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Transcriptome analysis of synaptoneurosomes identifies neuroplasticity genes overexpressed in incipient Alzheimer's disease.

Williams C, Mehrian Shai R, Wu Y, Hsu YH, Sitzer T, Spann B, McCleary C, Mo Y, Miller CA - PLoS ONE (2009)

Bottom Line: These patients also showed increased expression of neuroplasticity related genes, many encoding 3'UTR consensus sequences that regulate translation in the synapse.An increase in mRNA encoding the GluR2 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) was paralleled by elevated expression of the corresponding protein in IAD.These results imply a functional impact on synaptic transmission as GluR2, if inserted, maintains the receptors in a low conductance state.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Keck School of Medicine University of Southern California, Los Angeles, California, United States of America.

ABSTRACT
In Alzheimer's disease (AD), early deficits in learning and memory are a consequence of synaptic modification induced by toxic beta-amyloid oligomers (oAbeta). To identify immediate molecular targets downstream of oAbeta binding, we prepared synaptoneurosomes from prefrontal cortex of control and incipient AD (IAD) patients, and isolated mRNAs for comparison of gene expression. This novel approach concentrates synaptic mRNA, thereby increasing the ratio of synaptic to somal mRNA and allowing discrimination of expression changes in synaptically localized genes. In IAD patients, global measures of cognition declined with increasing levels of dimeric Abeta (dAbeta). These patients also showed increased expression of neuroplasticity related genes, many encoding 3'UTR consensus sequences that regulate translation in the synapse. An increase in mRNA encoding the GluR2 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) was paralleled by elevated expression of the corresponding protein in IAD. These results imply a functional impact on synaptic transmission as GluR2, if inserted, maintains the receptors in a low conductance state. Some overexpressed genes may induce early deficits in cognition and others compensatory mechanisms, providing targets for intervention to moderate the response to dAbeta.

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Related in: MedlinePlus

Oligomeric Aβ increases with dementia progression.Oligomeric Aβ dimer (dAβ) is detected with antibody 4G8 on immunoblots of A) whole homogenate or B) synaptoneurosomes prepared from patients with a range of MMSE scores (29-15). A band observed at <10 kD with a migration identical to dAβ, is detectable in IAD patients with MMSE scores of about 26 or less. In C) densitometry reveals that, when normalized to GAPDH, dAβ levels are inversely related to MMSE although patients with an ApoE4 allele (including one control) exhibit higher concentrations of dAβ than patients with comparable MMSE scores but no E4 allele. Homogenate (grey bar) and synaptoneurosome (white bar) samples show increasing dAβ in IAD as the disease progresses. Data are representative of 3 separate experiments. The ratio of dAβ to GAPDH is given in arbitrary units based on the integrated density value which is the sum of all pixel values after background correction (IDV).
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pone-0004936-g002: Oligomeric Aβ increases with dementia progression.Oligomeric Aβ dimer (dAβ) is detected with antibody 4G8 on immunoblots of A) whole homogenate or B) synaptoneurosomes prepared from patients with a range of MMSE scores (29-15). A band observed at <10 kD with a migration identical to dAβ, is detectable in IAD patients with MMSE scores of about 26 or less. In C) densitometry reveals that, when normalized to GAPDH, dAβ levels are inversely related to MMSE although patients with an ApoE4 allele (including one control) exhibit higher concentrations of dAβ than patients with comparable MMSE scores but no E4 allele. Homogenate (grey bar) and synaptoneurosome (white bar) samples show increasing dAβ in IAD as the disease progresses. Data are representative of 3 separate experiments. The ratio of dAβ to GAPDH is given in arbitrary units based on the integrated density value which is the sum of all pixel values after background correction (IDV).

Mentions: To correlate dementia profiles with oAβ expression, Western blots of homogenates from the frontal cortices of control, IAD and moderate to severe AD patients were probed with antibody 4G8, which detects oAβ1-42. A ∼9 kD band consistent with the dAβ was found and increased in intensity with degree of cognitive impairment, as defined by declining MMSE scores (Figure 2A, C). Additional bands of higher molecular weight were identified by MAb 4G8 in homogenates, but their variability of expression was not consistent with disease progression (Figure S2A). For instance, densitometric comparison of dAβ in control compared to IAD and control compared to AD patient groups showed a consistent increase as the disease progressed whereas an apparent tetramer (tAβ) did not increase in IAD and declined in AD (Figure S2B). Because of the small number of samples in each group, and variability within control and IAD groups, the change in dAβ is not significant. To discriminate the dAβ from the C-terminal stub, CT-83, which migrates close to 8 kD we used MAb 6E10 which confirmed the ∼9 kD species as dAβ (Figure S2C). Another predictor of dAβ expression is the ApoE4 genotype, as dimers were detected in all patients with at least one ApoE4 allele, including one control. A later evaluation of dAβ in IAD and AD with more patients in the IAD and AD groups, but without the confounding effect of one control with ApoE4 genotype and increased dAβ, showed the elevation of dAβ levels to be significant (data not shown). dAβ abundance in synaptoneurosome preparations also increased as the MMSE declined (Figure 2B). Comparison of the Aß dimer normalized to GAPDH in homogenates and synaptoneurosomes showed a consistent quantitative increase with the duration of disease (Figure 2C).


Transcriptome analysis of synaptoneurosomes identifies neuroplasticity genes overexpressed in incipient Alzheimer's disease.

Williams C, Mehrian Shai R, Wu Y, Hsu YH, Sitzer T, Spann B, McCleary C, Mo Y, Miller CA - PLoS ONE (2009)

Oligomeric Aβ increases with dementia progression.Oligomeric Aβ dimer (dAβ) is detected with antibody 4G8 on immunoblots of A) whole homogenate or B) synaptoneurosomes prepared from patients with a range of MMSE scores (29-15). A band observed at <10 kD with a migration identical to dAβ, is detectable in IAD patients with MMSE scores of about 26 or less. In C) densitometry reveals that, when normalized to GAPDH, dAβ levels are inversely related to MMSE although patients with an ApoE4 allele (including one control) exhibit higher concentrations of dAβ than patients with comparable MMSE scores but no E4 allele. Homogenate (grey bar) and synaptoneurosome (white bar) samples show increasing dAβ in IAD as the disease progresses. Data are representative of 3 separate experiments. The ratio of dAβ to GAPDH is given in arbitrary units based on the integrated density value which is the sum of all pixel values after background correction (IDV).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2654156&req=5

pone-0004936-g002: Oligomeric Aβ increases with dementia progression.Oligomeric Aβ dimer (dAβ) is detected with antibody 4G8 on immunoblots of A) whole homogenate or B) synaptoneurosomes prepared from patients with a range of MMSE scores (29-15). A band observed at <10 kD with a migration identical to dAβ, is detectable in IAD patients with MMSE scores of about 26 or less. In C) densitometry reveals that, when normalized to GAPDH, dAβ levels are inversely related to MMSE although patients with an ApoE4 allele (including one control) exhibit higher concentrations of dAβ than patients with comparable MMSE scores but no E4 allele. Homogenate (grey bar) and synaptoneurosome (white bar) samples show increasing dAβ in IAD as the disease progresses. Data are representative of 3 separate experiments. The ratio of dAβ to GAPDH is given in arbitrary units based on the integrated density value which is the sum of all pixel values after background correction (IDV).
Mentions: To correlate dementia profiles with oAβ expression, Western blots of homogenates from the frontal cortices of control, IAD and moderate to severe AD patients were probed with antibody 4G8, which detects oAβ1-42. A ∼9 kD band consistent with the dAβ was found and increased in intensity with degree of cognitive impairment, as defined by declining MMSE scores (Figure 2A, C). Additional bands of higher molecular weight were identified by MAb 4G8 in homogenates, but their variability of expression was not consistent with disease progression (Figure S2A). For instance, densitometric comparison of dAβ in control compared to IAD and control compared to AD patient groups showed a consistent increase as the disease progressed whereas an apparent tetramer (tAβ) did not increase in IAD and declined in AD (Figure S2B). Because of the small number of samples in each group, and variability within control and IAD groups, the change in dAβ is not significant. To discriminate the dAβ from the C-terminal stub, CT-83, which migrates close to 8 kD we used MAb 6E10 which confirmed the ∼9 kD species as dAβ (Figure S2C). Another predictor of dAβ expression is the ApoE4 genotype, as dimers were detected in all patients with at least one ApoE4 allele, including one control. A later evaluation of dAβ in IAD and AD with more patients in the IAD and AD groups, but without the confounding effect of one control with ApoE4 genotype and increased dAβ, showed the elevation of dAβ levels to be significant (data not shown). dAβ abundance in synaptoneurosome preparations also increased as the MMSE declined (Figure 2B). Comparison of the Aß dimer normalized to GAPDH in homogenates and synaptoneurosomes showed a consistent quantitative increase with the duration of disease (Figure 2C).

Bottom Line: These patients also showed increased expression of neuroplasticity related genes, many encoding 3'UTR consensus sequences that regulate translation in the synapse.An increase in mRNA encoding the GluR2 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) was paralleled by elevated expression of the corresponding protein in IAD.These results imply a functional impact on synaptic transmission as GluR2, if inserted, maintains the receptors in a low conductance state.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Keck School of Medicine University of Southern California, Los Angeles, California, United States of America.

ABSTRACT
In Alzheimer's disease (AD), early deficits in learning and memory are a consequence of synaptic modification induced by toxic beta-amyloid oligomers (oAbeta). To identify immediate molecular targets downstream of oAbeta binding, we prepared synaptoneurosomes from prefrontal cortex of control and incipient AD (IAD) patients, and isolated mRNAs for comparison of gene expression. This novel approach concentrates synaptic mRNA, thereby increasing the ratio of synaptic to somal mRNA and allowing discrimination of expression changes in synaptically localized genes. In IAD patients, global measures of cognition declined with increasing levels of dimeric Abeta (dAbeta). These patients also showed increased expression of neuroplasticity related genes, many encoding 3'UTR consensus sequences that regulate translation in the synapse. An increase in mRNA encoding the GluR2 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) was paralleled by elevated expression of the corresponding protein in IAD. These results imply a functional impact on synaptic transmission as GluR2, if inserted, maintains the receptors in a low conductance state. Some overexpressed genes may induce early deficits in cognition and others compensatory mechanisms, providing targets for intervention to moderate the response to dAbeta.

Show MeSH
Related in: MedlinePlus