Imbalance in the response of pre- and post-synaptic components to amyloidopathy.

Alzheimer's disease (AD)-associated synaptic dysfunction drives the progression of pathology from its earliest stages. Amyloid ß (Aß) species, both soluble and in plaque deposits, have been causally related to the progressive, structural and functional impairments observed in AD. It is, however, still unclear how Aß plaques develop over time and how they progressively affect local synapse density and turnover. Here we observed, in a mouse model of AD, that Aß plaques grow faster in the earlier stages of the disease and if their initial area is >500 µm2; this may be due to deposition occurring in the outer regions of the plaque, the plaque cloud. In addition, synaptic turnover is higher in the presence of amyloid pathology and this is paralleled by a reduction in pre- but not post-synaptic densities. Plaque proximity does not appear to have an impact on synaptic dynamics. These observations indicate an imbalance in the response of the pre- and post-synaptic terminals and that therapeutics, alongside targeting the underlying pathology, need to address changes in synapse dynamics.

Alzheimer's Disease-Related Dementias Summit 2016: National research priorities.

Goal 1 of the National Plan to Address Alzheimer's Disease is to prevent and effectively treat Alzheimer disease and Alzheimer disease-related dementias by 2025. To help inform the research agenda toward achieving this goal, the NIH hosts periodic summits that set and refine relevant research priorities for the subsequent 5 to 10 years. This proceedings article summarizes the 2016 Alzheimer's Disease-Related Dementias Summit, including discussion of scientific progress, challenges, and opportunities in major areas of dementia research, including mixed-etiology dementias, Lewy body dementia, frontotemporal degeneration, vascular contributions to cognitive impairment and dementia, dementia disparities, and dementia nomenclature.

Altered Synapse Stability in the Early Stages of Tauopathy.

Synapse loss is a key feature of dementia, but it is unclear whether synaptic dysfunction precedes degenerative phases of the disease. Here, we show that even before any decrease in synapse density, there is abnormal turnover of cortical axonal boutons and dendritic spines in a mouse model of tauopathy-associated dementia. Strikingly, tauopathy drives a mismatch in synapse turnover; postsynaptic spines turn over more rapidly, whereas presynaptic boutons are stabilized. This imbalance between pre- and post-synaptic stability coincides with reduced synaptically driven neuronal activity in pre-degenerative stages of the disease.

Conformation determines the seeding potencies of native and recombinant Tau aggregates.

Intracellular Tau inclusions are a pathological hallmark of several neurodegenerative diseases, collectively known as the tauopathies. They include Alzheimer disease, tangle-only dementia, Pick disease, argyrophilic grain disease, chronic traumatic encephalopathy, progressive supranuclear palsy, and corticobasal degeneration. Tau pathology appears to spread through intercellular propagation, requiring the formation of assembled "prion-like" species. Several cell and animal models have been described that recapitulate aspects of this phenomenon. However, the molecular characteristics of seed-competent Tau remain unclear. Here, we have used a cell model to understand the relationships between Tau structure/phosphorylation and seeding by aggregated Tau species from the brains of mice transgenic for human mutant P301S Tau and full-length aggregated recombinant P301S Tau. Deletion of motifs (275)VQIINK(280) and (306)VQIVYK(311) abolished the seeding activity of recombinant full-length Tau, suggesting that its aggregation was necessary for seeding. We describe conformational differences between native and synthetic Tau aggregates that may account for the higher seeding activity of native assembled Tau. When added to aggregated Tau seeds from the brains of mice transgenic for P301S Tau, soluble recombinant Tau aggregated and acquired the molecular properties of aggregated Tau from transgenic mouse brain. We show that seeding is conferred by aggregated Tau that enters cells through macropinocytosis and seeds the assembly of endogenous Tau into filaments.

Astrocytes and neuroinflammation in Alzheimer's disease.

Increased production of amyloid ß-peptide (Aß) and altered processing of tau in Alzheimer's disease (AD) are associated with synaptic dysfunction, neuronal death and cognitive and behavioural deficits. Neuroinflammation is also a prominent feature of AD brain and considerable evidence indicates that inflammatory events play a significant role in modulating the progression of AD. The role of microglia in AD inflammation has long been acknowledged. Substantial evidence now demonstrates that astrocyte-mediated inflammatory responses also influence pathology development, synapse health and neurodegeneration in AD. Several anti-inflammatory therapies targeting astrocytes show significant benefit in models of disease, particularly with respect to tau-associated neurodegeneration. However, the effectiveness of these approaches is complex, since modulating inflammatory pathways often has opposing effects on the development of tau and amyloid pathology, and is dependent on the precise phenotype and activities of astrocytes in different cellular environments. An increased understanding of interactions between astrocytes and neurons under different conditions is required for the development of safe and effective astrocyte-based therapies for AD and related neurodegenerative diseases.

Recommendations of the Alzheimer's disease-related dementias conference.

The National Alzheimer's Project Act, signed into law in 2011, mandates a National Plan to Address Alzheimer's Disease that is updated annually. In the Plan, the term Alzheimer disease includes not only Alzheimer disease (AD) proper, but also several specified related dementias, namely, frontotemporal, Lewy body, vascular, and mixed dementia. In response to a specific action item in the 2012 National Plan, the National Institute of Neurological Disorders and Stroke, in collaboration with the National Institute on Aging, convened panels of experts and conducted a 2-day public conference to develop research priorities and timelines for addressing Alzheimer disease-related dementias (ADRD) in 5 topic areas: multiple etiology dementias, health disparities, Lewy body dementias including dementia with Lewy bodies and Parkinson disease dementia, frontotemporal dementia and related tauopathies, and vascular contributions to ADRD. By design, the product was up to 8 prioritized research recommendations in each topic area including estimated timelines from when work on a recommendation is started to completion or to full implementation of an ongoing activity, and recognition of shared research themes across recommendations. These included increased education and training of both researchers and health care professionals, addressing health disparities, fundamental neurobiology research, advanced diagnostics, collaborative biosample repositories, and a focus on developing effective interventions to prevent or treat ADRD by the year 2025 as targeted by the National Plan.

A novel in vivo model of tau propagation with rapid and progressive neurofibrillary tangle pathology: the pattern of spread is determined by connectivity, not proximity.

Intracellular inclusions composed of hyperphosphorylated filamentous tau are a hallmark of Alzheimer's disease, progressive supranuclear palsy, Pick's disease and other sporadic neurodegenerative tauopathies. Recent in vitro and in vivo studies have shown that tau aggregates do not only seed further tau aggregation within neurons, but can also spread to neighbouring cells and functionally connected brain regions. This process is referred to as 'tau propagation' and may explain the stereotypic progression of tau pathology in the brains of Alzheimer's disease patients. Here, we describe a novel in vivo model of tau propagation using human P301S tau transgenic mice infused unilaterally with brain extract containing tau aggregates. Infusion-related neurofibrillary tangle pathology was first observed 2 weeks post-infusion and increased in a stereotypic, time-dependent manner. Contralateral and anterior/posterior spread of tau pathology was also evident in nuclei with strong synaptic connections (efferent and afferent) to the site of infusion, indicating that spread was dependent on synaptic connectivity rather than spatial proximity. This notion was further supported by infusion-related tau pathology in white matter tracts that interconnect these regions. The rapid and robust propagation of tau pathology in this model will be valuable for both basic research and the drug discovery process.

SLC20A2 and THAP1 deletion in familial basal ganglia calcification with dystonia.

Idiopathic basal ganglia calcification (IBGC) is characterized by bilateral calcification of the basal ganglia associated with a spectrum of neuropsychiatric and motor syndromes. In this study, we set out to determine the frequency of the recently identified IBGC gene SLC20A2 in 27 IBGC cases from the Mayo Clinic Florida Brain Bank using both Sanger sequencing and TaqMan copy number analysis to cover the complete spectrum of possible mutations. We identified SLC20A2 pathogenic mutations in two of the 27 cases of IBGC (7 %). Sequencing analysis identified a p.S113* nonsense mutation in SLC20A2 in one case. TaqMan copy number analysis of SLC20A2 further revealed a genomic deletion in a second case, which was part of a large previously reported Canadian IBGC family with dystonia. Subsequent whole-genome sequencing in this family revealed a 563,256-bp genomic deletion with precise breakpoints on chromosome 8 affecting multiple genes including SLC20A2 and the known dystonia-related gene THAP1. The deletion co-segregated with disease in all family members. The deletion of THAP1 in addition to SLC20A2 in the Canadian IBGC family may contribute to the severe and early onset dystonia in this family. The identification of an SLC20A2 genomic deletion in a familial form of IBGC demonstrates that reduced SLC20A2 in the absence of mutant protein is sufficient to cause neurodegeneration and that previously reported SLC20A2 mutation frequencies may be underestimated.

A plaque-specific antibody clears existing ß-amyloid plaques in Alzheimer's disease mice.

Aß Immunotherapy is a promising therapeutic approach for Alzheimer's disease. Preclinical studies demonstrate that plaque prevention is possible; however, the more relevant therapeutic removal of existing plaque has proven elusive. Monoclonal antibodies in development target both soluble and insoluble Aß peptide. We hypothesized that antibody specificity for deposited plaque was critical for plaque removal since soluble Aß peptide would block recognition of deposited forms. We developed a plaque-specific antibody that targets a modified Aß peptide (Aß(p3-42)), which showed robust clearance of pre-existing plaque without causing microhemorrhage. Interestingly, a comparator N-terminal Aß antibody 3D6, which binds both soluble and insoluble Aß(1-42), lacked efficacy for lowering existing plaque but manifested a significant microhemorrhage liability. Mechanistic studies suggested that the lack of efficacy for 3D6 was attributed to poor target engagement in plaques. These studies have profound implications for the development of therapeutic Aß antibodies for Alzheimer's disease.

Passive immunization with anti-Tau antibodies in two transgenic models: reduction of Tau pathology and delay of disease progression.

The microtubule-associated protein Tau plays a critical role in the pathogenesis of Alzheimer disease and several related disorders (tauopathies). In the disease Tau aggregates and becomes hyperphosphorylated forming paired helical and straight filaments, which can further condense into higher order neurofibrillary tangles in neurons. The development of this pathology is consistently associated with progressive neuronal loss and cognitive decline. The identification of tractable therapeutic targets in this pathway has been challenging, and consequently very few clinical studies addressing Tau pathology are underway. Recent active immunization studies have raised the possibility of modulating Tau pathology by activating the immune system. Here we report for the first time on passive immunotherapy for Tau in two well established transgenic models of Tau pathogenesis. We show that peripheral administration of two antibodies against pathological Tau forms significantly reduces biochemical Tau pathology in the JNPL3 mouse model. We further demonstrate that peripheral administration of the same antibodies in the more rapidly progressive P301S tauopathy model not only reduces Tau pathology quantitated by biochemical assays and immunohistochemistry, but also significantly delays the onset of motor function decline and weight loss. This is accompanied by a reduction in neurospheroids, providing direct evidence of reduced neurodegeneration. Thus, passive immunotherapy is effective at preventing the buildup of intracellular Tau pathology, neurospheroids, and associated symptoms, although the exact mechanism remains uncertain. Tau immunotherapy should therefore be considered as a therapeutic approach for the treatment of Alzheimer disease and other tauopathies.

Accelerated lipofuscinosis and ubiquitination in granulin knockout mice suggest a role for progranulin in successful aging.

Progranulin (PGRN) is involved in wound repair, inflammation, and tumor formation, but its function in the central nervous system is unknown. Roles in development, sexual differentiation, and long-term neuronal survival have been suggested. Mutations in the GRN gene resulting in partial loss of the encoded PGRN protein cause frontotemporal lobar degeneration with ubiquitin immunoreactive inclusions. We sought to understand the neuropathological consequences of loss of PGRN function throughout the lifespan of GRN-deficient ((-/+) and (-/-)) mice. An aged series of GRN-deficient and wild-type mice were compared by histology, immunohistochemistry, and electron microscopy. Although GRN-deficient mice were viable, GRN(-/-) mice were produced at lower than predicted frequency. Neuropathologically, GRN(-/+) were indistinguishable from controls; however, GRN(-/-) mice developed age-associated, abnormal intraneuronal ubiquitin-positive autofluorescent lipofuscin. Lipofuscin was noted in aged GRN(+/+) mice at levels comparable with those of young GRN(-/-) mice. GRN(-/-) mice developed microgliosis, astrogliosis, and tissue vacuolation, with focal neuronal loss and severe gliosis apparent in the oldest GRN(-/-) mice. Although no overt frontotemporal lobar degeneration with ubiquitin immunoreactive inclusions type- or TAR DNA binding protein-43-positive lesions were observed, robust lipofuscinosis and ubiquitination in GRN(-/-) mice is strikingly similar to changes associated with aging and cellular decline in humans and animal models. Our data suggests that PGRN plays a key role in maintaining neuronal function during aging and supports the notion that PGRN is a trophic factor essential for long-term neuronal survival.

Whole genome association analysis shows that ACE is a risk factor for Alzheimer's disease and fails to replicate most candidates from Meta-analysis.

For late onset Alzheimer's disease (LOAD), the only confirmed, genetic association is with the apolipoprotein E (APOE) locus on chromosome 19. Meta-analysis is often employed to sort the true associations from the false positives. LOAD research has the advantage of a continuously updated meta-analysis of candidate gene association studies in the web-based AlzGene database. The top 30 AlzGene loci on May 1(st), 2007 were investigated in our whole genome association data set consisting of 1411 LOAD cases and neuropathoiogicaiiy verified controls genotyped at 312,316 SNPs using the Affymetrix 500K Mapping Platform. Of the 30 "top AlzGenes", 32 SNPs in 24 genes had odds ratios (OR) whose 95% confidence intervals that did not include 1. Of these 32 SNPs, six were part of the Affymetrix 500K Mapping panel and another ten had proxies on the Affymetrix array that had >80% power to detect an association with α=0.001. Two of these 16 SNPs showed significant association with LOAD in our sample series. One was rs4420638 at the APOE locus (uncorrected p-value=4.58E-37) and the other was rs4293, located in the angiotensin converting enzyme (ACE) locus (uncorrected p-value=0.014). Since this result was nominally significant, but did not survive multiple testing correction for 16 independent tests, this association at rs4293 was verified in a geographically distinct German cohort (p-value=0.03). We present the results of our ACE replication aiongwith a discussion of the statistical limitations of multiple test corrections in whole genome studies.

Evidence for an association between KIBRA and late-onset Alzheimer's disease.

We recently reported evidence for an association between the individual variation in normal human episodic memory and a common variant of the KIBRA gene, KIBRA rs17070145 (T-allele). Since memory impairment is a cardinal clinical feature of Alzheimer's disease (AD), we investigated the possibility of an association between the KIBRA gene and AD using data from neuronal gene expression, brain imaging studies, and genetic association tests. KIBRA was significantly over-expressed and three of its four known binding partners under-expressed in AD-affected hippocampal, posterior cingulate and temporal cortex regions (P<0.010, corrected) in a study of laser-capture microdissected neurons. Using positron emission tomography in a cohort of cognitively normal, late-middle-aged persons genotyped for KIBRA rs17070145, KIBRA T non-carriers exhibited lower glucose metabolism than did carriers in posterior cingulate and precuneus brain regions (P<0.001, uncorrected). Lastly, non-carriers of the KIBRA rs17070145 T-allele had increased risk of late-onset AD in an association study of 702 neuropathologically verified expired subjects (P=0.034; OR=1.29) and in a combined analysis of 1026 additional living and expired subjects (P=0.039; OR=1.26). Our findings suggest that KIBRA is associated with both individual variation in normal episodic memory and predisposition to AD.

Mimicking aspects of frontotemporal lobar degeneration and Lou Gehrig's disease in rats via TDP-43 overexpression.

Since the discovery of neuropathological lesions made of TDP-43 and ubiquitin proteins in cases of frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS), there is a burst of effort on finding related familial mutations and developing animal models. We used an adeno-associated virus (AAV) vector for human TDP-43 expression targeted to the substantia nigra (SN) of rats. Though TDP-43 was expressed mainly in neuronal nuclei as expected, it was also expressed in the cytoplasm, and dotted along the plasma membrane of neurons. Cytoplasmic staining was both diffuse and granular, indicative of preinclusion lesions, over 4 weeks. Ubiquitin deposited in the cytoplasm, specifically in the TDP-43 group, and staining for microglia was increased dose-dependently by 1-2 logs in the TDP-43 group, while neurons were selectively obliterated. Neuronal death induced by TDP-43 was pyknotic and apoptotic. TDP-43 gene transfer caused loss of dopaminergic neurons in the SN and their axons in the striatum. Behavioral motor dysfunction resulted after TDP-43 gene transfer that was vector dose-dependent and progressive over time. The cytoplasmic expression, ubiquitination, and neurodegeneration mimicked features of the TDP-43 diseases, and the gliosis, apoptosis, and motor impairment may also be relevant to TDP-43 disease forms involving nigrostriatal degeneration.

Common variation in the miR-659 binding-site of GRN is a major risk factor for TDP43-positive frontotemporal dementia.

Loss-of-function mutations in progranulin (GRN) cause ubiquitin- and TAR DNA-binding protein 43 (TDP-43)-positive frontotemporal dementia (FTLD-U), a progressive neurodegenerative disease affecting approximately 10% of early-onset dementia patients. Here we expand the role of GRN in FTLD-U and demonstrate that a common genetic variant (rs5848), located in the 3'-untranslated region (UTR) of GRN in a binding-site for miR-659, is a major susceptibility factor for FTLD-U. In a series of pathologically confirmed FTLD-U patients without GRN mutations, we show that carriers homozygous for the T-allele of rs5848 have a 3.2-fold increased risk to develop FTLD-U compared with homozygous C-allele carriers (95% CI: 1.50-6.73). We further demonstrate that miR-659 can regulate GRN expression in vitro, with miR-659 binding more efficiently to the high risk T-allele of rs5848 resulting in augmented translational inhibition of GRN. A significant reduction in GRN protein was observed in homozygous T-allele carriers in vivo, through biochemical and immunohistochemical methods, mimicking the effect of heterozygous loss-of-function GRN mutations. In support of these findings, the neuropathology of homozygous rs5848 T-allele carriers frequently resembled the pathological FTLD-U subtype of GRN mutation carriers. We suggest that the expression of GRN is regulated by miRNAs and that common genetic variability in a miRNA binding-site can significantly increase the risk for FTLD-U. Translational regulation by miRNAs may represent a common mechanism underlying complex neurodegenerative disorders.

Early onset familial Alzheimer Disease with spastic paraparesis, dysarthria, and seizures and N135S mutation in PSEN1.

OBJECTIVE: Early onset familial Alzheimer disease (EOFAD) can be caused by mutations in genes for amyloid precursor protein, presenilin 1 (PSEN1), or presenilin 2 (PSEN2). There is considerable phenotypic variability in EOFAD, including some patients with spastic paraparesis. The objective is to describe clinical and neuropathologic features of a family with a PSEN1 mutation that has been reported previously, without autopsy confirmation, in a single Greek family whose affected members presented with memory loss in their 30s, as well as variable limb spasticity and seizures. METHODS: We prospectively evaluated 2 children (son and daughter) with EOFAD and reviewed medical records on their mother. Archival material from the autopsy of the mother was reviewed and postmortem studies were performed on the brain of the daughter. RESULTS: All 3 individuals in this family had disease onset in their 30s, with cognitive deficits in multiple domains, including memory, language, and attention, as well as less common features such as spastic dysarthria, limb spasticity, and seizures. At autopsy both the mother and her daughter had pathologic findings of Alzheimer disease, and histologic evidence of corticospinal tract degeneration. Genetic studies revealed a mutation in PSEN1 leading to an asparagine to serine substitution at amino acid residue 135 (N135S) in presenilin 1. CONCLUSIONS: This is the first description of neuropathologic findings in EOFAD owing to N135S PSEN1 mutation. The clinical phenotype was remarkable for spastic dysarthria, limb spasticity, and seizures, in addition to more typical features of EOFAD.

Progranulin gene mutation with an unusual clinical and neuropathologic presentation.

Progranulin gene (PGRN) mutations cause frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U). Patients usually present with a frontotemporal dementia syndrome and have prominent atrophy and neuronal loss in frontal and temporal cortices and the striatum, with neuronal intranuclear and cytoplasmic inclusions. Clinical, neuropathological, and genetic studies are reported on an individual with PGRN mutation and her family members. We describe a patient with a PGRN c.26C>A mutation who presented with progressive stuttering dysarthria, oculomotor abnormalities, choreic buccolingual movements, and mild parkinsonism. Two other family members were affected, one with a behavioral variant frontotemporal dementia syndrome, the other with a diagnosis of probable Alzheimer's disease. At autopsy there was no neuronal loss in the cortex or medial temporal lobe structures, but there was striatal gliosis. Immunohistochemistry for ubiquitin and TDP-43 revealed neuronal cytoplasmic and intranuclear inclusions as well as neurites. This study further expands the clinical and pathological spectrum of PGRN mutations, and suggests the diagnosis could be missed in some individuals with atypical presentations.

APOE epsilon 4 lowers age at onset and is a high risk factor for Alzheimer's disease; a case control study from central Norway.

BACKGROUND: The objective of this study was to analyze factors influencing the risk and timing of Alzheimer's disease (AD) in central Norway. The APOE epsilon4 allele is the only consistently identified risk factor for late onset Alzheimer's disease (LOAD). We have described the allele frequencies of the apolipoprotein E gene (APOE) in a large population of patients with AD compared to the frequencies in a cognitively-normal control group, and estimated the effect of the APOE epsilon4 allele on the risk and the age at onset of AD in this population. METHODS: 376 patients diagnosed with AD and 561 cognitively-normal control individuals with no known first degree relatives with dementia were genotyped for the APOE alleles. Allele frequencies and genotypes in patients and control individuals were compared. Odds Ratio for developing AD in different genotypes was calculated. RESULTS: Odds Ratio (OR) for developing AD was significantly increased in carriers of the APOE epsilon4 allele compared to individuals with the APOE epsilon3/epsilon3 genotype. Individuals carrying APOE epsilon4/epsilon4 had OR of 12.9 for developing AD, while carriers of APOE epsilon2/epsilon4 and APOE epsilon3/epsilon4 had OR of 3.2 and 4.2 respectively. The effect of the APOE epsilon4 allele was weaker with increasing age. Carrying the APOE epsilon2 allele showed no significant protective effect against AD and did not influence age at onset of the disease. Onset in LOAD patients was significantly reduced in a dose dependent manner from 78.4 years in patients without the APOE epsilon4 allele, to 75.3 in carriers of one APOE epsilon4 allele and 72.9 in carriers of two APOE epsilon4 alleles. Age at onset in early onset AD (EOAD) was not influenced by APOE epsilon4 alleles. CONCLUSION: APOE epsilon4 is a very strong risk factor for AD in the population of central Norway, and lowers age at onset of LOAD significantly.

Cognitive domain decline in healthy apolipoprotein E epsilon4 homozygotes before the diagnosis of mild cognitive impairment.

BACKGROUND: Memory declines more rapidly with age in apolipoprotein E (APOE) epsilon4 carriers than in APOE epsilon4 noncarriers, and APOE epsilon4 homozygotes' cognitive performances correlate with stressors. These changes could represent presymptomatic disease in some, despite their youth. OBJECTIVE: To show that presymptomatic APOE epsilon4 homozygotes experience greater psychometric decline at a younger age than APOE epsilon4 heterozygotes and noncarriers before the diagnosis of mild cognitive impairment (MCI) and Alzheimer disease (AD). DESIGN: Prospective observational study SETTING: Academic medical center. PARTICIPANTS: A total of 43 APOE epsilon4 homozygotes, 59 APOE epsilon4 heterozygotes, and 112 APOE epsilon4 noncarriers aged 50 to 69 years were cognitively healthy and matched at entry according to age, educational level, and sex. INTERVENTION: Neuropsychological battery given every 2 years. MAIN OUTCOME MEASURES: Predefined test and cognitive domain decline criteria applied to consecutive epochs. RESULTS: Of 214 participants, 48 showed no decline on any test, 126 showed decline on only 1 test in 1 or more domains, and 40 showed decline on 2 or more tests in 1 or more domains. Cognitive domain decline occurred in 4 of 10 APOE epsilon4 homozygotes 60 years and older at entry (40.0%) compared with 5 of 66 APOE epsilon4 heterozygotes and noncarriers (7.6%) (P = .02) and was more predictive of subsequent decline than nondomain decline (17 of 24 [70.8%] vs 29 of 70 [41.4%]; P = .01). Decline on any memory test was predictive of further decline (P < .001), as was memory domain decline (P = .006) in all genetic subgroups. Seven participants developed MCI (in 6) or AD (in 1), of whom 5 were APOE epsilon4 homozygotes (P = .008). Retrospective comparison showed that those who experienced multidomain, memory, and language domain decline had lower spatial and memory scores at entry than those who experienced no decline. CONCLUSIONS: APOE epsilon4 homozygotes in their 60s have higher rates of cognitive domain decline than APOE epsilon4 heterozygotes or noncarriers before the diagnosis of MCI and AD, thus confirming and characterizing the existence of a pre-MCI state in this genetic subset.