[Show abstract][Hide abstract] ABSTRACT: Null mutations in progranulin (PGRN) cause ubiquitin-positive frontotemporal dementia (FTD) linked to chromosome 17q21 (FTDU-17). Here we examined PGRN genetic variability in amyotrophic lateral sclerosis (ALS), a neurodegenerative motor neuron disease that overlaps with FTD at a clinical, pathologic, and epidemiologic level.
We sequenced all exons, exon-intron boundaries, and 5' and 3' regulatory regions of PGRN in a Belgian sample of 230 patients with ALS. The frequency of observed genetic variants was determined in 436 healthy control individuals. The contribution of eight frequent polymorphisms to ALS risk, onset age, and survival was assessed in an association study in the Belgian sample and a replication series of 308 Dutch patients with ALS and 345 Dutch controls.
In patients with ALS we identified 11 mutations, 5 of which were predicted to affect PGRN protein sequence or levels (four missense mutations and one 5' regulatory variant). Moreover, common variants (rs9897526, rs34424835, and rs850713) and haplotypes were significantly associated with a reduction in age at onset and a shorter survival after onset of ALS in both the Belgian and the Dutch studies.
PGRN acts as a modifier of the course of disease in patients with amyotrophic lateral sclerosis, through earlier onset and shorter survival.
[Show abstract][Hide abstract] ABSTRACT: We determined the prevalence of mutations in two major functional domains of the leucine-rich repeat kinase 2 gene (LRRK2) in Belgian Parkinson's disease (PD) patients (N=304) of which 18.1% were familial PD patients. Ten patients were heterozygous for five different missense mutations (3.29%) of whom six carried the same mutation p.R1441C (1.97%). All six p.R1441C carriers were familial PD patients explaining 10.7% of familial PD in the Belgian patient group. Moreover, they shared a common disease haplotype of 21 consecutive markers in a region of 438 kb, suggesting that they are distant descendants of a single common ancestor. Clinically, p.R1441C carriers had typical levodopa-responsive parkinsonism with tremor as the most common presenting feature. Their age at onset was highly variable and ranged from 39 to 73 years, suggesting the influence of modifying factors. The remaining four patients were heterozygous each for a novel missense mutation located in the Roc or kinase domain. The pathogenic nature of these mutations remains to be determined, though we have genetic evidence that at least some represent rare but benign variants rather than causal mutations. The latter observation indicates that prudence is needed in diagnostic testing of LRRK2 in PD patients. Functional data should underlie a conclusion on the pathogenic nature of some mutations that have not been conclusively linked to disease.
European Journal of HumanGenetics 05/2008; 16(4):471-9. · 4.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Genetic association of the dynamin binding protein gene (DNMBP) on chromosome 10 with late-onset Alzheimer's disease (AD) was reported among Japanese. Here, we assessed the genetic role of DNMBP in an extended Belgian AD group using a gene-wide association approach. A total of 18 SNPs across the DNMBP locus were genotyped in 555 late-onset AD patients and 638 healthy control individuals. Significant associations were observed for two SNPs (rs3740057 and rs10883421). Haplotype analysis identified association with haplotype blocks in the 3' region of DNMBP comprising rs2862919, rs11190302, rs10509739, rs2256700 and comprising rs3740057 and rs6584331. Stratification for APOE epsilon4 status showed that association was only present in the APOE epsilon4 negative subgroup. Sliding-window analyses provided further evidence for association with the 3'-end of DNMBP both for the total and for the APOE epsilon4 negative group. Taken together our findings underscore a role for DNMBP in the genetic risk for late-onset AD in the Belgian population.
Neurobiology of aging 04/2008; 30(12):2000-9. · 5.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The charged multivesicular body protein 2B gene (CHMP2B) was recently associated with frontotemporal lobar degeneration (FTLD) linked to chromosome 3 in a Danish FTLD family (FTD-3). In this family, a mutation in the acceptor splice site of exon 6 produced two aberrant transcripts predicting two C-truncated CHMP2B proteins due to a read through of intron 5 (p.Met178ValfsX2) and a cryptic splicing event within exon 6 (p.Met178LeufsX30). Extensive mutation analysis of CHMP2B in Belgian patients (N = 146) identified one nonsense mutation in exon 5 (c.493C>T) in a familial FTLD patient, predicting a C-truncated protein p.Gln165X analogous to the Danish mutant proteins. Overexpression of Belgian p.Gln165X in human neuroblastoma SK-N-SH cells showed the formation of large, aberrant endosomal structures that were highly similar to those observed for Danish p.Met178ValfsX2. Together, these data suggest that C-truncating mutations in CHMP2B might underlie the pathogenic mechanism in FTLD by disturbing endosome function. We also describe a missense mutation in exon 5 of CHMP2B (p.Asn143Ser) in a familial patient with cortical basal degeneration. However, the pathogenic character of this mutation remains elusive.
Human Molecular Genetics 01/2008; 17(2):313-22. · 6.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The nuclear TAR DNA binding protein (TDP-43) is deposited in ubiquitin-positive inclusions in frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS), two clinicopathologically overlapping neurodegenerative diseases. In this study we excluded mutations and copy number variations in the gene encoding TDP-43 (TARDBP) from an extended series of 173 FTD and 237 ALS patients. Further, we did not identify association of common genetic variants in these patients. Our data implicate that TDP-43 has no primary genetic role in the pathophysiological mechanisms underlying central nervous system neurodegeneration in these diseases.
Neurobiology of aging 01/2008; 30(8):1329-31. · 5.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Frontotemporal dementia (FTD) is the second most frequent type of neurodegenerative dementias. Mutations in the progranulin gene (GRN, PGRN) were recently identified in FTDU-17, an FTD subtype characterized by ubiquitin-immunoreactive inclusions and linkage to chromosome 17q21. We looked for PGRN mutations in a large series of 210 FTD patients (52 familial, 158 sporadic) to accurately evaluate the frequency of PGRN mutations in both sporadic and familial FTD, and FTD with associated motoneuron disease (FTD-MND), as well as to study the clinical phenotype of patients with a PGRN mutation. We identified nine novel PGRN null mutations in 10 index patients. The relative frequency of PGRN null mutations in FTD was 4.8% (10/210) and 12.8% (5/39) in pure familial forms. Interestingly, 5/158 (3.2%) apparently sporadic FTD patients carried a PGRN mutation, suggesting the possibility of de novo mutations or incomplete penetrance. In contrast, none of the 43 patients with FTD-MND had PGRN mutations, supporting that FTDU-17 and FTD-MND are genetically distinct. The clinical phenotype of PGRN mutation carriers was particular because of the wide range in onset age and the frequent occurrence of early apraxia (50%), visual hallucinations (30%), and parkinsonism (30%) during the course of the disease. This study supports that PGRN null mutations represent a more frequent cause of FTD than MAPT mutations (4.8% vs. 2.9%) but are not responsible for FTD-MND. It also demonstrates that half of the patients with a PGRN mutation in our series had no apparent family history of dementia. Taking this into account, genetic testing should be now considered more systematically, even in patients without obvious familial history of FTD.
Human Mutation 10/2007; 28(9):846-55. · 5.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Progranulin gene (PGRN) haploinsufficiency was recently associated with ubiquitin-positive frontotemporal lobar degeneration linked to chromosome 17q21 (FTLDU-17).
To assess whether PGRN genetic variability contributed to other common neurodegenerative brain diseases, such as Alzheimer disease (AD) or Parkinson disease (PD).
Mutation analysis of PGRN.
Memory Clinic of the Middelheim General Hospital. Patients We analyzed 666 Belgian patients with AD and 255 with PD.
Results of PGRN sequencing, PGRN transcript analysis, short tandem repeat genotyping, and neuropathologic analysis.
We identified 2 patients with AD and 1 patient with PD who carried the null mutation IVS0 + 5G>C, which we reported earlier in an extensively characterized Belgian founder family, DR8, segregating FTLDU. Postmortem pathologic diagnosis of the patient with PD revealed both FTLDU and Lewy body pathologic features. In addition, we identified in PGRN only 1 other null mutation, the nonsense mutation p.Arg535X, in 1 patient with probable AD. However, in vitro analysis predicted a PGRN C-truncated protein, although it remains to be elucidated if this shortened transcript leads to haploinsufficiency.
Our mutation data indicated that null mutations are rare in patients with AD (3/666 = 0.45%) and PD (1/255 = 0.39%). Also, AD and PD clinical diagnoses in patients who carry PGRN null mutations likely result from etiologic heterogeneity rather than PGRN haploinsufficiency.
[Show abstract][Hide abstract] ABSTRACT: Null mutations in the progranulin gene (GRN, PGRN) were recently identified as the causal mechanism underlying frontotemporal dementia (FTD) with ubiquitin-positive brain pathology linked to chromosome 17 (FTDU-17). In a Belgian and French FTD series comprising 332 patients, we reported 13 PGRN null mutations which were mainly nonsense and frameshift mutations resulting in premature stop codons. Here we report in the same patient series three missense mutations of which two (c.743C>T, p.Pro248Leu and c.1294C>T, p.Arg432Cys) were predicted in silico to severely affect protein folding and/or processing leading to PGRN protein haploinsufficiency. In addition, we observed three sequence variations in the 5' regulatory region that might potentially affect PGRN transcription activity. Our findings extend the mutation spectrum in PGRN leading to loss of functional PGRN as the basis for FTD.
Human Mutation 04/2007; 28(4):416. · 5.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Frontotemporal dementia (FTD) with ubiquitin-immunoreactive neuronal inclusions (both cytoplasmic and nuclear) of unknown nature has been linked to a chromosome 17q21 region (FTDU-17) containing MAPT (microtubule-associated protein tau). FTDU-17 patients have consistently been shown to lack a tau-immunoreactive pathology, a feature characteristic of FTD with parkinsonism linked to mutations in MAPT (FTDP-17). Furthermore, in FTDU-17 patients, mutations in MAPT and genomic rearrangements in the MAPT region have been excluded by both genomic sequencing and fluorescence in situ hybridization on mechanically stretched chromosomes. Here we demonstrate that FTDU-17 is caused by mutations in the gene coding for progranulin (PGRN), a growth factor involved in multiple physiological and pathological processes including tumorigenesis. Besides the production of truncated PGRN proteins due to premature stop codons, we identified a mutation within the splice donor site of intron 0 (IVS0 + 5G > C), indicating loss of the mutant transcript by nuclear degradation. The finding was made within an extensively documented Belgian FTDU-17 founder family. Transcript and protein analyses confirmed the absence of the mutant allele and a reduction in the expression of PGRN. We also identified a mutation (c.3G > A) in the Met1 translation initiation codon, indicating loss of PGRN due to lack of translation of the mutant allele. Our data provide evidence that PGRN haploinsufficiency leads to neurodegeneration because of reduced PGRN-mediated neuronal survival. Furthermore, in a Belgian series of familial FTD patients, PGRN mutations were 3.5 times more frequent than mutations in MAPT, underscoring a principal involvement of PGRN in FTD pathogenesis.
[Show abstract][Hide abstract] ABSTRACT: Genetic variations in promoter sequences that alter gene expression play a prominent role in increasing susceptibility to complex diseases. Also, expression levels of APP are essentially regulated by its core promoter and 5' upstream regulatory region and correlate with amyloid beta levels in Alzheimer disease (AD) brains. Here, we systematically sequenced the proximal promoter (-766/+204) and two functional distal regions (-2634/-2159 and -2096/-1563) of APP in two independent AD series with onset ages < or =70 years (Belgian sample, n=180; Dutch sample, n=111) and identified eight novel sequence variants. Three mutations (-118C-->A, -369C-->G, and -534G-->A) identified only in patients with AD showed, in vitro, a nearly twofold neuron-specific increase in APP transcriptional activity, similar to what is expected from triplication of APP in Down syndrome. These mutations either abolished (AP-2 and HES-1) or created (Oct1) transcription-factor binding sites involved in the development and differentiation of neuronal systems. Also, two of these clustered in the 200-bp region (-540/-340) of the APP promoter that showed the highest degree of species conservation. The present study provides evidence that APP-promoter mutations that significantly increase APP expression levels are associated with AD.
The American Journal of Human Genetics 07/2006; 78(6):936-46. · 10.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Among patients with frontotemporal lobar degeneration (FTLD), the respective frequencies of dominant 17q21-linked tau-negative FTLD (with unidentified molecular defect) and 17q21-linked tau-positive FTLD (due to MAPT mutations) remain unknown. Here, in a series of 98 genealogically unrelated Belgian FTLD patients, we identified an ancestral 8 cM MAPT containing haplotype in two patients belonging to multiplex families DR2 and DR8, without demonstrable MAPT mutations, in which FTLD was conclusively linked to 17q21 [maximum summed log of the odds (LOD) score of 5.28 at D17S931]. Interestingly, the same DR2-DR8 ancestral haplotype was observed in five additional familial FTLD patients, indicative of a founder effect. In the FTLD series, the DR2-DR8 ancestral haplotype explained 7% (7 out of 98) of FTLD and 17% (7 out of 42) of familial FTLD and was seven times more frequent than MAPT mutations (1 out of 98 or 1%). Clinically, DR2-DR8 haplotype carriers presented with FTLD often characterized by language impairment, and in one carrier the neuropathological diagnosis was FTLD with rare tau-negative ubiquitin-positive inclusions. Together, these results strongly suggest that the DR2-DR8 founder haplotype at 17q21 harbours a tau-negative FTLD causing mutation that is a much more frequent cause of FTLD in Belgium than MAPT mutations.
[Show abstract][Hide abstract] ABSTRACT: Two extended haplotypes exist across the tau gene-H1 and H2-with H1 consistently associated with increased risk of progressive supranuclear palsy (PSP). Using 15 haplotype tagging SNPs (htSNPs), capturing >95% of MAPT haplotype diversity, we performed association analysis in a US sample of 274 predominantly pathologically confirmed PSP patients and 424 matched control individuals. We found that PSP risk is associated with one of two major ancestral H1 haplotypes, H1B, increasing from 14% in control individuals to 22% in PSP patients (P<0.001). In young PSP patients, the H1B risk could be localized to a 22 kb regulatory region in intron 0 (P<0.001) and could be fully explained by one SNP, htSNP167, creating a LBP-1c/LSF/CP2 site, shown to regulate the expression of genes in other neurodegenerative disorders. Luciferase reporter data indicated that the 182 bp conserved regulatory region, in which htSNP167 is located, is transcriptionally active with both alleles differentially influencing expression. Further, we replicated the htSNP167 association in a second, independently ascertained US PSP patient-control sample. However, the htSNP association showed that H1 risk alone could not explain the overall differences in H1 and H2 frequencies in PSP patients and control individuals. Thus, risk variants on different H1 htSNP haplotypes and protective variants on H2 contribute to population risk for PSP.
Human Molecular Genetics 11/2005; 14(21):3281-92. · 6.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We obtained conclusive linkage of Alzheimer disease (AD) with a candidate region of 19.7 cM at 7q36 in an extended multiplex family, family 1270, ascertained in a population-based study of early-onset AD in the northern Netherlands. Single-nucleotide polymorphism and haplotype association analyses of a Dutch patient-control sample further supported the linkage at 7q36. In addition, we identified a shared haplotype at 7q36 between family 1270 and three of six multiplex AD-affected families from the same geographical region, which is indicative of a founder effect and defines a priority region of 9.3 cM. Mutation analysis of coding exons of 29 candidate genes identified one linked synonymous mutation, g.38030G-->C in exon 10, that affected codon 626 of the PAX transactivation domain interacting protein gene (PAXIP1). It remains to be determined whether PAXIP1 has a functional role in the expression of AD in family 1270 or whether another mutation at this locus explains the observed linkage and sharing. Together, our linkage data from the informative family 1270 and the association data in the population-based early-onset AD patient-control sample strongly support the identification of a novel AD locus at 7q36 and re-emphasize the genetic heterogeneity of AD.
The American Journal of Human Genetics 10/2005; 77(4):643-52. · 10.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Familial frontotemporal dementia (FTD), characterized by tau-negative, ubiquitin-positive inclusions at autopsy, is linked to a chromosomal region at 17q21 (FTDU-17), encompassing the gene encoding the microtubule associated protein tau, MAPT. Mutations in MAPT were previously identified in familial FTD with parkinsonism (FTDP-17); however, in FTDU-17 patients, no pathogenic mutations were found in exonic regions consistent with the lack of tauopathy in FTDU-17 brains. Here, we excluded mutations in MAPT by genomic sequencing of 138.5 kb in FTDU-17 patients. Next, to facilitate the identification of the actual underlying genetic defect, we assembled the 6.5 Mb FTDU-17 sequence. Annotation demonstrated that MAPT is surrounded by three highly homologous low-copy repeats (LCRs) in a region of 1.7 Mb. Using evolutionary studies, short tandem repeat-based linkage disequilibrium (LD) and macro-restriction mapping, we demonstrated that these LCRs are at the basis of a series of rearrangements in the MAPT genomic region. One is an inversion that occurred 3 million years ago and resulted in a common polymorphism in humans to date. This inversion plus flanking LCRs spanned approximately 1.3 Mb and was shown to underlie the extended LD and haplotypes H1 and H2 across MAPT. However, in the FTDU-17 families, we ascertained segregation analysis precluding a relationship between the FTDU-17 and the H1/H2 inversion. The presence of multiple homologous LCRs in the region predicts that other potentially more complex genomic rearrangements might be underlying FTDU-17.
Human Molecular Genetics 08/2005; 14(13):1753-62. · 6.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Familial Parkinson's disease (PD) has been linked to missense and genomic multiplication mutations of the alpha-synuclein gene (SNCA). Genetic variability within SNCA has been implicated in idiopathic PD in many populations. We now confirm and extend these findings, within a Belgian sample, using a high-resolution map of genetic markers across the SNCA locus. Our study implicates the SNCA promoter in susceptibility to PD, and more specifically defines a minimum promoter haplotype, spanning approximately 15.3kb of sequence, which is overrepresented in patients. Our findings represent a biomarker for PD and may have implications for patient diagnosis, longitudinal evaluation, and treatment.
Annals of Neurology 11/2004; 56(4):591-5. · 11.91 Impact Factor