Ultrastructural localization of fructose-1,6-bisphosphatase in mouse brain.

Fructose-1,6-bisphosphatase has been studied in adult mouse brain of different ages using an antibody directed against the liver isoform. The presence of liver fructose-1,6-bisphosphatase in cerebellum, cerebral cortex, and hippocampus was assayed using Western blot and different immunocytochemical techniques. Immunocytochemistry with peroxidase reaction product was used to locate fructose-1,6-bisphosphatase in both neurons and astrocytes in the same areas, as well as in the rest of the brain, at light and electron microscope levels.

Tau-knockout mice show reduced GSK3-induced hippocampal degeneration and learning deficits.

It has been proposed that deregulation of neuronal glycogen synthase kinase 3 (GSK3) activity may be a key feature in Alzheimer disease pathogenesis. We have previously generated transgenic mice that overexpress GSK3beta in forebrain regions including dentate gyrus (DG), a region involved in learning and memory acquisition. We have found that GSK3 overexpression results in DG degeneration.

Neuroimaging studies in Alzheimer's disease. A review.

Alzheimer's Disease (AD) is a progressive neurodegenerative disease associated with memory loss and gradual behavioral, functional and cognitive impairment. Conventional imaging studies, such as magnetic resonance or computed tomography have played a secondary role in AD diagnosis: While other causes of memory loss and cognitive deficit can be evaluated by these imaging methods, AD structural changes are not detected until very late in the course of the disease. Recent and more precise techniques have been developed to detect subtle changes not visualized with those imaging methods.

Kainic acid intraocular injections during the postnatal critical period induce plastic changes in the visual system.

Changes in the retino-collicular projection and in the number of optic nerve (ON) axons in adult rats were analyzed after partial loss of retinal ganglion cells (RGCs), induced by intravitreal injections of kainic acid (KA) on postnatal days 2-3 (P2-P3) or 10-12 (P10-P12). KA injected at P2-P3 decreased the volume of the adult contralateral superior colliculus (SC) and the density of the retino-collicular contralateral projection, but maintained the neonatal pattern in the ipsilateral projection from the un-injected eye. ON axon number was significantly increased in the un-injected eye but decreased in the KA-injected eye.

Hippocampal neuronal subpopulations are differentially affected in double transgenic mice overexpressing frontotemporal dementia and parkinsonism linked to chromosome 17 tau and glycogen synthase kinase-3beta.

Glycogen synthase kinase-3beta (GSK-3beta) has been proposed as the main kinase able to phosphorylate tau aberrantly in Alzheimer's disease and in related tauopathies. We have previously generated a double transgenic mouse line overexpressing the enzyme GSK-3beta and tau protein carrying a triple frontotemporal dementia and parkinsonism linked to chromosome 17 mutation whose expression patterns overlap in CA1 (pyramidal neurons) and dentate gyrus (granular neurons). Here, we have used this transgenic model to analyze how axonal and somatodendritic neuronal compartments are affected in the hippocampus.

Phosphorylated tau in neuritic plaques of APP(sw)/Tau (vlw) transgenic mice and Alzheimer disease.

We have previously reported that double-transgenic APP(SW)/Tau(VLW) mice show enhanced amyloid deposition, stronger tau hyperphosphorylation, increased sarkosyl tau polymers, and wider tau filaments when compared to simple mutant models. To validate these transgenic mice as models of Alzheimer disease pathology, in the present study we analyze tau phosphorylation at 12E8 and AT-8 epitopes in amyloid plaques. In APP(SW) mice, phospho-tau in plaque-associated neurites suggests a local direct effect of plaque-amyloid (and/or APP(SW)) on tau phosphorylation.

Ultrastructural localization of intraneuronal Abeta-peptide in Alzheimer disease brains.

Autopsied brain tissue from Alzheimer's disease patients and old non-demented controls was studied after immunocytochemistry with the 4G8 monoclonal antibody that recognizes amyloid-beta peptides. Intraneuronal 4G8-positive reaction product was detected in all of the studied brains. The same brain regions in the Alzheimer's disease samples consistently showed both more immunopositive neurons and more stained reaction product per neuron than those from the non-demented brains.

Inhibition of 26S proteasome activity by huntingtin filaments but not inclusion bodies isolated from mouse and human brain.

In Huntington's disease (HD), as in the rest of CAG triplet-repeat disorders, the expanded polyglutamine (polyQ)-containing proteins form intraneuronal fibrillar aggregates that are gathered into inclusion bodies (IBs). Since IBs contain ubiquitin and proteasome subunits, it was proposed that inhibition of proteasome activity might underlie pathogenesis of polyQ disorders. Recent in vitro enzymatic studies revealed the inability of eukaryotic proteasomes to digest expanded polyQ, thus suggesting that occasional failure of polyQ to exit the proteasome may interfere with its proteolytic function.

Full motor recovery despite striatal neuron loss and formation of irreversible amyloid-like inclusions in a conditional mouse model of Huntington's disease.

The primary mechanism responsible for Huntington's disease remains unknown. Postulated early pathogenic events include the following: impaired protein folding, altered protein degradation, mitochondrial dysfunction, and transcriptional dysregulation. Although related therapies can delay disease progression in mouse models, they target downstream and probably indirect effects of mutant-huntingtin expression.

Accelerated amyloid deposition, neurofibrillary degeneration and neuronal loss in double mutant APP/tau transgenic mice.

Even though the idea that amyloid beta peptide accumulation is the primary event in the pathogenesis of Alzheimer's disease has become the leading hypothesis, the causal link between aberrant amyloid precursor protein processing and tau alterations in this type of dementia remains controversial. We further investigated the role of beta-amyloid production/deposition in tau pathology and neuronal cell death in the mouse brain by crossing Tg2576 and VLW lines expressing human mutant amyloid precursor protein and human mutant tau, respectively. The resulting double transgenic mice showed enhanced amyloid deposition accompanied by neurofibrillary degeneration and overt neuronal loss in selectively vulnerable brain limbic areas.

Cooexpression of FTDP-17 tau and GSK-3beta in transgenic mice induce tau polymerization and neurodegeneration.

Here we have tested whether tau modification either by point mutation or by hyperphosphorylation can exert maximal pathogenic effects or if, on the contrary, both types of tau modifications can act synergistically to induce neuropathology. For this, we have combined transgenic mice overexpressing the enzyme GSK-3beta (Tet/GSK-3beta mice), with transgenic mice expressing Tau with a triple FTDP-17 mutation which develop prefibrillar tau-aggregates (VLW mice). Tet/GSK-3beta/VLW transgenic mice show tau hyperphosphorylation in hippocampal neurons.

Biochemical, ultrastructural, and reversibility studies on huntingtin filaments isolated from mouse and human brain.

Huntington's disease (HD) and eight additional inherited neurological disorders are caused by CAG triplet-repeat expansions leading to expanded polyglutamine-sequences in their respective proteins. These triplet-CAG repeat disorders have in common the formation of aberrant intraneuronal proteinaceous inclusions containing the expanded polyglutamine sequences. These aggregates have been postulated to contribute to pathogenesis caused by conformational toxicity, sequestration of other polyglutamine-containing proteins, or by interfering with certain enzymatic activities.

Neuronal induction of the immunoproteasome in Huntington's disease.

Huntington's disease (HD) inclusions are stained with anti-ubiquitin and anti-proteasome antibodies. This, together with proteasome activity studies on transfected cells, suggest that an impairment of the ubiquitin-proteasome system (UPS) may be key in HD pathogenesis. To test whether proteasome activity is impaired in vivo, we performed enzymatic assays for the three peptidase activities of the proteasome in brain extracts from the HD94 conditional mouse model of HD.

FTDP-17 mutations in tau transgenic mice provoke lysosomal abnormalities and Tau filaments in forebrain.

The tauopathies, which include Alzheimer's disease (AD) and frontotemporal dementias, are a group of neurodegenerative disorders characterized by filamentous Tau aggregates. That Tau dysfunction can cause neurodegeneration is indicated by pathogenic tau mutations in frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). To investigate how Tau alterations provoke neurodegeneration we generated transgenic mice expressing human Tau with four tubulin-binding repeats (increased by FTDP-17 splice donor mutations) and three FTDP-17 missense mutations: G272V, P301L, and R406W.

Ubiquitinated granular structures and initial neurofibrillary changes in the human brain.

Ubiquitin-positive dots and granular structures from insular, temporopolar, hippocampal and parahippocampal cortices of nondemented and Alzheimer's disease patients have been studied with both light and electron microscopes. The relationship of both types of ubiquitin-positive elements with pretangle neurons and neurofibrillary tangles has been analyzed by comparing adjacent or nearly adjacent sections immunostained for either ubiquitin or an antibody that recognizes hyperphosphorylated tau protein (AT-8). Moreover, a double protocol with both antibodies was used in order to obtain double-stained sections.

Apolipoprotein E immunoreactivity in neurons and neurofibrillary degeneration of aged non-demented and Alzheimer's disease patients.

Apolipoprotein E (ApoE) genotype is a risk factor for Alzheimer's disease (AD) but its relationship with neurofibrillary degeneration remains obscure. To further analyze this relationship, hippocampal, entorhinal, temporopolar, and insular cortices of 10 non-demented and 7 Alzheimer disease brains were studied with both light and electron microscopy. Focus was directed on pretangles and neurons starting to accumulate tangles.

Decreased nuclear beta-catenin, tau hyperphosphorylation and neurodegeneration in GSK-3beta conditional transgenic mice.

Glycogen synthase kinase-3beta (GSK-3beta) has been postulated to mediate Alzheimer's disease tau hyperphosphorylation, beta-amyloid-induced neurotoxicity and presenilin-1 mutation pathogenic effects. By using the tet-regulated system we have produced conditional transgenic mice overexpressing GSK-3beta in the brain during adulthood while avoiding perinatal lethality due to embryonic transgene expression. These mice show decreased levels of nuclear beta-catenin and hyperphosphorylation of tau in hippocampal neurons, the latter resulting in pretangle-like somatodendritic localization of tau.

Ultrastructural aspects of neurofibrillary tangle formation in aging and Alzheimer's disease.

Neurofibrillary tangles, one of the neuropathological signs of Alzheimer's disease, are frequently present in brains of aged nondemented people. Ultrastructurally, neurofibrillary tangles appear as paired helical and straight filaments. Both types of filaments, made of hyperphosphorylated tau protein, are present in neurons with neurofibrillary tangles.

Association of cholinesterases with amyloid in extracellular neurofibrillary tangles.

Double-labeling techniques conclusively demonstrated that extracellular neurofibrillary tangles immunoreactive for beta protein were also positive for cholinesterases. Ultrastructurally, cholinesterases decorated bundles of amyloid-like filaments, which appeared intermingled with straight filaments and cellular processes. A lighter labeling of esterases was also seen over most straight filaments.

Ultrastructural localization of butyrylcholinesterase in senile plaques in the brains of aged and Alzheimer disease patients.

Histochemical localization of butyrylcholinesterase has been carried out in primitive, perivascular, and classic plaques in the brains of both nondemented and Alzheimer disease (AD) patients. Butyrylcholinesterase histochemistry has been compared to amyloid beta-protein (A beta P) immunocytochemistry in adjacent sections. In small primitive plaques, most of the butyrylcholinesterase reaction product appears ultrastructurally located over plasma membranes of healthy-looking cell processes.

Alzheimer's disease-type neurofibrillary degeneration in verrucose dysplasias of the cerebral cortex.

Verrucose dysplasias, found at autopsy in the cerebral cortex of three elderly individuals (two without neurological disorders and one with motor neuron disease), are shown to present neurofibrillary degeneration of Alzheimer's disease type. This neurofibrillary degeneration immunoreacted with antibodies against abnormally phosphorylated tau (5E2 and AT8), disclosed acetyl- and butyrylcholinesterase activity, and was consistently stained with thioflavin-S. Cortical dysplasias, found either as isolated verrucose nodules or comprising multiple nodules, contained cell-sparse areas around which a peak of neurofibrillary changes was seen.

Microtubule-associated protein MAP1B showing a fetal phosphorylation pattern is present in sites of neurofibrillary degeneration in brains of Alzheimer's disease patients.

Alzheimer's disease results in the appearance of cytoskeletal disorders yielding pathological structures such a neurofibrillary tangles or dystrophic neurites. It has been previously described that the microtubule-associated protein, tau, modified by phosphorylation in serines adjacent to prolines, is a major component of these structures. Here, we show that another microtubule associated protein, MAP1B, aberrantly phosphorylated by a proline-dependent protein kinase, is a component of these previously mentioned structures.