Does epilepsy contribute to the clinical phenotype of C9orf72 mutation in fronto-temporal dementia?

C9orf72 mutation is the most common genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) worldwide. Recently, several reports of patients with FTD who carried the C9orf72 mutation and also manifested epilepsy have been published, since seizures occur in FTD at a higher rate than in the general population, the possible association between epilepsy and C9orf72 mutation remains to be clarified. In the attempt to understand whether epilepsy contributes to the phenotype of the C9orf72 mutation, we compared epilepsy occurrence in patients with FTD who carried the C9orf72 mutation and those who did not. In our sample of 84 patients with FTD, 7.1% of cases reported epilepsy, with no significant differences between subsamples of patients with FTD stratified according to the presence of the C9orf72 mutation or to family history of FTD/parkinsonism/motor neuron disease. Our findings did not support to the possibility that epilepsy represents a characteristic feature of the C9orf72 mutation, as suggested by recent case reports published in the English literature.

Alzheimer risk gene product Pyk2 suppresses tau phosphorylation and phenotypic effects of tauopathy

BACKGROUND

Genetic variation at the PTK2B locus encoding the protein Pyk2 influences Alzheimer's disease risk. Neurons express Pyk2 and the protein is required for Amyloid-β (Aβ) peptide driven deficits of synaptic function and memory in mouse models, but Pyk2 deletion has minimal effect on neuro-inflammation. Previous in vitro data suggested that Pyk2 activity might enhance GSK3β-dependent Tau phosphorylation and be required for tauopathy. Here, we examine the influence of Pyk2 on Tau phosphorylation and associated pathology.

METHODS

The effect of Pyk2 on Tau phosphorylation was examined in cultured Hek cells through protein over-expression and in iPSC-derived human neurons through pharmacological Pyk2 inhibition. PS19 mice overexpressing the P301S mutant of human Tau were employed as an in vivo model of tauopathy. Phenotypes of PS19 mice with a targeted deletion of Pyk2 expression were compared with PS19 mice with intact Pyk2 expression. Phenotypes examined included Tau phosphorylation, Tau accumulation, synapse loss, gliosis, proteomic profiling and behavior.

RESULTS

Over-expression experiments from Hek293T cells indicated that Pyk2 contributed to Tau phosphorylation, while iPSC-derived human neuronal cultures with endogenous protein levels supported the opposite conclusion. In vivo, multiple phenotypes of PS19 were exacerbated by Pyk2 deletion. In Pyk2-null PS19 mice, Tau phosphorylation and accumulation increased, mouse survival decreased, spatial memory was impaired and hippocampal C1q deposition increased relative to PS19 littermate controls. Proteomic profiles of Pyk2-null mouse brain revealed that several protein kinases known to interact with Tau are regulated by Pyk2. Endogenous Pyk2 suppresses LKB1 and p38 MAPK activity, validating one potential pathway contributing to increased Tau pathology.

CONCLUSIONS

The absence of Pyk2 results in greater mutant Tau-dependent phenotypes in PS19 mice, in part via increased LKB1 and MAPK activity. These data suggest that in AD, while Pyk2 activity mediates Aβ-driven deficits, Pyk2 suppresses Tau-related phenotypes.

Wild-type FUS corrects ALS-like disease induced by cytoplasmic mutant FUS through autoregulation

Mutations in FUS, an RNA-binding protein involved in multiple steps of RNA metabolism, are associated with the most severe forms of amyotrophic lateral sclerosis (ALS). Accumulation of cytoplasmic FUS is likely to be a major culprit in the toxicity of FUS mutations. Thus, preventing cytoplasmic mislocalization of the FUS protein may represent a valuable therapeutic strategy. FUS binds to its own pre-mRNA creating an autoregulatory loop efficiently buffering FUS excess through multiple proposed mechanisms including retention of introns 6 and/or 7. Here, we introduced a wild-type FUS gene allele, retaining all intronic sequences, in mice whose heterozygous or homozygous expression of a cytoplasmically retained FUS protein (Fus^∆NLS) was previously shown to provoke ALS-like disease or postnatal lethality, respectively. Wild-type FUS completely rescued the early lethality caused by the two Fus^∆NLS alleles, and improved the age-dependent motor deficits and reduced lifespan caused by heterozygous expression of mutant FUS^∆NLS. Mechanistically, wild-type FUS decreased the load of cytoplasmic FUS, increased retention of introns 6 and 7 in the endogenous mouse Fus mRNA, and decreased expression of the mutant mRNA. Thus, the wild-type FUS allele activates the homeostatic autoregulatory loop, maintaining constant FUS levels and decreasing the mutant protein in the cytoplasm. These results provide proof of concept that an autoregulatory competent wild-type FUS expression could protect against this devastating, currently intractable, neurodegenerative disease.

Psychotic symptoms in frontotemporal dementia with right frontotemporal atrophy

Frontotemporal dementia (FTD) often mimics a primary psychiatric disorder. A subset of patients with FTD presents with psychotic symptoms either during the course of illness and less often prior to the onset of cognitive decline. This leads to delay in diagnosis and inappropriate exposure to high dose antipsychotic medication. Among the predictors for psychotic symptoms, the involvement of specific anatomical regions such as right frontotemporal lobe has been reported in few studies. We report a case of FTD presenting as late-onset psychosis with right frontotemporal atrophy.

Fronto-temporal dementia: a case study and strategies and support for caregivers

Fronto-temporal dementia, also known as fronto-temporal lobular degeneration, is the second most common form of early-onset dementia with a prevalence equal to Alzheimer's dementia. Behavioural variant fronto-temporal dementia primarily involves the frontal and temporal lobes of the brain. Myelination of nerve fibres in these areas allow for highly synchronized action potential timing. Diagnosis is often significantly delayed because symptoms are insidious and appear as personality and behavioural changes such as lack of inhibition, apathy, depression, and being socially inappropriate rather than exhibiting marked memory reductions. In this article, a case study illustrates care strategies and family education. Management of severe behavioural symptoms requires careful evaluation and monitoring. Support is especially important and beneficial in the early to middle stages of dementia when nursing home placement may not be required based on the individual's condition.

Muscarinic Receptor-Dependent Long Term Depression in the Perirhinal Cortex and Recognition Memory are Impaired in the rTg4510 Mouse Model of Tauopathy

Neurodegenerative diseases affecting cognitive dysfunction, such as Alzheimer's disease and fronto-temporal dementia, are often associated impairments in the visual recognition memory system. Recent evidence suggests that synaptic plasticity, in particular long term depression (LTD), in the perirhinal cortex (PRh) is a critical cellular mechanism underlying recognition memory. In this study, we have examined novel object recognition and PRh LTD in rTg4510 mice, which transgenically overexpress tau_P301L. We found that 8-9 month old rTg4510 mice had significant deficits in long- but not short-term novel object recognition memory. Furthermore, we also established that PRh slices prepared from rTg4510 mice, unlike those prepared from wildtype littermates, could not support a muscarinic acetylcholine receptor-dependent form of LTD, induced by a 5 Hz stimulation protocol. In contrast, bath application of the muscarinic agonist carbachol induced a form of chemical LTD in both WT and rTg4510 slices. Finally, when rTg4510 slices were preincubated with the acetylcholinesterase inhibitor donepezil, the 5 Hz stimulation protocol was capable of inducing significant levels of LTD. These data suggest that dysfunctional cholinergic innervation of the PRh of rTg4510 mice, results in deficits in synaptic LTD which may contribute to aberrant recognition memory in this rodent model of tauopathy.

We are what we eat: How food is represented in our mind/brain

Despite the essential role of food in our lives, we have little understanding of the way our knowledge about food is organized in the brain. At birth, human infants exhibit very few food preferences, and do not yet know much about what is edible and what is not. A multisensory learning development will eventually turn young infants into omnivore adults, for whom deciding what to eat becomes an effortful task. Recognizing food constitutes an essential step in this decisional process. In this paper we examine how concepts about food are represented in the human brain. More specifically, we first analyze how brain-damaged patients recognize natural and manufactured food, and then examine these patterns in the light of the sensory-functional hypothesis and the domain-specific hypothesis. Secondly, we discuss how concepts of food are represented depending on whether we embrace the embodied view or the disembodied view. We conclude that research on food recognition and on the organization of knowledge about food must also take into account some aspects specific to food category, the relevance of which has not been sufficiently recognized and investigated to date.

Motor neuron intrinsic and extrinsic mechanisms contribute to the pathogenesis of FUS-associated amyotrophic lateral sclerosis

Motor neuron-extrinsic mechanisms have been shown to participate in the pathogenesis of ALS-SOD1, one familial form of amyotrophic lateral sclerosis (ALS). It remains unclear whether such mechanisms contribute to other familial forms, such as TDP-43 and FUS-associated ALS. Here, we characterize a single-copy mouse model of ALS-FUS that conditionally expresses a disease-relevant truncating FUS mutant from the endogenous murine Fus gene. We show that these mice, but not mice heterozygous for a Fus null allele, develop similar pathology as ALS-FUS patients and a mild motor neuron phenotype. Most importantly, CRE-mediated rescue of the Fus mutation within motor neurons prevented degeneration of motor neuron cell bodies, but only delayed appearance of motor symptoms. Indeed, we observed downregulation of multiple myelin-related genes, and increased numbers of oligodendrocytes in the spinal cord supporting their contribution to behavioral deficits. In all, we show that mutant FUS triggers toxic events in both motor neurons and neighboring cells to elicit motor neuron disease.

Adiponectin levels in the serum and cerebrospinal fluid of amyotrophic lateral sclerosis patients: possible influence on neuroinflammation?

BACKGROUND

Adiponectin (APN) is a key player in energy homeostasis strictly associated with cerebrovascular and neurodegenerative diseases. Since APN also belongs to anti-inflammatory-acting adipokines and may influence both neuroinflammation and neurodegenerative processes, we decided to study the APN levels in amyotrophic lateral sclerosis (ALS) and other neurodegenerative diseases.

METHODS

We assessed APN levels by ELISA immunoassay in both the serum and cerebrospinal fluid of a cohort of familial and sporadic ALS patients, characterized by normal body mass index and absence of dysautonomic symptoms. The screening of serum APN levels was also performed in patients affected by other neurological disorders, including fronto-temporal dementia (FTD) patients. Means were compared using the non-parametric Wilcoxon test, and Pearson's or Spearman's rho was used to assess correlations between variables.

RESULTS

In the whole ALS group, serum APN levels were not different when compared to the age- and sex-matched control group (CTR), but a gender-specific analysis enlightened a significant opposite APN trend between ALS males, characterized by lower values (ALS 9.8 ± 5.2 vs. CTR 15 ± 9.7 μg/ml), and ALS females, showing higher amounts (ALS 26.5 ± 11.6 vs. CTR 14.6 ± 5.2 μg/ml). This sex-linked difference was significantly enhanced in familial ALS cases (p ≤ 0.01). The APN levels in ALS cerebrospinal fluids were unrelated to serum values and not linked to sex and/or familiarity of the disease. Finally, the screening of serum APN levels in patients affected by other neurological disorders revealed the highest serum values in FTD patients.

CONCLUSIONS

Opposite serum APN levels are gender-related in ALS and altered in several neurological disorders, with the highest values in FTD, which shares with ALS several overlapping and neuropathological features. Further investigations are needed to clarify the possible involvement of APN in neuroinflammation and neurodegeneration. Possible involvement of APN in neuroinflammatory neurodegenerative diseases.

Vulnerability of microRNA biogenesis in FTD-ALS

The genetics of the neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) turn our attention to RNA metabolism, primarily because many of the identified diseases-associated genes encode for RNA-binding proteins. microRNAs (miRNAs) are endogenous noncoding RNAs that play critical roles in maintaining brain integrity. The current review sheds light on miRNA dysregulation in neurodegenerative diseases, focusing on FTD-ALS. We propose that miRNAs are susceptible to fail when protein factors that are critical for miRNA biogenesis malfunction. Accordingly, potential insufficiencies of the 'microprocessor' complex, the nucleo-cytoplasmic export of miRNA precursors or their processing by Dicer were recently reported. Furthermore, specific miRNAs are involved in the regulation of pathways that are essential for neuronal survival or function. Any change in the expression of these specific miRNAs or in their ability to recognize their target sequences will have negative consequences. Taken together, recent reports strengthens the hypothesis that dysregulation of miRNAs might play an important role in the pathogenesis of neurodegenerative diseases, and highlights the miRNA biogenesis machinery as an interesting target for therapeutic interventions for ALS as well as FTD. This article is part of a Special Issue entitled SI:RNA Metabolism in Disease.

CSF biomarkers for the differential diagnosis of Alzheimer's disease: A large-scale international multicenter study

INTRODUCTION

The aim of this study was to test the diagnostic value of cerebrospinal fluid (CSF) beta-amyloid (Aβ1-42), phosphorylated tau, and total tau (tau) to discriminate Alzheimer's disease (AD) dementia from other forms of dementia.

METHODS

A total of 675 CSF samples collected at eight memory clinics were obtained from healthy controls, AD dementia, subjective memory impairment, mild cognitive impairment, vascular dementia, Lewy body dementia (LBD), fronto-temporal dementia (FTD), depression, or other neurological diseases.

RESULTS

CSF Aβ1-42 showed the best diagnostic accuracy among the CSF biomarkers. At a sensitivity of 85%, the specificity to differentiate AD dementia against other diagnoses ranged from 42% (for LBD, 95% confidence interval or CI = 32-62) to 77% (for FTD, 95% CI = 62-90).

DISCUSSION

CSF Aβ1-42 discriminates AD dementia from FTD, but shows significant overlap with other non-AD forms of dementia, possibly reflecting the underlying mixed pathologies.

Relationships between Environmental Dependency and Closing-in in Patients with Fronto-temporal Dementia

Environmental dependency (ED) phenomena, including utilization behavior and imitation behavior, are clinical manifestations typically observed in patients with the behavioral variant of fronto-temporal dementia (bvFTD), who may also show the closing-in (CI) phenomenon. Here, we explored the neuropsychological correlates of ED and CI in bvFTD, and the association of ED with CI to clarify the mechanisms underlying these clinical manifestations. Thirty-one bvFTD patients underwent a wide cognitive assessment in addition to special tasks to detect occurrence of CI and ED phenomena. Both ED and CI phenomena were present in more than half of the sample. Logistic regression analyses revealed that both ED and CI phenomena were significantly associated with poor scores on frontal neuropsychological tests. Although ED and CI often co-occurred, 3/12 patients with CI did not show ED, and 5/18 patients with ED did not show CI. A logistic regression model showed that the presence of ED was not significantly associated to CI. CI and ED are associated to progressive derangement of frontal functions in bvFTD. However, specific frontal dysfunctions might explain the occurrence of either phenomenon in isolation.

The Role of TREM2 in Alzheimer's Disease and Other Neurological Disorders

Alzheimer's disease (AD) is the leading cause of dementia worldwide. Late-onset AD (LOAD), is the most common form of Alzheimer's disease, representing about >95% of cases and early-onset AD represents <5% of cases. Several risk factors have been discovered that are associated with AD, with advancing age being the most prominent. Other environmental risk factors include diabetes mellitus, level of physical activity, educational status, hypertension and head injury. The most well known genetic risk factor for LOAD is inheritance of the apolipoprotein (apo) E4 allele. Recently, rare variants of TREM2 have been reported as a significant risk factor for LOAD, comparable to inheritance of apoE4. In this review we will focus on the role(s) of TREM2 in AD as well as in other neurodegenerative disorders.

Multiple system atrophy is not caused by C9orf72 hexanucleotide repeat expansions

Multiple system atrophy (MSA) is a fatal neurodegenerative disorder of unknown etiology that presents with variable combinations of progressive ataxia, parkinsonism, and autonomic instability. Pathologic expansion of a hexanucleotide repeat in the C9orf72 gene has been demonstrated to cause neurodegeneration with diverse neurologic presentations. To test the hypothesis whether pathologic expansions in C9orf72 are a cause of MSA, we undertook genetic screening in 100 neuropathologically confirmed cases. No pathologic repeat expansions were detected suggesting that MSA is not a C9orf72-related neurodegenerative disease.

Lysosome size, motility and stress response regulated by fronto-temporal dementia modifier TMEM106B

Fronto-temporal lobar degeneration with TDP-43 (FTLD-TDP) is a fatal neurodegeneration. TMEM106B variants are linked to FTLD-TDP risk, and TMEM106B is lysosomal. Here, we focus on neuronal TMEM106B, and demonstrate co-localization and traffic with lysosomal LAMP-1. pH-sensitive reporters demonstrate that the TMEM106B C-terminus is lumenal. The TMEM106B N-terminus interacts with endosomal adaptors and other TMEM106 proteins. TMEM106B knockdown reduces neuronal lysosomal number and diameter by STED microscopy, and overexpression enlarges LAMP-positive structures. Reduction of TMEM106B increases axonally transported lysosomes, while TMEM106B elevation inhibits transport and yields large lysosomes in the soma. TMEM106B overexpression alters lysosomal stress signaling, causing a translocation of the mTOR-sensitive transcription factor, TFEB, to neuronal nuclei. TMEM106B loss-of-function delays TFEB translocation after Torin-1-induced stress. Enlarged TMEM106B-overexpressing lysosomes maintain organelle integrity longer after lysosomal photodamage than do control lysosomes, while small TMEM106B-knockdown lysosomes are more sensitive to illumination. Thus, neuronal TMEM106B plays a central role in regulating lysosomal size, motility and responsiveness to stress, highlighting the possible role of lysosomal biology in FTLD-TDP.

In vivo axonal transport deficits in a mouse model of fronto-temporal dementia

Background

Axonal transport is vital for neurons and deficits in this process have been previously reported in a few mouse models of Alzheimer's disease prior to the appearance of plaques and tangles. However, it remains to be determined whether axonal transport is defective prior to the onset of neurodegeneration. The rTg4510 mouse, a fronto-temporal dementia and parkinsonism-17 (FTDP-17) tauopathy model, over-express tau-P301L mutation found in familial forms of FTDP-17, in the forebrain driven by the calcium–calmodulin kinase II promoter. This mouse model exhibits tau pathology, neurodegeneration in the forebrain, and associated behavioral deficits beginning at 4–5 months of age.

Animal model

rTg4510 transgenic mice were used in these studies. Mice were given 2 μL of MnCl₂ in each nostril 1 h prior to Magnetic Resonance Imaging (MRI). Following MnCl₂ nasal lavage, mice were imaged using Manganese enhanced Magnetic Resonance Imaging (MEMRI) Protocol with TE = 8.5 ms, TR = 504 ms, FOV = 3.0 cm, matrix size = 128 × 128 × 128, number of cycles = 15 with each cycle taking approximately 2 min, 9 s, and 24 ms using Paravision software (BrukerBioSpin, Billerica, MA). During imaging, body temperature was maintained at 37.0 °C using an animal heating system (SA Instruments, Stony Brook, NY).

Data analysis

Resulting images were analyzed using Paravision software. Regions of interest (ROI) within the olfactory neuronal layer (ONL) and the water phantom consisting of one pixel (ONL) and 9 pixels (water) were selected and copied across each of the 15 cycles. Signal intensities (SI) of ONL and water phantom ROIs were measured. SI values obtained for ONL were then normalized the water phantom SI values. The correlation between normalized signal intensity in the ONL and time were assessed using Prism (GraphPad Software, San Diego, CA).

Results

Using the MEMRI technique on 1.5, 3, 5, and 10-month old rTg4510 mice and littermate controls, we found significant axonal transport deficits present in the rTg4510 mice beginning at 3 months of age in an age-dependent manner. Using linear regression analysis, we measured rates of axonal transport at 1.5, 3, 5, and 10 months of age in rTg4510 and WT mice. Axonal transport rates were observed in rTg4510 mice at 48% of WT levels at 3 months, 40% of WT levels at 5 months, and 30% of WT levels at 10 months of age. In order to determine the point at which tau appears in the cortex, we probed for phosphorylated tau levels, and found that pSer262 is present at 3 months of age, not earlier at 1.5 months of age, but observed no pathological tau species until 6 months of age, months after the onset of the transport deficits. In addition, we saw localization of tau in the ONL at 6 months of age.

Discussion

In our study, we identified the presence of age-dependent axonal transport deficits beginning at 3 months of age in rTg4510 mice. We correlated these deficits at 3 months to the presence of hyperphosphorylated tau in the brain and the presence within the olfactory epithelium. We observed tau pathology not only in the soma of these neurons but also within the axons and processes of these neurons. Our characterization of axonal transport in this tauopathy model provides a functional time point that can be used for future therapeutic interventions.

•

We used MEMRI to define axonal transport rate changes in the rTg4510 mouse.

•

We observed significant hyperphosphorylated tau starting at 3 months of age.

•

We found an age-dependent decline in axonal transport rates.

•

Declines in axonal transport correlated with increases in hyperphosphorylated tau.

Neuroimaging in dementia

Over the last few years, advances in neuroimaging have generated biomarkers, which increase diagnostic certainty, provide valuable information about prognosis, and suggest a particular pathology underlying the clinical dementia syndrome. We aim to review the evidence for use of already established imaging modalities, along with selected techniques that have a great potential to guide clinical decisions in the future. We discuss structural, functional and molecular imaging, focusing on the most common dementias: Alzheimer's disease, fronto-temporal dementia, dementia with Lewy bodies and vascular dementia. Finally, we stress the importance of conducting research using representative cohorts and in a naturalistic set up, in order to build a strong evidence base for translating imaging methods for a National Health Service. If we assess a broad range of patients referred to memory clinic with a variety of imaging modalities, we will make a step towards accumulating robust evidence and ultimately closing the gap between the dramatic advances in neurosciences and meaningful clinical applications for the maximum benefit of our patients.

Art and the brain: a view from dementia

OBJECTIVE

Art making encompasses a range of perceptual and cognitive functions involving widely distributed brain systems. The dementias impact on these systems in different ways, raising the possibility that each dementia has a unique artistic signature.

DESIGN

Here we use a review of the visual art of 14 artists with dementia (five Alzheimer's disease, seven fronto-temporal dementia and two dementia with Lewy bodies) to further our understanding of the neurobiological constituents of art production and higher artistic function.

RESULTS

Artists with Alzheimer's disease had prominent changes in spatial aspects of their art and attributes of colour and contrast. These qualities were preserved in the art of fronto-temporal dementia, which was characterised by perseverative themes and a shift towards realistic representation. The art of dementia with Lewy Bodies was characterised by simple, bizarre content.

CONCLUSIONS

The limitations of using visual aspects of individual artworks to infer the impact of dementia on art production are discussed with the need for a wider perspective encompassing changes in cognition, emotion, creativity and artistic personality. A novel classificatory scheme is presented to help characterise neural mechanisms of higher artistic functions in future studies.