Characterization of the repeat expansion size in C9orf72 in amyotrophic lateral sclerosis and frontotemporal dementia.

Hexanucleotide repeat expansions within the C9orf72 gene are the most important genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The difficulty of developing a precise method to determine the expansion size has hampered the study of possible correlations between the hexanucleotide repeat number and clinical phenotype. Here we characterize, through a new non-radioactive Southern blot protocol, the expansion size range in a series of 38 ALS and 22 FTD heterozygous carriers of >30 copies of the repeat. Maximum, median and modal hexanucleotide repeat number were higher in ALS patients than in FTD patients (P< 0.05 in all comparisons). A higher median number of repeats correlated with a bigger range of repeat sizes (Spearman's ρ = 0.743, P = 1.05 × 10(-11)). We did not find any correlation between age of onset or disease duration with the repeat size in neither ALS nor FTD mutation carriers. Clinical presentation (bulbar or spinal) in ALS patients did not correlate either with the repeat length. We finally analyzed two families with affected and unaffected repeat expansion carriers, compared the size of the repeat expansion between two monozygotic (MZ) twins (one affected of ALS and the other unaffected), and examined the expansion size in two different tissues (cerebellum and peripheral blood) belonging to the same FTD patient. The results suggested that the length of the C9orf72 repeat varies between family members, including MZ twins, and among different tissues from the same individual.

Cerebrospinal fluid ß-amyloid and phospho-tau biomarker interactions affecting brain structure in preclinical Alzheimer disease.

OBJECTIVE: To assess the relationships between core cerebrospinal fluid (CSF) biomarkers and cortical thickness (CTh) in preclinical Alzheimer disease (AD). METHODS: In this cross-sectional study, normal controls (n = 145) from the Alzheimer's Disease Neuroimaging Initiative underwent structural 3T magnetic resonance imaging (MRI) and lumbar puncture. CSF ß-amyloid1-42 (Aß) and phospho-tau181p (p-tau) levels were measured by Luminex assays. Samples were dichotomized using published cutoffs (Aß(+) /Aß(-) and p-tau(+) /ptau(-)). CTh was measured by Freesurfer. CTh difference maps were derived from interaction and correlation analyses. Clusters from the interaction analysis were isolated to analyze the directionality of the interaction by analysis of covariance. RESULTS: We found a significant biomarker interaction between CSF Aß and CSF p-tau levels affecting brain structure. Cortical atrophy only occurs in subjects with both Aß(+) and p-tau(+). The stratified correlation analyses showed that the relationship between p-tau and CTh is modified by Aß status and the relationship between Aß and CTh is modified by p-tau status. p-Tau-dependent thinning was found in different cortical regions in Aß(+) subjects but not in Aß(-) subjects. Cortical thickening was related to decreasing CSF Aß values in the absence of abnormal p-tau, but no correlations were found in p-tau(+) subjects. INTERPRETATION: Our data suggest that interactions between biomarkers in AD result in a 2-phase phenomenon of pathological cortical thickening associated with low CSF Aß, followed by atrophy once CSF p-tau becomes abnormal. These interactions should be considered in clinical trials in preclinical AD, both when selecting patients and when using MRI as a surrogate marker of efficacy.

Plasma phosphorylated TDP-43 levels are elevated in patients with frontotemporal dementia carrying a C9orf72 repeat expansion or a GRN mutation.

OBJECTIVES: About a half of patients with frontotemporal dementia (FTD) has deposition of phosphorylated TDP-43 protein (pTDP-43) in the brain. We studied pTDP-43 and total TDP-43 levels in plasma and cerebrospinal fluid (CSF) in healthy controls and patients with FTD, including those carrying a repeat expansion in the C9orf72 gene or a mutation in GRN. METHODS: We included 88 plasma samples of 10 C9orf72 expansion carriers, 5 GRN mutation carriers, 51 patients with FTD without a known mutation and 22 healthy controls. We also obtained CSF samples from 25 patients with FTD (2 with C9orf72 expansion and 3 with a GRN mutation) and 22 healthy controls. We measured pTDP-43 and total TDP-43 levels using sandwich ELISA. RESULTS: Patients carrying the C9orf72 repeat expansion or a GRN mutation had significantly higher plasma and CSF levels of pTDP-43 than the remaining patients with FTD (p<0.05). In addition, plasma pTDP-43 levels were higher in patients with FTD carrying a C9orf72 expansion or GRN mutations than in healthy controls (p<0.05). CONCLUSIONS: Our study shows that plasma pTDP-43 levels may be increased in some genetic forms of FTD known to be associated with TDP-43 proteinopathies.

Glucocerebrosidase mutations confer a greater risk of dementia during Parkinson's disease course.

Mutations in the glucocerebrosidase gene are associated with Parkinson's disease and Lewy body dementia. However, whether these alterations have any effect on the clinical course of Parkinson's disease is not clear. The glucocerebrosidase coding region was fully sequenced in 225 Parkinson's disease patients, 17 pathologically confirmed Lewy body dementia patients, and 186 controls from Spain. Twenty-two Parkinson's disease patients (9.8%) and 2 Lewy body dementia patients (11.8%) carried mutations in the glucocerebrosidase gene, compared with only 1 control (0.5%); P = .016 and P = .021 for Parkinson's disease and Lewy body dementia, respectively. The N370S and the L444P mutations represented 50% of the alterations. Two novel variants, L144V and S488T, and 7 previously described alterations were also found. Alterations in glucocerebrosidase were associated with a significant risk of dementia during the clinical course of Parkinson's disease (age at onset, years of evolution, and sex-adjusted odds ratio, 5.8; P = .001). Mutation carriers did not show worse motor symptoms, had good response to L-dopa, and tended to present the intermediate parkinsonian phenotype. Our findings suggest that mutations in the glucocerebrosidase gene not only increase the risk of both Parkinson's disease and Lewy body dementia but also strongly influence the course of Parkinson's disease with respect to the appearance of dementia.

Cerebrospinal Fluid Anti-Amyloid-ß Autoantibodies and Amyloid PET in Cerebral Amyloid Angiopathy-Related Inflammation.

We report a biomarker and genetic evaluation of four patients with cerebral amyloid angiopathy-related inflammation (CAA-ri) treated with corticosteroids. Patients presented with focal symptomatology and cognitive impairment. MRI revealed cortical microbleeds and asymmetrical hyperintense white matter lesions (WML). Cerebrospinal fluid (CSF) biomarker analyses showed increased anti-Aß autoantibodies, t-Tau, and p-Tau and decreased Aß40 and Aß42. After treatment, focal symptomatology disappeared, and WML and anti-Aß autoantibodies decreased. The APOEɛ4 allele was overrepresented. Florbetapir-PET showed cortical deposition with lower retention in swollen areas. In the case of suspected CAA-ri, both CSF anti-Aß autoantibodies levels and Florbetapir-PET could provide highly useful data to guide the correct diagnosis.

APOE-by-sex interactions on brain structure and metabolism in healthy elderly controls.

BACKGROUND: The APOE effect on Alzheimer Disease (AD) risk is stronger in women than in men but its mechanisms have not been established. We assessed the APOE-by-sex interaction on core CSF biomarkers, brain metabolism and structure in healthy elderly control individuals (HC). METHODS: Cross-sectional study. HC from the Alzheimer's Disease Neuroimaging Initiative with available CSF (n = 274) and/or 3T-MRI (n = 168) and/or a FDG-PET analyses (n = 328) were selected. CSF amyloid-ß1-42 (Aß1-42), total-tau (t-tau) and phospho-tau (p-tau181p) levels were measured by Luminex assays. We analyzed the APOE-by-sex interaction on the CSF biomarkers in an analysis of covariance (ANCOVA). FDG uptake was analyzed by SPM8 and cortical thickness (CTh) was measured by FreeSurfer. FDG and CTh difference maps were derived from interaction and group analyses. RESULTS: APOE4 carriers had lower CSF Aß1-42 and higher CSF p-tau181p values than non-carriers, but there was no APOE-by-sex interaction on CSF biomarkers. The APOE-by-sex interaction on brain metabolism and brain structure was significant. Sex stratification showed that female APOE4 carriers presented widespread brain hypometabolism and cortical thinning compared to female non-carriers whereas male APOE4 carriers showed only a small cluster of hypometabolism and regions of cortical thickening compared to male non-carriers. CONCLUSIONS: The impact of APOE4 on brain metabolism and structure is modified by sex. Female APOE4 carriers show greater hypometabolism and atrophy than male carriers. This APOE-by-sex interaction should be considered in clinical trials in preclinical AD where APOE4 status is a selection criterion.

Relationship between cortical thickness and cerebrospinal fluid YKL-40 in predementia stages of Alzheimer's disease.

Cerebrospinal fluid YKL-40 has been described as a marker of glial inflammation. We aimed to study the relationship between YKL-40 and brain structure and its interactions with core Alzheimer's disease (AD) biomarkers. We measured cortical thickness (CTh) and cerebrospinal fluid biomarkers (amyloid-ß 1-42 [Aß42], total tau, p-tau, and YKL-40) of 80 cognitively normal controls and 27 patients with amnestic mild cognitive impairment. Subjects were classified as Aß42+ (<550 pg/mL) or Aß42- (>550 pg/mL). CTh difference maps were derived from the interaction and correlation analyses in the whole sample and within clinical groups. There was a strong correlation between YKL-40 and markers of neurodegeneration (total tau and p-tau). In the whole sample, we found a negative correlation between YKL-40 and CTh in AD vulnerable areas in Aß42+ subjects but not in Aß42 participants. Our results suggest that YKL-40 could track the inflammatory processes associated to tau-related neurodegeneration in the presence of the AD pathophysiological process.

Relationship between ß-Secretase, inflammation and core cerebrospinal fluid biomarkers for Alzheimer's disease.

BACKGROUND: Biomarkers in the cerebrospinal fluid (CSF) can track specific pathophysiological pathways underlying Alzheimer's disease (AD). The connection between these biomarkers remains unclear. OBJECTIVE: To study six CSF biomarkers in a clinical cohort of patients with different neurodegenerative conditions. METHODS: We measured markers of amyloid-ß protein precursor (AßPP) processing (Aß42, sAßPPß, ß-secretase activity), neuronal damage (total tau, p-tau), and inflammation (YKL-40) in CSF from 194 participants with the following diagnoses: subjective cognitive impairment or non-amnestic mild cognitive impairment (na-SCI, n = 44), amnestic mild cognitive impairment (aMCI, n = 45), dementia of the Alzheimer type (DAT, n = 59), frontotemporal dementia (FTD, n = 22), and 24 cognitively normal controls. We compared biomarkers between clinical groups and CSF-profile groups, and we analyzed the correlation between biomarkers. RESULTS: CSF levels of sAßPPß were decreased in FTD patients compared to the other groups. YKL-40 was elevated in DAT and FTD, and also in aMCI patients. CSF Aß42 correlated positively with ß-secretase activity (RS = 0.262) and sAßPPß (RS = 0.341). CSF YKL-40 correlated positively with total tau (RS = 0.467) and p-tau (RS = 0.429). CSF p-tau and sAßPPß contributed significantly to distinguish DAT from FTD. CONCLUSIONS: CSF biomarkers of AßPP processing correlate with each other and are decreased in FTD. The inflammatory marker YKL-40 is increased in different neurodegenerative diseases, even in early stages, and it correlates with biomarkers of neurodegeneration. This suggests that inflammation is a common feature in AD and FTD. A combination of CSF biomarkers tracking distinct pathophysiological processes may be useful to classify subjects with neurodegenerative conditions.

Expansion mutation in C9ORF72 does not influence plasma progranulin levels in frontotemporal dementia.

A hexanucleotide repeat expansion in chromosome 9 open reading frame 72 (C9ORF72) gene has recently been described as a cause of familial and sporadic frontotemporal lobar degeneration. The aim of this study was to assess whether plasma progranulin (GRN) levels could be modulated by the presence of this repeat expansion. Sixty-five patients diagnosed with frontotemporal dementia and 10 family members with familial aggregation of disease were screened for the presence of the hexanucleotide repeat expansion in C9ORF72 gene, using a repeat-primed polymerase chain reaction method. Plasma GRN levels were measured in all subjects through enzyme-linked immunosorbent assay. Seven individuals with the repeat expansion were identified. No differences were found between C9ORF72 repeat expansion carriers and noncarriers (116.4 ± 21 ng/mL and 131.7 ± 36 ng/mL, respectively, p = 0.3). Analysis of family members did not disclose any difference in plasma GRN levels between carriers and noncarriers. In conclusion, plasma GRN levels are not influenced by the hexanucleotide repeat expansion in C9ORF72 gene, and therefore, cannot be used as a reliable biomarker to detect mutation carriers.