Caroline Graff

Understanding the order in which symptoms occur in genetic frontotemporal dementia (FTD) may provide valuable insight into disease progression. Here we use a methodology called Ordinal Subtype and Stage Inference (SuStaIn) in the GENetic FTD Initiative (GENFI) cohort to estimate a probable order in which symptoms occur, and identify different subtypes based on the pattern of symptom progression within the main genetic FTD mutation groups. 968 participants were included in the cross-sectional study: 280 C9orf72, 242 GRN and 101 MAPT mutation carriers, and 345 mutation-negative controls. 379 participants underwent longitudinal analysis: 162 C9orf72, 146 GRN and 71 MAPT mutation carriers. The standardised GENFI clinical assessment provided severity scores for all FTD-relevant symptoms ranging from 0 where symptoms are absent to 3 where symptoms are severe. Ordinal SuStaIn was run in each mutation group to generate symptom progression profiles for mutation carriers from each group. In the C9orf72 cohort, Ordinal SuStaIn identified three subtypes: subtype 1 with early behavioural and cognitive deficits, subtype 2 with impaired speech and swallowing, and subtype 3 with limb impairment. In the GRN cohort, SuStaIn identified two subtypes: subtype 1 with behavioural and cognitive deficits as well as limb motor involvement, and subtype 2 with early language impairment. The MAPT cohort was best described as a single subtype with a combination of cognitive (mainly semantic) and behavioural impairment with parkinsonism. SuStaIn stage significantly correlated with clinical severity scores for all the cohorts. The subtypes were somewhat longitudinally consistent, with a trend towards increased SuStaIn stage in each subtype over time. Identifying within-genotype data-driven subtypes of FTD is a novel approach for untangling the heterogeneity of this disorder, in turn drawing us closer to individualised care.

C9orf72 encodes a protein that is important for both typical neurodevelopment and homeostatic processes across the lifespan. Pathogenic C9orf72 repeat expansions constitute the most common genetic cause of frontotemporal lobar degeneration (FTLD). Collectively, preclinical models and clinical neuroimaging studies have observed smaller thalamic volumes in C9orf72 -associated FTLD, including in asymptomatic young adult C9orf72 repeat expansion carriers across 18 to 30 years old, supportive of potential neurodevelopmental origins. However, it is unknown whether asymptomatic young adult C9orf72 expansion carriers demonstrate volume differences in specific thalamic nuclei, as reported in older asymptomatic carriers and symptomatic patients; if so, normative transcriptomic patterns could reveal relevant neurodevelopmental and/or FTLD-related neurodegenerative processes. This study investigated volumetric MRI differences of the thalamic nuclei in asymptomatic young adult C9orf72 expansion carriers compared to non-carriers, and examined spatial associations with normative thalamic transcriptomics from 8 weeks post-conception through middle age. Young adult C9orf72 expansion carriers ( n =72) and non-carriers ( n =48) were enrolled in the Frontotemporal Dementia Prevention Initiative across Europe, Canada, and the USA (ages: 18-30 years; sex: 57% female). Spatial associations between young adult thalamic nuclei volumes and normative transcriptomics from the Allen Human Brain Atlas were examined using complementary data-driven and hypothesis-driven approaches. Spatial expression patterns of transcripts of interest were characterized across prenatal and postnatal neurodevelopment using BrainSpan data. Smaller volumes of the pulvinar, mediodorsal, and lateral nuclei were observed in young adult C9orf72 expansion carriers compared to non-carriers. These nuclei showed higher normative expression of transcripts involved concurrently in neurodevelopmental and C9orf72 -associated FTLD neurodegenerative processes (including lysosomal, autophagic, and small GTPase functions), and lower normative expression of CALB1 , a marker of prenatal human thalamic development. Normative expression of CALB2 (another human thalamic development marker) yielded positive correlations with C9orf72 across prenatal development to adulthood. These findings identify candidate transcripts that may provide insight into the molecular architecture leading to smaller thalamic nuclei volumes in C9orf72 -associated FTLD.

Background: Plasma and cerebrospinal fluid (CSF) protein biomarkers in amyotrophic lateral sclerosis (ALS) may provide insight into disease mechanisms and yield clinically useful biomarkers. Methods: Overall, 363 proteins in plasma and CSF from 198 patients with ALS and 125 matched controls were profiled using Olink assays. Associations with disease status, survival, and functional decline, as well as longitudinal biomarker stability across the disease course were assessed, together with network and enrichment analyses. ALS risk‐associated biomarkers were externally validated in the UK Biobank (UKB). Results: Overall, 125 proteins were significantly associated with at least one outcome (i.e., case status, risk, survival, or functional decline), and 21 were associated with three or more outcomes. NEFL was the most robust biomarker in plasma and CSF, alongside TNFRSF12A in plasma and CSF, EDA2R in plasma, and FABP4 in plasma and CSF. Most biomarkers remained stable longitudinally across the disease course. ALS risk‐associated biomarkers were replicated in UKB, in which > 3000 plasma proteins were measured in 52,990 participants, including 298 with ALS. Network and enrichment analyses highlighted their roles in immune response and extracellular‐matrix remodeling, and their enrichments in the brain and T‐cell subsets. Construction of an ALS risk‐prediction model achieved an ROC‐AUC of 0.72 in the UKB validation cohort. Conclusions: These findings suggest candidate protein biomarkers for ALS risk stratification, early detection, and clinical therapeutic monitoring.

Frontotemporal lobar degeneration (FTLD) is a common cause of early-onset dementias marked by progressive declines in behavior, cognition, and/or movement. FTLD neuropathologies, including TDP-43 proteinopathies and primary tauopathies, do not have reliable fluid biomarkers for in-vivo diagnosis nor biomarkers that directly correspond to FTLD clinical features. Fluid biomarkers that forecast and track FTLD clinical progression, irrespective of pathology or clinical syndrome, are urgently needed to improve clinical trial designs. We previously identified the ratio between two cerebrospinal fluid (CSF) synaptic proteins, YWHAG and NPTX2, as a prognostic biomarker of cognitive decline in Alzheimer’s disease (AD), independent of core AD pathologies, amyloid and tau. Here, we evaluate its utility in sporadic and familial FTLD compared to other neurodegenerative diseases. Using CSF assays from four independent cohorts (UCSF-MAC, ALLFTD, GENFI, PDBP), we find CSF YWHAG:NPTX2 is substantially elevated across all sporadic and familial FTLD syndromes, AD, and dementia with Lewy bodies. CSF YWHAG:NPTX2 robustly correlates with clinical severity across sporadic and familial FTLD ( C9orf72 , GRN , or MAPT mutations), independent of current gold-standard neurodegeneration biomarker neurofilament light (NfL). In presymptomatic familial FTLD, CSF YWHAG:NPTX2 is estimated to rise roughly a decade before symptom onset and improves prediction of imminent symptomatic conversion by 1.7-fold compared to plasma NfL alone, more than halving the estimated sample size required for an FTLD prevention clinical trial. These findings underscore CSF YWHAG:NPTX2 as a cross-dementia synaptic biomarker of cognitive decline and a promising biomarker for disease staging and prognosis across the clinico-pathological continuum of FTLD.

Neurodegenerative diseases (NDDs) are clinically and genetically heterogeneous, requiring neuropathology or molecular testing for a definitive diagnosis. Clinical whole genome sequencing (WGS) enables comprehensive variant calling across flexible gene lists that can be tailored to the clinical presentation. By allowing simultaneous detection of single-nucleotide variants, copy-number variants, structural variants, and repeat expansions, WGS has the potential to improve diagnostic yield, facilitate genetic counseling and support clinical trial inclusion. This study assesses the diagnostic performance of WGS in individuals with NDD. WGS in 500 individuals representing a wide spectrum of NDDs identified a disease-causing variant in 61 cases, resulting in a diagnostic yield of 12%. These variants were found in 16 different genes, with C9orf72 being the most prevalent. Repeat expansions represented the largest variant class, accounting for 35 of 61 LP/P cases (57%); most of which were C9orf72 expansions (31/35). In the largest phenotype groups, frontotemporal dementia (FTD) had the highest diagnostic yield (19%) followed by amyotrophic lateral sclerosis (ALS, 13%), whereas an underlying monogenic cause was expectedly low in Alzheimer disease (AD, 4%). A positive family history was present in the majority (74%) of FTD, ALS, combined ALS-FTD and AD cases with an LP/P finding. Clinical WGS provides a clear diagnostic advantage in NDDs marked by substantial clinical and genetic overlap. WGS enables comprehensive variant detection and mapping of genotype–phenotype relationships across the disease continuum. In FTD and ALS, these results support universal access to genetic testing independent of age at onset or family history.

Individuals with autosomal dominant frontotemporal dementia (FTD) exhibit considerable variability in disease onset and progression. Both modifiable and non-modifiable factors—such as sex, educational attainment or geographic region of residence—may contribute to this heterogeneity, potentially through their influence on cognitive reserve. The aim of the present study was to investigate the role of cognitive reserve modulators within the Genetic Frontotemporal dementia Initiative (GENFI) cohort. To this end, we used functional MRI (i.e. spatial chronnectome measures) and neurodegenerative markers (i.e. plasma neurofilament light chains levels) to determine disease stage using a Discriminative Event-Based Model (DEBM). We then examined how potential modulators influence the relationship between disease stage and cognitive performance. We analysed a total of 711 participants, including 106 patients with genetic FTD, 325 presymptomatic mutation carriers and 280 non-carriers healthy controls. Female participants showed a weaker association between disease stage and cognitive performance compared to males (P < 0.001), with difference becoming progressively more pronounced across symptomatic stages. Educational attainment exhibited a similar effect: individuals with higher education demonstrated an attenuated association compared to those with secondary or primary schooling (P < 0.001), with differences already detectable at prodromal disease stages. The effect of geographical region of residence was associated with education levels, but appeared to have an indirect and less strong influence. In summary, sex and educational attainment significantly affect the development and maintenance of cognitive reserve in individuals with genetic FTD. These findings underscore the importance of identifying disease-modifying interventions since the presymptomatic stages of the disease.

Background and Objectives: Converging evidence hints at neurodevelopmental effects in genetic frontotemporal degeneration (FTD). In cross-sectional studies, for some genes, young adult FTD variant carriers show differences in brain volumes and cognition compared to familial non-carriers. However, longitudinal trajectories may more sensitively capture FTD-related neurodevelopmental vs. neurodegenerative changes than cross-sectional approaches. This study examined longitudinal trajectories of brain volumes, executive function, and plasma biomarkers in young adult carriers compared to familial non-carriers, as measures of neurodevelopmental and neurodegenerative outcomes of FTD-causing variants. Methods: This longitudinal cohort study comprised participants, aged 18-30 years, from the FTD Prevention Initiative across Europe, Canada, and the USA. Genetic groups included C9orf72 (47%), MAPT (30%), and GRN (23%). Linear mixed-effects models were computed to assess longitudinal outcomes across age between groups, controlling for sex, scanner (for brain volumes), and education (for executive function); random effects accounted for between-subject variability nested within family membership. Results: Variant carriers ( n =147) and familial non-carriers ( n =113) did not differ in age (mean±SD, 25.9±3.2 years), sex (53% female), or number of visits (2.1±1.7). Young adult C9orf72 repeat expansion carriers exhibited smaller thalamic volumes than non-carriers at the reference age of 26 years ( b =-982.8mm ³ , SE=317.0, p= 0.0046, f ² =0.32), with relatively stable trajectories across ages 18-30 (i.e., no change over time). Trajectories of rostral anterior cingulate volumes differed in C9orf72 carriers and non-carriers across age, where carriers showed relatively stable trajectories and non-carriers showed age-appropriate declines ( b =64.4mm ³ , SE=29.9, p= 0.035, f ² =0.07). For MAPT and GRN , there were little to no differences in total brain, cortical, or subcortical volumes between groups and over time. No longitudinal differences were observed between carriers and non-carriers in executive function, or plasma NfL or GFAP for any genetic group. Discussion: C9orf72 repeat expansions were linked to smaller average thalamic volumes and stable trajectories between ages 18 to 30, supporting potential neurodevelopmental origins. The modest evidence supporting an absence of difference in neurodegenerative biomarkers and executive function suggests minimal early neurodegeneration and functional preservation in young adulthood.

Cerebrospinal fluid amyloid beta 42, total tau, and phosphorylated tau 181 are well accepted markers of Alzheimer’s disease. These biomarkers better reflect disease pathogenesis compared to clinical diagnosis. Here, we perform a genome wide association study meta-analysis including 18,948 individuals of European ancestry and identify 12 genome-wide significant loci across all three biomarkers, eight of them novel. We replicate the association of biomarkers with APOE , CR1 , GMNC/CCDC50 and C16orf95/MAP1LC3B . Novel loci include BIN1 for amyloid beta and GNA12, MS4A6A, SLCO1A2 with both total tau and phosphorylated tau 181, as well as additional loci on chr. 8, near ANGPT1 and chr. 9 near SMARCA2 . We also demonstrate that these variants have significant association with Alzheimer’s disease risk, disease progression and/or brain amyloidosis. The associated genes are implicated in lipid metabolism independent of APOE , coupled with autophagy and brain volume regulation driven by total tau and phosphorylated tau 181 dysregulation.

We aimed to understand longitudinal associations between Alzheimer’s disease (AD) biomarkers in Autosomal Dominant AD (ADAD) across estimated years to symptom onset (EYO). Forty-five individuals (19 mutation carriers [EYO = −7.9 ± 11.7 years, APP N = 11; PSEN1 N = 8]) from Swedish ADAD families participated. All received baseline 18F-Flurodeoxyglucose (FDG) PET and cognitive testing, and a subset (N = 26) plasma glial fibrillary acidic protein (GFAP) measurement. Follow-up data collection (including 106 FDG scans) was performed over 7.4 ± 6.4 years (visits ranged from 1–5, EYO = −25.8 to +10.3 years in mutation carriers). Mixed effects models were applied to determine longitudinal associations. APP and PSEN1 mutation carriers showed different FDG uptake profiles from EYO = −20 to −10 years, with a hypermetabolism before hypometabolism in PSEN1 mutation carriers. Early increases in plasma GFAP were primarily related to subcortical FDG decreases and cognitive changes in APP mutation carriers compared to non-carriers. We provide evidence for gene-dependent biomarker trajectories in ADAD.