Founder effect and estimation of the age of the Progranulin Thr272fs mutation in 14 Italian pedigrees with frontotemporal lobar degeneration

The Centre for Ageing Brain and Neurodegenerative Disorders, Neurology Unit, University of Brescia, Brescia, Italy.
Neurobiology of aging (Impact Factor: 4.85). 10/2010; 32(3):555.e1-8. DOI: 10.1016/j.neurobiolaging.2010.08.009
Source: PubMed

ABSTRACT Progranulin (PGRN) mutations have been recognized to be monogenic causes of frontotemporal lobar degeneration (FTLD). PGRN Thr272fs mutation in the Italian population has been previously identified. In the present study, we evaluated the occurrence of a founder effect studying 8 polymorphic microsatellite markers flanking the PGRN gene in 14 apparently unrelated families. We identified a common haplotype associated with PGRN Thr272fs carriers, assuming common ancestry. The inferred age analysis (range between 260 [95% credible set: 227-374] and 295 [95% credible set: 205-397] generations) places the introduction of the mutation back to the Neolithic era when the Celts, the population of that period, settled in Northern Italy. PGRN Thr272fs mutation appears to be as either behavioral frontotemporal dementia (80%) or primary progressive aphasia (20%), it was equally distributed between male and female, and the mean age at onset was 59.6 ± 5.9 (range 53-68). In 14 families, autosomal dominant pattern of inheritance was present in 64.2% of cases. No clinical predictors of disease onset were demonstrated. The identification of a large cohort of frontotemporal lobar degeneration (FTLD) patients with homogeneous genetic background well may be used in the search of disease modulators to elucidate genotype-phenotype correlations of progranulopathies.

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    ABSTRACT: A causative association was recently demonstrated between homozygous TREM2 mutations and frontotemporal dementia (FTD)-like syndrome and between heterozygous TREM2 exon2 genetic variations and late-onset Alzheimer's disease (AD). The objective of this study was to evaluate whether heterozygous TREM2 genetic variations might be associated to the risk of FTD. TREM2 exon 2 was sequenced in a group of 1030 subjects-namely, 352 patients fulfilling clinical criteria for FTD, 484 healthy control subjects (HCs), and 194 patients with AD. The mutation frequency and the associated clinical characteristics were analyzed. We identified 8 missense and nonsense mutations in TREM2 exon 2 in 24 subjects. These mutations were more frequent in patients with FTD than in HCs (4.0% vs. 1.0%, p = 0.005). In particular, TREM2 Q33X, R47H, T66M, and S116C mutations were found in FTD and were absent in HCs. These mutations were associated with either the semantic variant of primary progressive aphasia or the behavioral variant FTD phenotypes. The FTD and AD groups were not significantly different with regard to TREM2 genetic variation frequency (AD: 2.6%, p = 0.39). Heterozygous TREM2 mutations modulate the risk of FTD in addition to increasing susceptibility to AD. Additional studies are warranted to investigate the possible role of these mutations in the pathogenesis of neurodegenerative disorders.
    Neurobiology of aging 10/2013; 35(4). DOI:10.1016/j.neurobiolaging.2013.09.017 · 4.85 Impact Factor
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    ABSTRACT: IMPORTANCE Granulin (GRN) mutations represent one of the most frequent genetic causes of inherited frontotemporal dementia. The study of asymptomatic carriers of GRN Thr272fs mutation (aGRN+) provides a unique opportunity to study the natural history of the disease and the role of modulating factors on disease onset. It has been demonstrated that the TMEM106B polymorphism is associated with GRN-related frontotemporal dementia and affects age at onset in GRN mutation carriers. OBJECTIVE To ascertain whether TMEM106B genetic status modulates GRN disease by evaluating resting-state functional connectivity in aGRN+ individuals according to TMEM106 genetic variation. DESIGN, SETTING, AND PARTICIPANTS Academic tertiary referral center for neurodegenerative disorders in 17 asymptomatic carriers of aGRN+ and 14 healthy controls. MAIN OUTCOMES AND MEASURES Changes in resting-state functional connectivity, focusing on the default mode network, ventral and dorsal salience networks, executive network, frontoparietal networks, and attentive network and the effect of TMEM106B genotypes in aGRN+ participants and healthy controls (statistical nonparametric mapping). RESULTS aGRN+ participants showed decreased brain connectivity within the left frontoparietal network and increased connectivity in the executive network compared with healthy controls. The TMEM106B at-risk polymorphism (T/T) was associated with decreased connectivity within the ventral salience network (ie, middle frontal gyrus) and the left frontoparietal network (ie, left precuneus). CONCLUSIONS AND RELEVANCE This study suggests that the TMEM106B polymorphism modulates brain connectivity in aGRN+ individuals, with additional damage of the ventral salience network and left frontoparietal network observed. Genotyping TMEM106B is of importance in aGRN+ individuals for prognostic purposes and to assess early brain damage.
    12/2013; 71(2). DOI:10.1001/jamaneurol.2013.4835
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    01/2014; 4(1):95-102. DOI:10.1159/000355428


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May 17, 2014