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AbstractBackgroundWhite matter signal abnormalities (WMSA) are frequently observed on magnetic resonance imaging (MRI) scans of people with frontotemporal dementia (FTD). We hypothesized that carriers of mutations in progranulin (GRN+), chromosome 9 open reading frame 72 (C9orf72+) and microtubule associated protein tau (MAPT+) have increased rates of progression of WMSA compared to non‐carrier individuals prior to onset of dementia, and that different mutations may have different rates of WMSA accumulation.MethodParticipants were recruited through the ARTFL‐LEFFTDS Longitudinal Frontotemporal Lobar Degeneration (ALLFTD) Study. We selected participants with Clinical Dementia Rating scale (CDR) scores of 0 and 0.5. If a participant developed FTD during the follow‐up, we only analyzed observations collected before the conversion. WMSA were defined as hyperintensities on FLAIR MRI. Total WMSA volumes were normalized to the respective intracranial volumes. We used a linear mixed effects model, with random intercepts and slopes, to compare the baseline burden and the longitudinal progression of total WMSA volumes between mutation carriers and controls. The model was adjusted for baseline age, sex, education, baseline Montreal Cognitive Assessment (MoCA) scores, and MRI acquisition sites.ResultWe analyzed MRI data from 199 participants who had at least two MRI visits (46 C9orf72+, 17 GRN+, 35 MAPT+, 101 non‐carrier controls; up to five years of follow‐up). We did not find significant group differences in baseline demographic features, except that MAPT+ was younger than non‐carrier controls (average age: C9orf72+ = 47, GRN+ = 56, MAPT+ = 40, controls = 47). Baseline WMSA volumes were not significantly different between mutation carriers and controls. Longitudinally, the rates of WMSA volume increase in C9orf72+ and MAPT+ were comparable to controls; whereas, GRN+ had higher rates of WMSA volume increases compared to controls (p = 0.01).ConclusionWMSA may accumulate at higher rates in GRN+ prior to the onset of FTD, which is consistent with the frequent presence of white matter diseases observed in symptomatic FTD patients with GRN mutations. Future work is warranted to investigate the association between white matter structural changes and cognitive/psychiatric changes in FTD mutation carriers.

AbstractBackgroundNeuropsychiatric symptoms (NPS) often occur during the prodromal stage of frontotemporal dementia (FTD), as evidenced by the presence of early psychiatric diagnosis in approximately 50% of bvFTD patients prior to their dementia diagnosis. We hypothesized that carriers of mutations in progranulin (GRN+), chromosome 9 open reading frame 72 (C9orf72+) and microtubule associated protein tau (MAPT+) have increased baseline burden and rates of progression of NPS compared to non‐carrier individuals prior to onset of dementia symptoms based on the Clinical Dementia Rating (CDR) scale.MethodParticipants were recruited through the ARTFL‐LEFFTDS Longitudinal Frontotemporal Lobar Degeneration (ALLFTD) Study. NPS were assessed with Neuropsychiatric Inventory‐Questionnaire (NPI‐Q), Geriatric Depression Scale (GDS), Interpersonal Reactivity Index (IRI), Social Behaviour Checklist (SBOCL), and Behavioral Inhibition Scale (BIS) annually for up to five years. We selected participants with CDR scores of 0 and 0.5. If a participant’s CDR changed to above 0.5 during the follow‐up, we only analyzed observations collected before the conversion. We used mixed effects models to compare the baseline burden and the longitudinal progression of NPS measures between carriers and controls, adjusted for baseline age, sex, education, and baseline Montreal Cognitive Assessment (MoCA) scores.ResultWe analyzed data from 607 participants (111 C9orf72+, 47 GRN+, 67 MAPT+ and 382 non‐carrier controls). There were no significant group differences in baseline demographic features, except that MAPT+ was significantly younger than other groups (average age: C9orf72+ = 45, GRN+ = 53, MAPT+ = 41, controls = 54). Baseline NPS scores were not significantly different between carriers and controls, except that C9orf72+ had significantly lower GDS compared to controls (p = 0.002). Longitudinally, GRN+ (p = 0.02) and MAPT+ (p = 0.009) had significantly higher rates of NPI‐Q increases compared to controls, while the progression of NPI‐Q in C9orf72+ was comparable to controls. The rates of GDS, IRI, SBOCL and BIS progression were not significantly different between carriers and controls.ConclusionPrior to the onset of dementia, GRN+ and MAPT+ have a faster progression of NPS, as measured by NPI‐Q, compared to controls. Future work will investigate whether different mutation carriers are affected by specific type/cluster of symptoms.

AbstractIntroductionRemote smartphone assessments of cognition, speech/language, and motor functioning in frontotemporal dementia (FTD) could enable decentralized clinical trials and improve access to research. We studied the feasibility and acceptability of remote smartphone data collection in FTD research using the ALLFTD Mobile App (ALLFTD‐mApp).MethodsA diagnostically mixed sample of 214 participants with FTD or from familial FTD kindreds (asymptomatic: CDR®+NACC‐FTLD = 0 [N = 101]; prodromal: 0.5 [N = 49]; symptomatic ≥1 [N = 51]; not measured [N = 13]) were asked to complete ALLFTD‐mApp tests on their smartphone three times within 12 days. They completed smartphone familiarity and participation experience surveys.ResultsIt was feasible for participants to complete the ALLFTD‐mApp on their own smartphones. Participants reported high smartphone familiarity, completed ∼ 70% of tasks, and considered the time commitment acceptable (98% of respondents). Greater disease severity was associated with poorer performance across several tests.DiscussionThese findings suggest that the ALLFTD‐mApp study protocol is feasible and acceptable for remote FTD research.HIGHLIGHTS The ALLFTD Mobile App is a smartphone‐based platform for remote, self‐administered data collection. The ALLFTD Mobile App consists of a comprehensive battery of surveys and tests of executive functioning, memory, speech and language, and motor abilities. Remote digital data collection using the ALLFTD Mobile App was feasible in a multicenter research consortium that studies FTD. Data was collected in healthy controls and participants with a range of diagnoses, particularly FTD spectrum disorders. Remote digital data collection was well accepted by participants with a variety of diagnoses.

Abstract Transmembrane protein 106B (TMEM106B) is a tightly regulated glycoprotein predominantly localized to endosomes and lysosomes. Genetic studies have implicated TMEM106B haplotypes in the development of multiple neurodegenerative diseases with the strongest effect in frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP), especially in progranulin (GRN) mutation carriers. Recently, cryo-electron microscopy studies showed that a C-terminal fragment (CTF) of TMEM106B (amino acid residues 120–254) forms amyloid fibrils in the brain of patients with FTLD-TDP, but also in brains with other neurodegenerative conditions and normal ageing brain. The functional implication of these fibrils and their relationship to the disease-associated TMEM106B haplotype remain unknown. We performed immunoblotting using a newly developed antibody to detect TMEM106B CTFs in the sarkosyl-insoluble fraction of post-mortem human brain tissue from patients with different proteinopathies (n = 64) as well as neuropathologically normal individuals (n = 10) and correlated the results with age and TMEM106B haplotype. We further compared the immunoblot results with immunohistochemical analyses performed in the same study population. Immunoblot analysis showed the expected ∼30 kDa band in the sarkosyl-insoluble fraction of frontal cortex tissue in at least some individuals with each of the conditions evaluated. Most patients with GRN mutations showed an intense band representing TMEM106B CTF, whereas in most neurologically normal individuals it was absent or much weaker. In the overall cohort, the presence of TMEM106B CTFs correlated strongly with both age (rs = 0.539, P < 0.001) and the presence of the TMEM106B risk haplotype (rs = 0.469, P < 0.001). Although there was a strong overall correlation between the results of immunoblot and immunohistochemistry (rs = 0.662, P < 0.001), 27 cases (37%) were found to have higher amounts of TMEM106B CTFs detected by immunohistochemistry, including most of the older individuals who were neuropathologically normal and individuals who carried two protective TMEM106B haplotypes. Our findings suggest that the formation of sarkosyl-insoluble TMEM106B CTFs is an age-related feature which is modified by TMEM106B haplotype, potentially underlying its disease-modifying effect. The discrepancies between immunoblot and immunohistochemistry in detecting TMEM106B pathology suggests the existence of multiple species of TMEM106B CTFs with possible biological relevance and disease implications.

AbstractIntroductionEmpathy relies on fronto‐cingular and temporal networks that are selectively vulnerable in behavioral variant frontotemporal dementia (bvFTD). This study modeled when in the disease process empathy changes begin, and how they progress.MethodsFour hundred thirty‐one individuals with asymptomatic genetic FTD (n = 114), genetic and sporadic bvFTD (n = 317), and 163 asymptomatic non‐carrier controls were enrolled. In sub‐samples, we investigated empathy measured by the informant‐based Interpersonal Reactivity Index (IRI) at each disease stage and over time (n = 91), and its correspondence to underlying atrophy (n = 51).ResultsEmpathic concern (estimate = 4.38, 95% confidence interval [CI] = 2.79, 5.97; p < 0.001) and perspective taking (estimate = 5.64, 95% CI = 3.81, 7.48; p < 0.001) scores declined between the asymptomatic and very mild symptomatic stages regardless of pathogenic variant status. More rapid loss of empathy corresponded with subcortical atrophy.DiscussionLoss of empathy is an early and progressive symptom of bvFTD that is measurable by IRI informant ratings and can be used to monitor behavior in neuropsychiatry practice and treatment trials.

Abstract Type 2 immune cells and eosinophils are transiently present in lung tissue not only in pathology but also during normal postnatal development. However, the lung developmental processes underlying postnatal airway recruitment of eosinophils after birth remain unexplored. We determined that in mice, mature eosinophils are recruited to the lung during P3–14, which corresponds to the primary septation/alveolarization phase of lung development. Developmental eosinophils peaked during P10–14 and exhibited Siglec-Fmed/highCD11c−/low phenotypes, similar to allergic asthma models. By interrogating the lung transcriptome and proteome during peak eosinophil recruitment in postnatal development, we identified markers that functionally capture mesenchymal-epithelial interface establishment (Nes, Smo, Wnt5a, Nog) and provisional extracellular matrix (ECM) deposition (Tnc, Postn, Spon2, Thbs2) as key lung morphogenetic events associating with eosinophils. We identifiedTenascin-C (TNC) as one of the key ECM markers in the lung epithelial-mesenchymal interface at the RNA and protein levels, consistently associating with eosinophils in development and disease. By RNA-seq analysis, naïve murine eosinophils cultured with TNC-enriched ECM significantly induced expression of Siglec-F, CD11c, eosinophil peroxidase, and other markers typical for activated eosinophils in development and allergic inflammatory responses. TNC knockout mice had an altered eosinophil recruitment profile in development. Collectively, our results indicate that lung morphogenetic processes associated with heightened Type 2 immunity are not merely tissue “background” but specifically guide immune cells both in development and pathology.

AbstractBackgroundWhite matter signal abnormalities (WMSA) are frequently observed on magnetic resonance imaging (MRI) scans of people with frontotemporal dementia (FTD). We hypothesized that carriers of mutations in progranulin (GRN+), chromosome 9 open reading frame 72 (C9orf72+) and microtubule associated protein tau (MAPT+) have increased rates of progression of WMSA compared to non‐carrier individuals prior to onset of dementia, and that different mutations may have different rates of WMSA accumulation.MethodParticipants were recruited through the ARTFL‐LEFFTDS Longitudinal Frontotemporal Lobar Degeneration (ALLFTD) Study. We selected participants with Clinical Dementia Rating scale (CDR) scores of 0 and 0.5. If a participant developed FTD during the follow‐up, we only analyzed observations collected before the conversion. WMSA were defined as hyperintensities on FLAIR MRI. Total WMSA volumes were normalized to the respective intracranial volumes. We used a linear mixed effects model, with random intercepts and slopes, to compare the baseline burden and the longitudinal progression of total WMSA volumes between mutation carriers and controls. The model was adjusted for baseline age, sex, education, baseline Montreal Cognitive Assessment (MoCA) scores, and MRI acquisition sites.ResultWe analyzed MRI data from 199 participants who had at least two MRI visits (46 C9orf72+, 17 GRN+, 35 MAPT+, 101 non‐carrier controls; up to five years of follow‐up). We did not find significant group differences in baseline demographic features, except that MAPT+ was younger than non‐carrier controls (average age: C9orf72+=47, GRN+=56, MAPT+=40, controls=47). Baseline WMSA volumes were not significantly different between mutation carriers and controls. Longitudinally, the rates of WMSA volume increase in C9orf72+ and MAPT+ were comparable to controls; whereas, GRN+ had higher rates of WMSA volume increases compared to controls (p=0.01).ConclusionWMSA may accumulate at higher rates in GRN+ prior to the onset of FTD, which is consistent with the frequent presence of white matter diseases observed in symptomatic FTD patients with GRN mutations. Future work is warranted to investigate the association between white matter structural changes and cognitive/psychiatric changes in FTD mutation carriers.

AbstractA large proportion of familial frontotemporal dementia is caused by TAR DNA-binding protein 43 (transactive response DNA-binding protein 43 kDa) proteinopathies. Accordingly, carriers of autosomal dominant mutations in the genes associated with TAR DNA-binding protein 43 aggregation, such as Chromosome 9 open reading frame 72 (C9orf72) or progranulin (GRN), are at risk of later developing frontotemporal dementia. Brain imaging abnormalities that develop before dementia onset in mutation carriers may serve as proxies for the presymptomatic stages of familial frontotemporal dementia due to a genetic cause. Our study objective was to investigate brain MRI-based white-matter changes in predementia participants carrying mutations in C9orf72 or GRN genes. We analysed mutation carriers and their family member controls (noncarriers) from the University of British Columbia familial frontotemporal dementia study. First, a total of 42 participants (8 GRN carriers; 11 C9orf72 carriers; 23 noncarriers) had longitudinal T1-weighted MRI over ∼2 years. White-matter signal hypointensities were segmented and volumes were calculated for each participant. General linear models were applied to compare the baseline burden and the annualized rate of accumulation of signal abnormalities among mutation carriers and noncarriers. Second, a total of 60 participants (9 GRN carriers; 17 C9orf72 carriers; 34 noncarriers) had cross-sectional diffusion tensor MRI available. For each participant, we calculated the average fractional anisotropy and mean, radial and axial diffusivity parameter values within the normal-appearing white-matter tissues. General linear models were applied to compare whether mutation carriers and noncarriers had different trends in diffusion tensor imaging parameter values as they neared the expected age of onset. Baseline volumes of white-matter signal abnormalities were not significantly different among mutation carriers and noncarriers. Longitudinally, GRN carriers had significantly higher annualized rates of accumulation (estimated mean: 15.87%/year) compared with C9orf72 carriers (3.69%/year) or noncarriers (2.64%/year). A significant relationship between diffusion tensor imaging parameter values and increasing expected age of onset was found in the periventricular normal-appearing white-matter region. Specifically, GRN carriers had a tendency of a faster increase of mean and radial diffusivity values and C9orf72 carriers had a tendency of a faster decline of fractional anisotropy values as they reached closer to the expected age of dementia onset. These findings suggest that white-matter changes may represent early markers of familial frontotemporal dementia due to genetic causes. However, GRN and C9orf72 mutation carriers may have different mechanisms leading to tissue abnormalities.

ImportancePhysical activity is associated with cognitive health, even in autosomal dominant forms of dementia. Higher physical activity is associated with slowed cognitive and functional declines over time in adults carrying autosomal dominant variants for frontotemporal lobar degeneration (FTLD), but whether axonal degeneration is a potential neuroprotective target of physical activity in individuals with FTLD is unknown.ObjectiveTo examine the association between physical activity and longitudinal neurofilament light chain (NfL) trajectories in individuals with autosomal dominant forms of FTLD.Design, Setting, and ParticipantsThis cohort study included individuals from the ALLFTD Consortium, which recruited patients from sites in the US and Canada. Symptomatic and asymptomatic adults with pathogenic variants in one of 3 common genes associated with FTLD (GRN, C9orf72, or MAPT) who reported baseline physical activity levels and completed annual blood draws were assessed annually for up to 4 years. Genotype, clinical measures, and blood draws were collected between December 2014 and June 2019; data were analyzed from August 2021 to January 2022. Associations between reported baseline physical activity and longitudinal plasma NfL changes were assessed using generalized linear mixed-effects models adjusting for baseline age, sex, education, functional severity, and motor symptoms.ExposuresBaseline physical activity levels reported via the Physical Activity Scale for the Elderly. To estimate effect sizes, marginal means were calculated at 3 levels of physical activity: 1 SD above the mean represented high physical activity, 0 SD represented average physical activity, and 1 SD below the mean represented low physical activity.Main Outcomes and MeasuresAnnual plasma NfL concentrations were measured with single-molecule array technology.ResultsOf 160 included FTLD variant carriers, 84 (52.5%) were female, and the mean (SD) age was 50.7 (14.7) years. A total of 51 (31.8%) were symptomatic, and 77 carried the C9orf72 variant; 39, GRN variant; and 44, MAPT variant. Higher baseline physical activity was associated with slower NfL trajectories over time. On average, NfL increased 45.8% (95% CI, 22.5 to 73.7) over 4 years in variant carriers. Variant carriers with high physical activity demonstrated 14.0% (95% CI, −22.7 to −4.3) slower NfL increases compared with those with average physical activity and 30% (95% CI, −52.2 to −8.8) slower NfL increases compared with those with low physical activity. Within genotype, C9orf72 and MAPT carriers with high physical activity evidenced 18% to 21% (95% CI, −43.4 to −7.2) attenuation in NfL, while the association between physical activity and NfL trajectory was not statistically significant in GRN carriers. Activities associated with higher cardiorespiratory and cognitive demands (sports, housework, and yardwork) were most strongly correlated with slower NfL trajectories (vs walking and strength training).Conclusions and RelevanceIn this study, higher reported physical activity was associated with slower progression of an axonal degeneration marker in individuals with autosomal dominant FTLD. Physical activity may serve as a primary prevention target in FTLD.