studies of TDP-43 proteinopathy.
Cross-breeding of transgenic mice is commonly used to assess gene-gene interactions, particularly in the context of disease. Strain background changes can influence the phenotype of mouse models and can confound crossbreeding studies. We sought to determine if changing the strain background of a commonly used mouse model of tauopathy (rTg4510) would significantly impact the originally reported phenotype. On the original F1 FVB/N x 129S6 background, rTg4510 mice present with progressive cognitive decline, increased insoluble tau, robust tau pathology and age-dependent neurodegeneration. One of the most common strains in mouse modeling is C57BL/6. We and others have previously reported that this strain background alters the phenotypes of various models, including the JNPL3 model of tauopathy. To determine if the phenotype of rTg4510 mice was similarly affected by the introduction of the C57BL/6 background, we compared rTg4510 mice on the original F1 FVB/N x 129S6 background to rTg4510 mice on an F1 FVB/N x C57BL/6NTac (B6/NTac) background, herein termed rTg4510B6.
Despite a small, but significant increase in soluble human tau levels, young rTg4510B6 mice had equivalent levels of tau phosphorylation, aggregation and cognitive impairments as age-matched rTg4510 mice. At 6.5 months of age, rTg4510B6 mice displayed hyperphosphorylated insoluble tau and robust cortical tau neuropathology that was equivalent to age-matched rTg4510 mice; however, 10.5-month-old rTg4510B6 mice had greater amounts of phospho-tau in the cortex and hippocampus when compared to age-matched rTg4510 mice. Non-transgenic (NT) littermates of rTg4510B6 (NTB6) mice also had greater amounts of cortical and hippocampal phospho-tau at 10.5 months of age when compared to NT littermates of rTg4510 mice. Additionally, older rTg4510B6 mice had gross forebrain neurodegeneration that was equivalent to age-matched rTg4510 mice.
Overall, our data shows that introduction of the C57BL/6 strain into the rTg4510 mouse background modestly alters the tau pathology that was originally reported in rTg4510 on the F1 FVB/129 background. In contrast, behavioral and neurodegenerative outcomes were not altered. These studies support the use of the rTg4510 mouse model on a partial C57BL/6 strain background without losing fidelity of the phenotype and suggest that the C57BL/6 background does not inherently protect against tauopathy.
Transgenic mouse models; Strain background; C57BL/6; rTg4510; Tau; Tauopathy; Neurodegeneration; Behavior; Morris water maze
Participation in cognitively stimulating leisure activities such as crossword puzzles may delay onset of the memory decline in the preclinical stages of dementia, possibly via its effect on improving cognitive reserve. We followed 488 initially cognitively intact community residing individuals with clinical and cognitive assessments every 12–18 months in the Bronx Aging Study. We assessed the influence of crossword puzzle participation on the onset of accelerated memory decline as measured by the Buschke Selective Reminding Test in 101 individuals who developed incident dementia using a change point model. Crossword puzzle participation at baseline delayed onset of accelerated memory decline by 2.54 years. Inclusion of education or participation in other cognitively stimulating activities did not significantly add to the fit of the model beyond the effect of puzzles. Our findings show that late life crossword puzzle participation, independent of education, was associated with delayed onset of memory decline in persons who developed dementia. Given the wide availability and accessibility of crossword puzzles, their role in preventing cognitive decline should be validated in future clinical trials.
Dementia; Cognitive decline; Puzzles; Memory; Elderly; Neuropsychology
The clinical features of dementia with Lewy bodies (DLB) during wakefulness are well known. Other than REM sleep behavior disorder (RBD), only limited data exists on other sleep disturbances and disorders in DLB. We sought to characterize the polysomnographic (PSG) findings in a series of DLB patients with sleep-related complaints.
Retrospective study of patients with DLB who underwent clinical PSG at Mayo Clinic Rochester or Mayo Clinic Jacksonville over an almost 11 year span for evaluation of dream enactment behavior, excessive nocturnal movements, sleep apnea, hypersomnolence, or insomnia. The following variables were analyzed: respiratory disturbance index (RDI) in disordered breathing events/hour, periodic limb movement arousal index (PLMAI), arousals for no apparent reason (AFNAR), total arousal index (TAI), presence of REM sleep without atonia (RSWA), and percent sleep efficiency (SE).
Data on 78 patients (71M, 7F) were analyzed. The mean age was 71 ± 8 years. Seventy-five (96%) patients had histories of recurrent dream enactment during sleep with 83% showing confirmation of RSWA +/- dream enactment during PSG. Mean RDI = 11.9 ± 5.8, PLMAI = 5.9 ± 8.5, AFNARI = 10.7 ± 12.0, and TAI = 26.6 ± 17.4. SE was <80% in 72% of the sample, <70% in 49%, and <60% in 24%. In patients who did not show evidence of significant disordered breathing (23 with RDI<5), 62% of arousals were AFNARs. In those patients who had significant disordered breathing (55 with RDI ≥ 5), 36% of arousals were AFNARs. Six patients underwent evaluations with PSG plus MSLT. Two patients had mean initial sleep latencies less than five minutes, and both had RDI<5. No patient had any sleep onset rapid eye movement periods. Nineteen patients have undergone neuropathologic examination, and 18 have had limbic- or neocortical-predominant Lewy body pathology. One had progressive supranuclear palsy, but no REM sleep was recorded in prior PSG.
In patients with DLB and sleep-related complaints, several sleep disturbances in addition to RBD are frequently present. In this sample, about three quarters had a significant number of arousals not accounted for by a movement or breathing disturbance, and the primary sleep disorders do not appear to entirely account for the poor sleep efficiency in DLB, especially in those without a significant breathing disorder. Further studies are warranted to better understand the relationship between disturbed sleep, arousal and DLB; such characterization may provide insights into potential avenues of treatment of symptoms which could impact quality of life.
Sleep disorders; REM sleep behavior disorder; dementia with Lewy bodies; synucleinopathy
Expansions of the non-coding GGGGCC hexanucleotide repeat in the chromosome 9 open reading frame 72 (C9ORF72) gene were recently identified as the long sought-after cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) on chromosome 9p. In this study we aimed to determine whether the length of the normal - unexpanded - allele of the GGGGCC repeat in C9ORF72 plays a role in the presentation of disease or affects age at onset in C9ORF72 mutation carriers. We also studied whether the GGGGCC repeat length confers risk or affects age at onset in FTD and ALS patients without C9ORF72 repeat expansions. C9ORF72 genotyping was performed in 580 FTD, 995 ALS and 160 FTD-ALS patients and 1444 controls, leading to the identification of 211 patients with pathogenic C9ORF72 repeat expansions and an accurate quantification of the length of the normal alleles in all patients and controls. No meaningful association between the repeat length of the normal alleles of the GGGGCC repeat in C9ORF72 and disease phenotype or age at onset was observed in C9ORF72 mutation carriers or non-mutation carriers.
Amyotrophic lateral sclerosis; Frontotemporal Dementia; C9ORF72; Repeat-expansion disease; Association study
White matter hyperintensities (WMHs) associate with both cognitive slowing and motor dysfunction in the neurologically normal elderly. A full understanding of the pathology underlying this clinicoradiologic finding is currently lacking in autopsy-confirmed normal brains. To determine the histopathologic basis of WMH seen on MRI, we studied the relationship between postmortem fluid-attenuated inversion recovery (FLAIR) intensity and neuropathologic markers of white matter lesions (WMLs) that correspond to WMH in cognitively normal aging brains. Samples of periventricular (n = 24), subcortical (n = 26), and normal-appearing white matter (NAWM, n = 31) from 4 clinically and pathologically-confirmed normal cases were examined. FLAIR intensity, vacuolation, and myelin basic protein (MBP) immunoreactivity loss were significantly higher in periventricular WML vs. subcortical WML; both were higher than in NAWM. The subcortical WML and NAWM had significantly less axonal loss, astrocytic burden, microglial density, and oligodendrocyte loss than the periventricular WML. Thus, vacuolation, myelin density and small vessel density contribute to the rarefaction of white matter whereas axonal density, oligodendrocyte density, astroglial burden and microglial density did not. These data suggest that the age-related loss of MBP and a decrease in small vessel density, may contribute to vacuolation of white matter. The vacuolation enables interstitial fluid to accumulate, which contributes to the prolonged T2 relaxation and elevated FLAIR intensity in the white matter.
Digital microscopy; Fluid attenuated inversion recovery; Normal aging; Oligodendrocytes; Postmortem magnetic resonance imaging; White matter
The clinical features of the genetically determined forms of familial Parkinson’s disease (PD) have been described in multiple reports, but there have been few comparative neuropathologic studies. Five familial PD cases, with mutations in SNCA, were matched for age, sex, and Alzheimer type pathology with sporadic PD cases. Immunohistochemistry for phospho-tau and α-synuclein was performed in 8 brain regions. The frequency of tau pathology and the morphologic features of α-synuclein pathology in familial PD were compared with sporadic PD using semi-quantitative methods. In familial PD, there were significantly more tau positive extra-perikaryal spheroid-like and thread-like lesions than in the sporadic PD. There was no significant difference in the amount of α-synuclein positive neuronal perikaryal pathology between familial PD and sporadic PD, but α-synuclein positive oligodendroglial and neuritic lesions were significantly greater in familial PD compared to sporadic PD. In the substantia nigra, familial PD had more marked neuronal loss and fewer residential neurons with Lewy bodies than the sporadic PD, suggesting a close relationship between the severity of neuronal loss and Lewy body formation. The results show a diversity of pathological features of genetically determined familial PD, and they draw attention to the possible role of tau protein in neurodegeneration. Moreover, the presence of oligodendroglial inclusions at the light and electron microscopic levels in familial PD suggests that PD and multiple system atrophy form a continuum of α-synuclein pathology.
Pathological features; Lewy bodies; familial Parkinson’s disease; SNCA mutations
Alzheimer’s disease (AD) can be classified based on the relative density of neurofibrillary tangles (NFTs) in the hippocampus and association cortices into three subtypes: typical AD, hippocampal-sparing AD (HpSp AD), and limbic-predominant AD (LP AD). AD subtypes not only have pathologic, but also demographic, clinical, and genetic differences. Neurofibrillary tangle-predominant dementia (NFTD), a disorder with NFTs relatively restricted to limbic structures, shares this feature with LP AD raising the possibility that NFTD is a variant of AD. The objective criteria for pathologic diagnosis of NFTD are not available. A goal of this study was to design a mathematical algorithm that could diagnose NFTD from NFT and senile plaque (SP) counts in hippocampus and association cortices, analogous to that used to subtype AD. Moreover, we aimed to compare pathologic, demographic, clinical, and genetic features of NFTD (n = 18) with LP AD (n = 19), as well as the other AD subtypes, typical AD (n = 52) and HpSp AD (n = 17). Using digital microscopy, we confirmed that burden of phospho-tau (CP13) and of an NFT conformational epitope (Ab39) correlated with NFT densities and showed expected patterns across AD subtypes. HpSp AD had the highest and LP AD had the lowest burden of cortical CP13 and Ab39 immunoreactivity. On the other hand, cortical β-amyloid burden did not significantly differ between AD subtypes. Semi-quantitative assessment of SPs in the basal ganglia did show HpSp AD to have significantly more frequent presence of SPs compared to typical AD, which was more frequent than LP AD. Compared to LP AD, NFTD had an older age at disease onset and shorter disease duration, as well as lower Braak NFT stage. NFTs and SPs on thioflavin-S fluorescent microscopy, as well as CP13, Ab39, and Aβ immunoreactivities were very low in the frontal cortex of NFTD, differentiating NFTD from AD subtypes, including LP AD. MAPT H1H1 genotype frequency was high (~70 %) in NFTD and LP AD, and similar to typical AD, while APOE ε4 carrier state was low in NFTD. While it shares clinical similarities with regard to female sex predominance, onset in advanced age, and a slow cognitive decline, NFTD has significant pathologic differences from LP AD, suggesting that it may not merely be a variant of AD.
Alzheimer disease; Neurofibrillary tangle-predominant dementia; APOE; Digital microscopy; MAPT; Neurofibrillary tangles; Amyloid plaques; Basal ganglia