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1.  Tau Pathology in Frontotemporal Lobar Degeneration with C9ORF72 Hexanucleotide Repeat Expansion 
Acta neuropathologica  2012;125(2):289-302.
An expanded GGGGCC hexanucleotide repeat in C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration associated with TDP-43 pathology (FTLD-TDP). In addition to TDP-43-positive neuronal and glial inclusions, C9ORF72-linked FTLD-TDP has characteristic TDP-43-negative neuronal cytoplasmic and intranuclear inclusions as well as dystrophic neurites in the hippocampus and cerebellum. These lesions are immunopositive for ubiquitin and ubiquitin-binding proteins, such as sequestosome-1/p62 and ubiquilin-2. Studies examining the frequency of the C9ORF72 mutation in clinically probable Alzheimer’s disease (AD) have found a small proportion of AD cases with the mutation. This prompted us to systematically explore the frequency of Alzheimer type pathology in a series of 17 FTLD-TDP cases with mutations in C9ORF72 (FTLD-C9ORF72). We identified 4 cases with sufficient Alzheimer type pathology to meet criteria for intermediate-to-high likelihood AD. We compared AD pathology in the 17 FTLD-C9ORF72 to 13 cases of FTLD-TDP linked to mutations in the gene for progranulin (FTLD-GRN) and 36 cases of sporadic FTLD (sFTLD). FTLD-C9ORF72 cases had higher Braak neurofibrillary tangle stage than FTLD-GRN. Increased tau pathology in FTLD-C9ORF72 was assessed with thioflavin-S fluorescent microscopy-based neurofibrillary tangle counts and with image analysis of tau burden in temporal cortex and hippocampus. FTLD-C9ORF72 had significantly more neurofibrillary tangles and higher tau burden compared with FTLD-GRN. The differences were most marked in limbic regions. On the other hand, sFTLD and FTLD-C9ORF72 had a similar burden of tau pathology. These results suggest FTLD-C9ORF72 has increased propensity for tau pathology compared to FTLD-GRN, but not sFTLD. The accumulation of tau as well as lesions immunoreactive for ubiquitin and ubiquitin binding proteins (p62 and ubiquilin-2) suggests that mutations in C9ORF72 may involve disrupted protein degradation that favors accumulation of multiple different proteins.
doi:10.1007/s00401-012-1048-7
PMCID: PMC3551994  PMID: 23053135
frontotemporal lobar degeneration; C9ORF72; ubiquitin; p62; ubiquilin-2; tau
2.  Analysis of the C9orf72 repeat in Parkinson’s disease, essential tremor and restless legs syndrome 
Parkinsonism & related disorders  2012;19(2):198-201.
The hexanucleotide expanded repeat (GGGGCC) in intron 1 of the C9orf72 gene is recognized as the most common genetic form of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). However, as part of the clinical phenotype, some patients present with parkinsonism. The present study investigated the potential expansion or association of the C9orf72 repeat length with susceptibility to Parkinson’s disease and related disorders, essential tremor and restless legs syndrome. One restless legs syndrome patient was shown to harbor a repeat expansion, however on clinical follow-up this patient was observed to have developed frontotemporal dementia. There was no evidence of association of repeat length on disease risk or age-at-onset for any of the three disorders. Therefore the C9orf72 hexanucleotide repeat expansion appears to be specific to TDP-43 driven amyotrophic lateral sclerosis and dementia.
doi:10.1016/j.parkreldis.2012.09.013
PMCID: PMC3570692  PMID: 23084342
C9orf72; expanded repeat; PD; ET; RLS; genetic association
3.  Length of normal alleles of C9ORF72 GGGGCC repeat do not influence disease phenotype 
Neurobiology of aging  2012;33(12):2950.e5-2950.e7.
Expansions of the non-coding GGGGCC hexanucleotide repeat in the chromosome 9 open reading frame 72 (C9ORF72) gene were recently identified as the long sought-after cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) on chromosome 9p. In this study we aimed to determine whether the length of the normal - unexpanded - allele of the GGGGCC repeat in C9ORF72 plays a role in the presentation of disease or affects age at onset in C9ORF72 mutation carriers. We also studied whether the GGGGCC repeat length confers risk or affects age at onset in FTD and ALS patients without C9ORF72 repeat expansions. C9ORF72 genotyping was performed in 580 FTD, 995 ALS and 160 FTD-ALS patients and 1444 controls, leading to the identification of 211 patients with pathogenic C9ORF72 repeat expansions and an accurate quantification of the length of the normal alleles in all patients and controls. No meaningful association between the repeat length of the normal alleles of the GGGGCC repeat in C9ORF72 and disease phenotype or age at onset was observed in C9ORF72 mutation carriers or non-mutation carriers.
doi:10.1016/j.neurobiolaging.2012.07.005
PMCID: PMC3617405  PMID: 22840558
Amyotrophic lateral sclerosis; Frontotemporal Dementia; C9ORF72; Repeat-expansion disease; Association study
6.  Clinical and pathological features of familial frontotemporal dementia caused by C9ORF72 mutation on chromosome 9p 
Brain  2012;135(3):709-722.
Frontotemporal dementia and amyotrophic lateral sclerosis are closely related clinical syndromes with overlapping molecular pathogenesis. Several families have been reported with members affected by frontotemporal dementia, amyotrophic lateral sclerosis or both, which show genetic linkage to a region on chromosome 9p21. Recently, two studies identified the FTD/ALS gene defect on chromosome 9p as an expanded GGGGCC hexanucleotide repeat in a non-coding region of the chromosome 9 open reading frame 72 gene (C9ORF72). In the present study, we provide detailed analysis of the clinical features and neuropathology for 16 unrelated families with frontotemporal dementia caused by the C9ORF72 mutation. All had an autosomal dominant pattern of inheritance. Eight families had a combination of frontotemporal dementia and amyotrophic lateral sclerosis while the other eight had a pure frontotemporal dementia phenotype. Clinical information was available for 30 affected members of the 16 families. There was wide variation in age of onset (mean = 54.3, range = 34–74 years) and disease duration (mean = 5.3, range = 1–16 years). Early diagnoses included behavioural variant frontotemporal dementia (n = 15), progressive non-fluent aphasia (n = 5), amyotrophic lateral sclerosis (n = 9) and progressive non-fluent aphasia–amyotrophic lateral sclerosis (n = 1). Heterogeneity in clinical presentation was also common within families. However, there was a tendency for the phenotypes to converge with disease progression; seven subjects had final clinical diagnoses of both frontotemporal dementia and amyotrophic lateral sclerosis and all of those with an initial progressive non-fluent aphasia diagnosis subsequently developed significant behavioural abnormalities. Twenty-one affected family members came to autopsy and all were found to have transactive response DNA binding protein with Mr 43 kD (TDP-43) pathology in a wide neuroanatomical distribution. All had involvement of the extramotor neocortex and hippocampus (frontotemporal lobar degeneration-TDP) and all but one case (clinically pure frontotemporal dementia) had involvement of lower motor neurons, characteristic of amyotrophic lateral sclerosis. In addition, a consistent and relatively specific pathological finding was the presence of neuronal inclusions in the cerebellar cortex that were ubiquitin/p62-positive but TDP-43-negative. Our findings indicate that the C9ORF72 mutation is a major cause of familial frontotemporal dementia with TDP-43 pathology, that likely accounts for the majority of families with combined frontotemporal dementia/amyotrophic lateral sclerosis presentation, and further support the concept that frontotemporal dementia and amyotrophic lateral sclerosis represent a clinicopathological spectrum of disease with overlapping molecular pathogenesis.
doi:10.1093/brain/awr354
PMCID: PMC3286328  PMID: 22344582
frontotemporal dementia; frontotemporal lobar degeneration; amyotrophic lateral sclerosis; C9ORF72, TDP-43
7.  Clinical and pathological features of amyotrophic lateral sclerosis caused by mutation in the C9ORF72 gene on chromosome 9p 
Acta Neuropathologica  2012;123(3):409-417.
Two studies recently identified a GGGGCC hexanucleotide repeat expansion in a non-coding region of the chromosome 9 open reading frame 72 gene (C9ORF72) as the cause of chromosome 9p-linked amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). In a cohort of 231 probands with ALS, we identified the C9ORF72 mutation in 17 familial (27.4 %) and six sporadic (3.6%) cases. Patients with the mutation presented with typical motor features of ALS, although subjects with the C9ORF72 mutation had more frequent bulbar onset, compared to those without this mutation. Dementia was significantly more common in ALS patients and families with the C9ORF72 mutation and was usually early-onset FTD. There was striking clinical heterogeneity among the members of individual families with the mutation. The associated neuropathology was a combination of ALS with TDP-ir inclusions and FTLD-TDP. In addition to TDP-43-immunoreactive pathology, a consistent and specific feature of cases with the C9ORF72 mutation was the presence of ubiquitin-positive, TDP-43-negative inclusions in a variety of neuroanatomical regions, such as the cerebellar cortex. These findings support the C9ORF72 mutation as an important newly-recognized cause of ALS, provide a more detailed characterization of the associated clinical and pathological features and further demonstrate the clinical and molecular overlap between ALS and FTD.
doi:10.1007/s00401-011-0937-5
PMCID: PMC3322555  PMID: 22228244
amyotrophic lateral sclerosis; frontotemporal dementia; frontotemporal lobar degeneration; C9ORF72; TDP-43; chromosome 9p
8.  Pathogenicity of exonic indels in fused in sarcoma in amyotrophic lateral sclerosis 
Neurobiology of aging  2010;33(2):424.e23-424.e24.
Insertion and deletion variants (indels) within poly glycine tracts of fused in sarcoma (FUS) were initially reported as causative of disease in amyotrophic lateral sclerosis (ALS). Subsequent studies identified similar indels in controls and suggested that these indels may confer susceptibility to ALS. We aimed to elucidate the role of previously published and novel exonic indels in FUS in an extensive cohort of 630 ALS patients and 1063 controls. We detected indels in FUS exons 5, 6, 12 and 14 with similar frequencies in patients (0.95%) and controls (0.75%). Exonic indels in poly glycine tracts were also observed with similar frequencies. The largest indel (p.Gly138_Tyr143del) was observed in one control. In one patient, a 3 base pair deletion in exon 14 (p.Gly475del) was identified, however in-vitro studies did not reveal abnormal localization of p.Gly475del mutant FUS. These findings suggest that not all exonic indels in FUS cause disease.
doi:10.1016/j.neurobiolaging.2010.09.029
PMCID: PMC3130814  PMID: 21074900
9.  Clinical and neuropathologic heterogeneity of c9FTD/ALS associated with hexanucleotide repeat expansion in C9ORF72 
Acta Neuropathologica  2011;122(6):673-690.
Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) are part of a disease spectrum associated with TDP-43 pathology. Strong evidence supporting this is the existence of kindreds with family members affected by FTD, ALS or mixed features of FTD and ALS, referred to as FTD-MND. Some of these families have linkage to chromosome 9, with hexanucleotide expansion mutation in a noncoding region of C9ORF72. Discovery of the mutation defines c9FTD/ALS. Prior to discovery of mutations in C9ORF72, it was assumed that TDP-43 pathology in c9FTD/ALS was uniform. In this study, we examined the neuropathology and clinical features of 20 cases of c9FTD/ALS from a brain bank for neurodegenerative disorders. Included are six patients clinically diagnosed with ALS, eight FTD, one FTD-MND and four Alzheimer type dementia. Clinical information was unavailable for one patient. Pathologically, the cases all had TDP-43 pathology, but there were three major pathologic groups: ALS, FTLD-MND and FTLD-TDP. The ALS cases were morphologically similar to typical sporadic ALS with almost no extramotor TDP-43 pathology; all had oligodendroglial cytoplasmic inclusions. The FTLD-MND showed predominantly Mackenzie Type 3 TDP-43 pathology, and all had ALS-like pathology in motor neurons, but more extensive extramotor pathology, with oligodendroglial cytoplasmic inclusions and infrequent hippocampal sclerosis. The FTLD-TDP cases had several features similar to FTLD-TDP due to mutations in the gene for progranulin, including Mackenzie Type 1 TDP-43 pathology with neuronal intranuclear inclusions and hippocampal sclerosis. FTLD-TDP patients were older and some were thought to have Alzheimer type dementia. In addition to the FTD and ALS clinical presentations, the present study shows that c9FTD/ALS can have other presentations, possibly related to age of onset and presence of hippocampal sclerosis. Moreover, there is pathologic heterogeneity not only between ALS and FTLD, but within the FTLD group. Further studies are needed to address the molecular mechanism of clinical and pathological heterogeneity of c9FTD/ALS due to mutations in C9ORF72.
doi:10.1007/s00401-011-0907-y
PMCID: PMC3277860  PMID: 22083254
10.  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
11.  Ataxin-2 repeat-length variation and neurodegeneration 
Human Molecular Genetics  2011;20(16):3207-3212.
Expanded glutamine repeats of the ataxin-2 (ATXN2) protein cause spinocerebellar ataxia type 2 (SCA2), a rare neurodegenerative disorder. More recent studies have suggested that expanded ATXN2 repeats are a genetic risk factor for amyotrophic lateral sclerosis (ALS) via an RNA-dependent interaction with TDP-43. Given the phenotypic diversity observed in SCA2 patients, we set out to determine the polymorphic nature of the ATXN2 repeat length across a spectrum of neurodegenerative disorders. In this study, we genotyped the ATXN2 repeat in 3919 neurodegenerative disease patients and 4877 healthy controls and performed logistic regression analysis to determine the association of repeat length with the risk of disease. We confirmed the presence of a significantly higher number of expanded ATXN2 repeat carriers in ALS patients compared with healthy controls (OR = 5.57; P= 0.001; repeat length >30 units). Furthermore, we observed significant association of expanded ATXN2 repeats with the development of progressive supranuclear palsy (OR = 5.83; P= 0.004; repeat length >30 units). Although expanded repeat carriers were also identified in frontotemporal lobar degeneration, Alzheimer's and Parkinson's disease patients, these were not significantly more frequent than in controls. Of note, our study identified a number of healthy control individuals who harbor expanded repeat alleles (31–33 units), which suggests caution should be taken when attributing specific disease phenotypes to these repeat lengths. In conclusion, our findings confirm the role of ATXN2 as an important risk factor for ALS and support the hypothesis that expanded ATXN2 repeats may predispose to other neurodegenerative diseases, including progressive supranuclear palsy.
doi:10.1093/hmg/ddr227
PMCID: PMC3140823  PMID: 21610160
12.  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
13.  Atypical, slowly progressive behavioral variant frontotemporal dementia associated with C9ORF72 hexanucleotide expansion 
Background
Some patients meeting behavioral variant frontotemporal dementia (bvFTD) diagnostic criteria progress slowly and plateau at mild symptom severity. Such patients have mild neuropsychological and functional impairments, lack characteristic bvFTD brain atrophy, and have thus been referred to as bvFTD “phenocopies” or slowly progressive (bvFTD-SP). The few patients with bvFTD-SP that have been studied at autopsy have found no evidence of FTD pathology, suggesting that bvFTD-SP is neuropathologically distinct from other forms of FTD. Here, we describe two patients with bvFTD-SP with chromosome 9 open reading frame 72 (C9ORF72) hexanucleotide expansions.
Methods
Three hundred and eighty-four patients with FTD clinical spectrum and Alzheimer’s disease diagnoses were screened for C9ORF72 expansion. Two bvFTD-SP mutation carriers were identified. Neuropsychological and functional data, as well as brain atrophy patterns assessed using voxel-based morphometry (VBM), were compared with 44 patients with sporadic bvFTD and 85 healthy controls.
Results
Both patients were age 48 at baseline and met possible bvFTD criteria. In the first patient, VBM revealed thalamic and posterior insula atrophy. Over seven years, his neuropsychological performance and brain atrophy remained stable. In the second patient, VBM revealed cortical atrophy with subtle frontal and insular volume loss. Over two years, her neuropsychological and functional scores as well as brain atrophy remained stable.
Conclusions
C9ORF72 mutations can present with a bvFTD-SP phenotype. Some bvFTD-SP patients may have neurodegenerative pathology, and C9ORF72 mutations should be considered in patients with bvFTD-SP and a family history of dementia or motor neuron disease.
doi:10.1136/jnnp-2011-301883
PMCID: PMC3388906  PMID: 22399793
C9ORF72; C9FTD/ALS; frontotemporal dementia; genetics; dementia
14.  Neuroimaging signatures of frontotemporal dementia genetics: C9ORF72, tau, progranulin and sporadics 
Brain  2012;135(3):794-806.
A major recent discovery was the identification of an expansion of a non-coding GGGGCC hexanucleotide repeat in the C9ORF72 gene in patients with frontotemporal dementia and amyotrophic lateral sclerosis. Mutations in two other genes are known to account for familial frontotemporal dementia: microtubule-associated protein tau and progranulin. Although imaging features have been previously reported in subjects with mutations in tau and progranulin, no imaging features have been published in C9ORF72. Furthermore, it remains unknown whether there are differences in atrophy patterns across these mutations, and whether regional differences could help differentiate C9ORF72 from the other two mutations at the single-subject level. We aimed to determine the regional pattern of brain atrophy associated with the C9ORF72 gene mutation, and to determine which regions best differentiate C9ORF72 from subjects with mutations in tau and progranulin, and from sporadic frontotemporal dementia. A total of 76 subjects, including 56 with a clinical diagnosis of behavioural variant frontotemporal dementia and a mutation in one of these genes (19 with C9ORF72 mutations, 25 with tau mutations and 12 with progranulin mutations) and 20 sporadic subjects with behavioural variant frontotemporal dementia (including 50% with amyotrophic lateral sclerosis), with magnetic resonance imaging were included in this study. Voxel-based morphometry was used to assess and compare patterns of grey matter atrophy. Atlas-based parcellation was performed utilizing the automated anatomical labelling atlas and Statistical Parametric Mapping software to compute volumes of 37 regions of interest. Hemispheric asymmetry was calculated. Penalized multinomial logistic regression was utilized to create a prediction model to discriminate among groups using regional volumes and asymmetry score. Principal component analysis assessed for variance within groups. C9ORF72 was associated with symmetric atrophy predominantly involving dorsolateral, medial and orbitofrontal lobes, with additional loss in anterior temporal lobes, parietal lobes, occipital lobes and cerebellum. In contrast, striking anteromedial temporal atrophy was associated with tau mutations and temporoparietal atrophy was associated with progranulin mutations. The sporadic group was associated with frontal and anterior temporal atrophy. A conservative penalized multinomial logistic regression model identified 14 variables that could accurately classify subjects, including frontal, temporal, parietal, occipital and cerebellum volume. The principal component analysis revealed similar degrees of heterogeneity within all disease groups. Patterns of atrophy therefore differed across subjects with C9ORF72, tau and progranulin mutations and sporadic frontotemporal dementia. Our analysis suggested that imaging has the potential to be useful to help differentiate C9ORF72 from these other groups at the single-subject level.
doi:10.1093/brain/aws001
PMCID: PMC3286334  PMID: 22366795
frontotemporal dementia; magnetic resonance imaging; C9ORF72; tau; progranulin
15.  Clinicopathologic variability of the GRN A9D mutation, including amyotrophic lateral sclerosis 
Neurology  2013;80(19):1771-1777.
Objective:
We examined the clinical and pathologic phenotypes of GRN mutation carriers with the pathogenic A9D (g.26C>A) missense mutation.
Methods:
Three patients with GRN A9D mutations were evaluated clinically and came to autopsy with subsequent neuropathologic examination.
Results:
The clinical diagnoses of patients with GRN A9D mutations were amyotrophic lateral sclerosis, atypical extrapyramidal disorder, and behavioral variant frontotemporal dementia. Immunohistochemistry for TAR DNA-binding protein 43 (TDP-43) revealed variability in morphology and distribution of pathology. One patient had notable involvement of motor neurons in the spinal cord as well as type B TDP-43, whereas 2 other patients had type A TDP-43.
Conclusions:
The clinical presentation of the GRN A9D missense mutation is not restricted to behavioral variant frontotemporal dementia and may include aphasia, extrapyramidal features, and, notably, amyotrophic lateral sclerosis.
doi:10.1212/WNL.0b013e3182919059
PMCID: PMC3719429  PMID: 23596077
16.  Novel Mutations in TARDBP (TDP-43) in Patients with Familial Amyotrophic Lateral Sclerosis 
PLoS Genetics  2008;4(9):e1000193.
The TAR DNA-binding protein 43 (TDP-43) has been identified as the major disease protein in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitin inclusions (FTLD-U), defining a novel class of neurodegenerative conditions: the TDP-43 proteinopathies. The first pathogenic mutations in the gene encoding TDP-43 (TARDBP) were recently reported in familial and sporadic ALS patients, supporting a direct role for TDP-43 in neurodegeneration. In this study, we report the identification and functional analyses of two novel and one known mutation in TARDBP that we identified as a result of extensive mutation analyses in a cohort of 296 patients with variable neurodegenerative diseases associated with TDP-43 histopathology. Three different heterozygous missense mutations in exon 6 of TARDBP (p.M337V, p.N345K, and p.I383V) were identified in the analysis of 92 familial ALS patients (3.3%), while no mutations were detected in 24 patients with sporadic ALS or 180 patients with other TDP-43–positive neurodegenerative diseases. The presence of p.M337V, p.N345K, and p.I383V was excluded in 825 controls and 652 additional sporadic ALS patients. All three mutations affect highly conserved amino acid residues in the C-terminal part of TDP-43 known to be involved in protein-protein interactions. Biochemical analysis of TDP-43 in ALS patient cell lines revealed a substantial increase in caspase cleaved fragments, including the ∼25 kDa fragment, compared to control cell lines. Our findings support TARDBP mutations as a cause of ALS. Based on the specific C-terminal location of the mutations and the accumulation of a smaller C-terminal fragment, we speculate that TARDBP mutations may cause a toxic gain of function through novel protein interactions or intracellular accumulation of TDP-43 fragments leading to apoptosis.
Author Summary
The abnormal accumulation of disease proteins in neuronal cells of the brain is a characteristic feature of many neurodegenerative diseases. Rare mutations in the genes that encode the accumulating proteins have been identified in these disorders and are crucial for the development of cell and animal models used to study neurodegeneration. Recently, the TAR DNA-binding protein 43 (TDP-43) was identified as the disease accumulating protein in patients with frontotemporal lobar degeneration with ubiquitin inclusions (FTLD-U) and in amyotrophic lateral sclerosis (ALS). TDP-43 was also found in the brains of 20–30% of patients with Alzheimer's disease (AD). Here, we evaluated whether mutations in TDP-43 cause disease in a cohort of 296 patients presenting with FTLD, ALS or AD. We identified three missense mutations in three out of 92 familial ALS patients (3.3%), and no mutations in AD or FTLD patients. All the identified mutations clustered in exon 6, which codes for a highly conserved region in the C-terminal part of the TDP-43 protein, which is known to be involved in the interaction of TDP-43 with other proteins. We conclude that mutations in TDP-43 are a rare cause of familial ALS, but so far are not found in other neurodegenerative diseases.
doi:10.1371/journal.pgen.1000193
PMCID: PMC2527686  PMID: 18802454
17.  Common variation in the miR-659 binding-site of GRN is a major risk factor for TDP43-positive frontotemporal dementia 
Human Molecular Genetics  2008;17(23):3631-3642.
Loss-of-function mutations in progranulin (GRN) cause ubiquitin- and TAR DNA-binding protein 43 (TDP-43)-positive frontotemporal dementia (FTLD-U), a progressive neurodegenerative disease affecting ∼10% of early-onset dementia patients. Here we expand the role of GRN in FTLD-U and demonstrate that a common genetic variant (rs5848), located in the 3′-untranslated region (UTR) of GRN in a binding-site for miR-659, is a major susceptibility factor for FTLD-U. In a series of pathologically confirmed FTLD-U patients without GRN mutations, we show that carriers homozygous for the T-allele of rs5848 have a 3.2-fold increased risk to develop FTLD-U compared with homozygous C-allele carriers (95% CI: 1.50–6.73). We further demonstrate that miR-659 can regulate GRN expression in vitro, with miR-659 binding more efficiently to the high risk T-allele of rs5848 resulting in augmented translational inhibition of GRN. A significant reduction in GRN protein was observed in homozygous T-allele carriers in vivo, through biochemical and immunohistochemical methods, mimicking the effect of heterozygous loss-of-function GRN mutations. In support of these findings, the neuropathology of homozygous rs5848 T-allele carriers frequently resembled the pathological FTLD-U subtype of GRN mutation carriers. We suggest that the expression of GRN is regulated by miRNAs and that common genetic variability in a miRNA binding-site can significantly increase the risk for FTLD-U. Translational regulation by miRNAs may represent a common mechanism underlying complex neurodegenerative disorders.
doi:10.1093/hmg/ddn257
PMCID: PMC2581433  PMID: 18723524
18.  C9ORF72 repeat expansions in cases with previously identified pathogenic mutations 
Neurology  2013;81(15):1332-1341.
Objective:
To identify potential genetic modifiers contributing to the phenotypic variability that is detected in patients with repeat expansions in chromosome 9 open reading frame 72 (C9ORF72), we investigated the frequency of these expansions in a cohort of 334 subjects previously found to carry mutations in genes known to be associated with a spectrum of neurodegenerative diseases.
Methods:
A 2-step protocol, with a fluorescent PCR and a repeat-primed PCR, was used to determine the presence of hexanucleotide expansions in C9ORF72. For one double mutant, we performed Southern blots to assess expansion sizes, and immunohistochemistry to characterize neuropathology.
Results:
We detected C9ORF72 repeat expansions in 4 of 334 subjects (1.2% [or 1.8% of 217 families]). All these subjects had behavioral phenotypes and also harbored well-known pathogenic mutations in either progranulin (GRN: p.C466LfsX46, p.R493X, p.C31LfsX35) or microtubule-associated protein tau (MAPT: p.P301L). Southern blotting of one double mutant with a p.C466LfsX46 GRN mutation demonstrated a long repeat expansion in brain (>3,000 repeats), and immunohistochemistry showed mixed neuropathology with characteristics of both C9ORF72 expansions and GRN mutations.
Conclusions:
Our findings indicate that co-occurrence of 2 evidently pathogenic mutations could contribute to the pleiotropy that is detected in patients with C9ORF72 repeat expansions. These findings suggest that patients with known mutations should not be excluded from further studies, and that genetic counselors should be aware of this phenomenon when advising patients and their family members.
doi:10.1212/WNL.0b013e3182a8250c
PMCID: PMC3806926  PMID: 24027057
19.  CSF1R mutations link POLD and HDLS as a single disease entity 
Neurology  2013;80(11):1033-1040.
Objective:
Pigmented orthochromatic leukodystrophy (POLD) and hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS) are rare neurodegenerative disorders characterized by cerebral white matter abnormalities, myelin loss, and axonal swellings. The striking overlap of clinical and pathologic features of these disorders suggested a common pathogenesis; however, no genetic or mechanistic link between POLD and HDLS has been established. Recently, we reported that mutations in the colony-stimulating factor 1 receptor (CSF1R) gene cause HDLS. In this study, we determined whether CSF1R mutations are also a cause of POLD.
Methods:
We performed sequencing of CSF1R in 2 pathologically confirmed POLD families. For the largest family (FTD368), a detailed case report was provided and brain samples from 2 affected family members previously diagnosed with POLD were re-evaluated to determine whether they had HDLS features. In vitro functional characterization of wild-type and mutant CSF1R was also performed.
Results:
We identified CSF1R mutations in both POLD families: in family 5901, we found c.2297T>C (p.M766T), previously reported by us in HDLS family CA1, and in family FTD368, we identified c.2345G>A (p.R782H), recently reported in a biopsy-proven HDLS case. Immunohistochemical examination in family FTD368 showed the typical neuronal and glial findings of HDLS. Functional analyses of CSF1R mutant p.R782H (identified in this study) and p.M875T (previously observed in HDLS), showed a similar loss of CSF1R autophosphorylation of selected tyrosine residues in the kinase domain for both mutations when compared with wild-type CSF1R.
Conclusions:
We provide the first genetic and mechanistic evidence that POLD and HDLS are a single clinicopathologic entity.
doi:10.1212/WNL.0b013e31828726a7
PMCID: PMC3653204  PMID: 23408870
20.  Frontotemporal dementia due to C9ORF72 mutations 
Neurology  2012;79(10):1002-1011.
Objective:
To describe the phenotype of patients with C9FTD/ALS (C9ORF72) hexanucleotide repeat expansion.
Methods:
A total of 648 patients with frontotemporal dementia (FTD)–related clinical diagnoses and Alzheimer disease (AD) dementia were tested for C9ORF72 expansion and 31 carried expanded repeats (C9+). Clinical and neuroimaging data were compared between C9+ (15 behavioral variant FTD [bvFTD], 11 FTD–motor neuron disease [MND], 5 amyotrophic lateral sclerosis [ALS]) and sporadic noncarriers (48 bvFTD, 19 FTD-MND, 6 ALS).
Results:
All C9+ patients displayed clinical syndromes of bvFTD, ALS, or FTD-MND. At first evaluation, C9+ bvFTD patients had more delusions and greater impairment of working memory, but milder eating dysregulation compared to bvFTD noncarriers. C9+FTD-MND patients had a trend for longer survival and had an earlier age at onset than FTD-MND noncarriers. Voxel-based morphometry demonstrated more thalamic atrophy in FTD and FTD-MND carriers than in noncarriers.
Conclusions:
Patients with the C9ORF72 hexanucleotide repeat expansion develop bvFTD, ALS, or FTD-MND with similar clinical and imaging features to sporadic cases. Other FTD spectrum diagnoses and AD dementia appear rare or absent among C9+ individuals. Longer survival in C9+ FTD-MND suggests slower disease progression and thalamic atrophy represents a novel and unexpected feature.
doi:10.1212/WNL.0b013e318268452e
PMCID: PMC3430713  PMID: 22875087
21.  Frontotemporal dementia in a Brazilian Caucasian kindred with the C9orf72 mutation 
Archives of neurology  2012;69(9):1149-1153.
Objective
Describe the clinical features of a Brazilian C9orf72 frontotemporal dementia – amyotrophic lateral sclerosis (FTD-ALS) kindred, and compare them to other reported C9orf72 families and FTD-ALS causing mutations.
Design
Report of a kindred.
Setting
Dementia center at an University hospital.
Patients
One kindred encompassing 3 generations.
Results
The presence of a hexanucleotide (GGGGCC) expansion in C9orf72 was confirmed by repeat-primed PCR and Southern blot. The observed phenotypes were behavioral variant FTD and ALS with dementia, with significant variability in age of onset and duration of disease. Parkinsonian features with focal dystonia, visual hallucinations and more posterior atrophy on neuroimaging than is typical for FTD were seen.
Conclusions
bvFTD due to C9orf72 expansions displays some phenotypic heterogeneity, and may be associated with hallucinations, parkinsonism, focal dystonia, and posterior brain atrophy. Personality changes may precede by many years the diagnosis of dementia and may be a distinguishing feature of this mutation.
doi:10.1001/archneurol.2012.650
PMCID: PMC3625641  PMID: 22964910
22.  Characterization of frontotemporal dementia and/or amyotrophic lateral sclerosis associated with the GGGGCC repeat expansion in C9ORF72 
Brain  2012;135(3):765-783.
Numerous kindreds with familial frontotemporal dementia and/or amyotrophic lateral sclerosis have been linked to chromosome 9, and an expansion of the GGGGCC hexanucleotide repeat in the non-coding region of chromosome 9 open reading frame 72 has recently been identified as the pathogenic mechanism. We describe the key characteristics in the probands and their affected relatives who have been evaluated at Mayo Clinic Rochester or Mayo Clinic Florida in whom the hexanucleotide repeat expansion were found. Forty-three probands and 10 of their affected relatives with DNA available (total 53 subjects) were shown to carry the hexanucleotide repeat expansion. Thirty-six (84%) of the 43 probands had a familial disorder, whereas seven (16%) appeared to be sporadic. Among examined subjects from the 43 families (n = 63), the age of onset ranged from 33 to 72 years (median 52 years) and survival ranged from 1 to 17 years, with the age of onset <40 years in six (10%) and >60 in 19 (30%). Clinical diagnoses among examined subjects included behavioural variant frontotemporal dementia with or without parkinsonism (n = 30), amyotrophic lateral sclerosis (n = 18), frontotemporal dementia/amyotrophic lateral sclerosis with or without parkinsonism (n = 12), and other various syndromes (n = 3). Parkinsonism was present in 35% of examined subjects, all of whom had behavioural variant frontotemporal dementia or frontotemporal dementia/amyotrophic lateral sclerosis as the dominant clinical phenotype. No subject with a diagnosis of primary progressive aphasia was identified with this mutation. Incomplete penetrance was suggested in two kindreds, and the youngest generation had significantly earlier age of onset (>10 years) compared with the next oldest generation in 11 kindreds. Neuropsychological testing showed a profile of slowed processing speed, complex attention/executive dysfunction, and impairment in rapid word retrieval. Neuroimaging studies showed bilateral frontal abnormalities most consistently, with more variable degrees of parietal with or without temporal changes; no case had strikingly focal or asymmetric findings. Neuropathological examination of 14 patients revealed a range of transactive response DNA binding protein molecular weight 43 pathology (10 type A and four type B), as well as ubiquitin-positive cerebellar granular neuron inclusions in all but one case. Motor neuron degeneration was detected in nine patients, including five patients without ante-mortem signs of motor neuron disease. While variability exists, most cases with this mutation have a characteristic spectrum of demographic, clinical, neuropsychological, neuroimaging and especially neuropathological findings.
doi:10.1093/brain/aws004
PMCID: PMC3286335  PMID: 22366793
frontotemporal dementia; amyotrophic lateral sclerosis; motor neuron disease; TDP-43; neurogenetics; chromosome 9

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