Psychiatric symptoms of frontotemporal dementia and subcortical (co-)pathology burden: new insights.

Three subtypes of distinct pathological proteins accumulate throughout multiple brain regions and shape the heterogeneous clinical presentation of frontotemporal lobar degeneration (FTLD). Besides the main pathological subtypes, co-occurring pathologies are common in FTLD brain donors. The objective of this study was to investigate how the location and burden of (co-)pathology correlate to early psychiatric and behavioural symptoms of FTLD. Eighty-seven brain donors from The Netherlands Brain Bank cohort (2008-2017) diagnosed with FTLD were included: 46 FTLD-TAR DNA-binding protein 43 (FTLD-TDP), 34 FTLD-tau, and seven FTLD-fused-in-sarcoma (FTLD-FUS). Post-mortem brain tissue was dissected into 20 standard regions and stained for phosphorylated TDP-43, phosphorylated tau, FUS, amyloid-ß, and α-synuclein. The burden of each pathological protein in each brain region was assessed with a semi-quantitative score. Clinical records were reviewed for early psychiatric and behavioural symptoms. Whole-brain clinico-pathological partial correlations were calculated (local false discovery rate threshold = 0.01). Elaborating on the results, we validated one finding using a quantitative assessment of TDP-43 pathology in the granular layer of the hippocampus in FTLD-TDP brain donors with (n = 15) and without (n = 15) hallucinations. In subcortical regions, the presence of psychiatric symptoms showed positive correlations with increased hippocampal pathology burden: hallucinations with TDP-43 in the granular layer (R = 0.33), mania with TDP-43 in CA1 (R = 0.35), depression with TDP-43 in CA3 and with parahippocampal tau (R = 0.30 and R = 0.23), and delusions with CA3 tau (R = 0.26) and subicular amyloid-ß (R = 0.25). Behavioural disinhibition showed positive correlations with tau burden in the thalamus (R = 0.29) and with both TDP-43 and amyloid-ß burden in the subthalamus (R = 0.23 and R = 0.24). In the brainstem, the presence of α-synuclein co-pathology in the substantia nigra correlated with disinhibition (R = 0.24), tau pathology in the substantia nigra correlated with depression (R = 0.25) and in the locus coeruleus with both depression and perseverative/compulsive behaviour (R = 0.26 and R = 0.32). The quantitative assessment of TDP-43 in the granular layer validated the higher burden of TDP-43 pathology in brain donors with hallucinations compared to those without hallucinations (P = 0.007). Our results show that psychiatric symptoms of FTLD are linked to subcortical pathology burden in the hippocampus, and hallucinations are linked to a higher burden of TDP-43 in the granular layer. Co-occurring non-FTLD pathologies in subcortical regions could contribute to configuring the clinical phenotype of FTLD.

Apolipoprotein L1 is increased in frontotemporal lobar degeneration post-mortem brain but not in ante-mortem cerebrospinal fluid.

AIMS: Frontotemporal Dementia (FTD) is caused by frontal-temporal lobar degeneration (FTLD), characterized mainly by brain protein aggregates of tau (FTLD-Tau) or TDP-43 (FTLD-TDP). The clinicopathological heterogeneity makes ante-mortem diagnosis of these pathological subtypes challenging. Our proteomics study showed increased Apolipoprotein L1 (APOL1) levels in CSF from FTD patients, which was prominently expressed in FTLD-Tau. We aimed to understand APOL1 expression in FTLD post-mortem brain tissue and to validate its potential as a CSF biomarker for FTD and its pathological subtypes. METHODS: APOL1 levels were analyzed in the frontal cortex of FTLD (including FTLD-Tau and FTLD-TDP) and non-demented controls by immunohistochemistry (FTLD total = 18 (12 FTLD-Tau and 6 FTLD-TDP); controls = 9), western blot (WB), and a novel prototype ELISA (FTLD total = 44 (21 FTLD-Tau and 23 FTLD-TDP); controls = 9). The association of APOL1 immunoreactivity with phosphorylated Tau (pTau) and TDP-43 (pTDP-43) immunoreactivity was assessed. CSF APOL1 was analyzed in confirmed FTD patients (n = 27, including 12 FTLD-Tau and 15 FTLD-TDP) and controls (n = 15) using the same ELISA. RESULTS: APOL1 levels were significantly increased in FTLD post-mortem tissue compared to controls as measured by immunohistochemistry, WB, and ELISA. However, no differences between the pathological subtypes were observed. APOL1 immunoreactivity was present in neuronal and glial cells but did not co-localize with pTau or pTDP-43. CSF APOL1 levels were comparable between FTD patients and controls and between pathological subtypes. CONCLUSION: APOL1 is upregulated in FTLD pathology irrespective of the subtypes, indicating a role of this novel protein in FTD pathophysiology. The APOL1 levels detected in brain tissue were not mirrored in the CSF, limiting its potential as a specific FTD biofluid-based biomarker using our current immunoassay.

The severity of behavioural symptoms in FTD is linked to the loss of GABRQ-expressing VENs and pyramidal neurons.

AIMS: The loss of von Economo neurons (VENs) and GABA receptor subunit theta (GABRQ) containing neurons is linked to early changes in social-emotional cognition and is seen in frontotemporal dementia (FTD) due to C9orf72 repeat expansion. We investigate the vulnerability of VENs and GABRQ-expressing neurons in sporadic and genetic forms of FTD with different underlying molecular pathology and their association with the presence and severity of behavioural symptoms. METHODS: We quantified VENs and GABRQ-immunopositive neurons in the anterior cingulate cortex (ACC) in FTD with underlying TDP43 (FTLD-TDP) (n = 34), tau (FTLD-tau) (n = 24) or FUS (FTLD-FUS) (n = 8) pathology, neurologically healthy controls (n = 12) and Alzheimer's disease (AD) (n = 7). Second, we quantified VENs and the GABRQ-expressing population in relation to presence of behavioural symptoms in the first years of disease onset. RESULTS: The number of VENs and GABRQ-expressing neurons and the ratio of VENs and GABRQ-expressing neurons over total Layer 5 neuronal population decreased in FTLD-TDP and FTLD-FUS, but not in FTLD-tau, compared to control and AD. The severity of early behavioural symptoms in all donors correlated with a lower VEN and GABRQ neuronal count. CONCLUSION: We show that in FTD, a loss of VENs together with GABRQ-expressing pyramidal neurons is associated with TDP43 and FUS pathology. No significant loss was found in donors with FTLD-tau pathology; however, this could be due to the specific MAPT mutation studied and small sporadic FTLD-tau sample size. Overall, we show the GABRQ-expressing population correlates with behavioural changes and suggest they are key in modulating behaviour in FTD.

Frontotemporal Dementia: Correlations Between Psychiatric Symptoms and Pathology.

OBJECTIVE: The pathology of frontotemporal dementia, termed frontotemporal lobar degeneration (FTLD), is characterized by distinct molecular classes of aggregated proteins, the most common being TAR DNA-binding protein-43 (TDP-43), tau, and fused in sarcoma (FUS). With a few exceptions, it is currently not possible to predict the underlying pathology based on the clinical syndrome. In this study, we set out to investigate the relationship between pathological and clinical presentation at single symptom level, including neuropsychiatric features. METHODS: The presence or absence of symptoms from the current clinical guidelines, together with neuropsychiatric features, such as hallucinations and delusions, were scored and compared across pathological groups in a cohort of 150 brain donors. RESULTS: Our cohort consisted of 68.6% FTLD donors (35.3% TDP-43, 28% tau, and 5.3% FUS) and 31.3% non-FTLD donors with a clinical diagnosis of frontotemporal dementia and a different pathological substrate, such as Alzheimer's disease (23%). The presence of hyperorality points to FTLD rather than non-FTLD pathology (p < 0.001). Within the FTLD group, hallucinations in the initial years of the disease were related to TDP-43 pathology (p = 0.02), including but not limited to chromosome 9 open reading frame 72 (C9orf72) repeat expansion carriers. The presence of perseverative or compulsive behavior was more common in the TDP-B and TDP-C histotypes (p = 0.002). INTERPRETATION: Our findings indicate that neuropsychiatric features are common in FTLD and form an important indicator of underlying pathology. In order to allow better inclusion of patients in targeted molecular trials, the routine evaluation of patients with frontotemporal dementia should include the presence and nature of neuropsychiatric symptoms. ANN NEUROL 2020;87:950-961.

Heterogeneous distribution of tau pathology in the behavioural variant of Alzheimer's disease.

OBJECTIVE: The clinical phenotype of the rare behavioural variant of Alzheimer's disease (bvAD) is insufficiently understood. Given the strong clinico-anatomical correlations of tau pathology in AD, we investigated the distribution of tau deposits in bvAD, in-vivo and ex-vivo, using positron emission tomography (PET) and postmortem examination. METHODS: For the tau PET study, seven amyloid-ß positive bvAD patients underwent [18F]flortaucipir or [18F]RO948 PET. We converted tau PET uptake values into standardised (W-)scores, adjusting for age, sex and mini mental state examination in a 'typical' memory-predominant AD (n=205) group. W-scores were computed within entorhinal, temporoparietal, medial and lateral prefrontal, insular and whole-brain regions-of-interest, frontal-to-entorhinal and frontal-to-parietal ratios and within intrinsic functional connectivity network templates. For the postmortem study, the percentage of AT8 (tau)-positive area in hippocampus CA1, temporal, parietal, frontal and insular cortices were compared between autopsy-confirmed patients with bvAD (n=8) and typical AD (tAD;n=7). RESULTS: Individual regional W-scores ≥1.96 (corresponding to p<0.05) were observed in three cases, that is, case #5: medial prefrontal cortex (W=2.13) and anterior default mode network (W=3.79), case #2: lateral prefrontal cortex (W=2.79) and salience network (W=2.77), and case #7: frontal-to-entorhinal ratio (W=2.04). The remaining four cases fell within the normal distributions of the tAD group. Postmortem AT8 staining indicated no group-level regional differences in phosphorylated tau levels between bvAD and tAD (all p>0.05). CONCLUSIONS: Both in-vivo and ex-vivo, patients with bvAD showed heterogeneous distributions of tau pathology. Since key regions involved in behavioural regulation were not consistently disproportionally affected by tau pathology, other factors are more likely driving the clinical phenotype in bvAD.

Von Economo Neurons and Fork Cells: A Neurochemical Signature Linked to Monoaminergic Function.

The human anterior cingulate and frontoinsular cortices are distinguished by 2 unique Layer 5 neuronal morphotypes, the von Economo neurons (VENs) and fork cells, whose biological identity remains mysterious. Insights could impact research on diverse neuropsychiatric diseases to which these cells have been linked. Here, we leveraged the Allen Brain Atlas to evaluate mRNA expression of 176 neurotransmitter-related genes and identified vesicular monoamine transporter 2 (VMAT2), gamma-aminobutyric acid (GABA) receptor subunit θ (GABRQ), and adrenoreceptor α-1A (ADRA1A) expression in human VENs, fork cells, and a minority of neighboring Layer 5 neurons. We confirmed these results using immunohistochemistry or in situ hybridization. VMAT2 and GABRQ expression was absent in mouse cerebral cortex. Although VMAT2 is known to package monoamines into synaptic vesicles, in VENs and fork cells its expression occurs in the absence of monoamine-synthesizing enzymes or reuptake transporters. Thus, VENs and fork cells may possess a novel, uncharacterized mode of cortical monoaminergic function that distinguishes them from most other mammalian Layer 5 neurons.

Stage-dependent nigral neuronal loss in incidental Lewy body and Parkinson's disease.

To gain a better understanding of the significance of α-synuclein pathological conditions during disease progression in Parkinson's disease, we investigated whether 1) nigral neuronal loss in incidental Lewy body disease and Parkinson's disease donors is associated with the local burden α-synuclein pathological conditions during progression of pathological conditions; 2) the burden and distribution of α-synuclein pathological conditions are related to clinical measures of disease progression. Post-mortem tissue and medical records of 24 Parkinson's disease patients, 20 incidental Lewy body disease donors, and 12 age-matched controls were obtained from the Netherlands Brain Bank for morphometric analysis. We observed a 20% decrease in nigral neuronal cell density in incidental Lewy body disease compared with controls. Nigral neuronal loss (12%) was already observed before the appearance α-synuclein aggregates. The progression from Braak α-synuclein stage 3 to 4 was associated with a significant decline in neuronal cell density (46%). Nigral neuronal loss increased with later Braak α-synuclein stages but did not vary across consecutive Braak α-synuclein stages. We observed a negative correlation between neuronal density and local α-synuclein burden in the substantia nigra of Parkinson's disease patients (ρ = -0.54), but no relationship with Hoehn & Yahr stage or disease duration. In conclusion, our findings cast doubt on the pathogenic role of α-synuclein aggregates in elderly, but do suggest that the severity of neurodegeneration and local burden of α-synuclein pathological conditions are closely coupled during disease progression in Parkinson's disease.

Movement disorders are linked to TDP-43 burden in the substantia nigra of FTLD-TDP brain donors.

Movement disorders (MD) have been linked to degeneration of the substantia nigra (SN) in Parkinson's disease and include bradykinesia, rigidity, and tremor. They are also present in frontotemporal dementia (FTD), where MD have been linked to frontotemporal lobar degeneration with tau pathology (FTLD-tau). Although MD can also occur in FTLD with TDP-43 pathology (FTLD-TDP), the local pathology in the SN of FTLD-TDP patients with MD is currently unexplored. The aims of this study are to characterize the frequency and the nature of MD in a cohort of FTLD-TDP brain donors and to investigate the relationship between the presence of MD, the nigral neuronal loss, and the TDP-43 burden in the SN. From our cohort of FTLD-TDP patients (n = 53), we included 13 donors who presented with MD (FTLD-MD+), and nine age-sex matched donors without MD (FTLD-MD-) for whom the SN was available. In these donors, the TDP-43 burden and the neuronal density in the SN were assessed with ImageJ and Qupath software. The results were compared between the two groups using T-test. We found that the TDP-43 burden in the SN was higher in FTLD-MD+ (mean 3,43%, SD ± 2,7) compared to FTLD-MD- (mean 1,21%, SD ± 0,67) (p = 0,04), while no significant difference in nigral neuronal density was found between the groups (p = 0,09). 17% of FTLD-TDP patients developed MD, which present as symmetric akinetic-rigid parkinsonism or CBS. Given the absence of a significant nigral neuronal cell loss, TDP-43 induced neuronal dysfunction could be sufficient to cause MD.

Increased G3BP2-Tau interaction in tauopathies is a natural defense against Tau aggregation.

Many RNA-binding proteins (RBPs), particularly those associated with RNA granules, promote pathological protein aggregation in neurodegenerative diseases. Here, we demonstrate that G3BP2, a core component of stress granules, directly interacts with Tau and inhibits Tau aggregation. In the human brain, the interaction of G3BP2 and Tau is dramatically increased in multiple tauopathies, and it is independent of neurofibrillary tangle (NFT) formation in Alzheimer's disease (AD). Surprisingly, Tau pathology is significantly elevated upon loss of G3BP2 in human neurons and brain organoids. Moreover, we found that G3BP2 masks the microtubule-binding region (MTBR) of Tau, thereby inhibiting Tau aggregation. Our study defines a novel role for RBPs as a line of defense against Tau aggregation in tauopathies.

Electroconvulsive therapy is associated with increased immunoreactivity of neuroplasticity markers in the hippocampus of depressed patients.

Electroconvulsive therapy (ECT) is an effective therapy for depression, but its cellular effects on the human brain remain elusive. In rodents, electroconvulsive shocks increase proliferation and the expression of plasticity markers in the hippocampal dentate gyrus (DG), suggesting increased neurogenesis. Furthermore, MRI studies in depressed patients have demonstrated increases in DG volume after ECT, that were notably paralleled by a decrease in depressive mood scores. Whether ECT also triggers cellular plasticity, inflammation or possibly injury in the human hippocampus, was unknown. We here performed a first explorative, anatomical study on the human post-mortem hippocampus of a unique, well-documented cohort of bipolar or unipolar depressed patients, who had received ECT in the 5 years prior to their death. They were compared to age-matched patients with a depressive disorder who had not received ECT and to matched healthy controls. Upon histopathological examination, no indications were observed for major hippocampal cell loss, overt cytoarchitectural changes or classic neuropathology in these 3 groups, nor were obvious differences present in inflammatory markers for astrocytes or microglia. Whereas the numbers of proliferating cells expressing Ki-67 was not different, we found a significantly higher percentage of cells positive for Doublecortin, a marker commonly used for young neurons and cellular plasticity, in the subgranular zone and CA4 / hilus of the hippocampus of ECT patients. Also, the percentage of positive Stathmin 1 cells was significantly higher in the subgranular zone of ECT patients, indicating neuroplasticity. These first post-mortem observations suggest that ECT has no damaging effects but may rather have induced neuroplasticity in the DG of depressed patients.

AAGGG repeat expansions trigger RFC1-independent synaptic dysregulation in human CANVAS Neurons.

Cerebellar ataxia with neuropathy and vestibular areflexia syndrome (CANVAS) is a late onset, recessively inherited neurodegenerative disorder caused by biallelic, non-reference pentameric AAGGG(CCCTT) repeat expansions within the second intron of replication factor complex subunit 1 (RFC1). To investigate how these repeats cause disease, we generated CANVAS patient induced pluripotent stem cell (iPSC) derived neurons (iNeurons) and utilized calcium imaging and transcriptomic analysis to define repeat-elicited gain-of-function and loss-of-function contributions to neuronal toxicity. AAGGG repeat expansions do not alter neuronal RFC1 splicing, expression, or DNA repair pathway functions. In reporter assays, AAGGG repeats are translated into pentapeptide repeat proteins that selectively accumulate in CANVAS patient brains. However, neither these proteins nor repeat RNA foci were detected in iNeurons, and overexpression of these repeats in isolation did not induce neuronal toxicity. CANVAS iNeurons exhibit defects in neuronal development and diminished synaptic connectivity that is rescued by CRISPR deletion of a single expanded allele. These phenotypic deficits were not replicated by knockdown of RFC1 in control neurons and were not rescued by ectopic expression of RFC1. These findings support a repeat-dependent but RFC1-independent cause of neuronal dysfunction in CANVAS, with important implications for therapeutic development in this currently untreatable condition.

The proliferative capacity of the subventricular zone is maintained in the parkinsonian brain.

There are many indications that neurogenesis is impaired in Parkinson's disease, which might be due to a lack of dopamine in the subventricular zone. An impairment in neurogenesis may have negative consequences for the development of new therapeutic approaches in Parkinson's disease, as neural stem cells are a potential source for endogenous repair. In this study, we examined the subventricular zone of 10 patients with Parkinson's disease and 10 age- and sex-matched controls for proliferation and neural stem cell numbers. We also included five cases with incidental Lewy body disease, which showed Parkinson's disease pathology but no clinical symptoms and thus did not receive dopaminergic treatment. We quantified the neural stem cell number and proliferative capacity in the subventricular zone of these three donor groups. We found subventricular neural stem cells in each donor, with a high variation in number. We did not observe significant differences in neural stem cell number or in proliferation between the groups. Additionally, we were able to culture neural stem cells from post-mortem brain of several patients with Parkinson's disease, confirming the presence of viable neural stem cells in these brains. We have also examined the subventricular zone of a chronic, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinson's disease mouse model, and again found no effect of dopaminergic denervation on precursor proliferation. Lastly, we investigated the proliferation capacity of two different human neural stem cell lines in response to dopamine. Both cell lines did not respond with a change in proliferation to treatment with dopamine agonists and an antagonist. In summary, the adult neural stem cell pool in the subventricular zone was not clearly affected in the human parkinsonian brain or a Parkinson's disease mouse model. Furthermore, we did not find evidence that dopamine has a direct effect on human neural stem cell proliferation in vitro. Thus, we conclude that the number of adult neural stem cells is probably not diminished in the parkinsonian brain and that dopamine depletion most likely has no effect on human neural stem cells.

Research Criteria for the Behavioral Variant of Alzheimer Disease: A Systematic Review and Meta-analysis.

Importance: The behavioral variant of Alzheimer disease (bvAD) is characterized by early and predominant behavioral deficits caused by AD pathology. This AD phenotype is insufficiently understood and lacks standardized clinical criteria, limiting reliability and reproducibility of diagnosis and scientific reporting. Objective: To perform a systematic review and meta-analysis of the bvAD literature and use the outcomes to propose research criteria for this syndrome. Data Sources: A systematic literature search in PubMed/MEDLINE and Web of Science databases (from inception through April 7, 2021) was performed in duplicate. Study Selection: Studies reporting on behavioral, neuropsychological, or neuroimaging features in bvAD and, when available, providing comparisons with typical amnestic-predominant AD (tAD) or behavioral variant frontotemporal dementia (bvFTD). Data Extraction and Synthesis: This analysis involved random-effects meta-analyses on group-level study results of clinical data and systematic review of the neuroimaging literature. The study was performed following Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Main Outcomes and Measures: Behavioral symptoms (neuropsychiatric symptoms and bvFTD core clinical criteria), cognitive function (global cognition, episodic memory, and executive functioning), and neuroimaging features (structural magnetic resonance imaging, [18F]fluorodeoxyglucose-positron emission tomography, perfusion single-photon emission computed tomography, amyloid positron emission tomography, and tau positron emission tomography). Results: The search led to the assessment of 83 studies, including 13 suitable for meta-analysis. Data were collected for 591 patients with bvAD. There was moderate to substantial heterogeneity and moderate risk of bias across studies. Cases with bvAD showed more severe behavioral symptoms than tAD (standardized mean difference [SMD], 1.16 [95% CI, 0.74-1.59]; P < .001) and a trend toward less severe behavioral symptoms compared with bvFTD (SMD, -0.22 [95% CI, -0.47 to 0.04]; P = .10). Meta-analyses of cognitive data indicated worse executive performance in bvAD vs tAD (SMD, -1.03 [95% CI, -1.74 to -0.32]; P = .008) but not compared with bvFTD (SMD, -0.61 [95% CI, -1.75 to 0.53]; P = .29). Cases with bvAD showed a nonsignificant difference of worse memory performance compared with bvFTD (SMD, -1.31 [95% CI, -2.75 to 0.14]; P = .08) but did not differ from tAD (SMD, 0.43 [95% CI, -0.46 to 1.33]; P = .34). The neuroimaging literature revealed 2 distinct bvAD neuroimaging phenotypes: an AD-like pattern with relative frontal sparing and a relatively more bvFTD-like pattern characterized by additional anterior involvement, with the AD-like pattern being more prevalent. Conclusions and Relevance: These data indicate that bvAD is clinically most similar to bvFTD, while it shares most pathophysiological features with tAD. Based on these insights, we propose research criteria for bvAD aimed at improving the consistency and reliability of future research and aiding the clinical assessment of this AD phenotype.

Right temporal variant frontotemporal dementia is pathologically heterogeneous: a case-series and a systematic review.

Although the right temporal variant frontotemporal dementia (rtvFTD) is characterised by distinct clinical and radiological features, its underlying histopathology remains elusive. Being considered a right-sided variant of semantic variant primary progressive aphasia (svPPA), TDP-43 type C pathology has been linked to the syndrome, but this has not been studied in detail in large cohorts. In this case report and systematic review, we report the autopsy results of five subjects diagnosed with rtvFTD from our cohort and 44 single rtvFTD subjects from the literature. Macroscopic pathological evaluation of the combined results revealed that rtvFTD demonstrated either a frontotemporal or temporal evolution, even if the degeneration started in the right temporal lobe initially. FTLD-TDP type C was the most common underlying pathology in rtvFTD, however, in 64% of rtvFTD, other underlying pathologies than FTLD-TDP type C were present, such as Tau-MAPT and FTLD-TDP type A and B. Additionally, accompanying motor neuron or corticospinal tract degeneration was observed in 28% of rtvFTD patients. Our results show that in contrast to the general assumption, rtvFTD might not be a pure FTLD-TDP type C disorder, unlike its left temporal counterpart svPPA. Large sample size pathological studies are warranted to understand the diverse pathologies of the right and left temporal variants of frontotemporal dementia.

Unfolded protein response activation in C9orf72 frontotemporal dementia is associated with dipeptide pathology and granulovacuolar degeneration in granule cells.

A repeat expansion in the C9orf72 gene is the most prevalent genetic cause of frontotemporal dementia (C9-FTD). Several studies have indicated the involvement of the unfolded protein response (UPR) in C9-FTD. In human neuropathology, UPR markers are strongly associated with granulovacuolar degeneration (GVD). In this study, we aim to assess the presence of UPR markers together with the presence of dipeptide pathology and GVD in post mortem brain tissue from C9-FTD cases and neurologically healthy controls. Using immunohistochemistry we assessed the presence of phosphorylated PERK, IRE1α and eIF2α in the frontal cortex, hippocampus and cerebellum of C9-FTD (n = 18) and control (n = 9) cases. The presence of UPR activation markers was compared with the occurrence of pTDP-43, p62 and dipeptide repeat (DPR) proteins (poly(GA), -(GR) & -(GP)) as well as casein kinase 1 delta (CK1δ), a marker for GVD. Increased presence of UPR markers was observed in the hippocampus and cerebellum in C9-FTD compared to control cases. In the hippocampus, overall levels of pPERK and peIF2α were higher in C9-FTD, including in granule cells of the dentate gyrus (DG). UPR markers were also observed in granule cells of the cerebellum in C9-FTD. In addition, increased levels of CK1δ were observed in granule cells in the DG of the hippocampus and granular layer of the cerebellum in C9-FTD. Double-labelling experiments indicate a strong association between UPR markers and the presence of dipeptide pathology as well as GVD. We conclude that UPR markers are increased in C9-FTD and that their presence is associated with dipeptide pathology and GVD. Increased presence of UPR markers and CK1δ in granule cells in the cerebellum and hippocampus could be a unique feature of C9-FTD.

Translation of GGC repeat expansions into a toxic polyglycine protein in NIID defines a novel class of human genetic disorders: The polyG diseases.

Neuronal intranuclear inclusion disease (NIID) is a neurodegenerative disease characterized by the presence of intranuclear inclusions of unknown origin. NIID is caused by an expansion of GGC repeats in the 5' UTR of the NOTCH2NLC (N2C) gene. We found that these repeats are embedded in a small upstream open reading frame (uORF) (uN2C), resulting in their translation into a polyglycine-containing protein, uN2CpolyG. This protein accumulates in intranuclear inclusions in cell and mouse models and in tissue samples of individuals with NIID. Furthermore, expression of uN2CpolyG in mice leads to locomotor alterations, neuronal cell loss, and premature death of the animals. These results suggest that translation of expanded GGC repeats into a novel and pathogenic polyglycine-containing protein underlies the presence of intranuclear inclusions and neurodegeneration in NIID.

Neuropathology of FMR1-premutation carriers presenting with dementia and neuropsychiatric symptoms.

CGG repeat expansions within the premutation range (55-200) of the FMR1 gene can lead to Fragile X-associated tremor/ataxia syndrome and Fragile X-associated neuropsychiatric disorders. These CGG repeats are translated into a toxic polyglycine-containing protein, FMRpolyG. Pathology of Fragile X-associated tremor/ataxia syndrome and Fragile X-associated neuropsychiatric disorders comprises FMRpolyG- and p62-positive intranuclear inclusions. Diagnosing a FMR1-premutation carrier remains challenging, as the clinical features overlap with other neurodegenerative diseases. Here, we describe two male cases with Fragile X-associated neuropsychiatric disorders-related symptoms and mild movement disturbances and novel pathological features that can attribute to the variable phenotype. Macroscopically, both donors did not show characteristic white matter lesions on MRI; however, vascular infarcts in cortical- and sub-cortical regions were identified. Immunohistochemistry analyses revealed a high number of FMRpolyG intranuclear inclusions throughout the brain, which were also positive for p62. Importantly, we identified a novel pathological vascular phenotype with inclusions present in pericytes and endothelial cells. Although these results need to be confirmed in more cases, we propose that these vascular lesions in the brain could contribute to the complex symptomology of FMR1-premutation carriers. Overall, our report suggests that Fragile X-associated tremor/ataxia syndrome and Fragile X-associated neuropsychiatric disorders may present diverse clinical involvements resembling other types of dementia, and in the absence of genetic testing, FMRpolyG can be used post-mortem to identify premutation carriers.

Refining the Spectrum of Neuronal Intranuclear Inclusion Disease: A Case Report.

Neuronal intranuclear inclusion disease (NIID) is a rare heterogeneous progressive neurodegenerative disease characterized by the presence of eosinophilic hyaline intranuclear inclusions in neuronal and glial cells of the CNS, peripheral cells of the autonomic nervous system, visceral organs and skin. The clinical presentation is broadly heterogeneous and includes limb weakness, dementia, seizures, ataxia, and parkinsonism. High-intensity signal in the corticomedullary junction on brain MRI is a characteristic finding in NIID. We describe a 65-year-old patient presenting with mild cognitive impairment, evolving in dementia with behavioral disturbances and parkinsonism. Brain MRI showed mild global cortical atrophy, more pronounced in the cingulate and temporal cortex and mild leukoaraiosis, but no high-intensity signal in corticomedullary junction on diffusion weighted imaging. Neuropathological examination showed p62- and optineurin-positive neuronal intranuclear inclusions in the hippocampus and in some subcortical structures. Glial cells did not present any intranuclear inclusions, and no spongiotic changes proximal to the U-fibers or diffuse myelin pallor were disclosed in the white matter. We report on a case with pathological features of NIID showing different neuroimaging and pathological findings. We noted an absence of typical MRI abnormalities, lack of intranuclear inclusions in glial cells, and prominent involvement of hippocampal neurons, refining the clinico-pathological spectrum of the disease.

Early recognition and treatment of neuropsychiatric symptoms to improve quality of life in early Alzheimer's disease: protocol of the BEAT-IT study.

BACKGROUND: Neuropsychiatric symptoms (NPS) are very common in patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD) dementia and are associated with various disadvantageous clinical outcomes including a negative impact on quality of life, caregiver burden, and accelerated disease progression. Despite growing evidence of the efficacy of (non)pharmacological interventions to reduce these symptoms, NPS remain underrecognized and undertreated in memory clinics. The BEhavioural symptoms in Alzheimer's disease Towards early Identification and Treatment (BEAT-IT) study is developed to (1) investigate the neurobiological etiology of NPS in AD and (2) study the effectiveness of the Describe, Investigate, Create, Evaluate (DICE) approach to structure and standardize the current care of NPS in AD. By means of the DICE method, we aim to improve the quality of life of AD patients with NPS and their caregivers who visit the memory clinic. This paper describes the protocol for the intervention study that incorporates the latter aim. METHODS: We aim to enroll a total of 150 community-dwelling patients with MCI or AD and their caregivers in two waves. First, we will recruit a control group who will receive care as usual. Next, the second wave of participants will undergo the DICE method. This approach consists of the following steps: (1) describe the context in which NPS occur, (2) investigate the possible causes, (3) create and implement a treatment plan, and (4) evaluate whether these interventions are effective. Primary outcomes are the quality of life of patients and their caregivers. Secondary outcomes include NPS change, caregiver burden, caregivers' confidence managing NPS, psychotropic medication use, the experiences of patients and caregivers who underwent the DICE method, and the cost-effectiveness of the intervention. CONCLUSIONS: This paper describes the protocol of an intervention study that is part of the BEAT-IT study and aims to improve current recognition and treatment of NPS in AD by structuring and standardizing the detection and treatment of NPS in AD using the DICE approach. TRIAL REGISTRATION: The trial was registered on the Netherlands Trial Registry ( NTR7459 ); registered 6 September 2018.