CADASIL mutations impair Notch3 glycosylation by Fringe.

Mutations in the NOTCH3 gene trigger adult-onset stroke and vascular dementia in patients with CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy). All CADASIL mutations described to date affect the epidermal growth factor-like (EGF-like) repeats located in the extracellular domain of the Notch3 receptor. These domains are also the target of sequential complex O-linked glycosylation mediated by protein O-fucosyltransferase 1 and Fringe.

Delta-catenin at the synaptic-adherens junction.

Delta-catenin belongs to the p120-catenin (p120(ctn)) protein family, which is characterized by ten, characteristically spaced Armadillo repeats that bind to the juxtamembrane segment of the classical cadherins. Delta-catenin is the only member of this family that is expressed specifically in neurons, where it binds to PDZ domain proteins in the post-synaptic compartment. As a component of both adherens and synaptic junctions, delta-catenin can link the adherens junction to the synapse and, thereby, coordinate synaptic input with changes in the adherens junction.

Development of a fluorescent high throughput assay for tau aggregation.

A high throughput assay for measuring tau aggregation using fluorescent resonance energy transfer (FRET) is described. Full-length recombinant tau labeled with Cy3 or Cy5 dye is used as ligand, and the induction of aggregation is accomplished by the addition of arachidonic acid. In the presence of this fatty acid, tau aggregation is measured by FRET in a 384-well format.

Phosphorylated tau and the neurodegenerative foldopathies.

Many studies have implicated phosphorylated tau in the Alzheimer disease process. However, the cellular fate of phosphorylated tau has only recently been described. Recent work has shown that tau phosphorylation at substrate sites for the kinases Cdk5 and GSK3-beta can trigger the binding of tau to the chaperones Hsc70 and Hsp27.

Galpha12 directly interacts with PP2A: evidence FOR Galpha12-stimulated PP2A phosphatase activity and dephosphorylation of microtubule-associated protein, tau.

The Galpha(12/13) family of heterotrimeric G proteins modulate multiple cellular processes including regulation of the actin cytoskeleton. Galpha(12/13) interact with several cytoskeletal/scaffolding proteins, and in a yeast two-hybrid screen with Galpha(12), we detected an interaction with the scaffolding subunit (Aalpha) of the Ser/Thr phosphatase, protein phosphatase 2A (PP2A). PP2A dephosphorylates multiple substrates including tau, a microtubule-associated protein that is hyperphosphorylated in neurofibrillary tangles.

Attenuated hippocampus-dependent learning and memory decline in transgenic TgAPPswe Fischer-344 rats.

Alzheimer's disease (AD) is characterized by increased beta amyloid (Abeta) levels, extracellular Abeta deposits in senile plaques, neurofibrillary tangles, and neuronal loss. However, the physiological role of normal levels of Abeta and its parent protein, the amyloid precursor protein (APP) are unknown. Here we report that low-level transgenic (Tg) expression of the Swedish APP mutant gene (APPswe) in Fischer-344 rats results in attenuated age-dependent cognitive performance decline in 2 hippocampus-dependent learning and memory tasks compared with age-matched nontransgenic Fischer-344 controls.

Activation of the neuronal c-Abl tyrosine kinase by amyloid-beta-peptide and reactive oxygen species.

The deposition and accumulation of amyloid-beta-peptide (Abeta) in the brain are considered a sine qua non for Alzheimer's disease. The experimental delivery of fibrilized Abeta serves as a cellular model for several facets of the disease including the induction of synaptic dysfunction and apoptosis. c-Abl kinase is involved in the regulation of apoptosis and its pro-apoptotic function is in part mediated by its interaction with p73, a p53 homologue.

Deletion of the neuron-specific protein delta-catenin leads to severe cognitive and synaptic dysfunction.

Delta-catenin (delta-catenin) is a neuron-specific catenin, which has been implicated in adhesion and dendritic branching. Moreover, deletions of delta-catenin correlate with the severity of mental retardation in Cri-du-Chat syndrome (CDCS), which may account for 1% of all mentally retarded individuals. Interestingly, delta-catenin was first identified through its interaction with Presenilin-1 (PS1), the molecule most frequently mutated in familial Alzheimer's Disease (FAD).

Wnt-1 expression in PC12 cells induces exon 15 deletion and expression of L-APP.

The metabolism of amyloid precursor protein (APP) is central to Alzheimer's disease pathogenesis. Recent data have linked APP and presenilin to the Wnt/wingless signaling pathway. To assess affects of Wnt stimulation on APP isoform expression, we infected PC12 cells and C57MG cells with a retrovirus containing murine Wnt-1.

Development of an assay to screen for inhibitors of tau phosphorylation by cdk5.

A high-throughput assay for tau phosphorylation by cdk5/p25 is described. Full-length recombinant tau was used as a substrate in the presence of saturating adenosine triphosphate (ATP). Using PHF-1, an antibody directed specifically against 2 tau phosphorylation epitopes (serine 396 and serine 404), an enzyme-linked immunosorbent assay (ELISA)-based colorimetric assay was formatted in 384-well plates.

Binding of tau to heat shock protein 27 leads to decreased concentration of hyperphosphorylated tau and enhanced cell survival.

Pathological hyperphosphorylated tau is the principal component of paired helical filaments, a pathological hallmark of Alzheimer disease (AD) and a strong candidate for a neurotoxic role in AD and other neurodegenerative disorders. Here we show that heat shock protein 27 (Hsp27) preferentially binds pathological hyperphosphorylated tau and paired helical filaments tau directly but not non-phosphorylated tau. The formation of this complex altered the conformation of pathological hyperphosphorylated tau and reduced its concentration by facilitating its degradation and dephosphorylation.

Identification of many microRNAs that copurify with polyribosomes in mammalian neurons.

Localized translation in mammalian dendrites may play a role in synaptic plasticity and contribute to the molecular basis for learning and memory. The regulatory mechanisms that control localized translation in neurons are not well understood. We propose a role for microRNAs (miRNAs), a class of noncoding RNAs, as mediators of neuronal translational regulation.

Distribution pattern of Notch3 mutations suggests a gain-of-function mechanism for CADASIL.

Mutations in Notch3 cause the syndrome CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy). The mechanism by which these mutations result in a CADASIL phenotype has been widely speculated upon. A first step toward understanding a disease mechanism is to learn whether the mutations result in the loss of Notch3 function, in particular, its role in signaling or in the gain of a novel function.

CHIP-Hsc70 complex ubiquitinates phosphorylated tau and enhances cell survival.

The microtubule-binding protein tau has been implicated in the neurofibrillary pathology of Alzheimer's disease. Within affected cells, ubiquitinated and hyperphosphorylated tau assembles into massive filamentous polymers. Eventually these tangle-bearing neurons die.

BACE1 suppression by RNA interference in primary cortical neurons.

Extracellular deposition of amyloid-beta (Abeta) aggregates in the brain represents one of the histopathological hallmarks of Alzheimer's disease (AD). Abeta peptides are generated from proteolysis of the amyloid precursor proteins (APPs) by beta- and gamma-secretases. Beta-secretase (BACE1) is a type I integral membrane glycoprotein that can cleave APP first to generate C-terminal 99- or 89-amino acid membrane-bound fragments containing the N terminus of Abeta peptides (betaCTF).

Neuropsychological profile of a large kindred with familial Alzheimer's disease caused by the E280A single presenilin-1 mutation.

It was hypothesized that subjective memory complaints represent the earliest sign of dementia in carriers of the presenilin-1 (PS1) mutation. A total of 122 subjects (44 males, 78 females) were included in this study. Forty of them were positive for the mutation in the PS1 gene (mutation positive, MP) whereas 82 showed negative results (mutation negative, MN).

A microRNA array reveals extensive regulation of microRNAs during brain development.

Several hundred microRNAs (miRNAs) have recently been cloned from a wide range of organisms across phylogeny. Despite the high degree of conservation of miRNAs, their functions in general, and in mammals particularly, are just beginning to be defined. Here we show that an oligonucleotide DNA array can be successfully used for the simultaneous analysis of miRNA expression profiles from tissues or cells.

Apolipoprotein Eepsilon4 modifies Alzheimer's disease onset in an E280A PS1 kindred.

We previously have identified a large kindred from Colombia in which Alzheimer's disease (AD) is caused by the E280A presenilin 1 (PS1) mutation. The objective of this study was to examine whether environmental and genetic factors are responsible for variation in the phenotypic expression of the E280A PS1 mutation. We genotyped coding and promoter polymorphisms of the APOE gene in carriers of the E280A PS1 mutation.

Dual regulation of neuronal morphogenesis by a delta-catenin-cortactin complex and Rho.

Delta-catenin is a neuronal protein that contains 10 Armadillo motifs and binds to the juxtamembrane segment of classical cadherins. We report that delta-catenin interacts with cortactin in a tyrosine phosphorylation-dependent manner. This interaction occurs within a region of the delta-catenin sequence that is also essential for the neurite elongation effects.

Beyond phrenology, at last.

Although integration is a widely acknowledged goal in neuroscience, our approach to the function of biological entities often places boundaries that defy integration. Mapping across systems - from the genome to cognitive function - will require innovative methods that can identify every contributing component to a function, and instantaneously scale numerous changes in large data sets to consequences over the entire biological hierarchy.

Transcriptional profiling reveals regulated genes in the hippocampus during memory formation.

Transcriptional profiling (TP) offers a powerful approach to identify genes activated during memory formation and, by inference, the molecular pathways involved. Trace eyeblink conditioning is well suited for the study of regional gene expression because it requires the hippocampus, whereas the highly parallel task, delay conditioning, does not. First, we determined when gene expression was most regulated during trace conditioning.

Discovery of compounds that will prevent tau pathology.

Tau is certainly a reasonable target for the development of compounds to prevent neurofibrillary pathology, particularly in the fronto-temporal dementias. Although the mechanism of the filamentous accumulations remains unclear, sufficient knowledge is in place to move forward with high throughput screens. In fact, the development of compounds from such screens will ultimately be the only way to validate the target.

Spatial learning and memory is preserved in rats after early development in a microgravity environment.

This study evaluated the cognitive mapping abilities of rats that spent part of their early development in a microgravity environment. Litters of male and female Sprague-Dawley rat pups were launched into space aboard the National Aeronautics and Space Administration space shuttle Columbia on postnatal day 8 or 14 and remained in space for 16 days. These animals were designated as FLT groups.

RNAi functions in cultured mammalian neurons.

In a wide range of organisms, double-stranded RNA triggers posttranscriptional gene silencing or RNA interference (RNAi). Small interfering RNAs, the 21-nt double-stranded RNA intermediates of this natural pathway, have became a powerful tool to knock down specific gene expression in mammalian cell lines and potentially will be useful for the analysis of loss-of-function phenotypes. In mammalian primary neuronal cultures, where genetic manipulations are especially difficult, RNAi might be developed into a highly efficacious tool to study the roles of specific genes in neuron development and functioning.