PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-11 (11)
 

Clipboard (0)
None

Select a Filter Below

Journals
more »
Year of Publication
Document Types
1.  A nonsense mutation in PRNP associated with clinical Alzheimer's disease☆ 
Neurobiology of Aging  2014;35(11):2656.e13-2656.e16.
Here, we describe a nonsense haplotype in PRNP associated with clinical Alzheimer's disease. The patient presented an early-onset of cognitive decline with memory loss as the primary cognitive problem. Whole-exome sequencing revealed a nonsense mutation in PRNP (NM_000311, c.C478T; p.Q160*; rs80356711) associated with homozygosity for the V allele at position 129 of the protein, further highlighting how very similar genotypes in PRNP result in strikingly different phenotypes.
doi:10.1016/j.neurobiolaging.2014.05.013
PMCID: PMC4175176  PMID: 24958194
Alzheimer's disease; Prion; PRNP; Nonsense mutation; Exome sequencing
2.  A nonsense mutation in PRNP associated with clinical Alzheimer’s disease 
Neurobiology of aging  2014;35(11):2656.e13-2656.e16.
Here, we describe a nonsense haplotype in PRNP associated with clinical Alzheimer’s disease. The patient presented an early-onset of cognitive decline with memory loss as the primary cognitive problem. Whole-exome sequencing revealed a nonsense mutation in PRNP (NM_000311, c.C478T; p.Q160*; rs80356711) associated with homozygosity for the V allele at position 129 of the protein, further highlighting how very similar genotypes in PRNP result in strikingly different phenotypes.
doi:10.1016/j.neurobiolaging.2014.05.013
PMCID: PMC4175176  PMID: 24958194
Alzheimer’s disease; Prion; PRNP; Nonsense mutation; Exome sequencing
3.  Genetic modifiers in carriers of repeat expansions in the C9ORF72 gene 
Background
Hexanucleotide repeat expansions in chromosome 9 open reading frame 72 (C9ORF72) are causative for frontotemporal dementia (FTD) and motor neuron disease (MND). Substantial phenotypic heterogeneity has been described in patients with these expansions. We set out to identify genetic modifiers of disease risk, age at onset, and survival after onset that may contribute to this clinical variability.
Results
We examined a cohort of 330 C9ORF72 expansion carriers and 374 controls. In these individuals, we assessed variants previously implicated in FTD and/or MND; 36 variants were included in our analysis. After adjustment for multiple testing, our analysis revealed three variants significantly associated with age at onset (rs7018487 [UBAP1; p-value = 0.003], rs6052771 [PRNP; p-value = 0.003], and rs7403881 [MT-Ie; p-value = 0.003]), and six variants significantly associated with survival after onset (rs5848 [GRN; p-value = 0.001], rs7403881 [MT-Ie; p-value = 0.001], rs13268953 [ELP3; p-value = 0.003], the epsilon 4 allele [APOE; p-value = 0.004], rs12608932 [UNC13A; p-value = 0.003], and rs1800435 [ALAD; p-value = 0.003]).
Conclusions
Variants identified through this study were previously reported to be involved in FTD and/or MND, but we are the first to describe their effects as potential disease modifiers in the presence of a clear pathogenic mutation (i.e. C9ORF72 repeat expansion). Although validation of our findings is necessary, these variants highlight the importance of protein degradation, antioxidant defense and RNA-processing pathways, and additionally, they are promising targets for the development of therapeutic strategies and prognostic tests.
Electronic supplementary material
The online version of this article (doi:10.1186/1750-1326-9-38) contains supplementary material, which is available to authorized users.
doi:10.1186/1750-1326-9-38
PMCID: PMC4190282  PMID: 25239657
C9ORF72; Frontotemporal dementia; Motor neuron disease; Genetic modifier; Repeat expansion
4.  TMEM106B p.T185S regulates TMEM106B protein levels: implications for frontotemporal dementia 
Journal of neurochemistry  2013;126(6):781-791.
Frontotemporal lobar degeneration (FTLD) is the second leading cause of dementia in individuals under age 65. In many patients, the predominant pathology includes neuronal cytoplasmic or intranuclear inclusions of ubiquitinated TAR DNA binding protein 43 (FTLDTDP). Recently, a genome-wide association study identified the first FTLD-TDP genetic risk factor, in which variants in and around the TMEM106B gene (top SNP rs1990622) were significantly associated with FTLD-TDP risk. Intriguingly, the most significant association was in FTLD-TDP patients carrying progranulin (GRN) mutations. Here we investigated to what extent the coding variant, rs3173615 (p.T185S) in linkage disequilibrium with rs1990622, affects progranulin protein (PGRN) biology and TMEM106B protein regulation.
First, we confirmed the association of TMEM106B variants with FTLD-TDP in a new cohort of GRN mutation carriers. We next generated and characterized a TMEM106B-specific antibody for investigation of this protein. Enzyme-linked immunoassay analysis of PGRN levels showed similar effects upon T185 and S185 TMEM106B overexpression. However, overexpression of T185 consistently led to higher TMEM106B protein levels than S185. Cycloheximide treatment experiments revealed that S185 degrades faster than T185 TMEM106B, potentially due to differences in N-glycosylation at residue N183. Together, our results provide a potential mechanism by which TMEM106B variants lead to differences in FTLD-TDP risk.
doi:10.1111/jnc.12329
PMCID: PMC3766501  PMID: 23742080
TMEM106B; frontotemporal dementia; progranulin; glycosylation
5.  Prion-like domain mutations in hnRNPs cause multisystem proteinopathy and ALS 
Nature  2013;495(7442):467-473.
Summary
Algorithms designed to identify canonical yeast prions predict that ~250 human proteins, including several RNA-binding proteins associated with neurodegenerative disease, harbor a distinctive prion-like domain (PrLD) enriched in uncharged polar amino acids and glycine. PrLDs in RNA-binding proteins are essential for the assembly of ribonucleoprotein granules. However, the interplay between human PrLD function and disease is not understood. Here, we define pathogenic mutations in PrLDs of hnRNPA2/B1 and hnRNPA1 in families with inherited degeneration affecting muscle, brain, motor neuron and bone, and a case of familial ALS. Wild-type hnRNPA2 and hnRNPA1 display an intrinsic tendency to assemble into self-seeding fibrils, which is exacerbated by the disease mutations. Indeed, the pathogenic mutations strengthen a ‘steric zipper’ motif in the PrLD, which accelerates formation of self-seeding fibrils that cross-seed polymerization of wild-type hnRNP. Importantly, the disease mutations promote excess incorporation of hnRNPA2 and hnRNPA1 into stress granules and drive the formation of cytoplasmic inclusions in animal models that recapitulate the human pathology. Thus, dysregulated polymerization caused by a potent mutant ‘steric zipper’ motif in a PrLD can initiate degenerative disease. Related proteins with PrLDs must be considered candidates for initiating and perhaps propagating proteinopathies of muscle, brain, motor neuron and bone.
doi:10.1038/nature11922
PMCID: PMC3756911  PMID: 23455423
6.  TREM2 Variants in Alzheimer's Disease 
The New England journal of medicine  2012;368(2):117-127.
BACKGROUND
Homozygous loss-of-function mutations in TREM2, encoding the triggering receptor expressed on myeloid cells 2 protein, have previously been associated with an autosomal recessive form of early-onset dementia.
METHODS
We used genome, exome, and Sanger sequencing to analyze the genetic variability in TREM2 in a series of 1092 patients with Alzheimer's disease and 1107 controls (the discovery set). We then performed a meta-analysis on imputed data for the TREM2 variant rs75932628 (predicted to cause a R47H substitution) from three genomewide association studies of Alzheimer's disease and tested for the association of the variant with disease. We genotyped the R47H variant in an additional 1887 cases and 4061 controls. We then assayed the expression of TREM2 across different regions of the human brain and identified genes that are differentially expressed in a mouse model of Alzheimer's disease and in control mice.
RESULTS
We found significantly more variants in exon 2 of TREM2 in patients with Alzheimer's disease than in controls in the discovery set (P = 0.02). There were 22 variant alleles in 1092 patients with Alzheimer's disease and 5 variant alleles in 1107 controls (P<0.001). The most commonly associated variant, rs75932628 (encoding R47H), showed highly significant association with Alzheimer's disease (P<0.001). Meta-analysis of rs75932628 genotypes imputed from genomewide association studies confirmed this association (P = 0.002), as did direct genotyping of an additional series of 1887 patients with Alzheimer's disease and 4061 controls (P<0.001). Trem2 expression differed between control mice and a mouse model of Alzheimer's disease.
CONCLUSIONS
Heterozygous rare variants in TREM2 are associated with a significant increase in the risk of Alzheimer's disease. (Funded by Alzheimer's Research UK and others.)
doi:10.1056/NEJMoa1211851
PMCID: PMC3631573  PMID: 23150934
7.  Expanded GGGGCC hexanucleotide repeat in non-coding region of C9ORF72 causes chromosome 9p-linked frontotemporal dementia and amyotrophic lateral sclerosis 
Neuron  2011;72(2):245-256.
SUMMARY
Several families have been reported with autosomal dominant frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS), genetically linked to chromosome 9p21. Here we report an expansion of a non-coding GGGGCC hexanucleotide repeat in the gene C9ORF72 that is strongly associated with disease in a large FTD/ALS kindred, previously reported to be conclusively linked to chromosome 9p. This same repeat expansion was identified in the majority of our families with a combined FTD/ALS phenotype and TDP-43 based pathology. Analysis of extended clinical series found the C9ORF72 repeat expansion to be the most common genetic abnormality in both familial FTD (11.7%) and familial ALS (22.5%). The repeat expansion leads to the loss of one alternatively spliced C9ORF72 transcript and to formation of nuclear RNA foci, suggesting multiple disease mechanisms. Our findings indicate that repeat expansion in C9ORF72 is a major cause of both FTD and ALS.
doi:10.1016/j.neuron.2011.09.011
PMCID: PMC3202986  PMID: 21944778
8.  Mutations in the colony stimulating factor 1 receptor (CSF1R) cause hereditary diffuse leukoencephalopathy with spheroids 
Nature Genetics  2011;44(2):200-205.
Hereditary diffuse leukoencephalopathy with spheroids (HDLS) is an autosomal dominantly inherited central nervous system white matter disease with variable clinical presentations including personality and behavioral changes, dementia, depression, parkinsonism, seizures, and others1,2. We combined genome-wide linkage analysis with exome sequencing and identified 14 different mutations affecting the tyrosine kinase domain of the colony stimulating factor receptor 1 (encoded by CSF1R) in 14 families affected by HDLS. In one kindred, the de novo occurrence of the mutation was confirmed. Follow-up sequencing analyses identified an additional CSF1R mutation in a patient clinically diagnosed with corticobasal syndrome (CBS). In vitro, CSF-1 stimulation resulted in the rapid autophosphorylation of selected tyrosine-residues in the kinase domain of wild-type but not mutant CSF1R, suggesting that HDLS may result from a partial loss of CSF1R function. Since CSF1R is a critical mediator of microglial proliferation and differentiation in the brain, our findings suggest an important role for microglial dysfunction in HDLS pathogenesis.
doi:10.1038/ng.1027
PMCID: PMC3267847  PMID: 22197934
9.  C9ORF72 repeat expansions and other FTD gene mutations in a clinical AD patient series from Mayo Clinic 
Alzheimer disease (AD) and frontotemporal dementia (FTD) are two frequent forms of primary neurodegenerative dementias with overlapping clinical symptoms. Pathogenic mutations of the amyloid precursor protein (APP) and presenilins 1 and 2 (PSEN1, PSEN2) genes have been linked to familial early-onset forms of AD; however, more recently mutations in the common FTD genes encoding the microtubule associated protein tau (MAPT), progranulin (GRN) and C9ORF72, have also been reported in clinically diagnosed AD patients. To access the contribution of mutations in a well-characterized series of patients, we systematically performed genetic analyses of these EOAD and FTD genes in a novel cohort of 227 unrelated probands clinically diagnosed as probable AD which were ascertained at Mayo Clinic Florida between 1997 and 2011. All patients showed first symptoms of dementia before 70 years. We identified 9 different pathogenic mutations in the EOAD genes in a total of 11 patients explaining 4.8% of the patient population. Two mutations were novel: PSEN1 p.Pro218Leu and PSEN2 p.Phe183Ser. Importantly, mutations were also identified in all FTD genes: one patient carried a MAPT p.R406W mutation, one patient carried the p.Arg198Glyfs19X loss-of-function mutation in GRN and two patients were found to carry expanded GGGGCC repeats in the non-coding region of C9ORF72. Together the FTD genes explained the disease in 1.8% of our probable AD population. The identification of mutations in all major FTD genes in this novel cohort of clinically diagnosed AD patients underlines the challenges associated with the differential diagnosis of AD and FTD resulting from overlapping symptomatology and has important implications for molecular diagnostic testing and genetic counseling of clinically diagnosed AD patients. Our findings suggest that in clinically diagnosed AD patients, genetic analyses should include not only the well-established EOAD genes APP, PSEN1 and PSEN2 but also genes that are usually associated with FTD. Finally, the overall low frequency of mutation carriers observed in our study (6.6%) suggests the involvement of other as yet unknown genetic factors associated with AD.
PMCID: PMC3560455  PMID: 23383383
Alzheimer’s disease; frontotemporal dementia; amyloid precursor protein; presenilin 1; presenilin 2; progranulin; microtubule associated protein tau; C9ORF72; mutation; diagnosis.
10.  Clinical, neuroimaging and neuropathological features of a new chromosome 9p-linked FTD-ALS family 
Background
Frontotemporal dementia-amyotrophic lateral sclerosis (FTD-ALS) is a heritable form of FTD, but the gene(s) responsible for the majority of autosomal dominant FTD-ALS cases have yet to be found. Previous studies have identified a region on chromosome 9p that is associated with FTD and ALS.
Methods
The authors report the clinical, volumetric MRI, neuropathological and genetic features of a new chromosome 9p-linked FTD-ALS family, VSM-20.
Results
Ten members of family VSM-20 displayed heterogeneous clinical phenotypes of isolated behavioural-variant FTD (bvFTD), ALS or a combination of the two. Parkinsonism was common, with one individual presenting with a corticobasal syndrome. Analysis of structural MRI scans from five affected family members revealed grey- and white-matter loss that was most prominent in the frontal lobes, with mild parietal and occipital lobe atrophy, but less temporal lobe atrophy than in 10 severity-matched sporadic bvFTD cases. Autopsy in three family members showed a consistent and unique subtype of FTLD-TDP pathology. Genome-wide linkage analysis conclusively linked family VSM-20 to a 28.3 cM region between D9S1808 and D9S251 on chromosome 9p, reducing the published minimal linked region to a 3.7 Mb interval. Genomic sequencing and expression analysis failed to identify mutations in the 10 known and predicted genes within this candidate region, suggesting that next-generation sequencing may be needed to determine the mutational mechanism associated with chromosome 9p-linked FTD-ALS.
Conclusions
Family VSM-20 significantly reduces the region linked to FTD-ALS on chromosome 9p. A distinct pattern of brain atrophy and neuropathological findings may help to identify other families with FTD-ALS caused by this genetic abnormality.
doi:10.1136/jnnp.2009.204081
PMCID: PMC3017222  PMID: 20562461
11.  De Novo Truncating FUS Gene Mutation as a Cause of Sporadic Amyotrophic Lateral Sclerosis 
Human mutation  2010;31(5):E1377-E1389.
Mutations in the gene encoding fused in sarcoma (FUS) were recently identified as a novel cause of amyotrophic lateral sclerosis (ALS), emphasizing the genetic heterogeneity of ALS. We sequenced the genes encoding superoxide dismutase (SOD1), TAR DNA-binding protein 43 (TARDBP) and FUS in 99 sporadic and 17 familial ALS patients ascertained at Mayo Clinic. We identified two novel mutations in FUS in two out of 99 (2.0%) sporadic ALS patients and established the de novo occurrence of one FUS mutation. In familial patients, we identified three (17.6%) SOD1 mutations, while FUS and TARDBP mutations were excluded. The de novo FUS mutation (g.10747A>G; IVS13-2A>G) affects the splice-acceptor site of FUS intron 13 and was shown to induce skipping of FUS exon 14 leading to the C-terminal truncation of FUS (p.G466VfsX14). Subcellular localization studies showed a dramatic increase in the cytoplasmic localization of FUS and a reduction of normal nuclear expression in cells transfected with truncated compared to wild-type FUS. We further identified a novel in-frame insertion/deletion mutation in FUS exon 12 (p.S402 P411delinsGGGG) which is predicted to expand a conserved poly-glycine motif. Our findings extend the mutation spectrum in FUS leading to ALS and describe the first de novo mutation in FUS.
doi:10.1002/humu.21241
PMCID: PMC2922682  PMID: 20232451
FUS/TLS; fused in sarcoma; amyotrophic lateral sclerosis; de novo mutation; FUS splice-site mutation; FUS truncating mutation

Results 1-11 (11)