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V M Lee

Publications and source records attributed to V M Lee.

At least 91 records · Page 5Linked to original sources
PubMed2000

Increased 8,12-iso-iPF2alpha-VI in Alzheimer's disease: correlation of a noninvasive index of lipid peroxidation with disease severity.

The isoprostane 8,12-iso-iPF2alpha-VI is a sensitive and specific marker of in vivo lipid peroxidation. We found elevated levels in the urine, blood, and cerebrospinal fluid of patients with Alzheimer's disease (AD) that correlated with measures of cognitive and functional impairment, established biomarkers of AD pathology (cerebrospinal fluid tau and amyloid) and the number of apolipoprotein E epsilon4 alleles. These results suggest that 8,12-iso-iPF2alpha-VI is a useful biomarker of oxidative damage in AD.

Aged↗
PubMed2000

Frontotemporal dementia with novel tau pathology and a Glu342Val tau mutation.

It is unclear how tau gene mutations cause frontotemporal dementia (FTD) with parkinsonism linked to chromosome 17 (FTDP-17), but those in exon 10 (E10) or the following intron may be pathogenic by altering E10 splicing, perturbing the normal 1:1 ratio of four versus three microtubule-binding repeat tau (4R:3R tau ratio) and forming tau inclusions. We report on a 55-year old woman with frontotemporal dementia and a family history of FTDP-17 in whom we found a novel E12 (Glu342Val) tau gene mutation, prominent frontotemporal neuron loss, intracytoplasmic tau aggregates, paired helical tau filaments, increased 4R tau messenger RNA, increased 4R tau without E2 or E3 inserts, decreased 4R tau with these inserts, and a 4R:3R tau ratio greater than 1 in gray and white matter. Thus, this novel Glu342Val mutation may cause FTDP-17 by unprecedented mechanisms that alter splicing of E2, E3, and E10 to preferentially increase 4R tau without amino terminal inserts and promote aggregation of tau filaments into cytopathic inclusions.

Brain↗
PubMed1999

Differential effects of spinal cord gray and white matter on process outgrowth from grafted human NTERA2 neurons (NT2N, hNT).

To investigate host effects on grafts of pure, postmitotic, human neurons, we assessed the morphologic and molecular phenotype of purified NTera2N (NT2N, hNT) neurons implanted into the spinal cord of athymic nude mice. NT2N neurons were implanted into both spinal cord gray matter and white matter of neonatal, adolescent, and adult mice and were evaluated at postimplantation times up to 15 months. NT2N neurons remained at the implantation site and showed process integration into all host areas, and each graft exhibited similar phenotypic features regardless of location or host age at implantation. Evidence of host oligodendrocyte ensheathment of NT2N neuronal processes was seen, and grafted NT2N neurons acquired and maintained the morphologic and molecular phenotype of mature neurons. The microenvironments of host gray matter and white matter appear to exert differential effects on implanted neuronal processes, because consistent differences were noted in the morphologies of graft processes extending into white matter versus gray matter. NT2N processes extended for long distances (>2 cm) within white matter, whereas NT2N processes located within gray matter had shorter trajectories. This suggests that NT2N neurons integrate similarly into spinal cord gray matter and white matter, but they extend processes that respond differentially to gray matter and white matter cues. Further studies of the model system described here may identify the host molecular signals that support and direct integration of grafted human neurons as well as the outgrowth of their processes in the nervous system.

Aging↗
PubMed1999

Axon pathology in Parkinson's disease and Lewy body dementia hippocampus contains alpha-, beta-, and gamma-synuclein.

Pathogenic alpha-synuclein (alphaS) gene mutations occur in rare familial Parkinson's disease (PD) kindreds, and wild-type alphaS is a major component of Lewy bodies (LBs) in sporadic PD, dementia with LBs (DLB), and the LB variant of Alzheimer's disease, but beta-synuclein (betaS) and gamma-synuclein (gammaS) have not yet been implicated in neurological disorders. Here we show that in PD and DLB, but not normal brains, antibodies to alphaS and betaS reveal novel presynaptic axon terminal pathology in the hippocampal dentate, hilar, and CA2/3 regions, whereas antibodies to gammaS detect previously unrecognized axonal spheroid-like lesions in the hippocampal dentate molecular layer. The aggregation of other synaptic proteins and synaptic vesicle-like structures in the alphaS- and betaS-labeled hilar dystrophic neurites suggests that synaptic dysfunction may result from these lesions. Our findings broaden the concept of neurodegenerative "synucleinopathies" by implicating betaS and gammaS, in addition to alphaS, in the onset/progression of PD and DLB.

Axons↗
PubMed1999

Expression of beta-amyloid precursor protein-CD3gamma chimeras to demonstrate the selective generation of amyloid beta(1-40) and amyloid beta(1-42) peptides within secretory and endocytic compartments.

Amyloid beta-protein (Abeta) is the main constituent of amyloid fibrils found in senile plaques and cerebral vessels in Alzheimer's disease (AD) and is derived by proteolysis from the beta-amyloid precursor protein (APP). We have analyzed the amyloidogenic processing of APP using chimeric proteins stably transfected in Chinese hamster ovary cells. The extracellular and transmembrane domains of APP were fused to the cytoplasmic region derived from the CD3 gamma chain of the T cell antigen receptor (CD3gamma). CD3gamma contains an endoplasmic reticulum (ER) retention motif (RKK), in the absence of which the protein is targeted to lysosomes without going through the cell surface (Letourneur, F., and Klausner, R.D. (1992) Cell 69, 1143-1157). We used the wild-type sequence of CD3gamma to create an APP chimera predicted to remain in the ER (gammaAPP(ER)). Deletion of the RKK motif at the C terminus directed the protein directly to the lysosomes (gammaAPP(LYS)). A third chimera was created by removing both lysosomal targeting signals in addition to RKK (gammaAPP(DeltaDelta)). This last construct does not contain known targeting signals and consequently accumulates at the cell surface. We show by immunofluorescence and by biochemical methods that all three APP chimeras localize to the predicted compartments within the cell, thus providing a useful model to study the processing of APP. We found that Abeta(1-40) is generated in the early secretory and endocytic pathways, whereas Abeta(1-42) is made mainly in the secretory pathway. More importantly, we provide evidence that, unlike in neuronal models, both ER/intermediate compartment- and endocytic-derived Abeta forms can enter the secretable pool. Finally, we directly demonstrate that lysosomal processing is not involved in the generation or secretion of either Abeta(1-40) or Abeta(1-42).

Amino Acid Sequence↗
PubMed1999

Neurofilaments of aged rats: the strengthened interneurofilament interaction and the reduced amount of NF-M.

Amyotrophic lateral sclerosis is an age-related neurological disease, characterized by neurofilament (NF) accumulation in primary axons followed by degeneration of motor neurons. To elucidate age-related factors that might lead to pathological NF accumulation, NFs were compared between young and aged rats. Electron microscopic examination of sciatic nerve axons revealed that NFs were more than twice as densely packed in aged rat axons (542 +/- 180 NFs/mm2) as in young adult rat axons (211 +/- 73 NFs/mm2). The NFs isolated from aged rats also appeared to be more aggregated than those from young rats. Phosphorylation at the head or tail domains was studied as a possible candidate affecting NF organization. Western blotting with phosphorylation-dependent antibodies showed higher phosphorylation of NF-H in the tail domains of aged rat spinal cord NFs, but dephosphorylation did not diminish the differences in aggregation between aged and young rat NFs. On the other hand, when NFs were phosphorylated by A-kinase on their head domains, the extent of phosphorylation in NF-M of aged rat NFs was only one-third of young rat NFs. We found that aged rat NFs contained only 60% of the NF-M of young rat NFs in molar ratio compared to NF-L. These results raise a possibility that the decreased amount of NF-M induces the aggregates of isolated NFs and the higher packing density of NF in aged rat axons.

Aging↗
PubMed1999

Formation of compact myelin is required for maturation of the axonal cytoskeleton.

Although traditional roles ascribed to myelinating glial cells are structural and supportive, the importance of compact myelin for proper functioning of the nervous system can be inferred from mutations in myelin proteins and neuropathologies associated with loss of myelin. Myelinating Schwann cells are known to affect local properties of peripheral axons (de Waegh et al., 1992), but little is known about effects of oligodendrocytes on CNS axons. The shiverer mutant mouse has a deletion in the myelin basic protein gene that eliminates compact myelin in the CNS. In shiverer mice, both local axonal features like phosphorylation of cytoskeletal proteins and neuronal perikaryon functions like cytoskeletal gene expression are altered. This leads to changes in the organization and composition of the axonal cytoskeleton in shiverer unmyelinated axons relative to age-matched wild-type myelinated fibers, although connectivity and patterns of neuronal activity are comparable. Remarkably, transgenic shiverer mice with thin myelin sheaths display an intermediate phenotype indicating that CNS neurons are sensitive to myelin sheath thickness. These results indicate that formation of a normal compact myelin sheath is required for normal maturation of the neuronal cytoskeleton in large CNS neurons.

Animals↗
PubMed1999

Traumatic brain injury in young, amyloid-beta peptide overexpressing transgenic mice induces marked ipsilateral hippocampal atrophy and diminished Abeta deposition during aging.

Traumatic brain injury (TBI) is an epigenetic risk factor for Alzheimer's disease (AD). To test the hypothesis that TBI contributes to the onset and/or progression of AD-like beta-amyloid peptide (Abeta) deposits, we studied the long-term effects of TBI in transgenic mice that overexpress human Abeta from a mutant Abeta precursor protein (APP) minigene driven by a platelet derived (PD) growth factor promoter (PDAPP mice). TBI was induced in 4-month-old PDAPP and wild type (WT) mice by controlled cortical impact (CCI). Because Abeta begins to deposit progressively in the PDAPP brain by 6 months, we examined WT and PDAPP mice at 2, 5, and 8 months after TBI or sham treatment (i.e., at 6, 9, and 12 months of age). Hippocampal atrophy in the PDAPP mice was more severe ipsilateral versus contralateral to TBI, and immunohistochemical studies with antibodies to different Abeta peptides demonstrated a statistically significant reduction in hippocampus and cingulate cortex Abeta deposits ipsilateral versus contralateral to CCI in 9-12 month-old PDAPP mice. Hippocampal atrophy and reduced Abeta deposits were not seen in hippocampus or cingulate cortex of sham-injured PDAPP mice or in any WT mice. These data suggest that the vulnerability of brain cells to Abeta toxicity increases and that the accumulation of Abeta deposits decrease in the penumbra of CCI months after TBI. Thus, in addition to providing unique opportunities for elucidating genetic mechanisms of AD, transgenic mice that recapitulate AD pathology also may be relevant animal models for investigating the poorly understood role that TBI and other epigenetic risk factors play in the onset and/or progression of AD.

Alzheimer Disease↗
PubMed1999

Epitope mapping of LB509, a monoclonal antibody directed against human alpha-synuclein.

Alpha-synuclein is a 140 amino acid protein that forms the major component of the abnormal filaments that make up the Lewy bodies and Lewy neurites of Parkinson's disease and dementia with Lewy bodies. It is also the major component of the filamentous glial cytoplasmic inclusions of multiple system atrophy. Here we have used recombinant alpha-synucleins and peptide competition to show that the monoclonal anti-alpha-synuclein antibody LB509 recognizes amino acids 115-122 of human alpha-synuclein. The antibody strongly labelled filaments extracted from multiple system atrophy brain, showing the presence of residues 115-122 of alpha-synuclein. LB509 failed to react with mouse, rat and zebra finch alpha-synuclein, because of amino acid differences with human alpha-synuclein. Since LB509 recognizes human but not rodent alpha-synuclein, it will be a useful reagent for the characterization of mouse lines transgenic for human alpha-synuclein.

Animals↗
PubMed1999

Mice with disrupted midsized and heavy neurofilament genes lack axonal neurofilaments but have unaltered numbers of axonal microtubules.

Mammalian neurofilaments are assembled from the light (NF-L), midsized (NF-M), and heavy (NF-H) neurofilament proteins. While NF-M and NF-H cannot self-assemble into homopolymers, the data concerning NF-L has been more contradictory. In vitro bovine, porcine, and murine NF-L can homopolymerize in the absence of other subunits. However, in vivo studies suggest that neither rat nor mouse NF-L can form filaments when transfected alone into cells lacking endogenous intermediate filaments. By contrast, human NF-L forms homopolymers in similar cell lines. Recently we generated mice with null mutations in the NF-M and NF-H genes. To determine if mouse NF-L can homopolymerize in mouse axons, NF-M and NF-H null mutants were bred to create a line of double mutant animals. Here we show that axons in NF-M/H double mutant animals are largely devoid of 10-nm filaments. Instead, the axoplasm is transformed to a microtubule-based cytoskeleton-although the lack of any increase in tubulin levels per unit length of nerve or of increases in microtubule numbers relative to myelin sheath thickness argues that microtubules are not increased in response to the loss of neurofilaments. Thus in vivo rodent neurofilaments are obligate heteropolymers requiring NF-L plus either NF-M or NF-H to form a filamentous network.

Animals↗
PubMed1999

High tolerance and delayed elastic response of cultured axons to dynamic stretch injury.

Although axonal injury is a common feature of brain trauma, little is known of the immediate morphological responses of individual axons to mechanical injury. Here, we developed an in vitro model system that selectively stretches axons bridging two populations of human neurons derived from the cell line N-Tera2. We found that these axons demonstrated a remarkably high tolerance to dynamic stretch injury, with no primary axotomy at strains <65%. In addition, the axolemma remained impermeable to small molecules after injury unless axotomy had occurred. We also found that injured axons exhibited the behavior of "delayed elasticity" after injury, going from a straight orientation before injury to developing an undulating course as an immediate response to injury, yet gradually recovering their original orientation. Surprisingly, some portions of the axons were found to be up to 60% longer immediately after injury. Subsequent to returning to their original length, injured axons developed swellings of appearance remarkably similar to that found in brain-injured humans. These findings may offer insight into mechanical-loading conditions leading to traumatic axonal injury and into potential mechanisms of axon reassembly after brain trauma.

Axons↗
PubMed1999

Missense and silent tau gene mutations cause frontotemporal dementia with parkinsonism-chromosome 17 type, by affecting multiple alternative RNA splicing regulatory elements.

Frontotemporal dementia with parkinsonism, chromosome 17 type (FTDP-17) is caused by mutations in the tau gene, and the signature lesions of FTDP-17 are filamentous tau inclusions. Tau mutations may be pathogenic either by altering protein function or gene regulation. Here we show that missense, silent, and intronic tau mutations can increase or decrease splicing of tau exon 10 (E10) by acting on 3 different cis-acting regulatory elements. These elements include an exon splicing enhancer that can either be strengthened (mutation N279(K)) or destroyed (mutation Delta280(K)), resulting in either constitutive E10 inclusion or the exclusion of E10 from tau transcripts. E10 contains a second regulatory element that is an exon splicing silencer, the function of which is abolished by a silent FTDP-17 mutation (L284(L)), resulting in excess E10 inclusion. A third element inhibiting E10 splicing is contained in the intronic sequences directly flanking the 5' splice site of E10 and intronic FTDP-17 mutations in this element enhance E10 inclusion. Thus, tau mutations cause FTDP-17 by multiple pathological mechanisms, which may explain the phenotypic heterogeneity observed in FTDP-17, as exemplified by an unusual family described here with tau pathology as well as amyloid and neuritic plaques.

Aged↗
PubMed1999

Functional synapses are formed between human NTera2 (NT2N, hNT) neurons grown on astrocytes.

The formation of functional synapses is a late milestone of neuronal differentiation. The establishment of functional synapses can be used to assess neuronal characteristics of different cell lines. In the present study, we examined the in vitro conditions that influence the ability of human neurons derived from the NT2 cell line (NT2N neurons) to establish synapses. The morphologic, immunologic, and electrophysiologic characteristics of these synapses was examined. In the absence of astrocytes, NT2N neurons rarely formed synapses and their action potentials were weak and uncommon. In contrast, when plated on primary astrocytes, NT2N neurons were able to form both glutamatergic excitatory (71%) and GABAergic inhibitory (29%) functional synapses whose properties (kinetics, ion selectivity, pharmacology, and ultrastructure) were similar to those of synapses of neurons in primary cultures. In addition, coculture of NT2N neurons with astrocytes modified the morphology of the neurons and extended their in vitro viability to more than 1 year. Because astrocyte-conditioned medium did not produce these effects, we infer that direct contact between NT2N neurons and astrocytes is required. These results suggest that NT2N neurons are similar to primary neurons in their synaptogenesis and their requirement for glial support for optimal survival and maturation. This system provides a model for further investigations into the neurobiology of synapses formed by human neurons.

2-Amino-5-phosphonovalerate↗
PubMed1999

Mutant and wild type human alpha-synucleins assemble into elongated filaments with distinct morphologies in vitro.

alpha-Synuclein is a soluble presynaptic protein which is pathologically redistributed within intracellular lesions characteristic of several neurodegenerative diseases. Here we demonstrate that wild type and two mutant forms of alpha-synuclein linked to familial Parkinson's disease (Ala30 --> Pro and Ala53 --> Thr) self-aggregate and assemble into 10-19-nm-wide filaments with distinct morphologies under defined in vitro conditions. Immunogold labeling demonstrates that the central region of all these filaments are more robustly labeled than the N-terminal or C-terminal regions, suggesting that the latter regions are buried within the filaments. Since in vitro generated alpha-synuclein filaments resemble the major ultrastructural elements of authentic Lewy bodies that are hallmark lesions of Parkinson's disease, we propose that self-aggregating alpha-synuclein is the major subunit protein of these filamentous lesions.

Amino Acid Substitution↗
PubMed1999

A distinct familial presenile dementia with a novel missense mutation in the tau gene.

We report a Japanese family with early onset hereditary frontotemporal dementia and a novel missense mutation (Ser305Asn) in the tau gene. The patients presented with personality changes followed by impaired cognition and memory as well as disorientation, but minimal Parkinsonism. Imaging studies showed fronto-temporal atrophy with ventricular dilatation more on the left, and postmortem examination of the brain revealed numerous neurofibrillary tangles (NFTs) with an unusual morphology and distribution. Silver-stained sections showed ring-shaped NFTs partially surrounding the nucleus that were most prominent in frontal, temporal, insular and postcentral cortices, as well as in dentate gyrus. Cortical NFTs were restricted primarily to layer II, and were composed of straight tubules. Numerous glial cells containing coiled bodies and abundant neuropil threads were detected in cerebral white matter, hippocampus, basal ganglia, diencephalon and brain stem, but no senile plaques or other diagnostic lesions were seen. Both the glial and neuronal tangles were stained by antibodies to phosphorylation-independent and phosphorylation-dependent epitopes in tau. Thus, this novel mutation causes a distinct familial tauopathy.

Adult↗
PubMed1999

Antibodies to alpha-synuclein detect Lewy bodies in many Down's syndrome brains with Alzheimer's disease.

Immunohistochemical examination of 20 Down's syndrome brains, using antibodies to alpha-, beta-, and gamma-synuclein, demonstrated many alpha-synuclein-positive Lewy bodies and dystrophic neurites in 50% of amygdala samples from Down's syndrome brains with Alzheimer's disease. Similar lesions were less common in other regions of these brains, none of which contained beta-synuclein or gamma-synuclein abnormalities. Thus, alpha-synuclein-positive Lewy bodies and neuritic processes frequently occur with Alzheimer's disease in Down's syndrome brains.

Aged↗
PubMed1999

From genotype to phenotype: a clinical pathological, and biochemical investigation of frontotemporal dementia and parkinsonism (FTDP-17) caused by the P301L tau mutation.

Frontotemporal dementia is a heterogeneous, often inherited disorder that typically presents with the insidious onset of behavioral and personality changes. Two genetic loci have been identified and mutations in tau have been causally implicated in a subset of families linked to one of these loci on chromosome 17q21-22. In this study, linkage analysis was performed in a large pedigree, the MN family, suggesting chromosome 17q21-22 linkage. Mutational analysis of the tau coding region identified a C-to-T change in exon 10 that resulted in the conversion of proline to a leucine (P301L) that segregated with frontotemporal dementia in this family. The clinical and pathological findings in the MN family emphasize the significant overlap between Pick's disease, corticobasal degeneration, and frontotemporal dementia and challenge some of the current dogma surrounding this condition. Pathological studies of two brains from affected members of Family MN obtained at autopsy demonstrate numerous tau-positive inclusions that were most prominent in the frontal lobes, anterior temporal lobes, and brainstem structures, as well as Pick-like bodies and associated granulovacuolar degeneration. These Pick-like bodies were observed in 1 patient with motor neuron disease. Because exon 10 is present only in tau mRNA coding for a protein with four microtubule binding repeats (4R), this mutation should selectively affect 4Rtau isoforms. Indeed, immunoblotting demonstrated that insoluble 4Rtau is selectively aggregated in both gray and white matter of affected individuals. Although there was significant pathological similarity between the 2 cases, the pattern of degenerative changes and tau-positive inclusions was not identical, suggesting that other genetic or epigenetic factors can significantly modify the regional topology of neurodegeneration in this condition.

Brain↗