Driving force to detect Alzheimer's disease biomarkers: application of a thioflavine T@Er-MOF ratiometric fluorescent sensor for smart detection of presenilin 1, amyloid ß-protein and acetylcholine.

Currently, the highly sensitive detection of Alzheimer's Disease (AD) biomarkers, namely presenilin 1, amyloid ß-protein (Aß), and acetylcholine (ACh), is vital to helping us prevent and diagnose AD. In this work, a novel metal-organic framework [Er(L)(DMF)1.27]n (Er-MOF) (H3L = terphenyl-3,4'',5-tricarboxylic acid) has been synthesized by solvothermal and ultrasonic methods. Further, through the post-synthesis assembly strategy, the fluorescent dye thioflavine T (ThT) has been introduced into Er-MOF to construct a dual-emission ThT@Er-MOF ratiometric fluorescent sensor. This is the first time that ThT@Er-MOF has been successfully applied in the highly sensitive detection of three main Alzheimer's disease biomarkers in the cerebrospinal fluid through three different low cost and facile detection strategies. Firstly, with the spilted DNA strategy, this is the first time that ThT@Er-MOF can be applied in the label-free detection of SSODN (part of the presenilin 1 gene). Secondly, for the detection of Aß, because ThT can be specifically combined with Aß and has an excellent characteristic fluorescence band, the dual-emission ThT@Er-MOF sensor can be selectively applied to detect Aß over the analog protein, which shows far more sensitivity than other Aß sensors. Thirdly, through the acetylcholine esterase (AchE) enzymatic cleavage and release strategy, ThT@Er-MOF enhances the detection of acetylcholine (ACh) with a low limit of detection (LOD) value (0.03226 nM). It should be noticed that the three different detection methods are low cost and facile. This study also provides the first example of utilizing laser scanning confocal microscopy (LSCM) to investigate the fluorescence resonance energy transfer (FRET) detection mechanism by ThT@Er-MOF in more detail. The location of FRET occurrence and FRET efficiency can also be investigated by LSCM, which can be helpful to understand the FRET detection process by these unique MOF-based hybrid materials.

A novel mutation in PSEN1 (p.T119I) in an Argentine family with early- and late-onset Alzheimer's disease.

Mutations in PSEN1 are the most common cause of early-onset Alzheimer's disease (AD). In this article, we present an Argentine family with autosomal dominant early- and late-onset AD. The proband and 6 family members were available for genetic testing and clinical and neuropsychological assessments. Cerebrospinal fluid biomarkers were analyzed in the proband and a cousin (mutation carrier), who also underwent positron emission tomography using F-18-2-fluoro-2-deoxy-D-glucose and Pittsburgh compound B. Exon sequencing of PSEN1, PSEN2, and APP revealed a novel heterozygous variant in PSEN1 (c.356C>T; p.T119I). Median age of onset in the family was 56 years. However, the proband's uncle showed initial symptoms at age 71. Although no DNA was available, he was an obligate carrier because his daughter (proband's cousin) carried the mutation. Both the proband and his cousin exhibited biomarker evidence (cerebrospinal fluid or imaging) of underlying Alzheimer's pathology. Overall, our results support that the PSEN1 p.T119I variant is likely pathogenic.

CSF Presenilin-1 complexes are increased in Alzheimer's disease.

BACKGROUND: Presenilin-1 (PS1) is the active component of the amyloid precursor protein cleaving γ-secretase complex. PS1 protein is a transmembrane protein containing multiple hydrophobic regions which presence in cerebrospinal fluid (CSF) has not been measured to date. This study assesses whether PS1 and other components of the γ-secretase complex are present in CSF. RESULTS: Here, we show that PS1 is present in ventricular post-mortem and lumbar ante-mortem CSF, and plasma as 100-150-kDa hetero-complexes containing both the N- and C-terminal fragments (NTF and CTF) of the protein. Immunoprecipitation and immunoblotting with different antibodies confirmed the identity of the PS1 species. The γ-secretase components, APH-1 (anterior pharynx-defective 1) and PEN-2 (presenilin enhancer 2), as well as presenilin-2 (PS2) fragments, co-exist within these CSF complexes, while nicastrin is not detected. These CSF-PS1 complexes differ from active γ-secretase membrane-complexes, and may represent nonspecific aggregation of the PS1 protein. Levels of PS1 complexes are increased in CSF samples from autopsy-confirmed Alzheimer's disease (AD) cases and were found to be more stable than complexes in CSF from control subjects. Despite similar levels of total PS1 in CSF from probable AD patients and cognitively normal subjects, an increased proportion of highly stable PS1 complexes were observed in AD CSF. CONCLUSIONS: Our data suggest that fragments of the PS1 protein present in CSF as complexes may be useful as a biomarker for AD.

Distinct patterns of APP processing in the CNS in autosomal-dominant and sporadic Alzheimer disease.

Autosomal-dominant Alzheimer disease (ADAD) is a genetic disorder caused by mutations in Amyloid Precursor Protein (APP) or Presenilin (PSEN) genes. Studies from families with ADAD have been critical to support the amyloid cascade hypothesis of Alzheimer disease (AD), the basis for the current development of amyloid-based disease-modifying therapies in sporadic AD (SAD). However, whether the pathological changes in APP processing in the CNS in ADAD are similar to those observed in SAD remains unclear. In this study, we measured ß-site APP-cleaving enzyme (BACE) protein levels and activity, APP and APP C-terminal fragments in brain samples from subjects with ADAD carrying APP or PSEN1 mutations (n = 18), patients with SAD (n = 27) and age-matched controls (n = 22). We also measured sAPPß and BACE protein levels, as well as BACE activity, in CSF from individuals carrying PSEN1 mutations (10 mutation carriers and 7 non-carrier controls), patients with SAD (n = 32) and age-matched controls (n = 11). We found that in the brain, the pattern in ADAD was characterized by an increase in APP ß-C-terminal fragment (ß-CTF) levels despite no changes in BACE protein levels or activity. In contrast, the pattern in SAD in the brain was mainly characterized by an increase in BACE levels and activity, with less APP ß-CTF accumulation than ADAD. In the CSF, no differences were found between groups in BACE activity or expression or sAPPß levels. Taken together, these data suggest that the physiopathological events underlying the chronic Aß production/clearance imbalance in SAD and ADAD are different. These differences should be considered in the design of intervention trials in AD.

Brain imaging and fluid biomarker analysis in young adults at genetic risk for autosomal dominant Alzheimer's disease in the presenilin 1 E280A kindred: a case-control study.

BACKGROUND: We have previously characterised functional brain abnormalities in young adults at genetic risk for late-onset Alzheimer's disease. To gain further knowledge on the preclinical phase of Alzheimer's disease, we sought to characterise structural and functional MRI, CSF, and plasma biomarkers in a cohort of young adults carrying a high-penetrance autosomal dominant mutation that causes early-onset Alzheimer's disease. METHODS: Between January and August, 2010, 18-26-year-old presenilin 1 (PSEN1) E280A mutation carriers and non-carriers from the Colombian Alzheimer's Prevention Initiative Registry in Medellín Antioquia, Colombia, had structural MRI, functional MRI during associative memory encoding and novel viewing and control tasks, and cognitive assessments. Consenting participants also had lumbar punctures and venepunctures. Outcome measures were task-dependent hippocampal or parahippocampal activations and precuneus or posterior cingulate deactivations, regional grey matter reductions, CSF Aß(1-42), total tau and phospho-tau(181) concentrations, and plasma Aß(1-42) concentrations and Aß(1-42):Aß(1-40) ratios. Structural and functional MRI data were compared using automated brain mapping algorithms and search regions related to Alzheimer's disease. Cognitive and fluid biomarkers were compared using Mann-Whitney tests. FINDINGS: 44 participants were included: 20 PSEN1 E280A mutation carriers and 24 non-carriers. The carrier and non-carrier groups did not differ significantly in their dementia ratings, neuropsychological test scores, or proportion of apolipoprotein E (APOE) ɛ4 carriers. Compared with non-carriers, carriers had greater right hippocampal and parahippocampal activation (p=0·001 and p<0·014, respectively, after correction for multiple comparisons), less precuneus and posterior cingulate deactivation (all p<0·010 after correction), and less grey matter in several parietal regions (all p<0·002 uncorrected and corrected p=0·009 in the right parietal search region). In the 20 participants (ten PSEN1 E280A mutation carriers and ten non-carriers) who had lumbar punctures and venepunctures, mutation carriers had higher CSF Aß(1-42) concentrations (p=0·008) and plasma Aß(1-42) concentrations (p=0·01) than non-carriers. INTERPRETATION: Young adults at genetic risk for autosomal dominant Alzheimer's disease have functional and structural MRI findings and CSF and plasma biomarker findings consistent with Aß(1-42) overproduction. Although the extent to which the underlying brain changes are either neurodegenerative or developmental remain to be determined, this study shows the earliest known biomarker changes in cognitively normal people at genetic risk for autosomal dominant Alzheimer's disease. FUNDING: Banner Alzheimer's Foundation, Nomis Foundation, Anonymous Foundation, Forget Me Not Initiative, Boston University Department of Psychology, Colciencias, National Institute on Aging, National Institute of Neurological Disorders and Stroke, and the State of Arizona.

CSF studies facilitate DNA diagnosis in familial Alzheimer's disease due to a presenilin-1 mutation.

In sporadic Alzheimer's disease (AD), cerebrospinal fluid (CSF) analysis is becoming increasingly relevant to establish an early diagnosis. We present a case of familial AD due to a presenilin-1 mutation in which CSF studies suggested appropriate DNA diagnostics. A 38 year old Dutch man presented with dementia, spastic paraparesis, and frontal executive function impairments, mimicking familial Creutzfeldt Jakob disease and frontotemporal dementia. CSF studies, revealing increased total tau and phosphorylated-tau levels with decreased amyloid-beta42, distinguished familial AD from Creutzfeldt Jakob disease and frontotemporal dementia. A causative p.L424R PSEN1 mutation was subsequently identified.