No association of CSF biomarkers with APOEepsilon4, plaque and tangle burden in definite Alzheimer's disease.

The CSF biomarkers beta-amyloid peptide (Abeta(1-42)), total tau protein (T-tau) and tau phosphorylated at threonine 181 (P-tau(181P)) were determined in autopsy-confirmed Alzheimer's disease patients in order to study possible associations with the epsilon4 allele of APOE and density and spread of plaques (SP) and tangles (NFT). CSF levels of Abeta(1-42), T-tau and P-tau(181P) were determined in 50 Alzheimer's disease patients using commercially available single parameter ELISA kits (INNOTEST(R)). Genomic DNA was extracted from whole blood and the APOE genotype was determined using standard methods. Tangle burden was assessed by means of Braak's NFT stages (I-VI), whereas the plaque burden was assessed by means of Braak's SP stages (A-C). CSF biomarker levels were not different when comparing epsilon4 carriers (n = 21) and non-carriers (n = 29) (P > 0.05 for all comparisons). No significant correlations between the number of epsilon4 alleles (0, 1 or 2) and CSF levels of Abeta(1-42) (Spearman Rank Order: r = -0.057, P = 0.695), T-tau (r = 0.104, P = 0.472) and P-tau(181P) (r = 0.062, P = 0.668) were found. Braak's SP (Abeta(1-42): r = -0.155, P = 0.280; T-tau: r = -0.044, P = 0.763; P-tau(181P): r = -0.010, P = 0.947) and NFT (Abeta(1-42): r = -0.145, P = 0.315; T-tau: r = 0.117, P = 0.415; P-tau(181P): r = 0.150, P = 0.296) stages were not significantly correlated with CSF biomarker levels. In conclusion, CSF levels of Abeta(1-42), T-tau and P-tau(181P) were not associated with epsilon4, tangle or plaque burden in 50 autopsy-confirmed Alzheimer's disease patients. In the light of future biomarker applications like monitoring of disease progression and as allocortical neuropathological changes significantly contribute to clinical symptoms, the concept of in vivo surrogate biomarkers should be further explored.

Alzheimer and Parkinson diagnoses in progranulin null mutation carriers in an extended founder family.

BACKGROUND: Progranulin gene (PGRN) haploinsufficiency was recently associated with ubiquitin-positive frontotemporal lobar degeneration linked to chromosome 17q21 (FTLDU-17). OBJECTIVE: To assess whether PGRN genetic variability contributed to other common neurodegenerative brain diseases, such as Alzheimer disease (AD) or Parkinson disease (PD). DESIGN: Mutation analysis of PGRN. SETTING: Memory Clinic of the Middelheim General Hospital. Patients We analyzed 666 Belgian patients with AD and 255 with PD. MAIN OUTCOME MEASURES: Results of PGRN sequencing, PGRN transcript analysis, short tandem repeat genotyping, and neuropathologic analysis. RESULTS: We identified 2 patients with AD and 1 patient with PD who carried the null mutation IVS0 + 5G>C, which we reported earlier in an extensively characterized Belgian founder family, DR8, segregating FTLDU. Postmortem pathologic diagnosis of the patient with PD revealed both FTLDU and Lewy body pathologic features. In addition, we identified in PGRN only 1 other null mutation, the nonsense mutation p.Arg535X, in 1 patient with probable AD. However, in vitro analysis predicted a PGRN C-truncated protein, although it remains to be elucidated if this shortened transcript leads to haploinsufficiency. CONCLUSIONS: Our mutation data indicated that null mutations are rare in patients with AD (3/666 = 0.45%) and PD (1/255 = 0.39%). Also, AD and PD clinical diagnoses in patients who carry PGRN null mutations likely result from etiologic heterogeneity rather than PGRN haploinsufficiency.

Genetic risk and transcriptional variability of amyloid precursor protein in Alzheimer's disease.

It is well established that Alzheimer's disease causing mutations in APP, PSEN1 and PSEN2 lead to a relative increased production of Abeta42, thereby fostering its deposition in plaques. Recently others and we showed that amyloid precursor protein (APP) overproduction, either as a result of genomic locus duplication or altered regulatory sequences in the APP promoter region, leads to early-onset disease. Here, we have expanded our study of genetic variability in the APP promoter to a large group of well-documented Belgian patients (n = 750, mean onset age = 75.0 +/- 8.6, range = 37-96). We identified three different APP promoter mutations (-369C-->G, -534G-->A and -479C-->T) in seven patients. In patients with onset < or =70 years (n = 204), we identified one patient carrying the London APP V717I mutation while no patients carried an APP locus duplication, indicating that APP promoter mutations (n = 2) were more frequently associated with increased risk for early-onset Alzheimer's disease. The two mutations (-369C-->G and -534G-->A) increasing APP promoter activity by nearly 2-fold and mimicking an APP duplication, appeared in probands of families with multiple patients with dementia. The -479C-->T mutation that increased APP expression only mildly (1.2-fold), was observed in four patients with onset ages ranging from 62 to 79 years (mean 71.5 years), suggesting that its contribution to disease risk is more pronounced at later age due to modulating factors. In conclusion, we provided evidence that mutations in APP regulatory sequences are more frequent than APP coding mutations, and that increased APP transcriptional activity constitutes a risk factor for Alzheimer's disease with onset ages inversely correlated with levels of APP expression.

Dense-core plaques in Tg2576 and PSAPP mouse models of Alzheimer's disease are centered on vessel walls.

Occurrence of amyloid beta (Abeta) dense-core plaques in the brain is one of the chief hallmarks of Alzheimer's disease (AD). It is not yet clear what factors are responsible for the aggregation of Abeta in the formation of these plaques. Using Tg2576 and PSAPP mouse models that exhibit age-related development of amyloid plaques similar to that observed in AD, we showed that approximately 95% of dense plaques in Tg2576 and approximately 85% in PSAPP mice are centered on vessel walls or in the immediate perivascular regions. Stereoscopy and simulation studies focusing on smaller plaques suggested that vascular associations for both Tg2576 and PSAPP mice were dramatically higher than those encountered by chance alone. We further identified ultrastructural microvascular abnormalities occurring in association with dense plaques. Although occurrence of gross cerebral hemorrhage was infrequent, we identified considerable infiltration of the serum proteins immunoglobulin and albumin in association with dense plaques. Together with earlier evidence of vascular clearance of Abeta, our data suggest that perturbed vascular transport and/or perivascular enrichment of Abeta leads to the formation of vasocentric dense plaques in Tg2576 and PSAPP mouse models of AD.

Synaptopodin and 4 novel genes identified in primary sensory neurons.

We performed differential gene expression profiling in the peripheral nervous system by comparing the transcriptome of sensory neurons with the transcriptome of lower motor neurons. Using suppression subtractive cDNA hybridization, we identified 5 anonymous transcripts with a predominant expression in sensory neurons. We determined the gene structures and predicted the functional protein domains. The 4930579P15Rik gene encodes for a novel inhibitor of protein phosphatase-1 and 9030217H17Rik was found to be the mouse gene synaptopodin. We performed in situ hybridization for all genes in mouse embryos, and found expression predominantly in the primary class of sensory neurons. Expression of 4930579P15Rik and synaptopodin was restricted to craniospinal sensory ganglia. Neither synaptopodin, nor any known family member of 4930579P15Rik, has ever been described in sensory neurons. The identification of protein domains and expression patterns allows further functional analysis of these novel genes in relation to the development and biology of sensory neurons.

In vitro studies of Flemish, Dutch, and wild-type beta-amyloid provide evidence for two-staged neurotoxicity.

Mutations in the beta-amyloid (Abeta) sequence of the amyloid precursor protein gene (APP) present with variable disease phenotypes. While patients with the Dutch APP mutation (E693Q) have predominantly hemorrhagic strokes, Flemish APP (A692G) patients develop both strokes and Alzheimer's disease (AD). To determine whether these diverse clinical and pathological presentations are due to mutant Abeta or APP, we studied the effect of Flemish, Dutch, and wild-type Abeta/APP on phosphorylation of specific tau epitopes observed in AD. No effect was observed in differentiated SH-SY5Y cells either stably expressing APP or treated with synthetic Abeta(12-42). However, we did observe a paradoxical temporal difference in the neurotoxic potential of mutant and wild-type Abeta. While long 24-h incubation at physiological levels of Abeta (2 microM) showed a higher amount of apoptosis for Dutch Abeta, a short 2-h incubation showed elevated apoptosis for Flemish and wild-type Abeta. The altered aggregating properties of Abeta, with Dutch Abeta aggregating faster and Flemish Abeta slower than wild type, elucidated a discrete two-phase Abeta neurotoxicity. We propose here that, at least in vitro, Abeta might be neurotoxic in an initial phase due to its soluble oligomeric or other early toxic Abeta intermediate(s), which is perhaps distinct from the late neurotoxicity incurred by aggregated larger assemblies of Abeta.

Dense-core senile plaques in the Flemish variant of Alzheimer's disease are vasocentric.

Alzheimer's disease (AD) is characterized by deposition of beta-amyloid (Abeta) in diffuse and senile plaques, and variably in vessels. Mutations in the Abeta-encoding region of the amyloid precursor protein (APP) gene are frequently associated with very severe forms of vascular Abeta deposition, sometimes also accompanied by AD pathology. We earlier described a Flemish APP (A692G) mutation causing a form of early-onset AD with a prominent cerebral amyloid angiopathy and unusually large senile plaque cores. The pathogenic basis of Flemish AD is unknown. By image and mass spectrometric Abeta analyses, we demonstrated that in contrast to other familial AD cases with predominant brain Abeta42, Flemish AD patients predominantly deposit Abeta40. On serial histological section analysis we further showed that the neuritic senile plaques in APP692 brains were centered on vessels. Of a total of 2400 senile plaque cores studied from various brain regions from three patients, 68% enclosed a vessel, whereas the remainder were associated with vascular walls. These observations were confirmed by electron microscopy coupled with examination of serial semi-thin plastic sections, as well as three-dimensional observations by confocal microscopy. Diffuse plaques did not associate with vessels, or with neuritic or inflammatory pathology. Together with earlier in vitro data on APP692, our analyses suggest that the altered biological properties of the Flemish APP and Abeta facilitate progressive Abeta deposition in vascular walls that in addition to causing strokes, initiates formation of dense-core senile plaques in the Flemish variant of AD.

APOE epsilon4 and Alzheimer's disease: positive association in a Colombian clinical series and review of the Latin-American studies

OBJECTIVE: As the strength of the association between the APOE epsilon4 allele and Alzheimer's disease (AD) varies across ethnic groups, we studied if there was such an association in Colombian patients. METHOD: We performed apolipoprotein E (APOE) genotyping in a clinical sample of 83 unrelated AD patients, predominantly late-onset (>65 yrs) including familial ( n =30) and sporadic AD cases (n= 53) diagnosed according to NINCDS-ADRDA criteria and assessed by a multi-disciplinary team. Control subjects (n = 44) had no significant cognitive impairment by medical interview and neuro-psychological testing. RESULTS: We found a high association (OR= 5.1 95 percentCI 1.9 -13.6) between APOE epsilon4 and AD, in this series with predominantly late-onset cases with familial aggregation in 24 cases (28.9 percent). A significant negative association was found between epsilon2 and AD (OR= 0.2 95 percent CI 0.05-0.75). CONCLUSION: Further population-based surveys in Colombia are warranted to precise a possible dose effect of APOE epsilon4