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In JoVE (1)
Other Publications (3)
Articles by Yitshak I. Francis in JoVE
JoVE Neuroscience
Preparation of Oligomeric β-amyloid1-42 and Induction of Synaptic Plasticity Impairment on Hippocampal Slices
Taub Institute for Research on Alzheimer's Disease and Aging Brain, Columbia University
One feature of Alzheimer's Disease is the elevation of Aβ1-42 peptide. Here we provide a protocol for preparing synthetic Aβ1-42 oligomers, which impairs hippocampal Long-Term Potentiation, a cellular correlate of memory. This procedure is useful for investigating mechanisms of Aβ-induced pathology and drug screening.
Other articles by Yitshak I. Francis on PubMed
CREB-binding Protein Activation by Presenilin 1 but Not by Its M146L Mutant
The transcriptional coactivator CREB-binding protein plays a key role in regulating gene expression in a number of different cell types. Recently, a report has suggested a link between CREB-binding protein and presenilins, which are mutated in many cases of early onset Alzheimer's disease. Thus, presenilin 1 and 2 double knockout mice showed reductions in CREB-binding protein levels and in cAMP response element-dependent gene expression in the cerebral cortex, which is likely to contribute to the subsequent neuronal degeneration. This suggests that the inactivation of CREB-binding protein caused by mutation in presenilin 1 may be involved in the disease process. We have shown that wild-type presenilin 1 stimulates the transcriptional activity ability of CREB-binding protein whereas presenilin 1 M146L mutant did not produce such an effect. The activation of CREB-binding protein by wild-type presenilin 1 involves the PI 3-kinase, p38 mitogen-activated protein kinase (MAPK) and p42/p44 MAPK pathways and targets primarily the C terminus of CREB-binding protein. To our knowledge, this is the first report that shows regulation of CREB-binding protein activity by wild-type presenilin 1 and not by its M146L mutant, and suggests a mechanism in which mutation of presenilin 1 may lead to neurodegeneration.
P300 Activation by Presenilin 1 but Not by Its M146L Mutant
The transcriptional co-activator p300 plays an important role in regulating gene expression in a number of different cell types. We have shown that wild type (WT) Presenilin 1 (PS1) stimulates the transcriptional activity ability of CREB Binding Protein (CBP), a close homolog of p300, whereas the Alzheimer's disease (AD) associated mutant of PS1 does not have this effect. A recent report has suggested that mutant PS1 can also disrupt the TCF/beta-catenin/CBP interaction but has no effect on the TCF/beta-catenin/p300 interaction. This suggests that the malregulation of CBP, but not of p300, caused by mutation in PS1 may be involved in the disease process. Here we show that wild type PS1 stimulates the transcriptional activity ability of p300 whereas an Alzheimer's disease-associated mutant of PS1 did not produce this effect. To our knowledge, this is the first report that shows regulation of p300 activity by WT PS1 and not by mutant PS1, indicating that like CBP, p300 can be differentially regulated by WT PS1 compared to its AD-associated mutant.
Dysregulation of Histone Acetylation in the APP/PS1 Mouse Model of Alzheimer's Disease
Epigenetic mechanisms such as post-translational histone modifications are increasingly recognized for their contribution to gene activation and silencing in the brain. Histone acetylation in particular has been shown to be important both in hippocampal long-term potentiation (LTP) and memory formation in mice. The involvement of the epigenetic modulation of memory formation has also been proposed in neuropathological models, although up to now no clear-cut connection has been demonstrated between histone modifications and the etiology of Alzheimer's disease (AD). Thus, we have undertaken preclinical studies in the APP/PS1 mouse model of AD to determine whether there are differences in histone acetylation levels during associative memory formation. After fear conditioning training, levels of hippocampal acetylated histone 4 (H4) in APP/PS1 mice were about 50% lower than in wild-type littermates. Interestingly, acute treatment with a histone deacetylase inhibitor, Trichostatin A (TSA), prior to training rescued both acetylated H4 levels and contextual freezing performance to wild-type values. Moreover, TSA rescued CA3-CA1 LTP in slices from APP/PS1 mice. Based on this evidence, we propose the hypothesis that epigenetic mechanisms are involved in the altered synaptic function and memory associated with AD. In this respect, histone deacetylase inhibitors represent a new therapeutic target to effectively counteract disease progression.
