Native mutant huntingtin in human brain: evidence for prevalence of full-length monomer

Huntington disease (HD) is caused by polyglutamine expansion in the N terminus of huntingtin (htt). Analysis of human postmortem brain lysates by SDS-PAGE and Western blot reveals htt as full-length and fragmented. Here we used Blue Native PAGE (BNP) and Western blots to study native htt in human postmortem brain. Antisera against htt detected a single band broadly migrating at 575-850 kDa in control brain and at 650-885 kDa in heterozygous and Venezuelan homozygous HD brains. Anti-polyglutamine antisera detected full-length mutant htt in HD brain. There was little htt cleavage even if lysates were pretreated with trypsin, indicating a property of native htt to resist protease cleavage. A soluble mutant htt fragment of about 180 kDa was detected with anti-htt antibody Ab1 (htt-(1-17)) and increased when lysates were treated with denaturants (SDS, 8 M urea, DTT, or trypsin) before BNP. Wild-type htt was more resistant to denaturants. Based on migration of in vitro translated htt fragments, the 180-kDa segment terminated ≈htt 670-880 amino acids. If second dimension SDS-PAGE followed BNP, the 180-kDa mutant htt was absent, and 43-50 kDa htt fragments appeared. Brain lysates from two HD mouse models expressed native full-length htt; a mutant fragment formed if lysates were pretreated with 8 M urea + DTT. Native full-length mutant htt in embryonic HD(140Q/140Q) mouse primary neurons was intact during cell death and when cell lysates were exposed to denaturants before BNP. Thus, native mutant htt occurs in brain and primary neurons as a soluble full-length monomer.

SORCS1 alters amyloid precursor protein processing and variants may increase Alzheimer's disease risk

OBJECTIVE

Sorting mechanisms that cause the amyloid precursor protein (APP) and the β-secretases and γ-secretases to colocalize in the same compartment play an important role in the regulation of Aβ production in Alzheimer's disease (AD). We and others have reported that genetic variants in the Sortilin-related receptor (SORL1) increased the risk of AD, that SORL1 is involved in trafficking of APP, and that underexpression of SORL1 leads to overproduction of Aβ. Here we explored the role of one of its homologs, the sortilin-related VPS10 domain containing receptor 1 (SORCS1), in AD.

METHODS

We analyzed the genetic associations between AD and 16 SORCS1-single nucleotide polymorphisms (SNPs) in 6 independent data sets (2,809 cases and 3,482 controls). In addition, we compared SorCS1 expression levels of affected and unaffected brain regions in AD and control brains in microarray gene expression and real-time polymerase chain reaction (RT-PCR) sets, explored the effects of significant SORCS1-SNPs on SorCS1 brain expression levels, and explored the effect of suppression and overexpression of the common SorCS1 isoforms on APP processing and Aβ generation.

RESULTS

Inherited variants in SORCS1 were associated with AD in all datasets (0.001 < p < 0.049). In addition, SorCS1 influenced APP processing. While overexpression of SorCS1 reduced γ-secretase activity and Aβ levels, the suppression of SorCS1 increased γ-secretase processing of APP and the levels of Aβ.

INTERPRETATIONS

These data suggest that inherited or acquired changes in SORCS1 expression or function may play a role in the pathogenesis of AD.

Neuropathological heterogeneity in frontotemporal lobar degeneration with TDP-43 proteinopathy: a quantitative study of 94 cases using principal components analysis

Studies suggest that frontotemporal lobar degeneration with transactive response DNA-binding protein of 43 kDa (TDP-43) proteinopathy (FTLD-TDP) is heterogeneous with division into four or five subtypes. To determine the degree of heterogeneity and the validity of the subtypes, we studied neuropathological variation within the frontal and temporal lobes of 94 cases of FTLD-TDP using quantitative estimates of density and principal components analysis (PCA). A PCA based on the density of TDP-43 immunoreactive neuronal cytoplasmic inclusions, oligodendroglial inclusions, neuronal intranuclear inclusions, and dystrophic neurites, surviving neurons, enlarged neurons, and vacuolation suggested that cases were not segregated into distinct subtypes. Variation in the density of the vacuoles was the greatest source of variation between cases. A PCA based on TDP-43 pathology alone suggested that cases of FTLD-TDP with progranulin (GRN) mutation segregated to some degree. The pathological phenotype of all four subtypes overlapped but subtypes 1 and 4 were the most distinctive. Cases with coexisting motor neuron disease (MND) or hippocampal sclerosis (HS) also appeared to segregate to some extent. We suggest: (1) pathological variation in FTLD-TDP is best described as a 'continuum' without clearly distinct subtypes, (2) vacuolation was the single greatest source of variation and reflects the 'stage' of the disease, and (3) within the FTLD-TDP 'continuum' cases with GRN mutation and with coexisting MND or HS may have a more distinctive pathology.

Memory performance is related to amyloid and tau pathology in the hippocampus

OBJECTIVE

To determine the relation of amyloid and tau pathology in the hippocampal formation to decline in memory and other cognitive functions in Alzheimer's disease (AD).

METHODS

Regression models were used to relate semiquantitative measurements of amyloid plaques, neurofibrillary tangles (NFTs) and neuropil threads (NTs) at autopsy with antemortem performance in memory, abstract/visuospatial and language domains in two independent samples (n = 41, n = 66) that had repeated neuropsychological measurements before death.

RESULTS

In both groups, the number of NFTs in the entorhinal cortex, subiculum and CA1 region was inversely associated with memory performance at the last visit before death. However, the number of amyloid plaques and NTs in the entorhinal cortex was also inversely related to poor memory function. Moreover, as the number of plaques or NTs increased in any region of the hippocampal formation, there was a more rapid decline in memory performance over time; a similar decline was associated with increasing numbers of NFTs in the CA1 or subiculum. In contrast, there was no association between amyloid plaques, NFTs or NTs in the frontal or parietal lobe and performance in memory, nor was there an association between plaques, NFTs or NTs in the hippocampal formation and cognitive functions unrelated to memory.

DISCUSSION

This study implicates both amyloid deposition and tau pathology in the hippocampus as an early and late cause of decline in memory function over time in AD. Memory performance appears to be specifically related to the amount of amyloid plaques, NFTs and NTs in the entorhinal cortex and hippocampus.

Association of glucocerebrosidase mutations with dementia with lewy bodies

BACKGROUND

Mutations in the glucocerebrosidase (GBA) gene are associated with Lewy body (LB) disorders.

OBJECTIVE

To determine the relationship of GBA mutations and APOE4 genotype to LB and Alzheimer disease (AD) pathological findings.

DESIGN

Case-control study.

SETTING

Academic research.

PARTICIPANTS

The 187 subjects included patients with primary neuropathological diagnoses of LB disorders with or without AD changes (95 cases), randomly selected patients with AD (without significant LB pathological findings; 60 cases), and controls with neither LB nor AD pathological findings (32 cases).

MAIN OUTCOME MEASURES

GBA mutation status, APOE4 genotype, LB pathological findings (assessed according to the third report of the Dementia With Lewy Body Consortium), and Alzheimer plaque and tangle pathological findings (rated by criteria of Braak and Braak, the Consortium to Establish a Registry for Alzheimer Disease, and the National Institute on Aging-Reagan Institute).

RESULTS

GBA mutations were found in 18% (34 of 187) of all subjects, including 28% (27 of 95) of those with primary LB pathological findings compared with 10% (6 of 60) of those with AD pathological findings and 3% (1 of 32) of those without AD or LB pathological findings (P=.001). GBA mutation status was significantly associated with the presence of cortical LBs (odds ratio, 6.48; 95% confidence interval, 2.45-17.16; P<.001), after adjusting for sex, age at death, and presence of APOE4. GBA mutation carriers were significantly less likely to meet AD pathological diagnostic (National Institute on Aging-Reagan Institute intermediate or high likelihood) criteria (odds ratio, 0.35; 95% confidence interval, 0.15-0.79; P=.01) after adjustment for sex, age at death, and APOE4.

CONCLUSION

GBA mutations may be associated with pathologically "purer" LB disorders, characterized by more extensive (cortical) LB, and less severe AD pathological findings and may be a useful marker for LB disorders.

Five siRNAs targeting three SNPs may provide therapy for three-quarters of Huntington's disease patients

Among dominant neurodegenerative disorders, Huntington's disease (HD) is perhaps the best candidate for treatment with small interfering RNAs (siRNAs) [1-9]. Invariably fatal, HD is caused by expansion of a CAG repeat in the Huntingtin gene, creating an extended polyglutamine tract that makes the Huntingtin protein toxic [10]. Silencing mutant Huntingtin messenger RNA (mRNA) should provide therapeutic benefit, but normal Huntingtin likely contributes to neuronal function [11-13]. No siRNA strategy can yet distinguish among the normal and disease Huntingtin alleles and other mRNAs containing CAG repeats [14]. siRNAs targeting the disease isoform of a heterozygous single-nucleotide polymorphism (SNP) in Huntingtin provide an alternative [15-19]. We sequenced 22 predicted SNP sites in 225 human samples corresponding to HD and control subjects. We find that 48% of our patient population is heterozygous at a single SNP site; one isoform of this SNP is associated with HD. Several other SNP sites are frequently heterozygous. Consequently, five allele-specific siRNAs, corresponding to just three SNP sites, could be used to treat three-quarters of the United States and European HD patient populations. We have designed and validated selective siRNAs for the three SNP sites, laying the foundation for allele-specific RNA interference (RNAi) therapy for HD.

Direct quantification of CSF alpha-synuclein by ELISA and first cross-sectional study in patients with neurodegeneration

Because accumulation of alpha-synuclein (alphaS) in the brain is a hallmark of Parkinson disease (PD) and related disorders, we examined its occurrence in human cerebrospinal fluid (CSF). Following affinity enrichment and trypsin digestion of CSF collected from a neurologically healthy donor, we identified several alphaS-derived peptides by mass spectrometry. The concentration of alphaS amounted to <0.001% of the CSF proteome. We then built, validated and optimized a sandwich-type, enzyme-linked immunoadsorbent assay (ELISA) to measure total alphaS levels in unconcentrated CSF. In a cross-sectional study of 100 living donors, we examined cell-free CSF samples from subjects clinically diagnosed with advanced PD, dementia with Lewy bodies (DLB), Alzheimer disease (AD), and a group of non-neurodegenerative disease controls (NCO). In these four groups the CSF alphaS concentrations ranged from 0.8 to 16.2 pg/microl. Mean CSF alphaS values were lower in donors with a primary synucleinopathy (PD, DLB: n=57) than in the other two groups (AD, NCO: n=35; p=0.025). By contrast, living Creutzfeldt-Jakob disease patients showed markedly elevated CSF alphaS levels (n=8; mean, 300 pg/microl; p<0.001). Our results unequivocally confirm the presence of alphaS in adult human CSF. In a first feasibility study employing a novel ELISA, we found relatively low CSF alphaS concentrations in subjects with parkinsonism linked to synucleinopathy, PD and DLB. In definite prion disease cases, we recorded a marked rise in total CSF alphaS resulting from rapid cell death. Our results will likely aid future biomarker explorations in neurodegenerative conditions and facilitate target validation studies.

Progranulin mutations and amyotrophic lateral sclerosis or amyotrophic lateral sclerosis-frontotemporal dementia phenotypes

OBJECTIVE

Mutations in the progranulin (PGRN) gene were recently described as the cause of ubiquitin positive frontotemporal dementia (FTD). Clinical and pathological overlap between amyotrophic lateral sclerosis (ALS) and FTD prompted us to screen PGRN in patients with ALS and ALS-FTD.

METHODS

The PGRN gene was sequenced in 272 cases of sporadic ALS, 40 cases of familial ALS and in 49 patients with ALS-FTD.

RESULTS

Missense changes were identified in an ALS-FTD patient (p.S120Y) and in a single case of limb onset sporadic ALS (p.T182M), although the pathogenicity of these variants remains unclear.

CONCLUSION

PGRN mutations are not a common cause of ALS phenotypes.

A Familial Form of Pallidoluysionigral Degeneration and Amyotrophic Lateral Sclerosis With Divergent Clinical Presentations

We describe a family with a rapidly progressive neurodegenerative disorder characterized by amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) but with unusual neuropathologic features that include pallidoluysionigral degeneration. The proband presented with primary progressive aphasia that evolved into mutism. He subsequently developed dementia with mild disinhibition and parkinsonism and late in the disease showed evidence of motor neuron disease. Two other cases (the proband's mother and maternal uncle) had features of ALS exclusively. All 3 had a young onset (fourth decade) and rapid clinical course, with average time from onset of symptoms to death of 4 years. Postmortem neuropathologic examination of the proband and his uncle showed ALS changes and extensive pallidoluysionigral degeneration without neurofibrillary tangles, ubiquitin inclusions, or detectable abnormalities in the dentate nucleus of the cerebellum. Although this exceptional combination of neuropathologic features has been described in rare cases of sporadic ALS-FTD, no pedigrees have ever been reported. In 2 affected members of this family, we failed to identify mutations in genes associated with weakness, movement disorders, or dementia, including ALS, FTD, selected spinocerebellar ataxias, and Huntington disease. Thus, this disorder may represent a novel autosomal dominantly inherited and rapidly progressive neurodegenerative disorder with a spectrum of clinical presentations but common neuropathologic features.

Multiple system atrophy in a patient with the spinocerebellar ataxia 3 gene mutation

The cerebellar variant of multiple system atrophy (MSA-C) has overlapping clinical features with the hereditary spinocerebellar ataxias (SCAs), but can usually be distinguished on a clinical basis. We describe a patient who developed a sporadic, late-onset, rapidly progressive neurodegenerative disorder consistent with MSA-C. Genetic testing, however, showed an abnormal expansion of one allele of the spinocerebellar ataxia 3 (SCA3) gene. The clinical impression of MSA-C was confirmed by identification of numerous alpha-synuclein-containing glial cytoplasmic inclusions on autopsy. These findings suggest that abnormal expansion of the SCA3 gene may be a risk factor for the development of MSA-C.

Expansile, enhancing cervical cord lesion with an associated syrinx secondary to demyelination. Case report and review of the literature

The authors describe the case of a patient with an enhancing, intramedullary cervical spinal cord lesion and associated syrinx. Biopsy sampling of the cervical lesion was performed, and the histological findings were consistent with a demyelinating process supporting the diagnosis of multiple sclerosis (MS). Syrinx formation associated with demyelinating disease has only been described in isolated cases, almost exclusively in Japanese patients with MS. A 22-year-old woman of Caribbean descent presented with a subacute, progressive myelopathy including symptoms of pain and weakness in all extremities, bladder incontinence, and the inability to ambulate. Magnetic resonance imaging of the brain and spinal cord demonstrated an enlarged cervical cord with enhancement and central cavitation consistent with a syrinx. The patient underwent a C3-7 laminoplasty and placement of a dural graft for cord decompression as well as fenestration of the central syrinx. Biopsy sampling of the lesion was performed, and the histopathological analysis, in conjunction with subsequent laboratory and diagnostic testing, supported the diagnosis of demyelinating disease. After treatment with a course of high-dose dexamethasone and inpatient rehabilitation therapy, the patient demonstrated significant clinical improvement. Spinal cord involvement is not uncommon in patients with demyelinating disease; however, enhancing lesions associated with extensive tissue loss and syrinx formation have rarely been reported. For the consulting neurological surgeon, demyelinating disease should be included in the differential diagnosis of such lesions given the level of complexity and risk to the patient associated with open biopsy of the spinal cord.

Eosinophilic vasculitis in an isolated central nervous system distribution

BACKGROUND

Eosinophilic vasculitis has been described as part of the Churg-Strauss syndrome, but affects the central nervous system (CNS) in <10% of cases; presentation in an isolated CNS distribution is rare. We present a case of eosinophilic vasculitis isolated to the CNS.

CASE REPORT

A 39-year-old woman with a history of migraine without aura presented to an institution (located in the borough of Queens, New York, USA; no academic affiliation) in an acute confusional state with concurrent headache and left-sided weakness and numbness. Laboratory evaluation showed increased cerebrospinal fluid (CSF) protein level, but an otherwise unremarkable serological investigation. Magnetic resonance imaging showed bifrontal polar gyral-enhancing brain lesions. Her symptoms resolved over 2 weeks without residual deficit. After 18 months, later the patient presented with similar symptoms and neuroradiological findings involving territories different from those in her first episode. Again, the CSF protein level was high. She had a raised C reactive protein level and erythrocyte sedimentation rate. Brain biopsy showed transmural, predominantly eosinophilic, inflammatory infiltrates of medium-sized leptomeningeal arteries without granulomas. She improved, without recurrence, when treated with a prolonged course of corticosteroids.

CONCLUSIONS

To our knowledge, this is the first case of non-granulomatous eosinophilic vasculitis isolated to the CNS. No aetiology for this patient's primary CNS eosinophilic vasculitis has yet been identified. Spontaneous resolution and recurrence of her syndrome is an unusual feature of the typical CNS vasculitis and may suggest an environmental epitope with immune reaction as the cause.

Ablation of the inflammatory enzyme myeloperoxidase mitigates features of Parkinson's disease in mice

Parkinson's disease (PD) is characterized by a loss of ventral midbrain dopaminergic neurons, which can be modeled by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Inflammatory oxidants have emerged as key contributors to PD- and MPTP-related neurodegeneration. Here, we show that myeloperoxidase (MPO), a key oxidant-producing enzyme during inflammation, is upregulated in the ventral midbrain of human PD and MPTP mice. We also show that ventral midbrain dopaminergic neurons of mutant mice deficient in MPO are more resistant to MPTP-induced cytotoxicity than their wild-type littermates. Supporting the oxidative damaging role of MPO in this PD model are the demonstrations that MPO-specific biomarkers 3-chlorotyrosine and hypochlorous acid-modified proteins increase in the brains of MPTP-injected mice. This study demonstrates that MPO participates in the MPTP neurotoxic process and suggests that inhibitors of MPO may provide a protective benefit in PD.

Model-guided microarray implicates the retromer complex in Alzheimer's disease

Although, in principle, gene expression profiling is well suited to isolate pathogenic molecules associated with Alzheimer's disease (AD), techniques such as microarray present unique analytic challenges when applied to disorders of the brain. Here, we addressed these challenges by first constructing a spatiotemporal model, predicting a priori how a molecule underlying AD should behave anatomically and over time. Then, guided by the model, we generated gene expression profiles of the entorhinal cortex and the dentate gyrus, harvested from the brains of AD cases and controls covering a broad age span. Among many expression differences, the retromer trafficking molecule VPS35 best conformed to the spatiotemporal model of AD. Western blotting confirmed the abnormality, establishing that VPS35 levels are reduced in brain regions selectively vulnerable to AD. VPS35 is the core molecule of the retromer trafficking complex and further analysis revealed that VPS26, another member of the complex, is also downregulated in AD. Cell culture studies, using small interfering RNAs or expression vectors, showed that VPS35 regulates Abeta peptide levels, establishing the relevance of the retromer complex to AD. Reviewing our findings in the context of recent studies suggests how downregulation of the retromer complex in AD can regulate local levels of Abeta peptide.

Progressive supranuclear palsy

In this case study, we describe the symptoms, neurological examination, clinical course, and neuropathology of a patient with progressive supranuclear palsy (PSP). PSP is a relatively uncommon neurodegenerative disorder with many features similar to those of Parkinson's disease. It is characterized by slow motor function, ocular movement abnormalities, dystonia, and cognitive disabilities. PSP is largely a sporadic disorder caused by accumulation of the protein tau in diverse regions of the central nervous system. It is thus classified as one of several tauopathies. The exact cause of the disease remains unknown, and treatment is often limited. The following case provides a framework to explore the manifestations of PSP, as well as the progress made in understanding the nature of this challenging disorder.

TP73 allelic expression in human brain and allele frequencies in Alzheimer's disease

Background

The p73 protein, a paralogue of the p53 tumor suppressor, is essential for normal development and survival of neurons. TP73 is therefore of interest as a candidate gene for Alzheimer's disease (AD) susceptibility. TP73 mRNA is transcribed from three promoters, termed P1 – P3, and there is evidence for an additional complexity in its regulation, namely, a variable allelic expression bias in some human tissues.

Methods

We utilized RT-PCR/RFLP and direct cDNA sequencing to measure allele-specific expression of TP73 mRNA, SNP genotyping to assess genetic associations with AD, and promoter-reporter assays to assess allele-specific TP73 promoter activity.

Results

Using a coding-neutral BanI polymorphism in TP73 exon 5 as an allelic marker, we found a pronounced allelic expression bias in one adult brain hippocampus, while 3 other brains (two adult; one fetal) showed approximately equal expression from both alleles. In a tri-ethnic elderly population of African-Americans, Caribbean Hispanics and Caucasians, a G/A single nucleotide polymorphism (SNP) at -386 in the TP73 P3 promoter was weakly but significantly associated with AD (crude O.R. for AD given any -386G allele 1.7; C.I. 1.2–2.5; after adjusting for age and education O.R. 1.5; C.I. 1.1–2.3, N= 1191). The frequency of the -386G allele varied by ethnicity and was highest in African-Americans and lowest in Caucasians. No significant differences in basal P3 promoter activity were detected comparing -386G vs. -386A promoter-luciferase constructs in human SK-NSH-N neuroblastoma cells.

Conclusions

There is a reproducible allelic expression bias in mRNA expression from the TP73 gene in some, though not all, adult human brains, and inter-individual variation in regulatory sequences of the TP73 locus may affect susceptibility to AD. However, additional studies will be necessary to exclude genetic admixture as an alternative explanation for the observed associations.

Huntington's disease

In this case study, we describe the symptoms, neurological exam, neuropsychological test results, and brain pathology of a man who died with Huntington's disease (HD). HD is a rare neurodegenerative disease. Like other movement disorders involving the basal ganglia, HD affects motor, cognitive, and psychiatric functioning. The disease follows an autosomal dominant pattern of inheritance, with onset of symptoms most commonly occurring in the late 30s or early 40s, as in this patient. HD is caused by an unstable expansion of the trinucleotide CAG, coding for glutamine, on chromosome 4. Despite knowledge of the gene mutation responsible for HD, no definitive treatment is currently available to slow or halt progression of the disease. However, symptomatic treatment can significantly improve the quality of life for patients with HD.

Selective reduction of soluble tau proteins in sporadic and familial frontotemporal dementias: an international follow-up study

Recently, biochemical criteria were proposed to complement histological criteria for the diagnosis of dementia lacking distinctive histopathology (DLDH), the most common pathological variant of frontotemporal dementias (FTDs), based on evidence of a selective reduction of soluble tau proteins in brains from a large cohort of sporadic DLDH and hereditary FTD (HDDD2 family) patients. To ensure that these findings are not unique to the populations included in the initial report, we extended the previous work by analyzing 22 additional DLDH brains from the United States and international centers. Our biochemical analyses here confirmed the previous findings by demonstrating substantial reductions in soluble brain tau in gray and white matter of 14 cases and moderate reductions in 6 cases of DLDH. We also analyzed brain samples from an additional affected HDDD2 family member, and remarkably, unlike other previously studied members of this kindred, this patient's brain contained substantial amounts of pathological or insoluble tau. These findings confirm and extend the definition of DLDH as a sporadic or familial "tau-less" tauopathy with reduced levels of soluble brain tau and no insoluble tau or fibrillary tau inclusions, and the data also underline the phenotypic heterogeneity of HDDD2, which parallels the phenotypic heterogeneity of other hereditary neurodegenerative FTD tauopathies caused by tau gene mutations.

Office of Rare Diseases neuropathologic criteria for corticobasal degeneration

A working group supported by the Office of Rare Diseases of the National Institutes of Health formulated neuropathologic criteria for corticobasal degeneration (CBD) that were subsequently validated by an independent group of neuropathologists. The criteria do not require a specific clinical phenotype, since CBD can have diverse clinical presentations, such as progressive asymmetrical rigidity and apraxia, progressive aphasia, or frontal lobe dementia. Cortical atrophy, ballooned neurons, and degeneration of the substantia nigra have been emphasized in previous descriptions and are present in CBD, but the present criteria emphasize tau-immunoreactive lesions in neurons, glia, and cell processes in the neuropathologic diagnosis of CBD. The minimal pathologic features for CBD are cortical and striatal tau-positive neuronal and glial lesions, especially astrocytic plaques and thread-like lesions in both white matter and gray matter, along with neuronal loss in focal cortical regions and in the substantia nigra. The methods required to make this diagnosis include histologic stains to assess neuronal loss, spongiosis and ballooned neurons, and a method to detect tau-positive neuronal and glial lesions. Use of either the Gallyas silver staining method or immunostains with sensitive tau antibodies is acceptable. In cases where ballooned neurons are sparse or difficult to detect, immunostaining for phospho-neurofilament or alpha-B-crystallin may prove helpful. Methods to assess Alzheimer-type pathology and Lewy body pathology are necessary to rule out other causes of dementia and Parkinsonism. Using these criteria provides good differentiation of CBD from other tauopathies, except frontotemporal dementia and Parkinsonism linked to chromosome 17, where additional clinical or molecular genetic information is required to make an accurate diagnosis.

Early phenotypes that presage late-onset neurodegenerative disease allow testing of modifiers in Hdh CAG knock-in mice

In Huntington's disease (HD), CAG repeats extend a glutamine tract in huntingtin to initiate the dominant loss of striatal neurons and chorea. Neuropathological changes include the formation of insoluble mutant N-terminal fragment, as nuclear/neuropil inclusions and filter-trap amyloid, which may either participate in the disease process or be a degradative by-product. In young Hdh knock-in mice, CAGs that expand the glutamine tract in mouse huntingtin to childhood-onset HD lengths lead to nuclear accumulation of full-length mutant huntingtin and later accumulation of insoluble fragment. Here we report late-onset neurodegeneration and gait deficits in older Hdh(Q111) knock-in mice, demonstrating that the nuclear phenotypes comprise early stages in a disease process that conforms to genetic and pathologic criteria determined in HD patients. Furthermore, using the early nuclear-accumulation phenotypes as surrogate markers, we show in genetic experiments that the disease process, initiated by full-length mutant protein, is hastened by co-expression of mutant fragment; therefore, accrual of insoluble-product in already compromised neurons may exacerbate pathogenesis. In contrast, timing of early disease events was not altered by normal huntingtin or by mutant caspase-1, two proteins shown to reduce inclusions and glutamine toxicity in other HD models. Thus, potential HD therapies in man might be directed at different levels: preventing the disease-initiating mechanism or slowing the subsequent progression of pathogenesis.

Selective loss of striatal preprotachykinin neurons in a phenocopy of Huntington's disease

Phenocopies of Huntington's disease (HD) are individuals with a family history, clinical symptoms, and occasionally pathological evidence of HD but without an expanded CAG repeat within the HD gene. We report on an HD phenocopy with selective loss of preprotachykinin (PPT) neurons, dysfunction of surviving PPT neurons, preservation of preproenkephalin (PPE) neurons within the striatum, and greater loss of immunohistochemical staining for substance P in terminals of striatal neurons projecting to the substantia nigra, than in those projecting to the internal pallidal segment. This case demonstrates the existence of one type of striatal lesion that may produce a clinical picture similar to HD, and raises the possibility of a rare hereditary disease that mimics HD.

Tau protein expression in frontotemporal dementias

The syndrome of frontotemporal dementia represents a diverse group of diseases presenting with behavioral and cognitive disturbances. The expression of the microtubule-associated protein tau was studied in postmortem samples of frontal cortex of 19 cases (12 Pick's disease A, B, C; 4 dementia lacking distinct histology; 3 motor neuron disease type) by Western blotting with a phosphorylation-independent anti-tau antibody. The presence of tau protein was detected in all cases evaluated, including the 11 brains classified as frontotemporal lobe degeneration (diagnostic categories Pick's disease B, C and dementia lacking distinct histology). These findings indicate that the recently reported decreased expression of tau protein in frontotemporal lobe degeneration represents pathogenic mechanism of neurodegeneration detectable only in a special subset of these disorders.

Novel amyloid precursor protein mutation in an Iowa family with dementia and severe cerebral amyloid angiopathy

Several mutations in the amyloid precursor protein (APP) gene have been found to associate with pathologic deposition of the beta-amyloid peptide (Abeta) in neuritic plaques or in the walls of cerebral vessels. We report a mutation at a novel site in APP in a three-generation Iowa family with autosomal dominant dementia beginning in the sixth or seventh decade of life. The proband and an affected brother had progressive aphasic dementia, leukoencephalopathy, and occipital calcifications. Neuropathological examination of the proband revealed severe cerebral amyloid angiopathy, widespread neurofibrillary tangles, and unusually extensive distribution of Abeta40 in plaques. The affected brothers shared a missense mutation in APP, resulting in substitution of asparagine for aspartic acid at position 694. This site corresponds to residue 23 of Abeta, thus differing from familial Alzheimer's disease mutations, which occur outside the Abeta sequence. Restriction enzyme analysis of DNA from 94 unrelated patients with sporadic cerebral amyloid angiopathy-related hemorrhage found no other instances of this mutation. These results suggest a novel site within Abeta that may promote its deposition and toxicity.

Up-regulation of the lysosomal system in experimental models of neuronal injury: implications for Alzheimer's disease

Previous studies established that the populations of neurons that frequently degenerate in Alzheimer's disease exhibit robust up-regulation of the lysosomal system. In this study, we investigated alterations of the lysosomal system during different forms of experimental injury in rat hippocampal neurons in culture, utilizing a combination of immunocytochemical and biochemical methods. Using triple-label immnocytochemistry for activated caspase-3, fragmentation of DNA and the microtubule-associated protein-2, we characterized treatment paradigms as models of the apoptotic (staurosporine, camptothecin), the oncotic (high-dose menadione, glutamate), and the mixed apoptotic and oncotic (low-dose menadione) pathways of neuronal death. Slowly developing apoptotic or slowly developing mixed apoptotic and oncotic forms of neuronal injury were associated with substantial increases in the number and size of cathepsin D-positive vesicles (late endosomes and mature lysosomes) as determined by immunocytochemistry, and elevated levels of cathepsin D by western blotting. In agreement with our previous findings in Alzheimer's disease, where lysosomal system activation was not restricted to overtly degenerating neurons, up-regulation of this system was also detected quite early during the course of experimental neuronal injury, preceding the development of dystrophic neurites, nuclear segmentation or fragmentation of DNA. These findings implicate lysosomal system activation, both in Alzheimer's disease and in experimental models of neuronal injury, as an important event associated with early stages of neurodegeneration.