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Presenilin-1 knockin mice reveal loss-of-function mechanism for familial Alzheimer's disease.

ABSTRACT: Presenilins play essential roles in memory formation, synaptic function, and neuronal survival. Mutations in the Presenilin-1 (PSEN1) gene are the major cause of familial Alzheimer's disease (FAD). How PSEN1 mutations cause FAD is unclear, and pathogenic mechanisms based on gain or loss of function have been proposed. Here, we generated Psen1 knockin (KI) mice carrying the FAD mutation L435F or C410Y. Remarkably, KI mice homozygous for either mutation recapitulate the phenotypes of Psen1(-/-) mice. Neither mutation altered Psen1 mRNA expression, but both abolished ?-secretase activity. Heterozygosity for the KI mutation decreased production of A?40 and A?42, increased the A?42/A?40 ratio, and exacerbated A? deposition. Furthermore, the L435F mutation impairs hippocampal synaptic plasticity and memory and causes age-dependent neurodegeneration in the aging cerebral cortex. Collectively, our findings reveal that FAD mutations can cause complete loss of Presenilin-1 function in vivo, suggesting that clinical PSEN mutations produce FAD through a loss-of-function mechanism.

SUBMITTER: Xia D

PROVIDER: S-EPMC4358812 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

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Presenilin-1 knockin mice reveal loss-of-function mechanism for familial Alzheimer's disease.

Xia Dan D Watanabe Hirotaka H Wu Bei B Lee Sang Hun SH Li Yan Y Tsvetkov Evgeny E Bolshakov Vadim Y VY Shen Jie J Kelleher Raymond J RJ

Neuron 20150301 5

Presenilins play essential roles in memory formation, synaptic function, and neuronal survival. Mutations in the Presenilin-1 (PSEN1) gene are the major cause of familial Alzheimer's disease (FAD). How PSEN1 mutations cause FAD is unclear, and pathogenic mechanisms based on gain or loss of function have been proposed. Here, we generated Psen1 knockin (KI) mice carrying the FAD mutation L435F or C410Y. Remarkably, KI mice homozygous for either mutation recapitulate the phenotypes of Psen1(-/-) mi ...[more]

PMID: 25741723

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Project description:The E693? (Osaka) mutation in APP is linked to familial Alzheimer's disease. While this mutation accelerates amyloid ? (A?) oligomerization, only patient homozygotes suffer from dementia, implying that this mutation is recessive and causes loss-of-function of amyloid precursor protein (APP). To investigate the recessive trait, we generated a new mouse model by knocking-in the Osaka mutation into endogenous mouse APP. The produced homozygous, heterozygous, and non-knockin littermates were compared for memory, neuropathology, and synaptic plasticity. Homozygotes showed memory impairment at 4 months, whereas heterozygotes did not, even at 8 months. Immunohistochemical and biochemical analyses revealed that only homozygotes displayed intraneuronal accumulation of A? oligomers at 8 months, followed by abnormal tau phosphorylation, synapse loss, glial activation, and neuron loss. These pathologies were not observed at younger ages, suggesting that a certain mechanism other than A? accumulation underlies the memory disturbance at 4 months. For the electrophysiology studies at 4 months, high-frequency stimulation evoked long-term potentiation in all mice in the presence of picrotoxin, but in the absence of picrotoxin, such potentiation was observed only in homozygotes, suggesting their GABAergic deficit. In support of this, the levels of GABA-related proteins and the number of dentate GABAergic interneurons were decreased in 4-month-old homozygotes. Since APP has been shown to play a role in dentate GABAergic synapse formation, the observed GABAergic depletion is likely associated with an impairment of the APP function presumably caused by the Osaka mutation. Oral administration of diazepam to homozygotes from 6 months improved memory at 8 months, and furthermore, prevented A? oligomer accumulation, indicating that GABAergic deficiency is a cause of memory impairment and also a driving force of A? accumulation. Our findings suggest that the Osaka mutation causes loss of APP function, leading to GABAergic depletion and memory disorder when wild-type APP is absent, providing a mechanism of the recessive heredity.

Dataset Information

Presenilin-1 knockin mice reveal loss-of-function mechanism for familial Alzheimer's disease.

Publications

Presenilin-1 knockin mice reveal loss-of-function mechanism for familial Alzheimer's disease.

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