A Cautionary Tale: Endogenous Biotinylated Proteins and Exogenously-Introduced Protein A Cause Antibody-Independent Artefacts in Western Blot Studies of Brain-Derived Proteins.

Antibodies are commonly used to detect or isolate proteins from biological samples. Much attention has been paid to the potential for poorly-characterized antibodies to lead to misleading results, but artefacts may also occur. Here, we recount two examples of antibody-independent artefacts that have confounded the interpretation of results in our search for molecular entities associated with memory loss in Alzheimer's disease (AD).

Human cerebrospinal fluid 6E10-immunoreactive protein species contain amyloid precursor protein fragments.

In a previous study, we reported that levels of two types of protein species-a type of ~55-kDa species and a type of ~15-kDa species-are elevated in the lumbar cerebrospinal fluid (CSF) of cognitively intact elderly individuals who are at risk for Alzheimer's disease (AD). These species are immunoreactive to the monoclonal antibody 6E10, which is directed against amino acids 6-10 of amyloid-β (Aβ), and their levels correlate with levels of total tau and tau phosphorylated at Thr181. In this study, we investigated the molecular composition of these AD-related proteins using immunoprecipitation (IP)/Western blotting coupled with IP/mass spectrometry.

Quantitative Comparison of Dense-Core Amyloid Plaque Accumulation in Amyloid-β Protein Precursor Transgenic Mice.

There exist several dozen lines of transgenic mice that express human amyloid-β protein precursor (AβPP) with Alzheimer's disease (AD)-linked mutations. AβPP transgenic mouse lines differ in the types and amounts of Aβ that they generate and in their spatiotemporal patterns of expression of Aβ assemblies, providing a toolkit to study Aβ amyloidosis and the influence of Aβ aggregation on brain function. More complete quantitative descriptions of the types of Aβ assemblies present in transgenic mice and in humans during disease progression should add to our understanding of how Aβ toxicity in mice relates to the pathogenesis of AD.

Quaternary Structure Defines a Large Class of Amyloid-β Oligomers Neutralized by Sequestration.

The accumulation of amyloid-β (Aβ) as amyloid fibrils and toxic oligomers is an important step in the development of Alzheimer's disease (AD). However, there are numerous potentially toxic oligomers and little is known about their neurological effects when generated in the living brain. Here we show that Aβ oligomers can be assigned to one of at least two classes (type 1 and type 2) based on their temporal, spatial, and structural relationships to amyloid fibrils.

Characterization of a Novel Mouse Model of Alzheimer's Disease--Amyloid Pathology and Unique β-Amyloid Oligomer Profile.

Amyloid plaques composed of β-amyloid (Aβ) protein are a pathological hallmark of Alzheimer's disease. We here report the generation and characterization of a novel transgenic mouse model of Aβ toxicity. The rTg9191 mice harbor a transgene encoding the 695 amino-acid isoform of human amyloid precursor protein (APP) with the Swedish and London mutations (APPNLI) linked to familial Alzheimer's disease, under the control of a tetracycline-response element, as well as a transgene encoding the tetracycline transactivator, under the control of the promoter for calcium-calmodulin kinase IIα.

More than a FAD: the in vivo effects of disease-linked presenilin-1 mutations.

Mutations in presenilins are linked to familial autosomal dominant Alzheimer's disease. In this issue of Neuron, Xia et al. (2015) show that a disease-linked mutation leads to loss of γ-secretase function, cognitive decline, and neurodegeneration when knocked into the mouse genome.

β-Amyloid oligomers in aging and Alzheimer's disease.

Alzheimer's disease (AD) is a fatal neurodegenerative disorder, and the most common cause of dementia in the elderly. The cause of AD is not known, but genetic evidence strongly supports the hypothesis that pathological aggregation of the β-amyloid protein (Aβ) triggers the disease process. AD has a long preclinical phase, lasting a decade or more.

Correlation of specific amyloid-β oligomers with tau in cerebrospinal fluid from cognitively normal older adults.

Importance: To improve the ability to develop treatments that prevent incipient Alzheimer disease (AD) from progressing to overt AD, it is important to understand the molecular basis of the earliest pathophysiological abnormalities and to determine how amyloid-β (Aβ) is involved very early in its pathogenesis.

Objective: To investigate 2 specific Aβ oligomers, Aβ trimers and Aβ*56, in human cerebrospinal fluid (CSF); evaluate the effects of aging and AD; and obtain support for the hypothesis that they may be pathogenic by determining their relationships to CSF tau.

Design: A CSF sampling study.

Grape seed polyphenolic extract specifically decreases aβ*56 in the brains of Tg2576 mice.

Amyloid-β (Aβ) oligomers, found in the brains of Alzheimer's disease (AD) patients and transgenic mouse models of AD, cause synaptotoxicity and memory impairment. Grape seed polyphenolic extract (GSPE) inhibits Aβ oligomerization in vitro and attenuates cognitive impairment and AD-related neuropathology in the brains of transgenic mice. In the current study, GSPE was administered to Tg2576 mice for a period of five months.

Probing the biology of Alzheimer's disease in mice.

Alzheimer's disease (AD), the most common cause of dementia among the elderly, may either represent the far end of a continuum that begins with age-related memory decline or a distinct pathobiological process. Although mice that faithfully model all aspects of AD do not yet exist, current mouse models have provided valuable insights into specific aspects of AD pathogenesis. We will argue that transgenic mice expressing amyloid precursor protein should be considered models of accelerated brain aging or asymptomatic AD, and the results of interventional studies in these mice should be considered in the context of primary prevention.

'Too much good news' - are Alzheimer mouse models trying to tell us how to prevent, not cure, Alzheimer's disease?

Scores of compounds ameliorate cognitive deficits or neuropathology in transgenic mouse models of Alzheimer's disease (AD), yet these triumphs in mice have not translated into successful therapies for people. Why have studies in mice failed to predict results of human trials? We argue that most transgenic mouse 'models of AD' actually simulate the asymptomatic phase of the disease, and the results of interventional studies in these mice should be considered in the context of disease prevention. In addition, recent advances in imaging technology and biomarker discovery should aid in comparisons of mouse and human neurological status and, importantly, might allow us to predict better the response of people to drugs tested in mice.

Gap junctional coupling and connexin immunoreactivity in rabbit retinal glia.

Gap junctions provide a pathway for the direct intercellular exchange of ions and small signaling molecules. Gap junctional coupling between retinal astrocytes and between astrocytes and Müller cells, the principal glia of vertebrate retinas, has been previously demonstrated by the intercellular transfer of gap-junction permeant tracers. However, functional gap junctions have yet to be demonstrated between mammalian Müller cells.

D-serine and serine racemase are present in the vertebrate retina and contribute to the physiological activation of NMDA receptors.

d-serine has been proposed as an endogenous modulator of N-methyl-d-aspartate (NMDA) receptors in many brain regions, but its presence and function in the vertebrate retina have not been characterized. We have detected d-serine and its synthesizing enzyme, serine racemase, in the retinas of several vertebrate species, including salamanders, rats, and mice and have localized both constituents to Müller cells and astrocytes, the two major glial cell types in the retina. Physiological studies in rats and salamanders demonstrated that, in retinal ganglion cells, d-serine can enhance excitatory currents elicited by the application of NMDA, as well as the NMDA receptor component of light-evoked synaptic responses.

Connexin immunoreactivity in glial cells of the rat retina.

The rat retina contains two types of macroglial cells, Müller cells, radial glial cells that are the principal macroglial cells of vertebrate retinas, and astrocytes associated with the surface vasculature. In addition to the often-described gap-junctional coupling between astrocytes, coupling also occurs between astrocytes and Müller cells. Immunohistochemistry and confocal microscopy were used to identify connexins in the retinas of pigmented rats.