Manel Fernández

Combined dementia-risk biomarkers in Parkinson's disease: A prospective longitudinal study

Neuropsychological (mostly posterior-cortical) deficits, quantitative magnetic resonance imaging (MRI) atrophy patterns, and low cerebrospinal fluid (CSF) levels of amyloid-β have been separately related to worsening cognition in Parkinsons disease (PD). However, these biomarkers have not been longitudinally assessed in combination as PD-dementia predictors. In this prospective longitudinal study, 27 non-demented PD patients underwent CSF, neuropsychological and 3-T brain-MRI studies at baseline and were re-assessed 18 months later in terms of progression to dementia (primary outcome) and longitudinal neuropsychological and cortical thickness changes (secondary outcomes). At follow-up 11 patients (41%) had progressed to dementia. Lower CSF amyloid-β, worse verbal learning, semantic fluency and visuoperceptual scores, and thinner superior-frontal/anterior cingulate and precentral regions were significant baseline dementia predictors in binary logistic regressions as quantitative and/or dichotomised traits. All participants without baseline biomarker abnormalities remained non-demented whereas all with abnormalities in each biomarker type progressed to dementia, with intermediate risk for those showing abnormalities in a single to two biomarker types (p = 0.006). Both the dementia-outcome and low baseline CSF amyloid-β were prospectively associated with limbic and posterior-cortical neuropsychological decline and frontal, limbic and posterior-cortical thinning from baseline to follow-up. These findings suggest that the combination of CSF amyloid-β, neuropsychological and cortical thickness biomarkers might provide a basis for dementia-risk stratification and progression monitoring in PD.

Identification of blood serum micro-RNAs associated with idiopathic and LRRK2 Parkinson's disease.

Blood‐cell‐free circulating micro‐RNAs (miRNAs) have been proposed as potential accessible biomarkers for neurodegenerative diseases such as Parkinsons disease (PD). Here we analyzed the serum levels of 377 miRNAs in a discovery set of 10 idiopathic Parkinsons disease (IPD) patients, 10 PD patients carriers of the LRRK2 G2019S mutation (LRRK2 PD), and 10 controls by using real‐time quantitative PCR‐based TaqMan MicroRNA arrays. We detected candidate differentially expressed miRNAs, which were further tested in a first validation set consisting of 20 IPD, 20 LRRK2 PD, and 20 control samples. We found four statistically significant miRNAs that were downregulated in either LRRK2 or IPD (miR‐29a, miR‐29c, miR‐19a, and miR‐19b). Subsequently, we validated these findings in a third set of samples consisting of 65 IPD and 65 controls and confirmed the association of downregulated levels of miR‐29c, miR‐29a, and miR‐19b in IPD. Differentially expressed miRNAs are predicted to target genes belonging to pathways related to ECM–receptor interaction, focal adhesion, MAPK, Wnt, mTOR, adipocytokine, and neuron projection. Results from our exploratory study indicate that downregulated levels of specific circulating serum miRNAs are associated with PD and suggest their potential use as noninvasive biomarkers for PD. Future studies should further confirm the association of these miRNAs with PD.

A preliminary study of the whole-genome expression profile of sporadic and monogenic early-onset Alzheimer's disease

Alzheimers disease (AD) is the most common neurodegenerative dementia. Approximately 10% of cases present at an age of onset before 65 years old, which in turn can be monogenic familial AD (FAD) or sporadic early-onset AD (sEOAD). Mutations in PSEN1, PSEN2, and APP genes have been linked with FAD. The aim of our study is to describe the brain whole-genome RNA expression profile of the posterior cingulate area in sEOAD and FAD caused by PSEN1 mutations (FAD-PSEN1). Fourteen patients (7 sEOAD and 7 FAD-PSEN1) and 7 neurologically healthy control subjects were selected and whole-genome expression was measured using Affymetrix Human Gene 1.1 microarrays. We identified statistically significant expression changes in sEOAD and FAD-PSEN1 brains with respect to control subjects (3183 and 3350 differentially expressed genes [DEG] respectively, false discovery rate-corrected p < 0.05). Of them, 1916 DEG were common between the 2 comparisons. We did not identify DEG between sEOAD and FAD-PSEN1. Microarray data were validated through real-time quantitative polymerase chain reaction. In silico analysis of DEG revealed an alteration in biological pathways related to intracellular signaling pathways (particularly calcium signaling), neuroactive ligand-receptor interactions, axon guidance, and long-term potentiation in both groups of patients. In conclusion, the altered biological final pathways in sEOAD and FAD-PSEN1 are mainly related with cell signaling cascades, synaptic plasticity, and learning and memory processes. We hypothesize that these 2 groups of early-onset AD with distinct etiologies and likely different could present a neurodegenerative process with potential different pathways that might converge in a common and similar final stage of the disease.

Sleep Disorders in Parkinsonian and Nonparkinsonian LRRK2 Mutation Carriers

Objective In idiopathic Parkinson disease (IPD) sleep disorders are common and may antedate the onset of parkinsonism. Based on the clinical similarities between IPD and Parkinson disease associated with LRRK2 gene mutations (LRRK2-PD), we aimed to characterize sleep in parkinsonian and nonmanifesting LRRK2 mutation carriers (NMC). Methods A comprehensive interview conducted by sleep specialists, validated sleep scales and questionnaires, and video-polysomnography followed by multiple sleep latency test (MSLT) assessed sleep in 18 LRRK2-PD (17 carrying G2019S and one R1441G mutations), 17 NMC (11 G2019S, three R1441G, three R1441C), 14 non-manifesting non-carriers (NMNC) and 19 unrelated IPD. Results Sleep complaints were frequent in LRRK2-PD patients; 78% reported poor sleep quality, 33% sleep onset insomnia, 56% sleep fragmentation and 39% early awakening. Sleep onset insomnia correlated with depressive symptoms and poor sleep quality. In LRRK2-PD, excessive daytime sleepiness (EDS) was a complaint in 33% patients and short sleep latencies on the MSLT, which are indicative of objective EDS, were found in 71%. Sleep attacks occurred in three LRRK2-PD patients and a narcoleptic phenotype was not observed. REM sleep behavior disorder (RBD) was diagnosed in three LRRK2-PD. EDS and RBD were always reported to start after the onset of parkinsonism in LRRK2-PD. In NMC, EDS was rarely reported and RBD was absent. When compared to IPD, sleep onset insomnia was more significantly frequent, EDS was similar, and RBD was less significantly frequent and less severe in LRRK2-PD. In NMC, RBD was not detected and sleep complaints were much less frequent than in LRRK2-PD. No differences were observed in sleep between NMC and NMNC. Conclusions Sleep complaints are frequent in LRRK2-PDand show a pattern that when compared to IPD is characterized by more frequent sleep onset insomnia, similar EDS and less prominent RBD. Unlike in IPD, RBD and EDS seem to be not markers of the prodromal stage of LRRK2-PD.

Age at Onset in LRRK2-Associated PD is Modified by SNCA Variants

Mutations in the leucine-rich repeat kinase 2 (LRRK2) and α-synuclein (SNCA) genes are known genetic causes of Parkinsons disease (PD). Recently, a genetic variant in SNCA has been associated with a lower age at onset in idiopathic PD (IPD). We genotyped the SNCA polymorphism rs356219 in 84 LRRK2-associated PD patients carrying the G2019S mutation. We found that a SNCA genetic variant is associated with an earlier age at onset in LRRK2-associated PD. Our results support the notion that SNCA variants can modify the pathogenic effect of LRRK2 mutations as described previously for IPD.

Microarray expression analysis in idiopathic and LRRK2-associated Parkinson's disease

LRRK2 mutations are the most common genetic cause of Parkinsons disease (PD). We performed a whole-genome RNA profiling of putamen tissue from idiopathic PD (IPD), LRRK2-associated PD (G2019S mutation), neurologically healthy controls and one asymptomatic LRRK2 mutation carrier, by using the Genechip Human Exon 1.0-ST Array. The differentially expressed genes found in IPD revealed an alteration of biological pathways related to long-term potentiation (LTP), GABA receptor signalling, and calcium signalling pathways, among others. These pathways are mainly related with cell signalling cascades and synaptic plasticity processes. They were also altered in the asymptomatic LRRK2 mutation carrier but not in the LRRK2-associated PD group. The expression changes seen in IPD might be attributed to an adaptive consequence of a dysfunction in the dopamine transmission. The lack of these altered molecular pathways in LRRK2-associated PD patients suggests that these cases could show a different molecular response to dopamine transmission impairment.

MicroRNA Association with Synucleinopathy Conversion in Rapid Eye Movement Behavior Disorder

Recently, we reported downregulated circulating levels of the microRNAs miR‐19b, miR‐29a, and miR‐29c in Parkinson disease. Here we investigated the expression of these microRNAs in serum samples from 56 patients with idiopathic rapid eye movement sleep behavior disorder, before and after their conversion into a synucleinopathy. Compared to controls, we found that the expression level of miR‐19b is downregulated in patients with idiopathic rapid eye movement sleep behavior disorder and antedates the diagnosis of Parkinson disease and dementia with Lewy bodies after 4.67 ± 2.61 years of follow‐up. Our findings indicate that dysregulation of the microRNA miR‐19b occurs in the prodromal stage of synucleinopathies. Ann Neurol 2015;77:895–901

Serum Progranulin Levels in Patients with Frontotemporal Lobar Degeneration and Alzheimer's Disease: Detection of GRN Mutations in a Spanish Cohort

Progranulin gene (GRN) mutations cause frontotemporal lobar degeneration (FTLD) with TDP43-positive inclusions, although its clinical phenotype is heterogeneous and includes patients classified as behavioral variant-FTLD (bvFTLD), progressive non-fluent aphasia (PNFA), corticobasal syndrome, Alzheimers disease (AD), or Parkinsons disease (PD). Our main objective was to study if low serum progranulin protein (PGRN) levels may detect GRN mutations in a Spanish cohort of patients with FTLD or AD. Serum PGRN levels were measured in 112 subjects: 17 bvFTLD, 20 PNFA, 4 semantic dementia, 34 sporadic AD, 9 AD-PSEN1 mutation carriers, 10 presymptomatic-PSEN1 mutation carriers, and 18 control individuals. We detected 5 patients with PGRN levels below 94 ng/mL: two of them had a clinical diagnosis of bvFTLD, two of PNFA, and one of AD. The screening for GRN mutations detected two probable pathogenic mutations (p.C366fsX1 and a new mutation: p.V279GfsX5) in three patients and one mutation of unclear pathogenic nature (p.C139R) in one patient. The other patient showed a normal GRN sequence but carried a PRNP gene mutation. We observed no differences in serum PGRN levels between controls (mean = 145.5 ng/mL, SD = 28.5) and the other neurodegenerative diseases, except for the carriers of pathological GRN gene mutations (mean = 50.5 ng/mL, SD = 21.2). Null GRN mutation carriers also showed lower serum PGRN levels than the patient who was a carrier of p.C139R (92.3 ng/mL) and the one who was a carrier of the PRNP mutation (76.9 ng/mL). In conclusion, we detected GRN null mutations in patients with severely reduced serum PGRN levels, but not in patients with slightly reduced PGRN levels.

Absence of LRRK2 mutations in a cohort of patients with idiopathic REM sleep behavior disorder.

Most patients with idiopathic REM sleep behavior disorder (IRBD) are diagnosed with the synucleinopathies Parkinson disease (PD) and dementia with Lewy bodies. Conversion rates have been estimated to be 35% at 5 years, 73% at 10 years, and 92% at 14 years after IRBD diagnosis.1 Accordingly, IRBD is considered as a marker of the prodromal stage of synucleinopathies. In PD, RBD occurs in about 50% of the patients and in 18% of them, RBD symptoms precede the onset of parkinsonism.2 Most cases of PD are sporadic, but approximately 5% to 10% of cases encompass monogenic forms caused by mutations in PD-associated genes. Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene represent the most common genetic cause of both familial PD and sporadic PD (sPD). Indeed, the G2019S mutation has been detected in up to 6% of familial and 3% of sPD cases in Europeans.3 Moreover, the LRRK2-associated PD form (LRRK2-PD) is clinical and neuropathologically similar to sPD lacking LRRK2 mutations.3

Brain transcriptomic profiling in idiopathic and LRRK2-associated Parkinson's disease

LRRK2 mutations are the most common genetic cause of Parkinsons disease (PD). We performed a whole-genome RNA profiling of locus coeruleus post-mortem tissue, a histopathologically affected brain tissue in PD, from idiopathic PD (IPD) and LRRK2-associated PD patients. The differentially expressed genes found in IPD and LRRK2-associated PD are involved in the gene ontology terms of synaptic transmission and neuron projection. In addition, differentially expressed genes in the IPD group are associated with immune system related pathways. Specifically, the study performed highlights the presence of differential expression of genes located in the chromosome 6p21.3 belonging to the class II HLA. Our findings support the hypothesis of a potential role of neuroinflammation and the involvement of the HLA genetic area in IPD pathogenesis. Future studies are necessary to shed light on the relation of immune system related pathways in the etiopathogenesis of PD.