Isabel Hernández

Background: Frontotemporal Dementia (FTD) is a heterogeneous group of disorders and the second most frequent cause of early onset dementia making it the highest number of inherited cases. Review Summary: FTD is characterized by considerable variability in clinical, genetic and histopathologic features. Patients may present symptoms ranging from behavioural disturbances to different language disorders, with or without motor neuron disorders or associated parkinsonism. Atrophy in frontal and temporal lobes is the most relevant radiological finding. In the last 10 years, the knowledge of this clinical entity has undergone remarkable changes both genetically and histopathologically, which have served to establish more consistent clinical criteria. Until now, 10 genes causative of FTLD have been described and up to four different proteins causative of atrophy have been detected in aggregates. Conclusion: This review is mostly addressed to clinicians and aims to provide basic knowledge of these neurodegenerative disorders and clarify the complex FTD scenario.

The identification of early, preferably presymptomatic, biomarkers and true etiologic factors for Alzheimer’s disease (AD) is the first step toward establishing effective primary and secondary prevention programs. Consequently, the search for a relatively inexpensive and harmless biomarker for AD continues. Despite intensive research worldwide, to date there is no definitive plasma or blood biomarker indicating high or low risk of conversion to AD. Magnetic resonance imaging and β -amyloid (Aβ) levels in three blood compartments (diluted in plasma, undiluted in plasma and cell-bound) were measured in 96 subjects (33 with mild cognitive impairment, 14 with AD and 49 healthy controls). Pearson correlations were completed between 113 regions of interest (ROIs) (45 subcortical and 68 cortical) and Aβ levels. Pearson correlation analyses adjusted for the covariates age, sex, apolipoprotein E (ApoE), education and creatinine levels showed neuroimaging ROIs were associated with Aβ levels. Two statistical methods were applied to study the major relationships identified: (1) Pearson correlation with phenotype added as a covariate and (2) a meta-analysis stratified by phenotype. Neuroimaging data and plasma Aβ measurements were taken from 630 Alzheimer’s Disease Neuroimaging Initiative (ADNI) subjects to be compared with our results. The left hippocampus was the brain region most correlated with Aβ(1 - 40) bound to blood cell pellets (partial correlation (pcor) = − 0.37, P = 0.0007) after adjustment for the covariates age, gender and education, ApoE and creatinine levels. The correlation remained almost the same (pcor = − 0.35, P = 0.002) if phenotype is also added as a covariate. The association between both measurements was independent of cognitive status. The left hemisphere entorhinal cortex also correlated with Aβ(1 - 40) cell-bound fraction. AB128 and ADNI plasma Aβ measurements were not related to any brain morphometric measurement. Association of cell-bound A β(1 - 40) in blood with left hippocampal volume was much stronger than previously observed in A β plasma fractions. If confirmed, this observation will require careful interpretation and must be taken into account for blood amyloid-based biomarker development.

Background: In order to identify novel loci associated with Alzheimer's disease (AD), we conducted a genome-wide association study (GWAS) in the Spanish population. Methods: We genotyped 1,128 individuals using the Affymetrix Nsp I 250K chip. A sample of 327 sporadic AD patients and 801 controls with unknown cognitive status from the Spanish general population were included in our initial study. To increase the power of the study, we combined our results with those of four other public GWAS datasets by applying identical quality control filters and the same imputation methods, which were then analyzed with a global meta-GWAS. A replication sample with 2,200 sporadic AD patients and 2,301 controls was genotyped to confirm our GWAS findings. Results: Meta-analysis of our data and independent replication datasets allowed us to confirm a novel genome-wide significant association of AD with the membrane-spanning 4-domains subfamily A (MS4A) gene cluster (rs1562990, P = 4.40E-11, odds ratio = 0.88, 95% confidence interval 0.85 to 0.91, n = 10,181 cases and 14,341 controls). Conclusions: Our results underscore the importance of international efforts combining GWAS datasets to isolate genetic loci for complex diseases.