Barbara A. Pickut

A novel presenilin 1 mutation associated with Pick's disease but not β‐amyloid plaques

Familial forms of frontotemporal dementia (FTD) with tauopathy are mostly caused by mutations in the gene encoding the microtubule‐associated protein tau (MAPT). However, rare forms of familial tauopathy without MAPT mutations have been reported, suggesting other tauopathy‐related genetic defects. Interestingly, two presenilin 1 (PS1) mutations (Leu113Pro and insArg352) recently have been associated with familial FTD albeit without neuropathological confirmation. We report here a novel PS1 mutation in a patient with Pick‐type tauopathy in the absence of extracellular β‐amyloid deposits. The mutation is predicted to substitute Gly→Val at codon position 183 (Gly183Val) and to affect the splice signal at the junction of the sixth exon and intron. Further clinical‐genetic investigation showed a positive family history of FTD‐like dementia and suggested that Gly183Val is associated with a phenotypically heterogeneous neurodegenerative disorder. Our results suggest PS1 as a candidate gene for Pick‐type tauopathy without MAPT mutations.

Genetic variability in progranulin contributes to risk for clinically diagnosed Alzheimer disease

Objective: Loss-of-function mutations in the progranulin gene (PGRN) were identified in frontotemporal lobar degeneration (FTLD) with ubiquitin-immunoreactive neuronal inclusions (FTLD-U). We assessed whether PGRN also contributes to genetic risk for Alzheimer disease (AD) in an extended Belgian AD patient group (n = 779, onset age 74.7 ± 8.7 years). Methods: A mutation analysis of the PGRN coding region was performed. The effect of missense mutations was assessed using in silico predictions and protein modeling. Risk effects of common genetic variants were estimated by logistic regression analysis and gene-based haplotype association analysis. Results: We observed seven missense mutations in eight patients (1.3%). Convincing pathogenic evidence was obtained for two missense mutations, p.Cys139Arg and p.Pro451Leu, affecting PGRN protein folding and leading to loss of PGRN by degradation of the misfolded protein. In addition, we showed that PGRN haplotypes were associated with increased risk for AD. Conclusions: Our data support a role for PGRN in patients with clinically diagnosed Alzheimer disease (AD). Further, we hypothesize that at least some PGRN missense mutations might lead to loss of functional protein. Whether the underlying pathology in our cases proves to be AD, frontotemporal lobar degeneration, or a combination of the two must await further investigations.

Prospective Belgian study of neurodegenerative and vascular dementia: APOE genotype effects.

Objective: The authors conducted a prospective study of neurodegenerative and vascular dementia in Belgium. Strict diagnostic inclusion criteria were used to include well defined patients and controls. The results of apolipoprotein E (APOE) genotype effect on risk and clinical characteristics are presented. Methods: APOE genotyping was performed in patients with probable Alzheimer’s disease (AD) (n=504), frontotemporal dementia (FTD) (n=47), vascular dementia (VaD) (n=152), mixed dementia (n=132), mild cognitive impairment (MCI) (n=44), Parkinson’s disease (PD) (n=30), dementia with Lewy bodies (DLB) (n=17), and multisystem atrophy (MSA)/progressive supranuclear palsy (PSP) (n=12). Results: The APOE allele frequencies of this Belgian control population (ε2: 6.9%; ε3: 76.2%; ε4: 16.9%) did not differ from those reported for other white populations. AD, MCI, and mixed dementia patients had higher APOE ε4 (32.9%, 38.6%, and 28.4% respectively) and lower APOE ε3 (62.2%, 53.4%, and 66.3%) frequencies compared with controls, whereas only AD and mixed dementia patients had lower APOE ε2 frequencies (4.9% and 5.3%). Apart from a borderline significant different distribution of APOE allele frequencies in VaD patients compared with controls, no other differences were detected. The influence of APOE ε4 on clinical features of dementia was limited to lower age at onset in AD patients and a less pronounced negative correlation between age at onset and number of ε4 alleles in MCI and mixed dementia patients. Conclusions: This study confirmed the risk association between APOE ε4 and AD. The observation that APOE ε4 is associated with mixed dementia reflected the role of AD in the aetiopathogenesis of this condition. Although MCI is an aetiologically heterogeneous syndrome, the increased APOE ε4 frequencies indicated that a large proportion of the MCI patients included in the study might be predisposed to develop AD.

Lrrk2 R1441C parkinsonism is clinically similar to sporadic Parkinson disease

Objective: Leucine-rich repeat kinase 2 (LRRK2) mutations are the most common cause of Parkinson disease (PD). Several dominantly inherited pathogenic substitutions have been identified in different domains of the Lrrk2 protein. Herein, we characterize the clinical and genetic features associated with Lrrk2 p.R1441C. Methods: We identified 33 affected and 15 unaffected LRRK2 c.4321C>T (p.R1441C) mutation carriers through an international consortium originating from three continents. The age-specific cumulative incidence of PD was calculated by Kaplan-Meier analysis. Results: The clinical presentation of Lrrk2 p.R1441C carriers was similar to sporadic PD and Lrrk2 p.G2019S parkinsonism. The mean age at onset for parkinsonism was 60 years, range 30–79 years; fewer than 20% of the patients had symptoms before the age 50 years, while by 75 years >90% of them had developed symptoms. Haplotype analysis suggests four independent founders for the p.R1441C mutation. Conclusions: The distribution in age at onset and clinical features in Lrrk2 p.R1441C patients are similar to idiopathic and Lrrk2 p.G2019S parkinsonism. Several independent founders of the p.R1441C substitution suggest this site is prone to recurrent mutagenesis. GLOSSARY: COR = C-terminal of Roc; GTPase = guanosine triphosphatase; LBD = Lewy body disease; PD = Parkinson disease; SNPs = single nucleotide polymorphisms.

Genetic variability in the mitochondrial serine protease HTRA2 contributes to risk for Parkinson disease.

In one genetic study, the high temperature requirement A2 (HTRA2) mitochondrial protein has been associated with increased risk for sporadic Parkinson disease (PD). One missense mutation, p.Gly399Ser, in its C‐terminal PDZ domain (from the initial letters of the postsynaptic density 95, PSD‐95; discs large; and zonula occludens‐1, ZO‐1 proteins [Kennedy, 1995 ]) resulted in defective protease activation, and induced mitochondrial dysfunction when overexpressed in stably transfected cells. Here we examined the contribution of genetic variability in HTRA2 to PD risk in an extended series of 266 Belgian PD patients and 273 control individuals. Mutation analysis identified a novel p.Arg404Trp mutation within the PDZ domain predicted to freeze HTRA2 in an inactive form. Moreover, we identified six patient‐specific variants in 5′ and 3′ regulatory regions that might affect HTRA2 expression as supported by data of luciferase reporter gene analyses. Our study confirms a role of the HTRA2 mitochondrial protein in PD susceptibility through mutations in its functional PDZ domain. In addition, it extends the HTRA2 mutation spectrum to functional variants possibly affecting transcriptional activity. The latter underpins a previously unrecognized role for altered HTRA2 expression as a risk factor relevant to parkinsonian neurodegeneration. Hum Mutat 29(6), 832–840, 2008.

Loss of Psychic Self-Activation After Paramedian Bithalamic Infarction

BACKGROUND AND PURPOSE Loss of psychic self-activation has been described after bilateral lesions to the globus pallidus, striatum, and white matter of the frontal lobes, but it is a very rare sign of bithalamic lesions. The exact functional-anatomic mechanism underlying loss of psychic self-activation following bithalamic lesions remains to be elucidated. CASE DESCRIPTION We present clinical, neuropsychological, structural, and functional neuroimaging data of an 18-month follow-up period of a man with prominent loss of psychic self-activation after coronary arteriography. Except for memory decline, accompanying symptoms remained restricted to the acute phase. The neurobehavioral syndrome consisted mainly of apathy, indifference, poor motivation, and flattened affect, and this remained unchanged during the entire follow-up period. MRI showed a bithalamic infarction involving the nucleus medialis thalami bilaterally. Single-photon emission CT revealed a severe relative hypoperfusion of both thalami, a relative hypoperfusion of both nuclei caudati, and a relative hypoperfusion mesiofrontally. CONCLUSIONS Single-photon emission CT data support the hypothesis that the neurobehavioral manifestations after bithalamic paramedian infarction are caused by disruption of the striatal-ventral pallidal-thalamic-frontomesial limbic loop. Probably, bilateral disruption at different levels of the striatal-ventral pallidal-thalamic-frontomesial loop may lead to a similar clinical picture consisting of loss of psychic self-activation.

A role for the cerebellum in motor speech planning: Evidence from foreign accent syndrome

A 3 year follow-up study was performed in a patient with foreign accent syndrome (FAS) as the sole cognitive manifestation of a left fronto-parietal stroke. The hypothesis of involvement of the right cerebellum in this motor speech planning disorder was investigated by means of functional neuroimaging (SPECT) and neurobehavioral assessments. Based on the close parallelism between the evolution of FAS symptoms and the perfusional changes in the right cerebellum, it is argued that FAS may result from a disruption of a close functional interplay between the supra- and infratentorial speech centers involved in motor speech planning.

Mindfulness based intervention in Parkinson's disease leads to structural brain changes on MRI : a randomized controlled longitudinal trial

OBJECTIVE The aim of the current study is to investigate structural changes on brain MRI using voxel based morphometry (VBM) related to an eight-week mindfulness based intervention (MBI) in Parkinsons Disease (PD). METHODS A total of 27 out of 30 PD patients completed a randomized controlled longitudinal trial. Fourteen patients participated in a structured eight-week program of MBI. Thirteen patients received usual care (UC) alone. MRI data sets of the brain were obtained at baseline and after eight weeks follow-up. VBM analysis was performed using DARTEL from the SPM8 software. The resulting difference maps were statistically compared to examine gray matter density (GMD) differences. Results were reported at p<0.001, uncorrected for multiple comparisons. RESULTS Increased GMD was found in the MBI compared to the UC group in the region of interest (ROI) analysis in the right amygdala, and bilaterally in the hippocampus. Whole brain analysis showed increased GMD in the left and right caudate nucleus, the left occipital lobe at the lingual gyrus and cuneus, the left thalamus, and bilaterally in the temporo-parietal junction. In contrast, GMD differences were found in the UC group in the left anterior lobe and dentate nucleus of the cerebellum. CONCLUSIONS To the best of our knowledge this is the first quantitative analysis of neurobiological effects of MBI in PD. Increased GMD was found in the MBI group in the neural networks that have been postulated to play an important role in PD. These areas have also been implicated in the functional networks mediating the benefits of meditation.

Aphasia following cerebellar damage: fact or fallacy?

Abstract During the past two decades, converging neuroscientific evidence has established the view that the human cerebellum participates in a much wider range of functions than conventionally accepted. As a consequence, the concept of ‘cerebellar cognition’ evolved from a mere afterthought to an exciting new multifaceted area of contemporary cognitive neuroscientific investigations. One of the major avenues of current research is the role of the cerebellum in non-motor language processing. Evidence from both neuroimaging and lesion-behaviour studies indicate that aside from its function in the execution of motor speech the cerebellum is also engaged in the processing of language at a higher level than the articulatory one. In this contribution we focus on this topic by an illustrative case in which an ischaemic lesion in the vascular territory of the right arteria cerebellaris superior induced a prefrontal aphasic syndrome and an agrammatism. In the total absence of any neuroradiological evidence for a structural lesion in the left frontal language areas, the hypothetical causative role of the right cerebellar lesion on the contralateral prefrontal aphasic symptomatology is advocated and supported by positive 99m Tc-hexamethylpropyleneamine oxime single-photon emission-computed tomography findings ( 99m Tc-HMPAO SPECT), revealing focal hypoperfusions in the clinically suspected areas. During longitudinal follow-up the regression of crossed cortical and subcortical left hemisphere diaschisis demonstrated by SPECT parallelled the changes in the neurolinguistic profile. The presented case adds evidence to the view that the phenomenon of so-called ‘crossed cerebello-cerebral diaschisis’, reflecting the distant functional impact of the right cerebellum on the contralateral prefrontal cortical areas, can be associated with an aphasic substrate. The co-occurrence of a right cerebellar lesion and an aphasic syndrome illustrates the pathophysiological hypothesis of a deactivation of prefrontal left hemisphere language functions due to the loss of excitatory impulses through cerebello-ponto-thalamo-cortical pathways.

Relative contribution of simple mutations vs. copy number variations in five Parkinson disease genes in the Belgian population

The relative contribution of simple mutations and copy number variations (CNVs) in SNCA, PARK2, PINK1, PARK7, and LRRK2 to the genetic etiology of Parkinson disease (PD) is still unclear because most studies did not completely analyze each gene. In a large group of Belgian PD patients (N=310) and control individuals (N=270), we determined the mutation frequency of both simple mutations and CNVs in these five PD genes, using direct sequencing, multiplex amplicon quantification (MAQ), and real‐time PCR assays. Overall, we identified 14 novel heterozygous variants, of which 11 were absent in control individuals. We observed eight PARK2 (multiple) exon multiplications in PD patients and one exon deletion in a control individual. Furthermore, we identified one SNCA whole‐gene duplication. The PARK2 and LRRK2 mutation frequencies in Belgian PD patients were similar to those reported in other studies. However, at this stage the true pathogenic nature of some heterozygous mutations in recessive genes remains elusive. Furthermore, though mutations is SNCA, PINK1, and PARK7 are rare, our identification of a SNCA duplication confirmed that screening of these genes remains meaningful. Hum Mutat 30:1–8, 2009.