Altered localization and functionality of TAR DNA Binding Protein 43 (TDP-43) in niemann- pick disease type C.

Niemann-Pick type C (NPC) disease is a lysosomal storage disorder characterized by the occurrence of visceral and neurological symptoms. At present, the molecular mechanisms causing neurodegeneration in this disease are unknown. Here we report the altered expression and/or mislocalization of the TAR-DNA binding protein 43 (TDP-43) in both NPC mouse and in a human neuronal model of the disease. We also report the neuropathologic study of a NPC patient's brain, showing that while TDP-43 is below immunohistochemical detection in nuclei of cerebellar Purkinje cells, it has a predominant localization in the cytoplasm of these cells. From a functional point of view, the TDP-43 mislocalization, that occurs in a human experimental neuronal model system, is associated with specific alterations in TDP-43 controlled genes. Most interestingly, treatment with N-Acetyl-cysteine (NAC) or beta-cyclodextrin (CD) can partially restore TDP-43 nuclear localization. Taken together, the results of these studies extend the role of TDP-43 beyond the Amyotrophic lateral sclerosis (ALS)/frontotemporal dementia (FTD)/Alzheimer disease (AD) spectrum. These findings may open novel research/therapeutic avenues for a better understanding of both NPC disease and the TDP-43 proteinopathy disease mechanism.

Phenotypic variability in three families with valosin-containing protein mutation.

BACKGROUND AND PURPOSE: The phenotype of IBMPFD [inclusion body myopathy with Paget's disease of the bone and frontotemporal dementia (FTD)] associated with valosin-containing protein (VCP) mutation is described in three families. METHODS: Probands were identified based on a pathological diagnosis of frontotemporal lobar degeneration with TDP-43-positive inclusions type IV. VCP sequencing was carried out. Clinical data on affected family members were reviewed. RESULTS: Ohio family: four subjects presented muscle weakness and wasting. (One subject had both neuropathic and myopathic findings and another subject showed only evidence of myopathy. The etiology of weakness could not be ascertained in the remaining two subjects.) Two individuals also showed Parkinsonism (with associated FTD in one of the two). The proband's brain displayed FTLD-TDP type IV and Braak stage five Parkinson's disease (PD). A VCP R191Q mutation was found. Pennsylvania family: 11 subjects developed IBMPFD. Parkinsonism was noted in two mutation carriers, whilst another subject presented with primary progressive aphasia (PPA). A novel VCP T262A mutation was found. Indiana family: three subjects developed IBMPFD. FTD was diagnosed in two individuals and suspected in the third one who also displayed muscle weakness. A VCP R159C mutation was found. CONCLUSIONS: We identified three families with IBMPFD associated with VCP mutations. Clinical and pathological PD was documented for the first time in members of two families. A novel T262A mutation was found. One individual had PPA: an uncommon presentation of IBMPFD.

Hypertension and incident dementia in community-dwelling elderly Yoruba Nigerians.

OBJECTIVES: To investigate the relationship between hypertension and dementia incidence in community-dwelling elderly Yoruba (aged 70 years and above) because of sparse information on dementia and its risk factors in developing countries. MATERIALS AND METHODS: Community-based, prospective study of consenting elderly Yoruba using two-stage design. Blood pressure was measured during the baseline evaluation at 2001 and hypertension was defined as BP ≥ 140/90 mmHg. Diagnosis of dementia and normal cognition was by consensus using standard criteria. Non-demented subjects from the 2001 evaluation wave were re-evaluated during the 2004 and 2007 waves for dementia. Logistic regression was used to examine the association of baseline hypertension and incident dementia, after adjusting for age, gender, education, and histories of stroke and smoking. P-values <0.05 were considered significant. RESULTS: During the 6-year follow-up, 120 individuals developed dementia, while 1633 remained non-demented. The frequency of hypertension in the demented group was significantly higher than in the non-demented (70.0% vs 60.2%, P = 0.034). Baseline hypertension was a significant risk factor for dementia (OR = 1.52; 95% CI 1.01-2.30). Higher systolic, diastolic or pulse pressure was associated with increased risk (P < 0.05). Participants with diastolic BP ≥ 90 mmHg were at a significantly greater risk than those with readings below 70 mmHg (OR = 1.65; 95% CI 1.01-2.69). CONCLUSIONS: Hypertension was associated with increased risk of dementia in elderly Yoruba and its appropriate treatment may lower the risk.

Use of anticholinergics and the risk of cognitive impairment in an African American population.

BACKGROUND: Anticholinergic properties of certain medications often go unrecognized, and are frequently used by the elderly population. Few studies have yet defined the long-term impact of these medications on the incidence of cognitive impairment. METHODS: We report a 6-year longitudinal, observational study, evaluating 1,652 community-dwelling African American subjects over the age of 70 years who were enrolled in the Indianapolis-Ibadan Dementia Project between 2001 and 2007 and who had normal cognitive function at baseline. The exposure group included those who reported the baseline use of possible or definite anticholinergics as determined by the Anticholinergic Cognitive Burden scale. Our main outcome measure was the incidence of cognitive impairment, defined as either dementia or cognitive impairment not dementia, or poor performance on a dementia screening instrument during the follow-up period. RESULTS: At baseline, 53% of the population used a possible anticholinergic, and 11% used a definite anticholinergic. After adjusting for age, gender, educational level, and baseline cognitive performance, the number of definite anticholinergics was associated with an increased risk of cognitive impairment (odds ratio [OR] 1.46, 95% confidence interval [CI] 1.07-1.99; p = 0.02), whereas the number of possible anticholinergics at baseline did not increase the risk (OR 0.96, 95% CI 0.85-1.09; p = 0.55). The risk of cognitive impairment among definite anticholinergic users was increased if they were not carriers of the APOE epsilon4 allele (OR 1.77, 95% CI 1.03-3.05; p = 0.04). CONCLUSIONS: Limiting the clinical use of definite anticholinergics may reduce the incidence of cognitive impairment among African Americans.

Clinicopathologic features of frontotemporal dementia with progranulin sequence variation.

BACKGROUND: Frontotemporal lobar degeneration with ubiquitin-immunoreactive (ub-ir) inclusions (FTLD-U) has been associated with frontotemporal dementia (FTD) and ALS. Recently, mutations in Progranulin (PGRN), predicted to cause premature truncation of the PGRN coding sequence, were found in patients with inherited FTLD-U and ub-ir neuronal intranuclear inclusions (NII). OBJECTIVE: To describe clinical, pathologic, and genetic features of three FTD patients having either a family history of FTD (A.III.1 and B.II.1) or of ALS (C.III.1). METHODS: Patients underwent a single clinical assessment, MRI, and [(18)F]fluorodeoxyglucose PET brain scan. Neuropathologic examination and genetic analyses were carried out. RESULTS: Patients presented clinically with the behavioral variant of FTD. Language dysfunctions were marked with comprehension being particularly affected. Neuroimaging revealed frontotemporal atrophy and glucose hypometabolism, with predominant left-side involvement, in Patients A.III.1 and B.II.1. Subject C.III.1 displayed mild atrophy and symmetric anterior hypometabolism. All patients were neuropathologically diagnosed with FTLD-U. Ub-ir NII were noted in Patients A.III.1 and B.II.1 but were absent in Patient C.III.1. The following PGRN sequence variations were found: IVS6-2A-->G (A.III.1), R493X (B.II.1), and R433W (C.III.1). IVS6-2A-->G may lead to skipping of exon 7 with consequent frameshift of the coding sequence and premature termination of PGRN translation. CONCLUSIONS: We have found two PGRN mutations associated with FTD, in affected individuals who are members of families with possible autosomal dominant FTD. A third PGRN sequence variation (R433W) was found in an FTD patient with family history of ALS.

Comparison of extent of tau pathology in patients with frontotemporal dementia with Parkinsonism linked to chromosome 17 (FTDP-17), frontotemporal lobar degeneration with Pick bodies and early onset Alzheimer's disease.

In order to gain insight into the pathogenesis of frontotemporal lobar degeneration (FTLD), the mean tau load in frontal cortex was compared in 34 patients with frontotemporal dementia linked to chromosome 17 (FTDP-17) with 12 different mutations in the tau gene (MAPT), 11 patients with sporadic FTLD with Pick bodies and 25 patients with early onset Alzheimer's disease (EOAD). Tau load was determined, as percentage of tissue occupied by stained product, by image analysis of immunohistochemically stained sections using the phospho-dependent antibodies AT8, AT100 and AT180. With AT8 and AT180 antibodies, the amount of tau was significantly (P < 0.001 in each instance) less than that in EOAD for both FTDP-17 (8.5% and 10.0% respectively) and sporadic FTLD with Pick bodies (16.1% and 10.0% respectively). With AT100, the amount of tau detected in FTDP-17 was 54% (P < 0.001) of that detected in EOAD, but no tau was detected in sporadic FTLD with Pick bodies using this particular antibody. The amount of insoluble tau deposited within the brain in FTDP-17 did not depend in any systematic way upon where the MAPT mutation was topographically located within the gene, or on the physiological or structural change generated by the mutation, regardless of which anti-tau antibody was used. Not only does the amount of tau deposited in the brain differ between the three disorders, but the pattern of phosphorylation of tau also varies according to disease. These findings raise important questions relating to the role of aggregated tau in neurodegeneration - whether this represents an adaptive response which promotes the survival of neurones, or whether it is a detrimental change that directly, or indirectly, brings about the demize of the affected cell.

Slow wave and rem sleep mechanisms are differently altered in hereditary pick disease associated with the TAU G389R mutation.

Sleep disturbances are found in the course of most dementing syndromes. We report a longitudinal polysomnographic and 18FDG-PET study in a 38-year-old male with FTDP17 carrying the Tau gene mutation G389R. All-night sleep EEG and wake cerebral glucose metabolism at rest (eyes/ears covered) of the preceding day were studied twice, eight months (Night 1; PET 1) and sixteen months (Night 2; PET 2) after the initial neurological evaluation. The Night 1 study showed sleep fragmentation associated to a short REM latency and a severe reduction of slow wave sleep, with relatively preserved NREM-REM sleep cycles; daytime PET 1 revealed severe cerebral glucose metabolic reductions in frontal and temporal areas, with relative preservation of remaining cortical regions and subcortical structures. On Night 2, the total sleep time was less than 5 hours, delta sleep and REM latency remained shortened and only two sleep cycles could be identified; daytime PET 2 exam revealed a greater cortical metabolic impairment and an involvement of subcortical brain regions as compared to PET 1. Post-mortem neuropathological data showed severe neuronal loss, spongiosis and gliosis that were mostly marked in cortical layers I, II, V and VI. In vivo, neurometabolic and post-mortem neuropathological data are consistent with and indicative of a severe dysfunction of intra- and trans-hemispheric regional connectivity and of cortico-thalamic circuits. These findings suggest that the decreased cortical and subcortical connectivity may have been the main pathophysiological mechanism responsible for delta sleep reduction and the cognitive decline.

Clinical and genetic studies of families with the tau N279K mutation (FTDP-17).

The tau N279K mutation was identified in four separately ascertained families in the United States, Japan, and France and in another recently discovered affected individual in Japan. The authors analyzed genealogical and clinical records and DNA samples. Average age at onset was 43 years; survival time was 7 years. All families exhibited similar clinical features, with parkinsonism, dementia, and supranuclear palsy uniformly seen. A founder effect indicated by a shared disease haplotype was seen only in two Japanese families. The N279K mutation can develop independently in different parts of the world.

Biochemical characterization of a neuroserpin variant associated with hereditary dementia.

Neuroserpin isolated from inclusion bodies in the brain of a patient with a neurodegenerative disease was characterized biochemically. The protein consisted of residues 20 to 410 of the neuroserpin precursor deduced from its cDNA sequence indicating the entire molecule was deposited. A minor amount started with residue 19 of the precursor, and the carboxyl terminus was heterogeneous ending at residues 405, 407, 409, and 410. Arg was present at position 52. No normal Ser52 was found indicating that only mutant neuroserpin was present in the inclusion bodies. The three potential Asn glycosylation sites all contained carbohydrate. DNA sequence analysis of exons 2 to 9 of the neuroserpin gene in the proband showed the published normal neuroserpin sequence except for the presence of both adenine and cytosine at the first position of codon 52, that indicates heterozygosity for both the normal Ser(AGT) and variant Arg(CGT) at this position in the expressed protein. Restriction fragment length polymorphism analysis of a polymerase chain reaction product from exon 2 revealed the propositus and his affected sibling both were heterozygous for the mutation whereas 100 unaffected controls were negative. Chemical characterization of the variant neuroserpin will significantly enhance the understanding of this protein in both normal physiology and neurodegenerative diseases.

Ectopic white matter neurons, a developmental abnormality that may be caused by the PSEN1 S169L mutation in a case of familial AD with myoclonus and seizures.

We report clinical, neuropathologic and molecular genetic data from an individual affected by a familial Alzheimer disease (AD) variant. The proband had an onset of dementia at age 29 followed by generalized seizures a year later. He died at age 40. Neuropathologically, he had severe brain atrophy and characteristic histopathologic lesions of AD. Three additional neuropathologic features need to be emphasized: 1) severe deposition of Abeta in the form of diffuse deposits in the cerebral and cerebellar cortices, 2) numerous Abeta deposits in the subcortical white matter and in the centrum semiovale, and 3) numerous ectopic neurons, often containing tau-immunopositive neurofibrillary tangles, in the white maner of the frontal and temporal lobes. A molecular genetic analysis of DNA extracted from brain tissue of the proband revealed a S169L mutation in the Presenilin 1 (PSEN1) gene. The importance of this case lies in the presence of ectopic neurons in the white matter, early-onset seizures, and a PSEN1 mutation. We hypothesize that the PSEN1 mutation may have a causal relationship with an abnormality in neuronal development.

A novel member of the netrin family, beta-netrin, shares homology with the beta chain of laminin: identification, expression, and functional characterization.

The netrins are a family of laminin-related molecules. Here, we characterize a new member of the family, beta-netrin. beta-Netrin is homologous to the NH(2) terminus of laminin chain short arms; it contains a laminin-like domain VI and 3.5 laminin EGF repeats and a netrin C domain. Unlike other netrins, this new netrin is more related to the laminin beta chains, thus, its name beta-netrin. An initial analysis of the tissue distribution revealed that kidney, heart, ovary, retina, and the olfactory bulb were tissues of high expression. We have expressed the molecule in a eukaryotic cell expression system and made antibodies to the expressed product. Both in situ hybridization and immunohistochemistry were used to describe the cellular source of beta-netrin and where beta-netrin is deposited. beta-Netrin is a basement membrane component; it is present in the basement membranes of the vasculature, kidney, and ovaries. In addition, beta-netrin is expressed in a limited set of fiber tracts within the brain, including the lateral olfactory tract and the vomeronasal nerve. Functional studies were performed and show that beta-netrin promotes neurite elongation from olfactory bulb explants. Together, these data suggest that beta-netrin is important in neural, kidney, and vascular development.

[Neurodegenerative disease associated with a mutation of codon 279 (N279K) in exon 10 of Tau protein]. / Maladie neuro-dégénérative associée à une mutation du codon 279 (N279K) de l'exon 10 du gène de la protéine Tau.

Frontotemporal dementia and Parkinsonism linked to chromosome 17 (FTDP-17) are related to pathogenic mutations of the Tau gene. One of these, located at codon 279, results in an asparagine to lysine substitution. It was detected in three unrelated families from different origins. This mutation affects splicing, allowing exon 10 to be incorporated more frequently in the Tau transcripts, causing an abnormal preponderance of three-over four-repeat isoforms in soluble tau and the presence of the four-repeat isoforms in the insoluble tau. To better understand this newly described pathology, we analysed data from the three previously reported families. The American family, described as "pallido-ponto-nigral degeneration" is a large family which has been extensively studied (13 neuropathological studies). The Japanese family was initially presented as "pallidonigroluysian degeneration with iron deposition" and recently found to be related to N279 K mutation. We reported clinical, pathological and genetic data from the French family. Clinical particularities are ocular movements alterations with vertical supranuclear palsy, extrapyramidal signs (rigidity, dyskinesia, with atypical resting and postural tremor) and progressive dementia. Partial or no L-DOPA responsiveness is noted. These features led to discuss progressive supranuclear palsy, in some cases. There is no amyotrophy, nor any sensibility to neuroleptics, both signs being observed in other FTDP-17 syndromes. Neuropathology and immunohistochemistry confirm the presence of Tau immunolabeled inclusions, affecting mainly neurons in brain stem nuclei and glial cells in supratentorial white matter. Neuronal loss, which is moderate in frontal and temporal cortex, is severe in substantia nigra and globus pallidum. It is variable in other subcortical structures. In these structures, it is associated with iron deposition. This latter may participate in the degenerative process of cells and led to death in some specific neurons. The selectivity of neuronal death in hereditary diseases, when compared to data concerning sporadic neurodegenerative diseases which share similar clinical signs and neuropathological lesions, reinforces the hypothesis of an increased vulnerability of some neuronal populations which express specific sets of tau isoforms. Neurons particularly involved in these diseases express exclusively exon 10 + tau isoforms.

Early-onset Alzheimer disease caused by a new mutation (V717L) in the amyloid precursor protein gene.

CONTEXT: Alzheimer disease is the most common form of dementia. Mutations in the genes amyloid precursor protein (APP), presenilin 1(PS1) and presenilin 2(PS2) have been found in early-onset familial forms of Alzheimer disease OBJECTIVE: To determine the cause of dementia in a family with early-onset illness. DESIGN, SETTING, AND PARTICIPANTS: A family with a history of dementia was referred to the Indiana Alzheimer Disease Center, Indianapolis. All the research in this study was done in a university or university hospital. The proband and her 4 siblings took part in the study. The proband, who is still alive, showed symptoms of Alzheimer disease at 38 years of age. Genomic DNA was obtained from blood samples of 5 family members. The APPandPS1genes of the proband were screened for mutations by amplification followed by direct sequencing. RESULTS: Sequence of exon 17 of the APPgene revealed a single nucleotide (guanine to cytosine) substitution in 1 allele, resulting in an amino acid change at codon 717 (valine to leucine). Each of the proband's siblings were tested for this mutation by direct sequencing. Two of the 4 were found to have the mutation; one of whom was recently clinically diagnosed at the age of 36 years. CONCLUSIONS: A novel mutation in the APPgene (V717L) has been found in a family with a history of dementia, beginning in the mid to late 30s. The age of onset in this family is earlier than most of the other families with Alzheimer disease who also have APPmutations. Arch Neurol. 2000.

Progress in hereditary tauopathies: a mutation in the Tau gene (G389R) causes a Pick disease-like syndrome.

We describe the clinical and pathologic phenotypes of the G389R mutation in exon 13 of the Tau gene. Progressive aphasia and memory disturbance are the initial signs and begin in the fourth or fifth decade of life, followed by apathy, indifference, hyperphagia, rigidity, pyramidal signs and dementia. Death occurs after two to five years. Magnetic resonance imaging and neuropathologic studies show frontal and temporal atrophy. Pick body-like and axonal filamentous inclusions found in the neocortex and subcortical white matter, respectively, are tau immunoreactive. Immunoblot analysis of sarkosyl-insoluble tau shows two major bands of 60 and 64 kDa that, upon dephosphorylation, resolve into four bands of three- and four-repeat isoforms. Isolated tau filaments are often straight and occasionally twisted. Recombinant mutant tau protein shows a reduced ability to promote microtubule assembly, suggesting that this may be the primary effect of the mutation. The present findings indicate that the G389R mutation in Tau can cause a dementia similar to that in Pick's disease.

Neuroserpin mutation S52R causes neuroserpin accumulation in neurons and is associated with progressive myoclonus epilepsy.

Mutations in the Neuroserpin gene have been reported to cause familial presenile dementia. We describe a new family in which the S52R Neuroserpin mutation is associated with progressive myoclonus epilepsy in 2 siblings. The proband presented myoclonus and epilepsy at age 24, his brother and mother presented a similar disorder when they were 25. A clinical diagnosis of progressive myoclonus epilepsy was made on the proband and his brother. Skin and liver biopsies did not reveal the presence of cytological alterations in the proband. His neurological status worsened over the subsequent 19 yr during which he became demented and had uncontrollable seizures. He died at 43 yr of age from aspiration pneumonia. Neuropathologically, eosinophilic bodies, which were positive for periodic acid-Schiff and immunoreactive with antibodies against human neuroserpin, were present in the perikarya and cell processes of the neurons. They were found in large numbers in the cerebral cortex and substantia nigra and to a lesser extent, in most subcortical gray areas, spinal cord, and dorsal root ganglia. By electron microscopy, the intracytoplasmic bodies were contained within the membranes of the rough endoplasmic reticulum. Occasionally neuroserpin immunopositivity was seen throughout the cytoplasm, even without the presence of well-defined bodies. Our study characterizes for the first time the neuropathologic phenotype associated with hereditary progressive myoclonus epilepsy caused by the S52R Neuroserpin mutation.

Presymptomatic Genetic Testing with an APP Mutation in Early-Onset Alzheimer Disease: A Descriptive Study of Sibship Dynamics.

Early-onset Alzheimer disease (AD) accounts for only 5% of all cases of Alzheimer disease. To date, mutations in three different genes, the Amyloid precursor protein (APP), Presenilin 1 (PS1), and Presenilin 2 (PS2), have been identified as causative in early-onset AD, making predictive testing possible. Predictive testing for early-onset Alzheimer disease is a relatively new phenomenon. This paper describes the process of identifying a new mutation in the APP gene associated with early-onset AD, notifying family members, and offering participation in research as well as predictive testing. The goal is to share the complexities of predictive testing in a sibship newly identified as being at risk for an adult-onset, incurable neurodegenerative disease.

Tau gene mutation G389R causes a tauopathy with abundant pick body-like inclusions and axonal deposits.

Exonic and intronic mutations in Tau cause familial neurodegenerative syndromes characterized by frontotemporal dementia and dysfunction of multiple cortical and subcortical circuits. Here we describe a G389R mutation in exon 13 of Tau. When 38 years old, the proband presented with progressive aphasia and memory disturbance, followed by apathy, indifference, and hyperphagia. Repeated magnetic resonance imaging showed the dramatic progression of cerebral atrophy. Positron emission tomography revealed marked glucose hypometabolism that was most severe in left frontal, temporal, and parietal cortical regions. Rigidity, pyramidal signs and profound dementia progressed until death at 43 years of age. A paternal uncle, who had died at 43 years of age, had presented with similar symptoms. The proband's brain showed numerous tau-immunoreactive Pick body-like inclusions in the neocortex and the fascia dentata of the hippocampus. In addition, large numbers of tau-positive filamentous inclusions were present in axons in the frontal, temporal, and parietal lobes. Immunoblot analysis of sarkosyl-insoluble tau showed 2 major bands of 60 and 64 kDa. Upon dephosphorylation, these bands resolved into 4 bands consisting of three- and four-repeat tau isoforms. Most isolated tau filaments were straight and resembled filaments found in Alzheimer disease and some frontotemporal dementias with tau mutations. A smaller number of twisted filaments was also observed. Biochemically, recombinant tau proteins with the G389R mutation showed a reduced ability to promote microtubule assembly, suggesting that this may be the primary effect of the mutation. Taken together, the present findings indicate that the G389R mutation in Tau can cause a dementing condition that closely resembles Pick's disease.

An olfactory sensory neuron line, odora, properly targets olfactory proteins and responds to odorants.

The site for interactions between the nervous system and much of the chemical world is in the olfactory sensory neuron (OSN). Odorant receptor proteins (ORPs) are postulated to mediate these interactions. However, the function of most ORPs has not been demonstrated in vivo or in vitro. For this and other reasons, we created a conditionally immortalized cell line derived from the OSN lineage, which we term odora. Odora cells, under control conditions, are phenotypically similar to the OSN progenitor, the globose basal cell. After differentiation, odora cells more closely resemble OSNs. Differentiated odora cells express neuronal and olfactory markers, including components of the olfactory signal transduction pathway. Unlike other cell lines, they also efficiently target exogenous ORPs to their surface. Strikingly, differentiated odora cells expressing ORPs respond to odorants, as measured by an influx of calcium. In particular, cells expressing one ORP demonstrate a specific response to only one type of tested odorant. Odora cells, therefore, are ideal models to examine the genesis and function of olfactory sensory neurons.

A mutation at codon 279 (N279K) in exon 10 of the Tau gene causes a tauopathy with dementia and supranuclear palsy.

Recently intronic and exonic mutations in the Tau gene have been found to be associated with familial neurodegenerative syndromes characterized not only by a predominantly frontotemporal dementia but also by the presence of neurological signs consistent with the dysfunction of multiple subcortical neuronal circuitries. Among families, the symptomatology appears to vary in quality and severity in relation to the specific Tau gene mutation and often may include parkinsonism, supranuclear palsies, and/or myoclonus, in addition to dementia. We carried out molecular genetic and neuropathological studies on two patients from a French family presenting, early in their fifth decade, a cognitive impairment and supranuclear palsy followed by an akinetic rigid syndrome and dementia. The proband died severely demented 7 years after the onset of the symptoms; currently, his brother is still alive although his disease is progressing. In both patients, we found a Tau gene mutation in exon 10 at codon 279, resulting in an asparagine to lysine substitution (N279K). Neuropathologically, widespread neuronal and glial tau accumulation in the cortex, basal ganglia, brain stem nuclei as well as in the white matter were the hallmark of the disease. These deposits were shown by immunohistochemistry and immunoelectron microscopy, using a battery of antibodies to phosphorylation-dependent and phosphorylation-independent epitopes present in multiple tau regions. In the neocortex, tau-immunopositive glial cells were more numerous than immunopositive neurons; the deeper cortical layers as well as the white matter adjacent to the cortex contained the largest amount of immunolabeled glial cells. In contrast, some brain stem nuclei contained more neurons with tau deposits than immunolabeled glial cells. The correlation of clinical, neuropathological and molecular genetic findings emphasize the phenotypic heterogeneity of diseases caused by Tau gene mutations. Furthermore, to test the effect of the N279K mutation and compare it with the effect of the P301L exon 10 mutation on alternative splicing of Tau exon 10, we used an exon amplification assay. Our results suggest that the N279K mutation affects splicing similar to the intronic mutations, allowing exon 10 to be incorporated more frequently in the Tau transcript.

Structure of tau exon 10 splicing regulatory element RNA and destabilization by mutations of frontotemporal dementia and parkinsonism linked to chromosome 17.

Coding region and intronic mutations in the tau gene cause frontotemporal dementia and parkinsonism linked to chromosome 17. Intronic mutations and some missense mutations increase splicing in of exon 10, leading to an increased ratio of four-repeat to three-repeat tau isoforms. Secondary structure predictions have led to the proposal that intronic mutations and one missense mutation destabilize a putative RNA stem-loop structure located close to the splice-donor site of the intron after exon 10. We have determined the three-dimensional structure of this tau exon 10 splicing regulatory element RNA by NMR spectroscopy. We show that it forms a stable, folded stem-loop structure whose thermodynamic stability is reduced by frontotemporal dementia and parkinsonism linked to chromosome 17 mutations and increased by compensatory mutations. By exon trapping, the reduction in thermodynamic stability is correlated with increased splicing in of exon 10.