Cause Of Familial Frontotemporal Dementia Research Articles

A longitudinal analysis of cerebral blood flow changes in genetic frontotemporal Dementia: Results from genfi

AbstractBackgroundMutations in the C9orf72, GRN, or MAPT genes are the most prevalent genetic causes of familial frontotemporal dementia (FTD). In a cross‐sectional study of genetic FTD, lower CBF was observed in presymptomatic FTD mutation carriers vs. controls from the same families in 6 regions of interest: the bilateral anterior cingulate cortex, the left medial temporal gyrus, the left and right insulae, and the left and right supramarginal gyri (Mutsaerts et. al. 2019). However, there have been no studies to date that identify longitudinal changes in CBF between FTD genetic subgroups (both presymptomatic and symptomatic) compared to controls.MethodWe compared longitudinal changes in CBF, as measured by ASL‐MRI, in 317 FTD mutation carriers (118 C9orf72, 141 GRN, and 58 MAPT) vs. 261 non‐carrier controls from the Genetic FTD Initiative (GENFI). Linear mixed effects models tested the main effect of carrier status, and its interaction with age, along with covariates of age, sex, site‐of‐scan against each subject’s mean regional cerebral blood flow within the regions of interest from Mutsaerts et al. (2019). Family membership was a random intercept in the model to control for similar genetic and environmental backgrounds.ResultDifferences between genetic subsets of FTD were apparent, with GRN carriers preferentially experiencing decreases within the salience network regions while MAPT carriers expressed differences within the left medial temporal gyrus and bilateral anterior cingulate gyrus. C9orf72 carriers only saw a decrease in CBF within the left insula. Significant interactions between carrier status and age were exclusively evident in MAPT carriers across all regions of interest.ConclusionDifferentiating CBF signatures were found to exist between the genetic FTD subgroups, with the most prominent changes being seen in GRN and MAPT subsets. Evidence continues to mount that CBF may be a viable biomarker in the earlier detection and delineation of genetic FTD variants.

HiPSC-derived GRN-deficient astrocytes delay spiking activity of developing neurons

Frontotemporal dementia (FTD) refers to a group of neurodegenerative disorders that are characterized by pathology predominantly localized to the frontal and temporal lobes. Approximately 40% of FTD cases are familial, and up to 20% of these are caused by heterozygous loss of function mutations in the gene encoding for progranulin (PGRN), GRN. The mechanisms by which loss of PGRN leads to FTD remain incompletely understood. While astrocytes and microglia have long been linked to the neuropathology of FTD due to mutations in GRN (FTD-GRN), a primary mechanistic role of these supporting cells have not been thoroughly addressed. In contrast, mutations in MAPT, another leading cause of familial FTD, greatly alters astrocyte gene expression leading to subsequent non-cell autonomous effects on neurons, suggesting similar mechanisms may be present in FTD-GRN. Here, we utilized human induced pluripotent stem cell (hiPSC)-derived neural tissue carrying a homozygous GRN R493X−/− knock-in mutation to investigate in vitro whether GRN mutant astrocytes have a non-cell autonomous effect on neurons. Using microelectrode array (MEA) analysis, we demonstrate that the development of spiking activity of neurons cultured with GRN R493X−/− astrocytes was significantly delayed compared to cultures with WT astrocytes. Histological analysis of synaptic markers in these cultures showed an increase in GABAergic synaptic markers and a decrease in glutamatergic synaptic markers during this period when activity was delayed. We also demonstrate that this effect may be due in-part to soluble factors. Overall, this work represents one of the first studies investigating astrocyte-induced neuronal pathology in GRN mutant hiPSCs, and supports the hypothesis of astrocyte involvement in the early pathophysiology of FTD.

Brain Metabolic Profile in Presymptomatic GRN Carriers Throughout a 5-Year Follow-up.

GRN variants are a frequent cause of familial frontotemporal dementia (FTD). Monitoring disease progression in asymptomatic carriers of genetic variants is a major challenge in delivering preventative therapies before clinical onset. This study aimed to assess the usefulness of fluorodeoxyglucose (FDG)-PET in identifying metabolic changes in presymptomatic GRN carriers (PS-GRN+) and to trace their longitudinal progression. Participants were longitudinally evaluated over 5 years in a prospective cohort study focused on GRN disease (Predict-PGRN). They underwent cognitive/behavioral assessment, plasma neurofilament measurement, brain MRI, and FDG-PET. Voxel-wise comparisons of structural and metabolic imaging data between 2 groups were performed for each time point. Longitudinal PET changes were evaluated with voxel-wise comparisons and the metabolic percent annual changes method. The association of regional brain metabolism with plasma neurofilament and cognitive changes was analyzed. Among the 80 individuals enrolled in the study, 58 (27 PS-GRN+ and 31 noncarriers) were included in the analyses. Cross-sectional comparisons between PS-GRN+ and controls found a significant hypometabolism in the left superior temporal sulcus (STS) region (encompassing the middle and superior temporal gyri), approximately 15 years before the expected disease onset, without significant cortical atrophy. The longitudinal metabolic decline over the following 5 years peaked around the right STS in carriers (p < 0.001), without significantly greater volume loss compared with that in controls. Their estimated annualized metabolic decrease (-1.37%) was higher than that in controls (-0.21%, p = 0.004). Lower glucose uptake was associated with higher neurofilament increase (p = 0.003) and lower frontal cognitive scores (p = 0.014) in PS-GRN+. This study detected brain metabolic changes in the STS region, preceding structural and cognitive alterations, thus contributing to the characterization of the pathochronology of preclinical GRN disease. Owing to the STS involvement in the perception of facially communicated cues, it is likely that its dysfunction contributes to social cognition deficits characterizing FTD. Overall, our study highlights brain metabolic changes as an early disease-tracking biomarker and proposes annualized percent decrease as a metric to monitor therapeutic response in forthcoming trials.

GRN Mutations Are Associated with Lewy Body Dementia.

Loss-of-function mutations in GRN are a cause of familial frontotemporal dementia, and common variants within the gene have been associated with an increased risk of developing Alzheimer's disease and Parkinson's disease. Although TDP-43-positive inclusions are characteristic of GRN-related neurodegeneration, Lewy body copathology has also been observed in many GRN mutation carriers. The objective of this study was to assess a Lewy body dementia (LBD) case-control cohort for pathogenic variants in GRN and to test whether there is an enrichment of damaging mutations among patients with LBD. We analyzed whole-genome sequencing data generated for 2591 European-ancestry LBD cases and 4032 neurologically healthy control subjects to identify disease-causing mutations in GRN. We identified six heterozygous exonic GRN mutations in seven study participants (cases: n=6; control subjects: n=1). Each variant was predicted to be pathogenic or likely pathogenic. We found significant enrichment of GRN loss-of-function mutations in patients with LBD compared with control subjects (Optimized Sequence Kernel Association Test P= 0.0162). Immunohistochemistry in three definite LBD cases demonstrated Lewy body pathology and TDP-43-positive neuronal inclusions. Our findings suggest that deleterious GRN mutations are a rare cause of familial LBD. © 2022 International Parkinson Movement Disorder Society. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Cerebellar integrity and contributions to cognition in C9orf72-mediated frontotemporal dementia

BackgroundThe GGGGCC hexanucleotide repeat expansion in the non-coding region of the chromosome 9 open reading frame 72 gene (C9orf72) is the most common genetic cause of familial frontotemporal dementia (FTD). This study aims to clarify the patterns of cerebellar atrophy in FTD patients with and without a C9orf72 repeat expansion compared with healthy controls and determine whether associations between cerebellar atrophy and cognition differ between patient groups. MethodsThirty C9orf72 repeat expansion-positive FTD patients, 30 C9orf72 repeat expansion-negative FTD patients, and 30 age-, sex-, and education-matched healthy controls underwent brain MRI and cognitive assessments. Patient groups were matched for clinical diagnosis, disease duration, general cognition, and disease severity. ResultsCompared with controls, the C9orf72 positive group showed cerebellar changes bilaterally involving the lobules V, VI, Crus I, Crus II, VIIb, VIIIa, left VIIIb, and right lobules I–IV. All these changes were localised within the regions affected in the C9orf72 negative group. No significant differences were found between patient groups. Correlation analyses with a liberal threshold found the cerebellar integrity to be associated with attention, language, and executive function in the C9orf72 positive group. In the C9orf72 negative group, these associations included attention, working memory, language, episodic memory, and executive function. ConclusionsThis study clarifies the impact of C9orf72 repeat expansion on cerebellar integrity in FTD. The findings reveal overlapping patterns of cerebellar atrophy in C9orf72 positive and negative groups. The associations with cognitive functions suggest that the type of pathology linked with cerebellar atrophy is another relevant variable to consider in future studies.

Novel TUBA4A Variant Associated With Familial Frontotemporal Dementia.

ObjectiveDespite the strong genetic component of frontotemporal dementia (FTD), a substantial proportion of patients remain genetically unresolved. We performed an in-depth study of a family with an autosomal dominant form of FTD to investigate the underlying genetic cause.MethodsFollowing clinical and pathologic characterization of the family, genetic studies included haplotype sharing analysis and exome sequencing. Subsequently, we performed immunohistochemistry, immunoblotting, and a microtubule repolymerization assay to investigate the potential impact of the candidate variant in tubulin alpha 4a (TUBA4A).ResultsThe clinical presentation in this family is heterogeneous, including behavioral changes, parkinsonian features, and uncharacterized dementia. Neuropathologic examination of 2 patients revealed TAR DNA binding protein 43 (TDP-43) pathology with abundant dystrophic neurites and neuronal intranuclear inclusions, consistent with frontotemporal lobar degeneration–TDP type A. We identified a likely pathogenic variant in TUBA4A segregating with disease. TUBA4A encodes for α-tubulin, which is a major component of the microtubule network. Variants in TUBA4A have been suggested as a rare genetic cause of amyotrophic lateral sclerosis (ALS) and have sporadically been reported in patients with FTD without supporting genetic segregation. A decreased trend of TUBA4A protein abundance was observed in patients compared with controls, and a microtubule repolymerization assay demonstrated disrupted α-tubulin function. As opposed to variants found in ALS, TUBA4A variants associated with FTD appear more localized to the N-terminus, indicating different pathogenic mechanisms.ConclusionsOur findings support the role of TUBA4A variants as rare genetic cause of familial FTD.

Analysis of C9orf72 Intermediate Alleles in a Retrospective Cohort of Neurological Patients: Risk Factors for Alzheimer's Disease?

C9orf72 hexanucleotide GGGGCC (G4C2) large repeat expansions within the first intron of the gene are a major cause of familial frontotemporal dementia, but also of apparently sporadic cases. Alleles with > 30 repeats are often considered pathogenic, but the repeat length threshold is still undefined. It is also unclear if C9orf72 intermediate alleles (9-30 repeats) have clinically significant effects. We correlated the presence of C9orf72 intermediate alleles with clinical diagnoses in a perspective cohort referred to a secondary memory clinic. All samples were genotyped with AmplideXPCR/CE C9ORF72 Kit (Asuragen, Inc), an optimized C9orf72 PCR amplification reagent. We showed that in patients with Alzheimer's disease (AD) the frequency of the intermediate repeat alleles was significantly increased versus controls (34/54, 63%AD versus 16/39, 41%CTRLs, *p = 0.01, OR 2.91 CI 95%1.230-6.077), whereas no significant differences (p > 0.05) were observed when comparing all other dementias with non-demented individuals. Our findings suggest that C9orf72 intermediate repeat units may represent a genetic risk factor, contributing to the occurrence of AD. Nevertheless, further longitudinal studies, including larger cohort of subjects with intermediate alleles with long-term follow-up, would be needed to confirm these results.

Human progranulin-expressing mice as a novel tool for the development of progranulin-modulating therapeutics

The granulin protein (also known as, and hereafter referred to as, progranulin) is a secreted glycoprotein that contributes to overall brain health. Heterozygous loss-of-function mutations in the gene encoding the progranulin protein (Granulin Precursor, GRN) are a common cause of familial frontotemporal dementia (FTD). Gene therapy approaches that aim to increase progranulin expression from a single wild-type allele, an area of active investigation for the potential treatment of GRN-dependent FTD, will benefit from the availability of a mouse model that expresses a genomic copy of the human GRN gene. Here we report the development and characterization of a novel mouse model that expresses the entire human GRN gene in its native genomic context as a single copy inserted into a defined locus (Hprt) in the mouse genome. We show that human and mouse progranulin are expressed in a similar tissue-specific pattern, suggesting that the two genes are regulated by similar mechanisms. Human progranulin rescues a phenotype characteristic of progranulin-null mice, the exaggerated and early deposition of the aging pigment lipofuscin in the brain, indicating that the two proteins are functionally similar. Longitudinal behavioural and neuropathological analyses revealed no significant differences between wild-type and human progranulin-overexpressing mice up to 18 months of age, providing evidence that long-term increase of progranulin levels is well tolerated in mice. Finally, we demonstrate that human progranulin expression can be increased in the brain using an antisense oligonucleotide that inhibits a known GRN-regulating micro-RNA, demonstrating that the transgene is responsive to potential gene therapy drugs. Human progranulin-expressing mice represent a novel and valuable tool to expedite the development of progranulin-modulating therapeutics.

Progranulin and TMEM106B: when two become wan

Mutations in GRN, which encodes progranulin, are a common cause of familial frontotemporal dementia (FTD). FTD is a devastating disease characterised by neuronal loss in the frontal and temporal lobes that leads to changes in personality, behaviour and language. There are no effective treatments for this complex condition. TMEM106B is a well-recognised risk factor for FTD caused by GRN mutation. While the specific relationship between progranulin and TMEM106B is unclear, it is well established that they are both required for correct lysosome function and trafficking. Elegant experiments have suggested that increased risk for FTD is due to elevated levels of TMEM106B (Nicholson etal, 2013; Gallagher etal, 2017). Therefore, recent work has explored the therapeutic potential of reducing TMEM106B levels, with initial results looking encouraging, as crossing a Grn-deficient mouse to a Tmem106b knockout showed a rescue in FTD-related behavioural defects and specific aspects of lysosome dysfunction (Klein etal, 2017). However, three independent studies in this issue report that completely removing Tmem106b from Grn knockout mice leads to clear exacerbation of phenotypes, causing severe motor deficits, neurodegeneration and enhanced lysosome abnormalities and gliosis. Remarkably, the double knockout mice also develop TDP-43 pathology-a hallmark of FTD patients with GRN mutations that have not been consistently observed in either of the single knockouts. These concurrent publications that all reach the same surprising but definitive conclusion are a cautionary tale in the control of TMEM106B levels as a potential therapeutic for FTD. They also re-ignite the debate as to whether loss or gain of TMEM106B function is critical for altering FTD risk.

Links Between the C9orf72 Repeat Expansion and Psychiatric Symptoms.

To present recent findings on the links between the C9orf72 expansion and psychiatric impairment. Repeat hexanucleotide expansions in the C9orf72 gene are a cause of familial frontotemporal dementia (FTD), amyotrophic lateral sclerosis (ALS), and the mixed phenotype, FTD-ALS. Symptomatic expansion carriers display higher rates of psychotic and other psychiatric symptoms than non-carriers. Neuroanatomical associations of these symptoms have been found in cortical and subcortical areas. Family members of symptomatic carriers have higher rates of primary neuropsychiatric disorders than control populations, and the C9orf72 expansion may contribute to this association. However, the expansion does not appear to directly cause primary psychiatric disorders. While there is strong evidence associating the C9orf72 expansion with psychotic symptoms in carriers and psychiatric disorders in their kindreds, the link between these two phenomena, if any, remains unclear.

C9orf72, a protein associated with amyotrophic lateral sclerosis (ALS) is a guanine nucleotide exchange factor.

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), two late onset neurodegenerative diseases, have been shown to share overlapping cellular pathologies and genetic origins. Studies suggest that a hexanucleotide repeat expansion in the first intron of the C9orf72 gene is the most common cause of familial FTD and ALS pathology. The C9orf72 protein is predicted to be a differentially expressed in normal and neoplastic cells domain protein implying that C9orf72 functions as a guanine nucleotide exchange factor (GEF) to regulate specific Rab GTPases. Reported studies thus far point to a putative role for C9orf72 in lysosome biogenesis, vesicular trafficking, autophagy and mechanistic target of rapamycin complex1 (mTORC1) signaling. Here we report the expression, purification and biochemical characterization of C9orf72 protein. We conclusively show that C9orf72 is a GEF. The distinctive presence of both Rab- and Rho-GTPase GEF activities suggests that C9orf72 may function as a dual exchange factor coupling physiological functions such as cytoskeleton modulation and autophagy with endocytosis.

Intrafamilial Phenotypic Variability in the C9orf72 Gene Expansion: 2 Case Studies.

The C9orf72 genetic mutation is the most common cause of familial frontotemporal dementia (FTD) and motor neuron disease (MND). Previous family studies suggest that while some common clinical features may distinguish gene carriers from sporadic patients, the clinical features, age of onset and disease progression vary considerably in affected patients. Whilst disease presentations may vary across families, age at disease onset appears to be relatively uniform within each family. Here, we report two individuals with a C9orf72 repeat expansion from two generations of the same family with markedly different age at disease onset, clinical presentation and disease progression: one who developed motor neuron and behavioural symptoms in their mid 40s and died 3 years later with confirmed TDP-43 pathology and MND; and a second who developed cognitive and mild behavioural symptoms in their mid 70s and 8 years later remains alive with only slow deterioration. This report highlights the phenotypic variability, including age of onset, within a family with the C9orf72 repeat expansion.

A comparative bioinformatic analysis of C9orf72.

C9orf72 is associated with frontotemporal dementia (FTD) and Amyotrophic Lateral Sclerosis (ALS), both of which are devastating neurodegenerative diseases. Findings suggest that an expanded hexanucleotide repeat in the non-coding region of the C9orf72 gene is the most common cause of familial FTD and ALS. Despite considerable efforts being made towards discerning the possible disease-causing mechanism/s of this repeat expansion mutation, the biological function of C9orf72 remains unclear. Here, we present the first comprehensive genomic study on C9orf72 gene. Analysis of the genomic level organization of C9orf72 across select species revealed architectural similarity of syntenic regions between human and mouse but a lack of conservation of the repeat-harboring intron 1 sequence. Information generated in this study provides a broad genomic perspective of C9orf72 which would form a basis for subsequent experimental approaches and facilitate future mechanistic and functional studies on this gene.

CSF neurofilament light concentration is increased in presymptomatic CHMP2B mutation carriers.

ObjectiveA rare cause of familial frontotemporal dementia (FTD) is a mutation in the CHMP2B gene on chromosome 3 (FTD-3), described in a Danish family. Here we examine whether CSF biomarkers change in the preclinical phase of the disease.MethodsIn this cross-sectional explorative study, we analyzed CSF samples from 16 mutation carriers and 14 noncarriers from the Danish FTD-3 family. CSF biomarkers included total tau (t-tau) and neurofilament light chain (NfL) as a marker for neurodegeneration, phosphorylated tau (p-tau) as a marker for tau pathology, β-amyloid (Aβ) 38, 40, and 42 (Aβ38, Aβ40, and Aβ42) to monitor Aβ metabolism, and YKL-40 as a marker of neuroinflammation. Aβ isoform concentrations were measured using a multiplexed immunoassay; t-tau, p-tau, NfL, and YKL-40 concentrations were measured using sandwich ELISAs.ResultsCSF NfL concentration was significantly increased in mutation carriers vs noncarriers. Further, CSF NfL concentration was significantly higher in symptomatic mutation carriers compared to presymptomatic carriers, and also significantly higher in presymptomatic carriers compared to noncarriers. No differences in t-tau and p-tau and YKL-40 concentrations between controls and mutation carriers were observed. CSF concentrations of the Aβ peptides Aβ38 and Aβ40 but not Aβ42 were significantly lower in mutation carriers compared to noncarriers.ConclusionsIncreased NfL levels in presymptomatic individuals and in symptomatic patients with FTD-3 indicate a continuous process of neurodegeneration from the presymptomatic to symptomatic state. Although not specific for FTD-3 pathology, our data suggest that CSF NfL could serve as a valuable biomarker to detect onset of neurodegeneration in FTD-3 mutation carriers.

Intermediate C9orf72 alleles in neurological disorders: does size really matter?

C9orf72 repeat expansions is a major cause of familial frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) worldwide. Sizes of <20 hexanucleotide repeats are observed in controls, while up to...

The clinical spectrum of sporadic and familial forms of frontotemporal dementia.

The term frontotemporal dementia (FTD) describes a clinically, genetically and pathologically diverse group of neurodegenerative disorders. Symptoms of FTD can present in individuals in their 20s through to their 90s, but the mean age at onset is in the sixth decade. The most common presentation is with a change in personality and impaired social conduct (behavioural variant FTD). Less frequently patients present with language problems (primary progressive aphasia). Both of these groups of patients can develop motor features consistent with either motor neuron disease (usually the amyotrophic lateral sclerosis variant) or parkinsonism (most commonly a progressive supranuclear palsy or corticobasal syndrome). In about a third of cases FTD is familial, with mutations in the progranulin, microtubule-associated protein tau and chromosome 9 open reading frame 72 genes being the major causes. Mutations in a number of other genes including TANK-binding kinase 1 are rare causes of familial FTD. This review aims to clarify the often confusing terminology of FTD, and outline the various clinical features and diagnostic criteria of sporadic and familial FTD syndromes. It will also discuss the current major challenges in FTD research and clinical practice, and potential areas for future research. This review clarifies the terminology of frontotemporal dementia (FTD) and summarizes the various clinical features and most recent diagnostic criteria of sporadic and familial FTD syndromes. It also discusses the current major challenges in FTD research and clinical practice, and highlights potential areas for future research.

Characterization of an FTLD-PDB family with the coexistence of SQSTM1 mutation and hexanucleotide (G4C2) repeat expansion in C9orf72 gene

The C9orf72 expansion is considered a major genetic cause of familial frontotemporal dementia (FTD) in several patients' cohorts. Interestingly, C9orf72 expansion carriers, present also abundant neuronal p62-positive inclusions. Although p62/SQSTM1 mutations were initially associated with Paget disease of bone (PDB), they have been also identified in FTD. We describe an FTD-PDB family in which the proband presented with behavioral FTD phenotype and concomitant Paget disease. The molecular genetic analysis revealed the co-occurrence of 2 mutations; the pathogenic C9orf72 expansion and p.P392L heterozygous missense mutation in SQSTM1 gene. Amongst the 6 family members analyzed, the p.P392L SQSTM1 mutation segregated as expected with PDB, whereas the C9orf72 expansion segregated with frontal cognitive impairment or dementia in all but one carrier. The coexistence of these conditions could be underestimated since neither patients with FTD nor patients with PDB undergo bone scintigraphy or cognitive assessment, respectively. The number of cases with double mutations could also be over looked as the molecular strategy adopted in most laboratories ends with the identification of one pathogenic mutation in one of the known causative genes. Therefore, we advocate for further clinical and molecular evaluation in suspect cases.

A novel mutation P112H in the TARDBP gene associated with frontotemporal lobar degeneration without motor neuron disease and abundant neuritic amyloid plaques

IntroductionAlthough TDP-43 is the main constituent of the ubiquitinated cytoplasmic inclusions in the most common forms of frontotemporal lobar degeneration, TARDBP mutations are not a common cause of familial frontotemporal dementia, especially in the absence of motor neuron disease.ResultsWe describe a pedigree presenting with a complex autosomal dominant disease, with a heterogeneous clinical phenotype, comprising unspecified dementia, parkinsonism, frontotemporal dementia and motor neuron disease. Genetic analyses identified a novel P112H TARDBP double variation located in exon 3 coding for the first RNA recognition motif of the protein (RRM1). This double mutation is probably pathogenic based on neuropathological findings, in silico prediction analysis and exome sequencing. The two autopsied siblings described here presented with frontotemporal dementia involving multiple cognitive domains and behavior but lacking symptoms of motor neuron disease throughout the disease course. The siblings presented with strikingly similar, although atypical, neuropathological features, including an unclassifiable TDP-43 inclusion pattern, a high burden of tau-negative β-amyloid neuritic plaques with an AD-like biochemical profile, and an unclassifiable 4-repeat tauopathy. The co-occurrence of multiple protein inclusions points to a pathogenic mechanism that facilitates misfolded protein interaction and aggregation or a loss of TDP-43 function that somehow impairs protein clearance.ConclusionsTARDBP mutation screening should be considered in familial frontotemporal dementia cases, even without signs or symptoms of motor neuron disease, especially when other more frequent causes of genetic frontotemporal dementia (i.e. GRN, C9ORF72, MAPT) have been excluded and when family history is complex and includes parkinsonism, motor neuron disease and frontotemporal dementia. Further investigations in this family may provide insight into the physiological functions of TARDBP.Electronic supplementary materialThe online version of this article (doi:10.1186/s40478-015-0190-6) contains supplementary material, which is available to authorized users.

Clinical heterogeneity of the C9orf72 genetic mutation in frontotemporal dementia

The C9orf72 genetic mutation represents the most common cause of familial frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). Studies over the last 2 years have revealed a number of key features of this mutation in the fields of clinical neurology, imaging, pathology, and genetics. Despite these efforts, the clinical phenotype appears to extend beyond FTD and ALS into the realm of psychiatric disease, and while highly variable survival rates have been reported, the clinical course of carriers remains relatively unexplored. This report describes two contrasting C9orf72 cases, one with a protracted indolent course dominated by neuropsychiatric features and the other with a rapidly progressive dementia. In both cases, initial structural brain imaging was relatively normal.

Early neuropsychological characteristics of progranulin mutation carriers.

Mutations in the progranulin gene (GRN) are a common cause of familial frontotemporal dementia. We used a comprehensive neuropsychological battery to investigate whether early cognitive changes could be detected in GRN mutation carriers before dementia onset. Twenty-four at-risk members from six families with known GRN mutations underwent detailed neuropsychological testing. Group differences were investigated by domains of attention, language, visuospatial function, verbal memory, non-verbal memory, working memory and executive function. There was a trend for mutation carriers (n=8) to perform more poorly than non-carriers (n=16) across neuropsychological domains, with significant between group differences for visuospatial function (p<.04; d=0.92) and working memory function (p<.02; d=1.10). Measurable cognitive differences exist before the development of frontotemporal dementia in subjects with GRN mutations. The neuropsychological profile of mutation carriers suggests early asymmetric, right hemisphere brain dysfunction that is consistent with recent functional imaging data from our research group and the broader literature.