The heritability and genetics of frontotemporal lobar degeneration

Researching the causal relationship between immune cells and frontotemporal Dementia: A Mendelian Randomization analysis

BACKGROUND

Frontotemporal dementia (FTD) is a prevalent dementia syndrome with poorly understood immunological underpinnings. Despite the widespread adoption of high-density genotyping technologies like SNPs and CNVs, and advances in genome-wide association studies (GWAS), the immunological mechanisms underlying FTD remain elusive. This study aims to elucidate the causal relationships between immune cell traits and FTD using Mendelian randomization (MR).

METHODS

We utilized summary data for FTD (cases = 129, controls = 392,463) from the FinnGen dataset and summary statistics for 731 immune cell traits from the GWAS catalog. These traits included morphological parameters (MP = 32), median fluorescence intensity (MFI = 389), absolute cell counts (AC = 118), and relative cell counts (RC = 192). Our approach encompassed forward MR (immune cell traits as exposure) and reverse MR (FTD as exposure), accompanied by rigorous sensitivity analyses to assess the robustness and heterogeneity of the findings.

RESULTS

FTD did not have a statistically significant impact on immune phenotypes. Notably, we identified 13 immune phenotypes as protective against FTD, including various T cell and B cell markers. Conversely, 8 phenotypes were associated with increased FTD risk, involving markers on myeloid cells and subsets of T and B cells; CONCLUSION: This MR study identifies specific immune phenotypes associated with FTD, highlighting potential pathways for future clinical research and therapeutic intervention.

ANXA11 Mutations in the FTD Spectrum: A Novel Finding in a Patient With Semantic Variant Primary Progressive Aphasia

BACKGROUND

Semantic variant primary progressive aphasia (svPPA) is typically a sporadic disorder, and few cases have been linked to ANXA11 mutations. Comprehensive analyses of genetic mutations in svPPA are limited. Furthermore, the clinical and genetic distinctions between typical svPPA and right temporal variant frontotemporal dementia (rtvFTD) are poorly understood.

METHODS

A 68-year-old patient with svPPA carrying a heterozygous ANXA11 c.119A>G (p.D40G) mutation underwent comprehensive neuropsychological, neuroimaging, and genetic assessments at baseline and at the one-year follow-up timepoint. Additionally, systematic reviews were conducted to identify reported cases of ANXA11 mutations in the FTD spectrum and the genetic mutations associated with svPPA. Clinical-genetic profiles of typical svPPA and rtvFTD were compared based on data from the literature.

RESULTS

Thirty-two patients with ANXA11 mutations were identified, including 11 with pure FTD phenotypes and the majority exhibiting FTD-amyotrophic lateral sclerosis (ALS). Among 167 svPPA-related cases, MAPT, GRN, and C9ORF72 mutations were most frequently implicated; ANXA11 mutations were primarily identified in East Asian patients. Comparative analysis revealed overlapping age at onset, disease duration, sex distribution, and APOE ε4 allele frequencies between typical svPPA and rtvFTD but differing clinical presentations.

CONCLUSIONS

This study reports a case of typical svPPA in China associated with the ANXA11 p.D40G mutation without ALS-related features. Our findings highlight the importance of ANXA11 mutations in FTD pathogenesis.

Deciphering distinct genetic risk factors for FTLD-TDP pathological subtypes via whole-genome sequencing

Frontotemporal lobar degeneration with neuronal inclusions of the TAR DNA-binding protein 43 (FTLD-TDP) is a fatal neurodegenerative disorder with only a limited number of risk loci identified. We report our comprehensive genome-wide association study as part of the International FTLD-TDP Whole-Genome Sequencing Consortium, including 985 patients and 3,153 controls compiled from 26 institutions/brain banks in North America, Europe and Australia, and meta-analysis with the Dementia-seq cohort. We confirm UNC13A as the strongest overall FTLD-TDP risk factor and identify TNIP1 as a novel FTLD-TDP risk factor. In subgroup analyzes, we further identify genome-wide significant loci specific to each of the three main FTLD-TDP pathological subtypes (A, B and C), as well as enrichment of risk loci in distinct tissues, brain regions, and neuronal subtypes, suggesting distinct disease aetiologies in each of the subtypes. Rare variant analysis confirmed TBK1 and identified C3AR1, SMG8, VIPR1, RBPJL, L3MBTL1 and ANO9, as novel subtype-specific FTLD-TDP risk genes, further highlighting the role of innate and adaptive immunity and notch signaling pathway in FTLD-TDP, with potential diagnostic and novel therapeutic implications.

Huntington's disease phenocopy syndromes revisited: a clinical comparison and next-generation sequencing exploration

BACKGROUND

Genetic testing for Huntington's disease (HD) was initially usually positive but more recently the negative rate has increased: patients with negative HD tests are described as having HD phenocopy syndromes (HDPC). This study examines their clinical characteristics and investigates the genetic causes of HDPC.

METHODS

Clinical data from neurogenetics clinics and HDPC gene-panel data were analysed. Additionally, a subset of 50 patients with HDPC underwent whole-genome sequencing (WGS) analysed via Expansion Hunter and Ingenuity Variant Analysis.

RESULTS

HDPC prevalence was estimated at 2.3-2.9 per 100 000. No clinical discriminators between patients with HD and HDPC could be identified. In the gene-panel data, deleterious variants and potentially deleterious variants were over-represented in cases versus controls. WGS analysis identified one ATXN1 expansion in a patient with HDPC.

CONCLUSIONS

The HDPC phenotype is consistent with HD, but the genotype is distinct. Both established deleterious variants and novel potentially deleterious variants in genes related to neurodegeneration contribute to HDPC.

Sex differences in the executive and behavioral reserve of autosomal dominant frontotemporal dementia

INTRODUCTION

Self-reported sex influences brain resilience, but its role in genetic frontotemporal dementia (FTD) remains unclear.

METHODS

We analyzed 394 genetic-FTD patients and 279 controls from the ALLFTD consortium, assessing annual neuropsychological performance and MRI-based cortical thickness. Clinical characteristics and cortical thickness were compared between sexes. We used the residuals of linear regression models, which predict each participant's cognitive and behavioral performance levels relative to cortical thickness, as a proxy for reserve. We then modeled sex differences in longitudinal trajectories with linear mixed-effects models.

RESULTS

Symptomatic females with genetic FTD had lower frontal cortical thickness than males, and the C9orf72 subgroup showed lower-than-expected frontal cortical thickness for a given level of executive functioning. Differences in cognitive reserve between sexes peaked near symptom onset but diminished thereafter.

DISCUSSION

Females with genetic FTD showed higher cognitive reserve than males, suggesting that self-reported sex modulates resilience to frontotemporal neurodegeneration.

HIGHLIGHTS

Females with genetic FTD showed higher cognitive reserve than males. Those differences were particularly pronounced in the C9orf72 and GRN subgroups. The higher cognitive reserve in females declined as the disease progressed.

Frontotemporal dementia. How to deal with its diagnostic complexity?

INTRODUCTION

Frontotemporal dementia (FTD) encompasses a group of heterogeneous neurodegenerative disorders. Aside from genetic cases, its diagnosis is challenging, particularly in the early stages when symptoms are ambiguous, and structural neuroimaging does not reveal characteristic patterns.

AREAS COVERED

The authors performed a comprehensive literature search through MEDLINE, Scopus, and Web of Science databases to gather evidence to aid the diagnostic process for suspected FTD patients, particularly in early phases, even in sporadic cases, ranging from established to promising tools. Blood-based biomarkers might help identify very early neuropathological stages and guide further evaluations. Subsequently, neurophysiological measures reflecting functional changes in cortical excitatory/inhibitory circuits, along with functional neuroimaging assessing brain network, connectivity, metabolism, and perfusion alterations, could detect specific changes associated to FTD even decades before symptom onset. As the neuropathological process advances, cognitive-behavioral profiles and atrophy patterns emerge, distinguishing specific FTD subtypes.

EXPERT OPINION

Emerging disease-modifying therapies require early patient enrollment. Therefore, a diagnostic paradigm shift is needed - from relying on typical cognitive and neuroimaging profiles of advanced cases to widely applicable biomarkers, primarily fluid biomarkers, and, subsequently, neurophysiological and functional neuroimaging biomarkers where appropriate. Additionally, exploring subjective complaints and behavioral changes detected by home-based technologies might be crucial for early diagnosis.

DNA methylation as a contributor to dysregulation of STX6 and other frontotemporal lobar degeneration genetic risk-associated loci

Frontotemporal Lobar Degeneration (FTLD) represents a spectrum of clinically, genetically, and pathologically heterogeneous neurodegenerative disorders characterised by progressive atrophy of the frontal and temporal lobes of the brain. The two major FTLD pathological subgroups are FTLD-TDP and FTLD-tau. While the majority of FTLD cases are sporadic, heterogeneity also exists within the familial cases, typically involving mutations in MAPT, GRN or C9orf72, which is not fully explained by known genetic mechanisms. We sought to address this gap by investigating the effect of epigenetic modifications, specifically DNA methylation variation, on genes associated with FTLD genetic risk in different FTLD subtypes. We compiled a list of genes associated with genetic risk of FTLD using text-mining databases and literature searches. Frontal cortex DNA methylation profiles were derived from three FTLD datasets containing different subgroups of FTLD-TDP and FTLD-tau: FTLD1m (N = 23) containing FTLD-TDP type A C9orf72 mutation carriers and TDP Type C sporadic cases, FTLD2m (N = 48) containing FTLD-Tau MAPT mutation carriers, FTLD-TDP Type A GRN mutation carriers, and FTLD-TDP Type B C9orf72 mutation carriers and FTLD3m (N = 163) progressive supranuclear palsy (PSP) cases, and corresponding controls. To investigate the downstream effects of DNA methylation further, we then leveraged transcriptomic and proteomic datasets for FTLD cases and controls to examine gene and protein expression levels. Our analysis revealed shared promoter region hypomethylation in STX6 across FTLD-TDP and FTLD-tau subtypes, though the largest effect size was observed in the PSP cases compared to controls (delta-beta = -32%, adjusted-p value=0.002). We also observed dysregulation of the STX6 gene and protein expression across FTLD subtypes. Additionally, we performed a detailed examination of MAPT, GRN and C9orf72 in subtypes with and without the presence of the genetic mutations and observed nominally significant differentially methylated CpGs in variable positions across the genes, often with unique patterns and downstream consequences in gene/protein expression in mutation carriers. We highlight the contribution of DNA methylation at different gene regions in regulating the expression of genes previously associated with genetic risk of FTLD, including STX6. We analysed the relationship of subtypes and presence of mutations with this epigenetic mechanism to increase our understanding of how these mechanisms interact in FTLD.

Proteomic analysis reveals distinct cerebrospinal fluid signatures across genetic frontotemporal dementia subtypes

We used an untargeted mass spectrometric approach, tandem mass tag proteomics, for the identification of proteomic signatures in genetic frontotemporal dementia (FTD). A total of 238 cerebrospinal fluid (CSF) samples from the Genetic FTD Initiative were analyzed, including samples from 107 presymptomatic (44 C9orf72, 38 GRN, and 25 MAPT) and 55 symptomatic (27 C9orf72, 17 GRN, and 11 MAPT) mutation carriers as well as 76 mutation-negative controls ("noncarriers"). We found shared and distinct proteomic alterations in each genetic form of FTD. Among the proteins significantly altered in symptomatic mutation carriers compared with noncarriers, we found that a set of proteins including neuronal pentraxin 2 and fatty acid binding protein 3 changed across all three genetic forms of FTD and patients with Alzheimer's disease from previously published datasets. We observed differential changes in lysosomal proteins among symptomatic mutation carriers with marked abundance decreases in MAPT carriers but not other carriers. Further, we identified mutation-associated proteomic changes already evident in presymptomatic mutation carriers. Weighted gene coexpression network analysis combined with gene ontology annotation revealed clusters of proteins enriched in neurodegeneration and glial responses as well as synapse- or lysosome-related proteins indicating that these are the central biological processes affected in genetic FTD. These clusters correlated with measures of disease severity and were associated with cognitive decline. This study revealed distinct proteomic changes in the CSF of patients with genetic FTD, providing insights into the pathological processes involved in the disease. In addition, we identified proteins that warrant further exploration as diagnostic and prognostic biomarker candidates.

The experience of "at-risk" status for familial frontotemporal dementia (fFTD) and its impact on reproductive decision-making: A qualitative study

Familial frontotemporal dementia (fFTD) is an autosomal dominant heritable form of FTD, onsetting in mid-life, characterized by behavioral and personality changes. Children of an affected parent are at 50% risk of inheriting the relevant fFTD gene variant and developing FTD. Genetic testing means a growing group of people are aware of or considering learning their risk status. This knowledge, combined with witnessing parents' symptoms, has implications for reproduction. This study explores attitudes and approaches to reproductive decision-making among those at risk for fFTD. Thirteen qualitative interviews were conducted with at-risk individuals, including parents and non-parents, and analyzed using Thematic Analysis to explore experiences of at-risk relatives of people with symptomatic FTD, attitudes toward reproductive decision-making, and, among parents, influences of genetic risk status on parenting. The themes identified were: (1) Fear of repetition of own experience with symptomatic relatives; (2) Approaches to mitigating repetition; (3) Responses to genetic risk in reproductive decision-making; (4) Accounting for timing in reproductive decision-making; (5) Challenges of disclosing genetic risk to children; (6) Other mitigating factors in reproductive decision-making. Findings highlight the key role of previous experiences with symptomatic relatives in shaping attitudes toward genetic risk status and approaches to managing it in reproductive decision-making. Findings highlight a need for responsive genetic counseling focused on exploring options alongside providing information and signposting to practical legal and financial support. Future research should specifically compare experiences in fFTD with experiences in other heritable neurodegenerative disorders and explore reproductive decision-making for couples where one partner is at risk of fFTD.

Neurofilament heavy phosphorylated epitopes as biomarkers in ageing and neurodegenerative disease

From the day we are born, the nervous system is subject to insult, disease and degeneration. Aberrant phosphorylation states in neurofilaments, the major intermediate filaments of the neuronal cytoskeleton, accompany and mediate many pathological processes in degenerative disease. Neuronal damage, degeneration and death can release these internal components to the extracellular space and eventually the cerebrospinal fluid and blood. Sophisticated assay techniques are increasingly able to detect their presence and phosphorylation states at very low levels, increasing their utility as biomarkers and providing insights and differential diagnosis for the earliest stages of disease. Although a variety of studies focus on single or small clusters of neurofilament phosphorylated epitopes, this review offers a wider perspective of the phosphorylation landscape of the neurofilament heavy subunit, a major intermediate filament component in both ageing and disease.

Behavioral variant frontotemporal dementia with pathogenic variant in MAPT presenting as dementia with Lewy body disease

A 75-year-old Chinese American man presented to behavioral neurology clinic for a second opinion of dementia with Lewy body disease (DLB). The clinical manifestations met the criteria for a probable DLB diagnosis. Yet, in-depth evaluation unveiled clinical history, family history, and neuroimaging evidences that suggested a diagnosis of behavioral variant frontotemporal dementia (FTD). A heterozygous pathogenic variant in the microtubule-associated protein Tau (MAPT) was identified through genetic testing and confirmed the diagnosis of autosomal dominant MAPT-related FTD. This case is the first reported instance of MAPT-related FTD presenting with well-formed visual hallucinations in an elderly Chinese American.

The genetics of TDP43-Type-C neurodegeneration: a whole genome sequencing study

Frontotemporal lobar degeneration-TDP Type C (TDP-C) is a unique neurodegenerative disease that starts by attacking the anterior temporal lobe leading to language and/or behavioral syndromes. Current literature on the genetic associations of TDP-C, which we have reviewed here, is uneven and lacks a discernible corpus of robust findings. In our study, we completed genome wide hypothesis-free analyses utilizing artificial Intelligence (AI) to identify rare and common variants associated with TDP-C. We then investigated ANXA11 and TARDBP in a hypothesis-driven analysis, since it was recently shown that TDP-43 and Annexin A11 co-aggregate in all TDP-C cases. 1) Whole genome sequencing was completed to identify pathogenic rare variants prioritized with Illumina's AI-based Emedgene software on 37 confirmed or probable TDP-C cases from the Northwestern-University Cohort. 2) A genome wide association study was then completed to identify common variants associated with TDP-C cases vs 290 controls. 3) Next, common and rare variants in TARDBP, and ANXA11 were investigated in TDP-C vs controls. These analyses identified novel genetic associations between FIG4 , UBQLN2 , INPP5A , and ANXA11 with TDP-C. Of these FIG4, UBQLN2 and ANXA11 have been associated previously with Amyotrophic lateral sclerosis (ALS). To further assess the observed potential genetic overlap between ALS and TDP-C, we leveraged Mendelian randomization (MR) to assess if the ALS genetic load is associated with TDP-C risk, and found evidence supporting this association. The genetic association of ANXA11 with TDP-C is particularly interesting in view of the recently discovered role of Annexin A11 in forming heterodimers with TDP-43 in all abnormal precipitates, a feature not found in TDP-A or TDP-B, which have no similar predilection for the anterior temporal lobe. In addition to the observed overlap between ALS genetics/ genetic load and TDP-C, it is worth mentioning that FIG4, INPP5A and ANXA11 have been implicated in the inositol metabolism pathway, a feature that remains to be elucidated mechanistically. Our TDP-C genetic literature review identified a surprising paucity of neuropathologically confirmed cases in published investigations. Nonetheless, the literature offers support for some of our findings and reemphasizes the absence of dominant or major pathogenic genes for TDP-C, another feature that sets this neuropathologic entity apart from TDP-A and TDP-B.

Frontoparietal network integrity supports cognitive function in pre-symptomatic frontotemporal dementia: Multimodal analysis of brain function, structure, and perfusion

INTRODUCTION

Genetic mutation carriers of frontotemporal dementia can remain cognitively well despite neurodegeneration. A better understanding of brain structural, perfusion, and functional patterns in the pre-symptomatic stage could inform accurate staging and potential mechanisms.

METHODS

We included 207 pre-symptomatic genetic mutation carriers and 188 relatives without mutations. The gray matter volume, cerebral perfusion, and resting-state functional network maps were co-analyzed using linked independent component analysis (LICA). Multiple regression analysis was used to investigate the relationship of LICA components to genetic status and cognition.

RESULTS

Pre-symptomatic mutation carriers showed an age-related decrease in the left frontoparietal network integrity, while non-carriers did not. Executive functions of mutation carriers became dependent on the left frontoparietal network integrity in older age.

DISCUSSION

The frontoparietal network integrity of pre-symptomatic mutation carriers showed a distinctive relationship to age and cognition compared to non-carriers, suggesting a contribution of the network integrity to brain resilience.

HIGHLIGHTS

A multimodal analysis of structure, perfusion, and functional networks. The frontoparietal network integrity decreases with age in pre-symptomatic carriers only. Executive functions of pre-symptomatic carriers dissociated from non-carriers.

Mechanisms of autophagy-lysosome dysfunction in neurodegenerative diseases

Autophagy is a lysosome-based degradative process used to recycle obsolete cellular constituents and eliminate damaged organelles and aggregate-prone proteins. Their postmitotic nature and extremely polarized morphologies make neurons particularly vulnerable to disruptions caused by autophagy-lysosomal defects, especially as the brain ages. Consequently, mutations in genes regulating autophagy and lysosomal functions cause a wide range of neurodegenerative diseases. Here, we review the role of autophagy and lysosomes in neurodegenerative diseases such as Alzheimer disease, Parkinson disease and frontotemporal dementia. We also consider the strong impact of cellular ageing on lysosomes and autophagy as a tipping point for the late-age emergence of related neurodegenerative disorders. Many of these diseases have primary defects in autophagy, for example affecting autophagosome formation, and in lysosomal functions, especially pH regulation and calcium homeostasis. We have aimed to provide an integrative framework for understanding the central importance of autophagic-lysosomal function in neuronal health and disease.

Connecting dementia risk loci to the CSF proteome identifies pathophysiological leads for dementia

Genome-wide association studies have successfully identified many genetic risk loci for dementia, but exact biological mechanisms through which genetic risk factors contribute to dementia remains unclear. Integrating CSF proteomic data with dementia risk loci could reveal intermediate molecular pathways connecting genetic variance to the development of dementia. We tested to what extent effects of known dementia risk loci can be observed in CSF levels of 665 proteins [proximity extension-based (PEA) immunoassays] in a deeply-phenotyped mixed memory clinic cohort [n = 502, mean age (standard deviation, SD) = 64.1 (8.7) years, 181 female (35.4%)], including patients with Alzheimer's disease (AD, n = 213), dementia with Lewy bodies (DLB, n = 50) and frontotemporal dementia (FTD, n = 93), and controls (n = 146). Validation was assessed in independent cohorts (n = 99 PEA platform, n = 198, mass reaction monitoring-targeted mass spectroscopy and multiplex assay). We performed additional analyses stratified according to diagnostic status (AD, DLB, FTD and controls separately), to explore whether associations between CSF proteins and genetic variants were specific to disease or not. We identified four AD risk loci as protein quantitative trait loci (pQTL): CR1-CR2 (rs3818361, P = 1.65 × 10-8), ZCWPW1-PILRB (rs1476679, P = 2.73 × 10-32), CTSH-CTSH (rs3784539, P = 2.88 × 10-24) and HESX1-RETN (rs186108507, P = 8.39 × 10-8), of which the first three pQTLs showed direct replication in the independent cohorts. We identified one AD-specific association between a rare genetic variant of TREM2 and CSF IL6 levels (rs75932628, P = 3.90 × 10-7). DLB risk locus GBA showed positive trans effects on seven inter-related CSF levels in DLB patients only. No pQTLs were identified for FTD loci, either for the total sample as for analyses performed within FTD only. Protein QTL variants were involved in the immune system, highlighting the importance of this system in the pathophysiology of dementia. We further identified pQTLs in stratified analyses for AD and DLB, hinting at disease-specific pQTLs in dementia. Dissecting the contribution of risk loci to neurobiological processes aids in understanding disease mechanisms underlying dementia.

Non-Alzheimer's amnestic mild cognitive impairment with medial temporal hypometabolism

INTRODUCTION

The increasing use of Alzheimer's disease (AD) biomarkers has led to the recognition of a subgroup of non-AD amnestic mild cognitive impairment (aMCI) patients who have medial temporal hypometabolism on fluorodeoxyglucose-positron emission tomography (FDG-PET).

METHODS

In this academic memory-clinic-based consecutive series, 16 non-AD aMCI patients and 28 AD controls matched for sex, age, and baseline Mini-Mental State Examination (MMSE) were followed for a median duration of 4.5 years. Our primary outcome was the MMSE decline rate over the subsequent years. We also determined the final diagnosis over time.

RESULTS

FDG-PET showed more pronounced medial temporal hypometabolism in non-AD cases and more inferior parietal lobule hypometabolism in AD controls. MMSE decline was slower in non-AD (β = -0.51) than in AD (β = -2.00) patients. Five non-AD cases developed frontotemporal dementia years after symptom onset, and one developed dementia with Lewy bodies.

DISCUSSION

Non-AD aMCI patients with medial temporal hypometabolism show slower cognitive decline.

Highlights

Non-AD aMCI with medial temporal hypometabolism shows slower cognitive decline than AD.FDG-PET revealed distinct metabolic patterns between non-AD aMCI and AD patients.Approximately one-third of non-AD aMCI cases developed frontotemporal dementia.Comprehensive diagnostic biomarkers are crucial for non-AD aMCI characterization.

C9orf72 repeat expansions modify risk for secondary motor and cognitive-behavioral symptoms in behavioral-variant frontotemporal degeneration and amyotrophic lateral sclerosis

In behavioral-variant frontotemporal degeneration (bvFTD) and amyotrophic lateral sclerosis (ALS), secondary motor or cognitive-behavioral symptoms, respectively, are associated with shorter survival. However, factors influencing secondary symptom development remain largely unexplored. We performed a retrospective evaluation of the entire disease course of individuals with ALS (n=172) and bvFTD (n=69). Only individuals who had neuropathological confirmation of TDP-43 proteinopathy at autopsy or a C9orf72 hexanucleotide repeat expansion were included for analysis. We examined the odds and hazard of secondary symptom development and assessed whether each was modified by the presence of a C9orf72 expansion or initial clinical syndrome. Binary logistic regression and Cox proportional hazard analyses revealed increased odds (OR=4.25 [95% CI 1.97-9.14], p<0.001) and an increased hazard (HR= 4.77 [95% CI 2.33-9.79], p<0.001) for developing secondary symptoms in those with a C9orf72 expansion compared to those without. Initial clinical syndrome (bvFTD or ALS), age at symptom onset, and sex were not associated with development of secondary symptoms. These data highlight the need for clinician vigilance to detect the onset of secondary motor and cognitive-behavioral symptoms in patients carrying a C9orf72 expansion, regardless of initial clinical syndrome. C9orf72 clinical care can be enhanced through coordination between cognitive and neuromuscular clinics.

Large-scale CSF proteome profiling identifies biomarkers for accurate diagnosis of Frontotemporal Dementia

Diagnosis of Frontotemporal dementia (FTD) and the specific underlying neuropathologies (frontotemporal lobar degeneration; FTLD- Tau and FTLD-TDP) is challenging, and thus fluid biomarkers are needed to improve diagnostic accuracy. We used proximity extension assays to analyze 665 proteins in cerebrospinal fluid (CSF) samples from a multicenter cohort including patients with FTD (n = 189), Alzheimer's Disease dementia (AD; n = 232), and cognitively unimpaired individuals (n = 196). In a subset, FTLD neuropathology was determined based on phenotype or genotype (FTLD-Tau = 87 and FTLD-TDP = 68). Forty three proteins were differentially regulated in FTD compared to controls and AD, reflecting axon development, regulation of synapse assembly, and cell-cell adhesion mediator activity pathways. Classification analysis identified a 14- and 13-CSF protein panel that discriminated FTD from controls (AUC: 0.96) or AD (AUC: 0.91). Custom multiplex panels confirmed the highly accurate discrimination between FTD and controls (AUCs > 0.96) or AD (AUCs > 0.88) in three validation cohorts, including one with autopsy confirmation (AUCs > 0.90). Six proteins were differentially regulated between FTLD-TDP and FTLD-Tau, but no reproducible classification model could be generated (AUC: 0.80). Overall, this study introduces novel FTD-specific biomarker panels with potential use in diagnostic setting.

An anti-sortilin affibody-peptide fusion inhibits sortilin-mediated progranulin degradation

Heterozygous loss-of-function mutations in the GRN gene are a common cause of frontotemporal dementia. Such mutations lead to decreased plasma and cerebrospinal fluid levels of progranulin (PGRN), a neurotrophic factor with lysosomal functions. Sortilin is a negative regulator of extracellular PGRN levels and has shown promise as a therapeutic target for frontotemporal dementia, enabling increased extracellular PGRN levels through inhibition of sortilin-mediated PGRN degradation. Here we report the development of a high-affinity sortilin-binding affibody-peptide fusion construct capable of increasing extracellular PGRN levels in vitro. By genetic fusion of a sortilin-binding affibody generated through phage display and a peptide derived from the progranulin C-terminus, an affinity protein (A3-PGRNC15*) with 185-pM affinity for sortilin was obtained. Treating PGRN-secreting and sortilin-expressing human glioblastoma U-251 cells with the fusion protein increased extracellular PGRN levels up to 2.5-fold, with an EC50 value of 1.3 nM. Our results introduce A3-PGRNC15* as a promising new agent with therapeutic potential for the treatment of frontotemporal dementia. Furthermore, the work highlights means to increase binding affinity through synergistic contribution from two orthogonal polypeptide units.

Clinical application of whole genome sequencing in young onset dementia: challenges and opportunities

INTRODUCTION

Young onset dementia (YOD) by its nature is difficult to diagnose. Despite involvement of multidisciplinary neurogenetics services, patients with YOD and their families face significant diagnostic delays. Genetic testing for people with YOD currently involves a staggered, iterative approach. There is currently no optimal single genetic investigation that simultaneously identifies the different genetic variants resulting in YOD.

AREAS COVERED

This review discusses the advances in clinical genomic testing for people with YOD. Whole genome sequencing (WGS) can be employed as a 'one stop shop' genomic test for YOD. In addition to single nucleotide variants, WGS can reliably detect structural variants, short tandem repeat expansions, mitochondrial genetic variants as well as capture single nucleotide polymorphisms for the calculation of polygenic risk scores.

EXPERT OPINION

WGS, when used as the initial genetic test, can enhance the likelihood of a precision diagnosis and curtail the time taken to reach this. Finding a clinical diagnosis using WGS can reduce invasive and expensive investigations and could be cost effective. These advances need to be balanced against the limitations of the technology and the genetic counseling needs for these vulnerable patients and their families.

Research trends and hotspots for frontotemporal dementia from 2000 to 2022: a bibliometric analysis

Background

Frontotemporal dementia (FTD) is a neurodegenerative disease with clinical, pathological, and genetic heterogeneity. FTD is receiving increasing attention because it is the second leading cause of early-onset dementia after Alzheimer's disease. This study aimed to analyse the research trends and hotspots of FTD from 2000 to 2022 using bibliometrics.

Methods

Papers related to FTD from 2000 to 2020 were systematically searched through the Web of Science Core Collection (WOSCC). Citespace and Vosviewer software were used to visually analyse the retrieved data of countries/regions, institutions, journals, authors, references, and keywords. Microsoft Excel was used to generate the annual publications and growth trends.

Results

There were 10,227 papers included in the bibliometric analysis. The annual publication output on FTD has increased significantly from 2000 to 2022, with papers published in 934 academic journals and 87 countries/regions. The Journal of Alzheimer's Disease was the most popular, with 488 papers about FTD. The most productive countries/regions, institutions, and authors are the United States (n = 4,037), the University of California San Francisco (n = 687), and Miller, Bruce L. (n = 427), respectively. The article by Katya Rascovsky and her colleagues published on Brain in 2011 was the most cocited paper, with 625 citations. The research hotspots in this field were the clinical diagnostic criteria, subdivision, and pathological mechanism of FTD, such as tau protein, chromosome 17, progranulin, TDP-43, and C9orf72.

Conclusion

The future research direction is based on biomarkers and pathological mechanisms to diagnose and differential diagnose FTD from the aspects of behavior, neuropathology, neuroimaging, and serum markers.

Unveiling New Genetic Variants Associated with Age at Onset in Alzheimer's Disease and Frontotemporal Lobar Degeneration Due to C9orf72 Repeat Expansions

Alzheimer's disease (AD) and Frontotemporal lobar degeneration (FTLD) represent the most common forms of neurodegenerative dementias with a highly phenotypic variability. Herein, we investigated the role of genetic variants related to the immune system and inflammation as genetic modulators in AD and related dementias. In patients with sporadic AD/FTLD (n = 300) and GRN/C9orf72 mutation carriers (n = 80), we performed a targeted sequencing of 50 genes belonging to the immune system and inflammation, selected based on their high expression in brain regions and low tolerance to genetic variation. The linear regression analyses revealed two genetic variants: (i) the rs1049296 in the transferrin (TF) gene, shown to be significantly associated with age at onset in the sporadic AD group, anticipating the disease onset of 4 years for each SNP allele with respect to the wild-type allele, and (ii) the rs7550295 in the calsyntenin-1 (CLSTN1) gene, which was significantly associated with age at onset in the C9orf72 group, delaying the disease onset of 17 years in patients carrying the SNP allele. In conclusion, our data support the role of genetic variants in iron metabolism (TF) and in the modulation of the calcium signalling/axonal anterograde transport of vesicles (CLSTN1) as genetic modulators in AD and FTLD due to C9orf72 expansions.

Frequency of C9orf72, GRN, and MAPT pathogenic variants in patients recruited at the Belgrade Memory Center

Most of the heritability in frontotemporal dementia (FTD) is accounted for by autosomal dominant hexanucleotide expansion in the chromosome 9 open reading frame 72 (C9orf72), pathogenic/likely pathogenic variants in progranulin (GRN), and microtubule-associated protein tau (MAPT) genes. Until now, there has been no systematic analysis of these genes in the Serbian population. Herein, we assessed the frequency of the C9orf72 expansion, pathogenic/likely pathogenic variants in GRN and MAPT in a well-characterized group of 472 subjects (FTD, Alzheimer's disease - AD, mild cognitive impairment - MCI, and unspecified dementia - UnD), recruited in the Memory Center, Neurology Clinic, University Clinical Center of Serbia. The C9orf72 repeat expansion was detected in 6.98% of FTD cases (13.46% familial; 2.6% sporadic). In the UnD subgroup, C9orf72 repeat expansions were detected in 4.08% (8% familial) individuals. Pathogenic variants in the GRN were found in 2.85% of familial FTD cases. Interestingly, no MAPT pathogenic/likely pathogenic variants were detected, suggesting possible geographical specificity. Our findings highlight the importance of wider implementation of genetic testing in neurological and psychiatric practice managing patients with cognitive-behavioral and motor symptoms.

Mutational Landscape of Alzheimer's Disease and Frontotemporal Dementia: Regional Variances in Northern, Central, and Southern Italy

Alzheimer's Disease (AD) and Frontotemporal Dementia (FTD) are the two major neurodegenerative diseases with distinct clinical and neuropathological profiles. The aim of this report is to conduct a population-based investigation in well-characterized APP, PSEN1, PSEN2, MAPT, GRN, and C9orf72 mutation carriers/pedigrees from the north, the center, and the south of Italy. We retrospectively analyzed the data of 467 Italian individuals. We identified 21 different GRN mutations, 20 PSEN1, 11 MAPT, 9 PSEN2, and 4 APP. Moreover, we observed geographical variability in mutation frequencies by looking at each cohort of participants, and we observed a significant difference in age at onset among the genetic groups. Our study provides evidence that age at onset is influenced by the genetic group. Further work in identifying both genetic and environmental factors that modify the phenotypes in all groups is needed. Our study reveals Italian regional differences among the most relevant AD/FTD causative genes and emphasizes how the collaborative studies in rare diseases can provide new insights to expand knowledge on genetic/epigenetic modulators of age at onset.

Deciphering Distinct Genetic Risk Factors for FTLD-TDP Pathological Subtypes via Whole-Genome Sequencing

Frontotemporal lobar degeneration with neuronal inclusions of the TAR DNA-binding protein 43 (FTLD-TDP) is a fatal neurodegenerative disorder with only a limited number of risk loci identified. We report our comprehensive genome-wide association study as part of the International FTLD-TDP Whole-Genome Sequencing Consortium, including 985 cases and 3,153 controls, and meta-analysis with the Dementia-seq cohort, compiled from 26 institutions/brain banks in the United States, Europe and Australia. We confirm UNC13A as the strongest overall FTLD-TDP risk factor and identify TNIP1 as a novel FTLD-TDP risk factor. In subgroup analyses, we further identify for the first time genome-wide significant loci specific to each of the three main FTLD-TDP pathological subtypes (A, B and C), as well as enrichment of risk loci in distinct tissues, brain regions, and neuronal subtypes, suggesting distinct disease aetiologies in each of the subtypes. Rare variant analysis confirmed TBK1 and identified VIPR1 , RBPJL , and L3MBTL1 as novel subtype specific FTLD-TDP risk genes, further highlighting the role of innate and adaptive immunity and notch signalling pathway in FTLD-TDP, with potential diagnostic and novel therapeutic implications.

Genetic and clinical landscape of Chinese frontotemporal dementia: dominance of TBK1 and OPTN mutations

BACKGROUND

Our study aims to evaluate the genetic and phenotypic spectrum of Frontotemporal dementia (FTD) gene variant carriers in Chinese populations, investigate mutation frequencies, and assess the functional properties of TBK1 and OPTN variants.

METHODS

Clinically diagnosed FTD patients underwent genetic analysis through exome sequencing, repeat-primed polymerase chain reaction, and Sanger sequencing. TBK1 and OPTN variants were biologically characterized in vitro using immunofluorescence, immunoprecipitation, and immunoblotting analysis. The frequencies of genes implicated in FTD in China were analyzed through a literature review and meta-analysis.

RESULTS

Of the 261 Chinese FTD patients, 61 (23.4%) carried potential causative variants in FTD-related genes, including MAPT (n = 17), TBK1 (n = 7), OPTN (n = 6), GRN (n = 6), ANXA11 (n = 4), CHMP2B (n = 3), C9orf72 GGGGCC repeats (n = 2), CYLD (n = 2), PRNP (n = 2), SQSTM1 (n = 2), TARDBP (n = 2), VCP (n = 1), CCNF (n = 1), CHCHD10 (n = 1), SIGMAR1 (n = 1), CHCHD2 (n = 1), FUS (n = 1), TMEM106B (n = 1), and UBQLN2 (n = 1). 29 variants can be considered novel, including the MAPT p.D54N, p.E342K, p.R221P, p.T263I, TBK1 p.E696G, p.I37T, p.E232Q, p.S398F, p.T78A, p.Q150P, p.W259fs, OPTN p.R144G, p.F475V, GRN p.V473fs, p.C307fs, p.R101fs, CHMP2B p.K6N, p.R186Q, ANXA11 p.Q155*, CYLD p.T157I, SQSTM1 p.S403A, UBQLN2 p.P509H, CCNF p.S160N, CHCHD10 p.A8T, SIGMAR1 p.S117L, CHCHD2 p.P53fs, FUS p.S235G & p.S236G, and TMEM106B p.L144V variants. Patients with TBK1 and OPTN variants presented with heterogeneous clinical phenotypes. Functional analysis demonstrated that TBK1 I37T and E232Q mutants showed decreased autophosphorylation, and the OPTN phosphorylation was reduced by the TBK1 I37T mutant. The OPTN-TBK1 complex formation was enhanced by the TBK1 E696G mutant, while OPTN R144G and F475V mutants exhibited reduced recruitment to autophagosomes compared to the wild-type. The overall frequency of TBK1 and OPTN in Chinese FTD patients was 2.0% and 0.3%, respectively.

CONCLUSIONS

Our study demonstrates the extensive genetic and phenotypic heterogeneity of Chinese FTD patients. TBK1 mutations are the second most frequent cause of clinical FTD after MAPT in the Chinese.

GRN mutation spectrum and genotype-phenotype correlation in Chinese dementia patients: data from PUMCH dementia cohort

BACKGROUND

METHODS: The GRN mutations, especially of the loss of function type, are causative of frontotemporal dementia (FTD). However, several GRN variants can be found in other neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease. So far, there have been over 300 GRN mutations reported globally. However, the genetic spectrum and phenotypic characteristics have not been fully elucidated in Chinese population.The participants were from the dementia cohort of Peking Union Medical College Hospital (n=1945). They received history inquiry, cognitive evaluation, brain imaging and exome sequencing. The dementia subjects carrying the rare variants of the GRN were included in this study. Those with the pathogenic or likely pathogenic variants of other dementia-related genes were excluded.

RESULTS

14 subjects carried the rare variants of GRN. They were clinically diagnosed with behavioural variant of FTD (n=2), non-fluent/agrammatic variant primary progressive aphasia (PPA, n=3), semantic variant PPA (n=1), AD (n=6) and mixed dementia (n=2). 13 rare variants of GRN were found, including 6 novel variants (W49X, S226G, M152I, A91E, G79E and A303S). The most prevalent symptom was amnesia (85.7%, 12/14), followed by psychiatric and behavioural disorder (78.6%, 11/14). In terms of lobar atrophy, temporal atrophy/hypometabolism was the most common (85.7%, 12/14), followed by parietal atrophy/hypometabolism (78.6%, 11/14).

CONCLUSION

The novel GRN variants identified in this study contribute to enrich the GRN mutation repertoire. There is phenotypic similarity and diversity among Chinese patients with the GRN mutations.

Progress in Primary Progressive Aphasia: A Review

We present a review of the definition, classification, and epidemiology of primary progressive aphasia (PPA); an update of the taxonomy of the clinical syndrome of PPA; and recent advances in the neuroanatomy, pathology, and genetics of PPA, as well as the search for biomarkers and treatment. PPA studies that have contributed to concepts of language organization and disease propagation in neurodegeneration are also reviewed. In addition, the issues of heterogeneity versus the relationships of the clinical phenotypes and their relationship to biological, pathological, and genetic advances are discussed, as is PPA's relationship to other conditions such as frontotemporal dementia, corticobasal degeneration, progressive supranuclear palsy, Pick disease, and amyotrophic lateral sclerosis. Arguments are presented in favor of considering these conditions as one entity versus many.

Reduced penetrance of gene variants causing amyotrophic lateral sclerosis

BACKGROUND

Amyotrophic lateral sclerosis overlaps aetiologically and genetically with frontotemporal dementia and occurs in both familial and apparently sporadic forms. The most commonly implicated genes are C9orf72, SOD1, TARDBP and FUS. Penetrance of disease-causing variants in these genes is known to be incomplete, but has not been well studied at population level.

OBJECTIVE

We sought to determine the population-level penetrance of pathogenic and likely pathogenic variants in genes commonly causing amyotrophic lateral sclerosis.

METHODS

Published epidemiological data for amyotrophic lateral sclerosis and frontotemporal dementia were used to calculate expected frequencies of disease-causing variants per gene at population level. Variant data from gnomAD and ClinVar databases were used to ascertain observed numbers of disease-causing variants and to estimate population-level penetrance per gene. Data for C9orf72 were obtained from the published literature.

RESULTS

Maximum population penetrance for either amyotrophic lateral sclerosis or frontotemporal dementia was found to be 33% for C9orf72 (95% CI (20.9 to 53.2)), 54% for SOD1 (95% CI (32.7 to 88.6)), 38% for TARDBP (95% CI (21.1 to 69.8)) and 19% for FUS (95% CI (13.0 to 28.4)).

CONCLUSION

Population-level penetrance of amyotrophic lateral sclerosis disease genes is reduced. This finding has implications for the genetic testing and counselling of affected individuals and their unaffected relatives.

Cerebrospinal fluid level of proNGF as potential diagnostic biomarker in patients with frontotemporal dementia

Introduction

Frontotemporal dementia (FTD) is an extremely heterogeneous and complex neurodegenerative disease, exhibiting different phenotypes, genetic backgrounds, and pathological states. Due to these characteristics, and to the fact that clinical symptoms overlap with those of other neurodegenerative diseases or psychiatric disorders, the diagnosis based only on the clinical evaluation is very difficult. The currently used biomarkers help in the clinical diagnosis, but are insufficient and do not cover all the clinical needs.

Methods

By the means of a new immunoassay, we have measured and analyzed the proNGF levels in 43 cerebrospinal fluids (CSF) from FTD patients, and compared the results to those obtained in CSF from 84 Alzheimer's disease (AD), 15 subjective memory complaints (SMC) and 13 control subjects.

Results

A statistically significant difference between proNGF levels in FTD compared to AD, SMC and controls subjects was found. The statistical models reveal that proNGF determination increases the accuracy of FTD diagnosis, if added to the clinically validated CSF biomarkers.

Discussion

These results suggest that proNGF could be included in a panel of biomarkers to improve the FTD diagnosis.

Phase 1 study of latozinemab in progranulin-associated frontotemporal dementia

INTRODUCTION

Heterozygous mutations in the GRN gene lead to reduced progranulin (PGRN) levels in plasma and cerebrospinal fluid (CSF) and are causative of frontotemporal dementia (FTD) with > 90% penetrance. Latozinemab is a human monoclonal immunoglobulin G1 antibody that is being developed to increase PGRN levels in individuals with FTD caused by heterozygous loss-of-function GRN mutations.

METHODS

A first-in-human phase 1 study was conducted to evaluate the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of multiple-dose intravenous administration of latozinemab in eight symptomatic participants with FTD caused by a heterozygous loss-of-function GRN mutation (FTD-GRN).

RESULTS

Latozinemab demonstrated favorable safety and PK/PD profiles. Multiple-dose administration of latozinemab increased plasma and CSF PGRN levels in participants with FTD-GRN to levels that approximated those seen in healthy volunteers.

DISCUSSION

Data from the first-in-human phase 1 study support further development of latozinemab for the treatment of FTD-GRN.

Highlights

GRN mutations decrease progranulin (PGRN) and cause frontotemporal dementia (FTD).Latozinemab is being developed as a PGRN-elevating therapy.Latozinemab demonstrated a favorable safety profile in a phase 1 clinical trial.Latozinemab increased PGRN levels in the CNS of symptomatic FTD-GRN participants.

Neuropsychiatric Symptoms in Frontotemporal Dementia: More Than Just Noise?

Background

Neuropsychiatric symptoms cause significant suffering and poor quality of life for patients and their caregivers. They are not considered specific to frontotemporal dementia (FTD); therefore, their clinical role and impact might be underestimated.

Objective

The aims of the present study are to: 1) describe the prevalence of neuropsychiatric symptoms in FTD starting from the prodromal stage, 2) define their association with disease severity, 3) identify symptoms which are unrelated to FTD-specific symptoms, and 4) assess their association with clinical features and outcomes.

Results

In this retrospective study, we analyzed data of 461 FTD patients, including behavioral variant of FTD (bvFTD, n = 318) and primary progressive aphasia (PPA, n = 143). Neuropsychiatric symptoms were assessed using the Neuropsychiatric Inventory, and patients' staging and global disease severity were estimated using the Clinical Dementia Rating plus NACC FTLD.

Results

The most common neuropsychiatric symptoms in prodromal FTD were irritability (48%), depression (35%), and anxiety (34%); delusions were reported in 6%of prodromal bvFTD cases. The severity of most neuropsychiatric symptoms increased with global disease severity. Psychosis (delusions and hallucinations) and mood symptoms (depression and anxiety) were mostly independent from FTD-specific symptoms. Psychosis was associated with older age, higher disease severity, shorter survival rate, and was higher in bvFTD than in PPA.

Conclusions

Neuropsychiatric symptoms are common in patients with FTD, also in the prodromal phase. Psychosis might be unrelated to FTD pathology, and be associated with worse clinical outcomes. The prompt detection and treatment of these symptoms might improve patient's management and quality of life.

Assessing network degeneration and phenotypic heterogeneity in genetic frontotemporal lobar degeneration by decoding FDG-PET

Genetic mutations causative of frontotemporal lobar degeneration (FTLD) are highly predictive of a specific proteinopathy, but there exists substantial inter-individual variability in their patterns of network degeneration and clinical manifestations. We collected clinical and 18Fluorodeoxyglucose-positron emission tomography (FDG-PET) data from 39 patients with genetic FTLD, including 11 carrying the C9orf72 hexanucleotide expansion, 16 carrying a MAPT mutation and 12 carrying a GRN mutation. We performed a spectral covariance decomposition analysis between FDG-PET images to yield unbiased latent patterns reflective of whole brain patterns of metabolism ("eigenbrains" or EBs). We then conducted linear discriminant analyses (LDAs) to perform EB-based predictions of genetic mutation and predominant clinical phenotype (i.e., behavior/personality, language, asymptomatic). Five EBs were significant and explained 58.52 % of the covariance between FDG-PET images. EBs indicative of hypometabolism in left frontotemporal and temporo-parietal areas distinguished GRN mutation carriers from other genetic mutations and were associated with predominant language phenotypes. EBs indicative of hypometabolism in prefrontal and temporopolar areas with a right hemispheric predominance were mostly associated with predominant behavioral phenotypes and distinguished MAPT mutation carriers from other genetic mutations. The LDAs yielded accuracies of 79.5 % and 76.9 % in predicting genetic status and predominant clinical phenotype, respectively. A small number of EBs explained a high proportion of covariance in patterns of network degeneration across FTLD-related genetic mutations. These EBs contained biological information relevant to the variability in the pathophysiological and clinical aspects of genetic FTLD, and for offering valuable guidance in complex clinical decision-making, such as decisions related to genetic testing.

The Diagnostic Landscape of Adult Neurogenetic Disorders

Neurogenetic diseases affect individuals across the lifespan, but accurate diagnosis remains elusive for many patients. Adults with neurogenetic disorders often undergo a long diagnostic odyssey, with multiple specialist evaluations and countless investigations without a satisfactory diagnostic outcome. Reasons for these diagnostic challenges include: (1) clinical features of neurogenetic syndromes are diverse and under-recognized, particularly those of adult-onset, (2) neurogenetic syndromes may manifest with symptoms that span multiple neurological and medical subspecialties, and (3) a positive family history may not be present or readily apparent. Furthermore, there is a large gap in the understanding of how to apply genetic diagnostic tools in adult patients, as most of the published literature focuses on the pediatric population. Despite these challenges, accurate genetic diagnosis is imperative to provide affected individuals and their families guidance on prognosis, recurrence risk, and, for an increasing number of disorders, offer targeted treatment. Here, we provide a framework for recognizing adult neurogenetic syndromes, describe the current diagnostic approach, and highlight studies using next-generation sequencing in different neurological disease cohorts. We also discuss diagnostic pitfalls, barriers to achieving a definitive diagnosis, and emerging technology that may increase the diagnostic yield of testing.

C9ORF72 Gene GGGGCC Hexanucleotide Expansion: A High Clinical Variability from Amyotrophic Lateral Sclerosis to Frontotemporal Dementia

The expanded GGGGCC hexanucleotide repeat (HRE) in the non-coding region of the C9ORF72 gene (C9ORF72-HRE) is the most common genetic cause of familial forms of amyotrophic lateral sclerosis (ALS), FTD, and concurrent ALS and FTD (ALS-FTD), in addition to contributing to the sporadic forms of these diseases. Both syndromes overlap not only genetically, but also sharing similar clinical and neuropathological findings, being considered as a spectrum. In this paper we describe the clinical-genetic findings in a Basque family with different manifestations within the spectrum, our difficulties in reaching the diagnosis, and a narrative review, carried out as a consequence, of the main features associated with C9ORF72-HRE. Family members underwent a detailed clinical assessment, neurological examination, and genetic analysis by repeat-primed PCR. We studied 10 relatives of a symptomatic carrier of the C9ORF72-HRE expansion. Two of them presented the expansion in the pathological range, one of them was symptomatic whereas the other one remained asymptomatic at 72 years. Given the great intrafamilial clinical variability of C9ORF72-HRE, the characterization of patients and family members with particular clinical and genetic subgroups within ALS and FTD becomes a bottleneck for medication development, in particular for genetically focused medicines for ALS and FTD.

Spatial transcriptomic patterns underlying regional vulnerability to amyloid-β and tau pathologies and their relationships to cognitive dysfunction in Alzheimer's disease

Amyloid-β (Aβ) and tau proteins accumulate within distinct neuronal systems in Alzheimer's disease (AD). Although it is not clear why certain brain regions are more vulnerable to Aβ and tau pathologies than others, gene expression may play a role. We studied the association between brain-wide gene expression profiles and regional vulnerability to Aβ (gene-to-Aβ associations) and tau (gene-to-tau associations) pathologies leveraging two large independent cohorts (n = 715) of participants along the AD continuum. We identified several AD susceptibility genes and gene modules in a gene co-expression network with expression profiles related to regional vulnerability to Aβ and tau pathologies in AD. In particular, we found that the positive APOE -to-tau association was only seen in the AD cohort, whereas patients with AD and frontotemporal dementia shared similar positive MAPT -to-tau association. Some AD candidate genes showed sex-dependent negative gene-to-Aβ and gene-to-tau associations. In addition, we identified distinct biochemical pathways associated with the gene-to-Aβ and the gene-to-tau associations. Finally, we proposed a novel analytic framework, linking the identified gene-to-pathology associations to cognitive dysfunction in AD at the individual level, suggesting potential clinical implication of the gene-to-pathology associations. Taken together, our study identified distinct gene expression profiles and biochemical pathways that may explain the discordance between regional Aβ and tau pathologies, and filled the gap between gene-to-pathology associations and cognitive dysfunction in individual AD patients that may ultimately help identify novel personalized pathogenetic biomarkers and therapeutic targets.

One Sentence Summary

We identified replicable cognition-related associations between regional gene expression profiles and selectively regional vulnerability to amyloid-β and tau pathologies in AD.

Prodromal language impairment in genetic frontotemporal dementia within the GENFI cohort

OBJECTIVE

To identify whether language impairment exists presymptomatically in genetic frontotemporal dementia (FTD), and if so, the key differences between the main genetic mutation groups.

METHODS

682 participants from the international multicentre Genetic FTD Initiative (GENFI) study were recruited: 290 asymptomatic and 82 prodromal mutation carriers (with C9orf72, GRN, and MAPT mutations) as well as 310 mutation-negative controls. Language was assessed using items from the Progressive Aphasia Severity Scale, as well as the Boston Naming Test (BNT), modified Camel and Cactus Test (mCCT) and a category fluency task. Participants also underwent a 3 T volumetric T1-weighted MRI from which regional brain volumes within the language network were derived and compared between the groups.

RESULTS

3% of asymptomatic (4% C9orf72, 4% GRN, 2% MAPT) and 48% of prodromal (46% C9orf72, 42% GRN, 64% MAPT) mutation carriers had impairment in at least one language symptom compared with 13% of controls. In prodromal mutation carriers significantly impaired word retrieval was seen in all three genetic groups whilst significantly impaired grammar/syntax and decreased fluency was seen only in C9orf72 and GRN mutation carriers, and impaired articulation only in the C9orf72 group. Prodromal MAPT mutation carriers had significant impairment on the category fluency task and the BNT whilst prodromal C9orf72 mutation carriers were impaired on the category fluency task only. Atrophy in the dominant perisylvian language regions differed between groups, with earlier, more widespread volume loss in C9orf72, and later focal atrophy in the temporal lobe in MAPT mutation carriers.

CONCLUSIONS

Language deficits exist in the prodromal but not asymptomatic stages of genetic FTD across all three genetic groups. Improved understanding of the language phenotype prior to phenoconversion to fully symptomatic FTD will help develop outcome measures for future presymptomatic trials.

A heterozygous splicing variant IVS9-7A > T in intron 9 of the MAPT gene in a patient with right-temporal variant frontotemporal dementia with atypical 4 repeat tauopathy

Right temporal variant frontotemporal dementia, also called right-predominant semantic dementia, often has an unclear position within the framework of the updated diagnostic criteria for behavioral variant frontotemporal dementia or primary progressive aphasia. Recent studies have suggested that this population may be clinically, neuropathologically, and genetically distinct from those with behavioral variant frontotemporal dementia or left-predominant typical semantic variant primary progressive aphasia. Here we describe a Japanese case of right temporal variant frontotemporal dementia with novel heterozygous MAPT mutation Adenine to Thymidine in intervening sequence (IVS) 9 at position -7 from 3' splicing site of intron 9/exon 10 boundary (MAPT IVS9-7A > T). Postmortem neuropathological analysis revealed a predominant accumulation of 4 repeat tau, especially in the temporal lobe, amygdala, and substantia nigra, but lacked astrocytic plaques or tufted astrocytes. Immunoelectron microscopy of the tau filaments extracted from the brain revealed a ribbon-like structure. Moreover, a cellular MAPT splicing assay confirmed that this novel variant promoted the inclusion of exon 10, resulting in the predominant production of 4 repeat tau. These data strongly suggest that the MAPT IVS9-7 A > T variant found in our case is a novel mutation that stimulates the inclusion of exon 10 through alternative splicing of MAPT transcript and causes predominant 4 repeat tauopathy which clinically presents as right temporal variant frontotemporal dementia.

Frontotemporal Dementia, Where Do We Stand? A Narrative Review

Frontotemporal dementia (FTD) is a neurodegenerative disease of growing interest, since it accounts for up to 10% of middle-age-onset dementias and entails a social, economic, and emotional burden for the patients and caregivers. It is characterised by a (at least initially) selective degeneration of the frontal and/or temporal lobe, generally leading to behavioural alterations, speech disorders, and psychiatric symptoms. Despite the recent advances, given its extreme heterogeneity, an overview that can bring together all the data currently available is still lacking. Here, we aim to provide a state of the art on the pathogenesis of this disease, starting with established findings and integrating them with more recent ones. In particular, advances in the genetics field will be examined, assessing them in relation to both the clinical manifestations and histopathological findings, as well as considering the link with other diseases, such as amyotrophic lateral sclerosis (ALS). Furthermore, the current diagnostic criteria will be explored, including neuroimaging methods, nuclear medicine investigations, and biomarkers on biological fluids. Of note, the promising information provided by neurophysiological investigations, i.e., electroencephalography and non-invasive brain stimulation techniques, concerning the alterations in brain networks and neurotransmitter systems will be reviewed. Finally, current and experimental therapies will be considered.

Plasma inflammation for predicting phenotypic conversion and clinical progression of autosomal dominant frontotemporal lobar degeneration

BACKGROUND

Measuring systemic inflammatory markers may improve clinical prognosis and help identify targetable pathways for treatment in patients with autosomal dominant forms of frontotemporal lobar degeneration (FTLD).

METHODS

We measured plasma concentrations of IL-6, TNFα and YKL-40 in pathogenic variant carriers (MAPT, C9orf72, GRN) and non-carrier family members enrolled in the ARTFL-LEFFTDS Longitudinal Frontotemporal Lobar Degeneration consortium. We evaluated associations between baseline plasma inflammation and rate of clinical and neuroimaging changes (linear mixed effects models with standardised (z) outcomes). We compared inflammation between asymptomatic carriers who remained clinically normal ('asymptomatic non-converters') and those who became symptomatic ('asymptomatic converters') using area under the curve analyses. Discrimination accuracy was compared with that of plasma neurofilament light chain (NfL).

RESULTS

We studied 394 participants (non-carriers=143, C9orf72=117, GRN=62, MAPT=72). In MAPT, higher TNFα was associated with faster functional decline (B=0.12 (0.02, 0.22), p=0.02) and temporal lobe atrophy. In C9orf72, higher TNFα was associated with faster functional decline (B=0.09 (0.03, 0.16), p=0.006) and cognitive decline (B=-0.16 (-0.22, -0.10), p<0.001), while higher IL-6 was associated with faster functional decline (B=0.12 (0.03, 0.21), p=0.01). TNFα was higher in asymptomatic converters than non-converters (β=0.29 (0.09, 0.48), p=0.004) and improved discriminability compared with plasma NfL alone (ΔR2=0.16, p=0.007; NfL: OR=1.4 (1.03, 1.9), p=0.03; TNFα: OR=7.7 (1.7, 31.7), p=0.007).

CONCLUSIONS

Systemic proinflammatory protein measurement, particularly TNFα, may improve clinical prognosis in autosomal dominant FTLD pathogenic variant carriers who are not yet exhibiting severe impairment. Integrating TNFα with markers of neuronal dysfunction like NfL could optimise detection of impending symptom conversion in asymptomatic pathogenic variant carriers and may help personalise therapeutic approaches.

Advances in the treatment and management of frontotemporal dementia

INTRODUCTION

Frontotemporal dementia (FTD) is a complex neurodegenerative disorder, characterized by a wide range of pathological conditions associated with the buildup of proteins such as tau and TDP-43. With a strong hereditary component, FTD often results from genetic variants in three genes - MAPT, GRN, and C9orf72.

AREAS COVERED

In this review, the authors explore abnormal protein accumulation in FTD and forthcoming treatments, providing a detailed analysis of new diagnostic advancements, including innovative markers. They analyze how these discoveries have influenced therapeutic strategies, particularly disease-modifying treatments, which could potentially transform FTD management. This comprehensive exploration of FTD from its molecular underpinnings to its therapeutic prospects offers a compelling overview of the current state of FTD research.

EXPERT OPINION

Notable challenges in FTD management involve identifying reliable biomarkers for early diagnosis and response monitoring. Genetic forms of FTD, particularly those linked to C9orf72 and GRN, show promise, with targeted therapies resulting in substantial progress in disease-modifying strategies. The potential of neuromodulation techniques, like tDCS and rTMS, is being explored, requiring further study. Ongoing trials and multi-disciplinary care highlight the continued push toward effective FTD treatments. With increasing understanding of FTD's molecular and clinical intricacies, the hope for developing effective interventions grows.

Latozinemab, a novel progranulin-elevating therapy for frontotemporal dementia

BACKGROUND

Heterozygous loss-of-function mutations in the progranulin (PGRN) gene (GRN) cause a reduction in PGRN and lead to the development of frontotemporal dementia (FTD-GRN). PGRN is a secreted lysosomal chaperone, immune regulator, and neuronal survival factor that is shuttled to the lysosome through multiple receptors, including sortilin. Here, we report the characterization of latozinemab, a human monoclonal antibody that decreases the levels of sortilin, which is expressed on myeloid and neuronal cells and shuttles PGRN to the lysosome for degradation, and blocks its interaction with PGRN.

METHODS

In vitro characterization studies were first performed to assess the mechanism of action of latozinemab. After the in vitro studies, a series of in vivo studies were performed to assess the efficacy of a mouse-cross reactive anti-sortilin antibody and the pharmacokinetics, pharmacodynamics, and safety of latozinemab in nonhuman primates and humans.

RESULTS

In a mouse model of FTD-GRN, the rodent cross-reactive anti-sortilin antibody, S15JG, decreased total sortilin levels in white blood cell (WBC) lysates, restored PGRN to normal levels in plasma, and rescued a behavioral deficit. In cynomolgus monkeys, latozinemab decreased sortilin levels in WBCs and concomitantly increased plasma and cerebrospinal fluid (CSF) PGRN by 2- to threefold. Finally, in a first-in-human phase 1 clinical trial, a single infusion of latozinemab caused a reduction in WBC sortilin, tripled plasma PGRN and doubled CSF PGRN in healthy volunteers, and restored PGRN to physiological levels in asymptomatic GRN mutation carriers.

CONCLUSIONS

These findings support the development of latozinemab for the treatment of FTD-GRN and other neurodegenerative diseases where elevation of PGRN may be beneficial. Trial registration ClinicalTrials.gov, NCT03636204. Registered on 17 August 2018, https://clinicaltrials.gov/ct2/show/NCT03636204 .

Syndromes associated with frontotemporal lobar degeneration change response patterns on visual analogue scales

Self-report scales are widely used in cognitive neuroscience and psychology. However, they rest on the central assumption that respondents engage meaningfully. We hypothesise that this assumption does not hold for many patients, especially those with syndromes associated with frontotemporal lobar degeneration. In this study we investigated differences in response patterns on a visual analogue scale between people with frontotemporal degeneration and controls. We found that people with syndromes associated with frontotemporal lobar degeneration respond with more invariance and less internal consistency than controls, with Bayes Factors = 15.2 and 14.5 respectively indicating strong evidence for a group difference. There was also evidence that patient responses feature lower entropy. These results have important implications for the interpretation of self-report data in clinical populations. Meta-response markers related to response patterns, rather than the values reported on individual items, may be an informative addition to future research and clinical practise.

Short tandem repeat expansions in sporadic amyotrophic lateral sclerosis and frontotemporal dementia

Pathogenic short tandem repeat (STR) expansions cause over 20 neurodegenerative diseases. To determine the contribution of STRs in sporadic amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), we used ExpansionHunter, REviewer, and polymerase chain reaction validation to assess 21 neurodegenerative disease-associated STRs in whole-genome sequencing data from 608 patients with sporadic ALS, 68 patients with sporadic FTD, and 4703 matched controls. We also propose a data-derived outlier detection method for defining allele thresholds in rare STRs. Excluding C9orf72 repeat expansions, 17.6% of clinically diagnosed ALS and FTD cases had at least one expanded STR allele reported to be pathogenic or intermediate for another neurodegenerative disease. We identified and validated 162 disease-relevant STR expansions in C9orf72 (ALS/FTD), ATXN1 [spinal cerebellar ataxia type 1 (SCA1)], ATXN2 (SCA2), ATXN8 (SCA8), TBP (SCA17), HTT (Huntington's disease), DMPK [myotonic dystrophy type 1 (DM1)], CNBP (DM2), and FMR1 (fragile-X disorders). Our findings suggest clinical and pathological pleiotropy of neurodegenerative disease genes and highlight their importance in ALS and FTD.

Temporal dynamics predict symptom onset and cognitive decline in familial frontotemporal dementia

INTRODUCTION

We tested whether changes in functional networks predict cognitive decline and conversion from the presymptomatic prodrome to symptomatic disease in familial frontotemporal dementia (FTD).

METHODS

For hypothesis generation, 36 participants with behavioral variant FTD (bvFTD) and 34 controls were recruited from one site. For hypothesis testing, we studied 198 symptomatic FTD mutation carriers, 341 presymptomatic mutation carriers, and 329 family members without mutations. We compared functional network dynamics between groups, with clinical severity and with longitudinal clinical progression.

RESULTS

We identified a characteristic pattern of dynamic network changes in FTD, which correlated with neuropsychological impairment. Among presymptomatic mutation carriers, this pattern of network dynamics was found to a greater extent in those who subsequently converted to the symptomatic phase. Baseline network dynamic changes predicted future cognitive decline in symptomatic participants and older presymptomatic participants.

DISCUSSION

Dynamic network abnormalities in FTD predict cognitive decline and symptomatic conversion.

HIGHLIGHTS

We investigated brain network predictors of dementia symptom onset Frontotemporal dementia results in characteristic dynamic network patterns Alterations in network dynamics are associated with neuropsychological impairment Network dynamic changes predict symptomatic conversion in presymptomatic carriers Network dynamic changes are associated with longitudinal cognitive decline.

Language impairment in the genetic forms of behavioural variant frontotemporal dementia

BACKGROUND

Behavioural variant fronto-temporal dementia (bvFTD) is characterised by a progressive change in personality in association with atrophy of the frontal and temporal lobes. Whilst language impairment has been described in people with bvFTD, little is currently known about the extent or type of linguistic difficulties that occur, particularly in the genetic forms.

METHODS

Participants with genetic bvFTD along with healthy controls were recruited from the international multicentre Genetic FTD Initiative (GENFI). Linguistic symptoms were assessed using items from the Progressive Aphasia Severity Scale (PASS). Additionally, participants undertook the Boston Naming Test (BNT), modified Camel and Cactus Test (mCCT) and a category fluency test. Participants underwent a 3T volumetric T1-weighted MRI, with language network regional brain volumes measured and compared between the genetic groups and controls.

RESULTS

76% of the genetic bvFTD cohort had impairment in at least one language symptom: 83% C9orf72, 80% MAPT and 56% GRN mutation carriers. All three genetic groups had significantly impaired functional communication, decreased fluency, and impaired sentence comprehension. C9orf72 mutation carriers also had significantly impaired articulation and word retrieval as well as dysgraphia whilst the MAPT mutation group also had impaired word retrieval and single word comprehension. All three groups had difficulties with naming, semantic knowledge and verbal fluency. Atrophy in key left perisylvian language regions differed between the groups, with generalised involvement in the C9orf72 group and more focal temporal and insula involvement in the other groups. Correlates of language symptoms and test scores also differed between the groups.

CONCLUSIONS

Language deficits exist in a substantial proportion of people with familial bvFTD across all three genetic groups. Significant atrophy is seen in the dominant perisylvian language areas and correlates with language impairments within each of the genetic groups. Improved understanding of the language phenotype in the main genetic bvFTD subtypes will be helpful in future studies, particularly in clinical trials where accurate stratification and monitoring of disease progression is required.

Autoimmunity and Frontotemporal Lobar Degeneration: From Laboratory Study to Clinical Practice

Frontotemporal lobar degeneration (FTLD) is a group of neurodegenerative diseases with heterogenous clinical, genetic, and pathological characteristics that show similar impairment of areas in the frontal and/or temporal lobes. Prime doctors' lack of awareness of this complex disease makes early identification and accurate intervention difficult. Autoimmune diseases and autoantibodies are manifestations of different levels of autoimmune reactions. This review presents research findings examining the relationship between autoimmunity and FTLD in terms of autoimmune diseases and autoantibodies with a focus on identifying potential diagnosis and treatment approaches. The findings indicate that the same or similar pathophysiological mechanisms may exist from clinical, genetic, and pathological perspectives. However, the existing evidence is not sufficient to extract substantial conclusions. On the basis of the current situation, we propose future research patterns using prospective studies on large populations and combined clinical and experimental research. Autoimmune reactions or, more generally, inflammatory reactions should receive increased attention from doctors and scientists of all disciplines.

Incidence of Syndromes Associated With Frontotemporal Lobar Degeneration in 9 European Countries

Importance

Diagnostic incidence data for syndromes associated with frontotemporal lobar degeneration (FTLD) in multinational studies are urgent in light of upcoming therapeutic approaches.

Objective

To assess the incidence of FTLD across Europe.

Design, Setting, and Participants

The Frontotemporal Dementia Incidence European Research Study (FRONTIERS) was a retrospective cohort study conducted from June 1, 2018, to May 31, 2019, using a population-based registry from 13 tertiary FTLD research clinics from the UK, the Netherlands, Finland, Sweden, Spain, Bulgaria, Serbia, Germany, and Italy and including all new FTLD-associated cases during the study period, with a combined catchment population of 11 023 643 person-years. Included patients fulfilled criteria for the behavioral variant of frontotemporal dementia (BVFTD), the nonfluent variant or semantic variant of primary progressive aphasia (PPA), unspecified PPA, progressive supranuclear palsy, corticobasal syndrome, or frontotemporal dementia with amyotrophic lateral sclerosis (FTD-ALS). Data were analyzed from July 19 to December 7, 2021.

Main Outcomes and Measures

Random-intercept Poisson models were used to obtain estimates of the European FTLD incidence rate accounting for geographic heterogeneity.

Results

Based on 267 identified cases (mean [SD] patient age, 66.70 [9.02] years; 156 males [58.43%]), the estimated annual incidence rate for FTLD in Europe was 2.36 cases per 100 000 person-years (95% CI, 1.59-3.51 cases per 100 000 person-years). There was a progressive increase in FTLD incidence across age, reaching its peak at the age of 71 years, with 13.09 cases per 100 000 person-years (95% CI, 8.46-18.93 cases per 100 000 person-years) among men and 7.88 cases per 100 000 person-years (95% CI, 5.39-11.60 cases per 100 000 person-years) among women. Overall, the incidence was higher among men (2.84 cases per 100 000 person-years; 95% CI, 1.88-4.27 cases per 100 000 person-years) than among women (1.91 cases per 100 000 person-years; 95% CI, 1.26-2.91 cases per 100 000 person-years). BVFTD was the most common phenotype (107 cases [40.07%]), followed by PPA (76 [28.46%]) and extrapyramidal phenotypes (69 [25.84%]). FTD-ALS was the rarest phenotype (15 cases [5.62%]). A total of 95 patients with FTLD (35.58%) had a family history of dementia. The estimated number of new FTLD cases per year in Europe was 12 057.

Conclusions and Relevance

The findings suggest that FTLD-associated syndromes are more common than previously recognized, and diagnosis should be considered at any age. Improved knowledge of FTLD incidence may contribute to appropriate health and social care planning and in the design of future clinical trials.

Motor symptoms in genetic frontotemporal dementia: developing a new module for clinical rating scales

OBJECTIVE

To investigate the optimal method of adding motor features to a clinical rating scale for frontotemporal dementia (FTD).

METHODS

Eight hundred and thirty-two participants from the international multicentre Genetic FTD Initiative (GENFI) study were recruited: 522 mutation carriers (with C9orf72, GRN and MAPT mutations) and 310 mutation-negative controls. A standardised clinical questionnaire was used to assess eight motor symptoms (dysarthria, dysphagia, tremor, slowness, weakness, gait disorder, falls and functional difficulties using hands). Frequency and severity of each motor symptom was assessed, and a principal component analysis (PCA) was performed to identify how the different motor symptoms loaded together. Finally, addition of a motor component to the CDR® plus NACC FTLD was investigated (CDR® plus NACC FTLD-M).

RESULTS

24.3% of mutation carriers had motor symptoms (31.7% C9orf72, 18.8% GRN, 19.3% MAPT) compared to 6.8% of controls. Slowness and gait disorder were the commonest in all genetic groups while tremor and falls were the least frequent. Symptom severity scores were similar to equivalent physical motor examination scores. PCA revealed that all motor symptoms loaded together so a single additional motor component was added to the CDR® plus NACC FTLD to form the CDR® plus NACC FTLD-M. Individual global scores were more severe with the CDR® plus NACC FTLD-M, and no patients with a clinically diagnosed motor disorder (ALS/FTD-ALS or parkinsonism) were classified anymore as asymptomatic (unlike the CDR® plus NACC FTLD alone).

CONCLUSIONS

Motor features are present in mutation carriers at all disease stages across all three genetic groups. Inclusion of motor symptoms in a rating scale that can be used in future clinical trials will not only ensure a more accurate severity measure is recorded but that a wider spectrum of FTD phenotypes can be included in the same trial.

C9orf72 expansions are the most common cause of genetic frontotemporal dementia in a Southeast Asian cohort

OBJECTIVE

Frontotemporal dementia (FTD) encompasses a spectrum of neurodegenerative disorders, including behavioural variant FTD (bvFTD), semantic variant primary progressive aphasia (svPPA) and non-fluent variant PPA (nfvPPA). While a strong genetic component is implicated in FTD, genetic FTD in Asia is less frequently reported. We aimed to investigate the frequency of Southeast Asian FTD patients harbouring known genetic FTD variants.

METHODS

A total of 60 FTD-spectrum patients (25 familial and 35 sporadic) from Singapore and the Philippines were included. All underwent next-generation sequencing and repeat-primed PCR for C9orf72 expansion testing. Neurofilament light chain (NfL) levels were measured in a subset of patients.

RESULTS

Overall, 26.6% (16/60 cases) carried pathogenic or likely pathogenic variants in a FTD-related gene, including: MAPT Gln351Arg (n = 1); GRN Cys92Ter (n = 1), Ser301Ter (n = 2), c.462 + 1G > C (n = 1); C9orf72 expansion (35-70 repeats; n = 8); TREM2 Arg47Cys (n = 1); and OPTN frameshift insertion (n = 2). Genetic mutations accounted for 48% (12/25) of patients with familial FTD, and 11.4% (4/35) of patients with sporadic FTD. C9orf72 repeat expansions were the most common genetic mutation (13.3%, 8/60), followed by GRN (6.7%, 4/60) variants. Within mutation carriers, plasma NfL was highest in a C9orf72 expansion carrier, and CSF NfL was highest in a GRN splice variant carrier.

INTERPRETATION

In our cohort, genetic mutations are present in one-quarter of FTD-spectrum cases, and up to half of those with family history. Our findings highlight the importance of wider implementation of genetic testing in FTD patients from Southeast Asia.