Tau-negative Frontotemporal Lobar Degeneration Research Articles

TDP-43-associated atrophy in brains with and without frontotemporal lobar degeneration

Transactive response DNA-binding protein of ∼43 kDa (TDP-43), a primary pathologic substrate in tau-negative frontotemporal lobar degeneration (FTLD), is also often found in the brains of elderly individuals without FTLD and is a key player in the process of neurodegeneration in brains with and without FTLD. It is unknown how rates and trajectories of TDP-43-associated brain atrophy compare between these two groups. Additionally, non-FTLD TDP-43 inclusions are not homogeneous and can be divided into two morphologic types: type-α and neurofibrillary tangle-associated type-β. Therefore, we explored whether neurodegeneration also varies due to the morphologic type. In this longitudinal retrospective study of 293 patients with 843 MRI scans spanning over ∼10 years, we used a Bayesian hierarchical linear model to quantify similarities and differences between the non-FTLD TDP-43 (type-α/type-β) and FTLD-TDP (n = 68) in both regional volume at various timepoints before death and annualized rate of atrophy. Since Alzheimer’s disease (AD) is a frequent co-pathology in non-FTLD TDP-43, we further divided types α/β based on presence/absence of intermediate-high likelihood AD: AD-TDP type-β (n = 90), AD-TDP type-α (n = 104), and Pure-TDP (n = 31, all type-α). FTLD-TDP was associated with faster atrophy rates in the inferior temporal lobe and temporal pole compared to all non-FTLD TDP-43 groups. The atrophy rate in the frontal lobe was modulated by age with younger FTLD-TDP having the fastest rates. Older FTLD-TDP showed a limbic predominant pattern of neurodegeneration. AD-TDP type-α showed faster rates of hippocampal atrophy and smaller volumes of amygdala, temporal pole, and inferior temporal lobe compared to AD-TDP type-β. Pure-TDP was associated with slowest rates and less atrophy in all brain regions. The results suggest that there are differences and similarities in longitudinal brain volume loss between FTLD-TDP and non-FTLD TDP-43. Within FTLD-TDP age plays a role in which brain regions are the most affected. Additionally, brain atrophy regional rates also vary by non-FTLD TDP-43 type.

Als and Ftd: Insights into the disease mechanisms and therapeutic targets

Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) are neurodegenerative disorders, related by signs of deteriorating motor and cognitive functions, and short survival. The causes are still largely unknown and no effective treatment currently exists. It has been shown that FTLD may coexist with ALS. The overlap between ALS and frontotemporal dementia (FTD), the clinical syndrome associated with FTLD, occurs at clinical, genetic, and pathological levels. The hallmark proteins of the pathognomonic inclusions are SOD-1, TDP-43 or FUS, rarely the disease is caused by mutations in the respective genes. Frontotemporal lobar degenerations (FTLD) is genetically, neuropathologically and clinically heterogeneous and may present with behavioural, language and occasionally motor disorder, respectively. Almost all cases of ALS, as well as tau-negative FTLD share a common neuropathology, neuronal and glial inclusion bodies containing abnormal TDP-43 protein, collectively called TDP-43 proteinopathy. Recent discoveries in genetics (e.g. C9orf72 hexanucleotide expansion) and the subsequent neuropathological characterization have revealed remarkable overlap between ALS and FTLD-TDP indicating common pathways in pathogenesis. For ALS, an anti-glutamate agent riluzole may be offered to slow disease progression (Level A), and a promising molecule, arimoclomol, is currently in clinical trials. Other compounds, however, are being trailed and some have shown encouraging results. As new therapeutic approaches continue to emerge by targeting SOD1, TDP-43, or GRN, we present some advances that are being made in our understanding of the molecular mechanisms of these diseases, which together with gene and stem cell therapies may translate into new treatment options.

FTLD-TDP-43 AND FTLD-FUS

Frontotemporal lobar degeneration (FTLD) is a neurodegenerative disease, which is now classified to three major molecular subgroups based on histopathological findings: FTLD-tau, FTLD-TDP-43, or FTLD-FUS. Before the discovery of TDP-43 in 2006, most tau-negative FTLD cases were collectively termed FTLD-U, and subsequently the majority of FTLD-U cases were in fact FTLD-TDP-43. In 2009, FUS was identified as one of the genes for familial ALS, and consequently most tau-negative and TDP-43-negative FTLD inclusions were found to be FUS-positive. Both TDP-43 and FUS are DNA/RNA-binding protein and alterations in RNA processing have been suggested in the pathogenesis, however the molecular mechanisms are still unclear. One of the common neuropathological features of FTLD including FTLD-tau is that these proteins are accumulated as inclusions in the nucleus and cytoplasm of both neuronal and glial cells. Recent reports suggest that these proteins are aggregation-prone and form amyloid-like or hydrogel aggregates. We investigated TDP-43 aggregation in cells by expressing various deletion mutants of TDP-43 and studied about the properties of synthetic peptides in the responsible region. We also investigated biochemical and prion-like properties of the abnormal TDP-43 in FTLD and ALS brains. We found that the region between 274 and 373 are responsible for aggregation of TDP-43. Synthetic TDP peptides 274–313 and 314–353 formed amyloid-like fibrils, and the trunsduction of these peptide fibrils into culture cells converted normal TDP-43 into aggregates with different C-terminal fragments of TDP-43 and different trypsin-resistant bands. We also analysed the trypsin-resistant bands of TDP-43 in FTLD and ALS by mass spectrometry, and found that the trypsin-resistant regions of FTLD and ALS are different. In addition, trunsduction of these pathological TDP-43 from brains of patients into cells induced TDP-43 aggregation. The results suggested that spreading of prion-like abnormal TDP-43 may account for the pathogenesis and progression of FTLD-TDP-43.

Proteomic analyses reveal that loss of TDP-43 affects RNA processing and intracellular transport

Transactive response DNA-binding protein 43 (TDP-43) is a predominantly nuclear, ubiquitously expressed RNA and DNA-binding protein. It recognizes and binds to UG repeats and is involved in pre-mRNA splicing, mRNA stability and microRNA metabolism. TDP-43 is essential in early embryonic development but accumulates in cytoplasmic aggregates in amyotrophic lateral sclerosis (ALS) and tau-negative frontotemporal lobar degeneration (FTLD). It is not known yet whether cytoplasmic aggregates of TDP-43 are toxic or protective but they are often associated with a loss of TDP-43 from the nucleus and neurodegeneration may be caused by a loss of normal TDP-43 function or a gain of toxic function. Here we present a proteomic study to analyze the effect of loss of TDP-43 on the proteome. MS data are available via ProteomeXchange with identifier PXD001668. Our results indicate that TDP-43 is an important regulator of RNA metabolism and intracellular transport. We show that Ran-binding protein 1 (RanBP1), DNA methyltransferase 3 alpha (Dnmt3a) and chromogranin B (CgB) are downregulated upon TDP-43 knockdown. Subsequently, transportin 1 level is increased as a result of RanBP1 depletion. Improper regulation of these proteins and the subsequent disruption of cellular processes may play a role in the pathogenesis of the TDP-43 proteinopathies ALS and FTLD.

Differential diagnosis of amyotrophic lateral sclerosis from Guillain–Barré syndrome by quantitative determination of TDP-43 in cerebrospinal fluid

The aim of this study was to investigate whether an increased level of TAR DNA-binding protein 43 (TDP-43) in the cerebrospinal fluid (CSF) could be a biomarker for amyotrophic lateral sclerosis (ALS) and facilitate differential diagnosis of ALS from peripheral motor neuropathy. TDP-43 is the major constituent of neuronal and glial inclusions that neuropathologically characterize both ALS and tau-negative frontotemporal lobar degeneration. Recent discoveries of various missense mutations in the TDP-43 gene in familial ALS indicate a pivotal role of the aberrant accumulation of TDP-43 in neurodegeneration. Increased TDP-43 in the CSF could be a hallmark of ALS and other TDP-43 proteinopathy. Sandwich enzyme-linked immunosorbent assay (ELISA) was established to measure the concentration of TDP-43 in biological fluids. Culture supernatants of cells transfected with various TDP-43 constructs were used to confirm that the ELISA detected TDP-43. TDP-43 in the culture supernatant of TDP-43 transfected cells was detected by immunoprecipitation with subsequent immunoblotting and concentrations were successfully measured by sandwich ELISA. We then measured TDP-43 concentrations in the CSF of patients with ALS and Guillain–Barré syndrome (GBS). TDP-43 concentrations in CSF were significantly higher in ALS than in GBS (p = 0.016). The sensitivity of the diagnostic test was 71.4% and the specificity was 84.6%. Quantitative determination of TDP-43 concentrations in the CSF by sandwich ELISA is a potential laboratory test for differentiating ALS from peripheral motor neuropathies such as GBS.

Synaptic changes in frontotemporal lobar degeneration: correlation with MAPT haplotype and APOE genotype

This immunohistochemical study quantified synaptic changes (synaptophysin and SNAP-25) in the frontal lobe of subjects with frontotemporal lobar degeneration (FTLD) and Alzheimer's disease (AD), and related these to APOE genotype and MAPT haplotype. Frontal neocortex (BA9) of post mortem brains from subjects with FTLD (n = 20), AD (n = 10) and age-matched controls (n = 9) were studied immunohistochemically for synaptophysin and SNAP-25. We report that patients with FTLD have a significant increase in synaptophysin and depletion in SNAP-25 proteins compared to both control subjects and individuals with AD (P < 0.001). The FTLD up-regulation of synaptophysin is disease specific (P < 0.0001), and is not influenced by age (P = 0.787) or cortical atrophy (P = 0.248). The SNAP-25 depletion is influenced by a number of factors, including family history and histological characteristics of FTLD, APOE genotype, MAPT haplotype and gender. Thus, more profound loss of SNAP-25 occurred in tau-negative FTLD, and was associated with female gender and lack of family history of FTLD. Presence of APOEε4 allele and MAPT H2 haplotype in FTLD had a significant influence on the expression of synaptic proteins, specifically invoking a decrease in SNAP-25. Our results suggest that synaptic expression in FTLD is influenced by a number of genetic factors which need to be taken into account in future neuropathological and biochemical studies dealing with altered neuronal mechanisms of the disease. The selective loss of SNAP-25 in FTLD may be closely related to the core clinical non-cognitive features of the disease.

Cerebrospinal fluid biomarker results in relation to neuropathological dementia diagnoses

Background Clinical dementia diagnoses are not always consistent with neuropathological findings. As correct diagnosis is important for treatment and care, new diagnostic possibilities for dementia are in demand. Cerebrospinal fluid biomarkers should ideally be able to identify ongoing processes in the brain, but need to be further compared with neuropathological findings for evaluation of their diagnostic validity. Methods This study included 43 patients with a clinical dementia disorder. All patients were neuropathologically examined at the University Hospital in Lund, Sweden, during the years 2001-2008, and all had a lumbar puncture carried out as part of the clinical investigation during the time of cognitive impairment. Results Of eight patients, five with Alzheimer's disease had elevated total tau protein (T-tau) and decreased amyloid beta 1-42 protein (Aβ42), while both values for the other three patients were normal. Slightly elevated T-tau and/or decreased Aβ42 were also seen in several patients with other dementia diagnoses such as Lewy body disease, frontotemporal lobar degeneration and vascular dementia. Furthermore, T-tau levels did not differ markedly between patients with morphologically tau-positive and tau-negative frontotemporal lobar degeneration. Also, seven of nine patients with Creutzfeldt-Jacob disease exhibited pronounced elevation in T-tau concentration. Conclusion From this rather limited study, being the first of its kind in Sweden, we may conclude that there is no perfect concordance between cerebrospinal fluid biomarker levels and pathological findings, which should be taken into account in the clinical diagnostic setting.

Global Analysis of TDP-43 Interacting Proteins Reveals Strong Association with RNA Splicing and Translation Machinery

TDP-43 is a highly conserved and ubiquitously expressed member of the heterogeneous nuclear ribonucleoprotein (hnRNP) family of proteins. Recently, TDP-43 was shown to be a major disease protein in the ubiquitinated inclusions characteristic of most cases of amyotrophic lateral sclerosis (ALS), tau-negative frontotemporal lobar degeneration (FTLD), and inclusion body myopathy. In these diseases, TDP-43 is redistributed from its predominantly nuclear location to ubiquitin-positive, cytoplasmic foci. The extent to which TDP-43 drives pathophysiology is unknown, but the identification of mutations in TDP-43 in familial forms of ALS and FTLD-U suggests an important role for this protein in pathogenesis. Little is known about TDP-43 function and only a few TDP-43 interacting proteins have been previously identified, which makes further insight into both the normal and pathological functions of TDP-43 difficult. Here we show, via a global proteomic approach, that TDP-43 has extensive interaction with proteins that regulate RNA metabolism. Some interactions with TDP-43 were found to be dependent on RNA-binding, whereas other interactions are RNA-independent. Disease-causing mutations in TDP-43 (A315T and M337V) do not alter its interaction profile. TDP-43 interacting proteins largely cluster into two distinct interaction networks, a nuclear/splicing cluster and a cytoplasmic/translation cluster, strongly suggesting that TDP-43 has multiple roles in RNA metabolism and functions in both the nucleus and the cytoplasm. Finally, we found numerous TDP-43 interactors that are known components of stress granules, and indeed, we find that TDP-43 is also recruited to stress granules.

TDP-43 and frontotemporal dementia

TAR DNA-binding protein of about 43 kDa (TDP-43) is the main ubiquitinated peptide in tau-negative frontotemporal lobar degeneration (FTLD). TDP-43 is typically a nuclear protein, and its aggregation and cytoplasmic translocation are thought to represent major steps in the pathogenesis of FTLD due to TDP-43 proteinopathy (FTLD-TDP). Certain clinical syndromes of frontotemporal dementia are preferentially associated with pathologic findings of FTLD-TDP, and TDP-43 pathology represents the connection between FTLD-TDP and amyotrophic lateral sclerosis. Recent advances in clinical, genetic, and pathologic studies of FTLD-TDP and amyotrophic lateral sclerosis have shed light on the potentially pathogenic role of TDP-43 and identified TDP-43 itself as a candidate biomarker for antemortem diagnosis of FTLD-TDP.

Evaluation of subcortical pathology and clinical correlations in FTLD-U subtypes

Frontotemporal lobar degeneration (FTLD) can be classified as tau-positive (FTLD-tau) and tau-negative FTLD. The most common form of tau-negative FTLD is associated with neuronal inclusions that are composed of TAR DNA-binding protein 43 (TDP-43) (FTLD-TDP). Recent evidence suggests that FTLD-TDP can be further subdivided into at least three major histologic variants based on patterns of TDP-43 immunoreactive neuronal cytoplasmic inclusions (NCI) and dystrophic neurites (DN) in neocortex and hippocampus. The aim of this study was to extend the histologic analysis to other brain regions and to determine if there were distinct clinical and pathologic characteristics of the FTLD-TDP subtypes. Thirty-nine FTLD-TDP cases were analyzed (Mackenzie type 1 n = 24, Mackenzie type 2 n = 9, Mackenzie type 3 n = 6). There was a highly significant association between clinical syndrome and FTLD-TDP subtype, with progressive non-fluent aphasia associated with type 1, semantic dementia with type 2, and behavioral variant frontotemporal dementia with types 1, 2 and 3. Semi-quantitative analysis of NCI and DN demonstrated different patterns of involvement in cortical, subcortical and brainstem areas that were characteristic for each of the three types of FTLD-TDP. Type 1 had a mixture of NCI and DN, as well as intranuclear inclusions in most cases and TDP-43 pathology at all levels of the neuraxis, but less in brainstem than supratentorial structures. Type 2 cases were characterized by predominance of long, thick DN in the cortex, as well as numerous NCI in hippocampus, amygdala and basal ganglia, but virtually no NCI and only sparse DN in diencephalon and brainstem. Type 3 had a paucity of DN at all levels of the neuraxis and significantly more NCI in the hypoglossal nucleus than the other types. These findings extend previously described clinicopathological associations of FTLD-TDP subtypes and support the notion that FTLD-TDP subtypes may be distinct clinicopathologic disorders.

Frontotemporal lobar degeneration with ubiquitin-positive, but TDP-43-negative inclusions

Frontotemporal lobar degeneration (FTLD) can be pathologically subdivided into tau-positive and tau-negative types. The most common tau-negative variant is FTLD with ubiquitin-immunoreactive lesions (FTLD-U). Recently, the TAR DNA binding protein 43 (TDP-43) was identified in neuronal inclusions in FTLD-U. After applying TDP-43 immunohistochemistry to a series of 44 cases of FTLD-U with no secondary pathology, three cases (7%) were identified with ubiquitin- and p62-positive neuronal cytoplasmic inclusions (NCI) that were negative for TDP-43. All the three cases had marked brain atrophy with striking atrophy of the striatum. Cases 1 and 2 presented at ages 43 and 38, respectively, as behavioral variant frontotemporal dementia (1 with positive family history) and had ubiquitin- and p62-positive NCI in frontotemporal neocortex and dentate granule cells of the hippocampus. Case 3 presented with the corticobasal syndrome. Unlike the other two cases, ubiquitin- and p62-positive NCI were also visible on hematoxylin and eosin stain. There were no neuronal intranuclear inclusions. Electron microscopic examination of the NCI in cases 2 and 3 revealed granulofilamentous inclusions. These cases confirm the existence of TDP-43-negative FTLD-U and extend the clinical and pathological spectrum of this disorder. The findings raise the possibly of an as yet identified protein that may play a pathogenic role in tau-negative FTLD.

Longitudinal decline in autopsy-defined frontotemporal lobar degeneration

The natural history of patients with pathologically proven frontotemporal lobar degeneration (FTLD) is important from clinical and biologic perspectives, but is not well documented quantitatively. We examine longitudinal decline in cognitive functioning in an autopsy-proven cohort of patients with the clinical diagnosis of a FTLD spectrum disorder or FTLD pathology using a panel of neuropsychological measures. Patients are categorized according to findings at autopsy into tau-positive FTLD, tau-negative FTLD, and frontal variant-Alzheimer disease (fvAD) subgroups. Patients decline significantly over time on all neuropsychological measures. Moreover, several measures differentiate between histopathologically distinct subgroups throughout the course of the disease process. This includes a significant double dissociation involving relative difficulty on a visual constructional measure in tau-positive patients compared to relatively impaired visual confrontation naming in tau-negative patients. Longitudinal measures of FAS naming fluency and animal naming fluency also distinguish tau-positive patients and tau-negative patients with FTLD from patients with fvAD. Other measures show significant decline but do not distinguish between histopathologic groups longitudinally. Our findings suggest different longitudinal patterns of cognitive decline in pathologically defined subgroups of patients. Measures consistently distinguishing between patient subgroups can be used to bolster diagnostic accuracy throughout the course of these diseases, while measures demonstrating undifferentiated longitudinal decline may serve as useful endpoints in treatment trials.

Tau Negative FTLD Without Abnormal TDP‐43 Immunoreactivity

Objective: To determine whether all cases of tau‐negative frontotemporal lobar degeneration (FTLD) show abnormal TDP‐43 immunoreactivity.Design/methods: The neuropathological database at Mayo Clinic, Florida, was queried to identify all cases of tau‐negative FTLD. Forty cases were identified that underwent analysis with TDP‐43 immunohistochemistry. Cases without abnormal TDP‐43 immunoreactivity were further analyzed with H&amp;E, PAS and silver stains, and with immunohistochemistry for phosphorylated tau, alpha‐synuclein, ubiquitin, neurofilament, alpha‐internexin and p62.Results: Of the 40 cases, 3 did not show abnormal TDP‐43 immunoreactivity. Cases 1 and 3 had clinical features of behavioral variant FTD while case 2 had features of the corticobasal syndrome. Case 3 had a positive family history. Case 1 had a pathological diagnosis of dementia lacking distinctive histology (DLDH) and case 2 basophilic inclusion body disease. Case 3 had ubiquitin‐positive but TDP‐43 negative neuronal inclusions and dystrophic neurites.Conclusion: Not all cases of tau‐negative FTLD have abnormal TDP‐43 immunoreactivity; basophilic inclusion body disease and DLDH are rare examples that do not. Given the positive family history and histological findings in case 3, there likely exists a yet to be identified gene and protein associated with tau negative FTLD.

Missense Mutations in the Progranulin Gene Linked to Frontotemporal Lobar Degeneration with Ubiquitin-immunoreactive Inclusions Reduce Progranulin Production and Secretion

Loss of function mutations in progranulin cause tau-negative frontotemporal lobar degeneration with ubiquitin-positive inclusions. A major protein component of these inclusions is TDP-43, which becomes hyperphosphorylated, ubiquitinated, and cleaved to generate C-terminal fragments, which apparently translocate from nuclei to the cytoplasm. Most progranulin mutations are nonsense mutations resulting in nonsense-mediated mRNA decay and consequently reduced progranulin protein levels. However, some missense mutations are described that occur within the signal sequence and mature progranulin. We now demonstrate that a progranulin mutation located within the signal sequence (PGRN A9D) results in cytoplasmic missorting with extremely low expression. In contrast, two other progranulin mutations (PGRN P248L and R432C) are expressed as immature proteins but are inefficiently transported through and partially degraded within the secretory pathway, resulting in a significantly reduced secretion. Thus apparently all progranulin mutations cause reduced protein expression or secretion, although by different cellular mechanisms. To investigate a putative relationship between reduced expression of progranulin and TDP-43 relocalization and deposition, we down-regulated progranulin in human cell lines and in zebrafish. Upon reduction of progranulin, neither a major redistribution of TDP-43 nor proteolytic processing to disease-characterizing C-terminal fragments could be observed.

Clinical Features of Pathologic Subtypes of Behavioral-Variant Frontotemporal Dementia

To identify clinical features in behavioral-variant frontotemporal dementia that may help predict tau-positive pathology. Clinical and historical features of patients with pathologically confirmed tau-positive and tau-negative frontotemporal lobar degeneration from 1970 to 2006 were retrospectively reviewed in a blinded fashion. The initial clinical features of those patients who eventually met consensus criteria for frontotemporal dementia were examined using univariate and cluster analyses to explore characteristics that may be associated with tau pathology. Fifty-six patients (24 tau-positive cases) were included in the analysis. There was no difference in demographics between the tau-positive and tau-negative cases. Univariate analysis showed that poor planning and/or judgment was more commonly associated with tau-positive pathology (P = .03). Cluster analysis using behavioral characteristics identified 2 groups of patients: cluster 1 contained mainly tau-positive cases (57%) and cluster 2 was mostly tau-negative cases (71%). Poor planning and/or judgment was a common presenting sign in the first group (P < .001), while the second group was more likely to present with impaired regulation of personal conduct (P < .001) and a decline in personal hygiene (P = .005). Poor planning and/or judgment was associated with behavioral-variant frontotemporal dementia patients who had tau-positive pathology. The constellation of impaired personal conduct and a paucity of dysexecutive symptoms identified tau-negative patients.

Increase in the relative expression of tau with four microtubule binding repeat regions in frontotemporal lobar degeneration and progressive supranuclear palsy brains

Some cases of familial frontotemporal dementia (FTD) leading to frontotemporal lobar degeneration (FTLD) are caused by mutations in tau on chromosome 17 (FTDP-17). Certain mutations alter the ratio between four (4R tau) and three (3R tau) repeat tau isoforms whereas cases with progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) mainly have 4R tau brain pathology. We assessed tau mRNA and protein levels in frontal cortex from 15 sporadic FTLD, 21 PSP, 5 CBD, 15 Alzheimer's disease (AD) and 16 control brains. Moreover, we investigated the disease association and possible tau splicing effects of the tau H1 haplotype. Cases with FTLD and PSP had lower tau mRNA levels than control brains. When analyzing 4R tau and 3R tau mRNA separately, control subjects displayed a 4R tau/3R tau ratio of 0.48. Surprisingly, FTLD brains displayed a more elevated ratio (1.32) than PSP brains (1.12). Also, several FTLD and PSP cases had higher 4R tau/3R tau mRNA than FTDP-17 cases, included as reference tissues, and the ratio increase was seen regardless of underlying histopathology, i.e. both for tau-positive and tau-negative FTLD cases. Furthermore, total tau protein levels were slightly decreased in both FTLD and AD as compared to control subjects. Finally, we confirmed the association of tau H1 with PSP, but could not find any haplotype-related effect on tau exon 10 splicing. In conclusion, we demonstrated increased but largely variable 4R tau/3R tau mRNA ratios in FTLD and PSP cases, suggesting heterogeneous pathophysiological processes within these disorders.

Hippocampal sclerosis in tau-negative frontotemporal lobar degeneration

Tau-negative frontotemporal lobar degeneration (FTLD) can be divided into those with motor neuron disease (FTLD-MND), and those without MND, but with ubiquitin-immunoreactive neuronal inclusions (FTLD-U). Some authors group FTLD-U and FTLD-MND together as tau-negative FTLD, but others separate them on the basis of clinical, pathologic and imaging differences. In 103 cases of pathologically confirmed, tau-negative FTLD (FTLD-MND and FTLD-U), we assessed the frequency of hippocampal sclerosis defined as neuronal loss in the subicular or CA1 regions of the hippocampus. The subjects in the FTLD-U group were older at death and had longer disease duration. After adjusting for age at death and disease duration, we found a significant difference in the frequency of hippocampal sclerosis in the FTLD-U group (79%) compared to FTLD-MND group (26%) ( p = 0.02). The difference in frequency of HpScl in FTLD-U compared to FTLD-MND is further evidence that they are separate clinicopathologic entities.

A Belgian ancestral haplotype harbours a highly prevalent mutation for 17q21-linked tau-negative FTLD

Among patients with frontotemporal lobar degeneration (FTLD), the respective frequencies of dominant 17q21-linked tau-negative FTLD (with unidentified molecular defect) and 17q21-linked tau-positive FTLD (due to MAPT mutations) remain unknown. Here, in a series of 98 genealogically unrelated Belgian FTLD patients, we identified an ancestral 8 cM MAPT containing haplotype in two patients belonging to multiplex families DR2 and DR8, without demonstrable MAPT mutations, in which FTLD was conclusively linked to 17q21 [maximum summed log of the odds (LOD) score of 5.28 at D17S931]. Interestingly, the same DR2-DR8 ancestral haplotype was observed in five additional familial FTLD patients, indicative of a founder effect. In the FTLD series, the DR2-DR8 ancestral haplotype explained 7% (7 out of 98) of FTLD and 17% (7 out of 42) of familial FTLD and was seven times more frequent than MAPT mutations (1 out of 98 or 1%). Clinically, DR2-DR8 haplotype carriers presented with FTLD often characterized by language impairment, and in one carrier the neuropathological diagnosis was FTLD with rare tau-negative ubiquitin-positive inclusions. Together, these results strongly suggest that the DR2-DR8 founder haplotype at 17q21 harbours a tau-negative FTLD causing mutation that is a much more frequent cause of FTLD in Belgium than MAPT mutations.

January 10 Highlights

Josephs et al. studied 127 cases of autopsy-confirmed frontotemporal lobar degeneration (FTLD), corticobasal degeneration (CBD), and progressive supranuclear palsy (PSP). They found that the prediction of tau-positive pathology from a CSD or PSP-like presentation was good, while the FTD-MND syndrome predicted motor neuron degeneration (MND). PSP and CBD accounted for most cases classified as progressive non-fluent aphasia. Frontal variant FTD was unpredictable in terms of its biochemistry. see page 41 Whitwell et al. studied two variants of tau-negative frontotemporal lobar degeneration and demonstrated a localized pattern of frontal lobe atrophy in cases with motor neuron degeneration, distinct from those without. see page 102 The editorial by Paul G. Ince and John C. Morris discusses these two articles from the Mayo Clinic which address clinical issues in the diagnosis of disorders …

Survival in two variants of tau-negative frontotemporal lobar degeneration: FTLD-U vs FTLD-MND

Pathologic diagnoses in frontotemporal lobar degeneration (FTLD) include tau-positive FTLD and tau-negative FTLD. Two variants of tau-negative FTLD are FTLD with motor neuron disease (FTLD-MND) and FTLD with motor neuron disease type inclusions but without motor neuron disease (FTLD-U). An analysis of patient outcomes in these cases reveals that FTLD-MND has significantly shorter survival than FTLD-U, suggesting that FTLD-MND is a more aggressive disease process.