Frontotemporal lobar degeneration (FTLD) with ubiquitin-positive, tau-negative inclusions, and linkage to chromosome 17 was recently found to be caused by mutations in the progranulin (PGRN) gene. In this study, we screened a group of 51 FTLD patients for PGRN mutations and identified a novel exon 6 splice donor site deletion (IVS6+5_8delGTGA) in 2 unrelated patients. This mutation displayed an altered splicing pattern generating 2 aberrant transcripts and causing frameshifts of the coding sequence, premature termination codons, and a near absence of PGRN mRNA from the mutated alleles most likely through nonsense-mediated decay. The subsequent PGRN haploinsufficiency is consistent with previously described PGRN mutations. We present a molecular characterization of the IVS6+5_8delGTGA mutation and also describe clinical and neuropathologic features from the 2 patients carrying this PGRN mutation. From the screening of these 51 FTLD patients, we could also identify the earlier reported mutation Gln130fs, and several coding sequence variants that are most likely nonpathogenic.

Frontotemporal lobar degeneration (FTLD) is the second most common cause of presenile dementia. The predominant neuropathology is FTLD with TAR DNA-binding protein (TDP-43) inclusions (FTLD-TDP). FTLD-TDP is frequently familial, resulting from mutations in GRN (which encodes progranulin). We assembled an international collaboration to identify susceptibility loci for FTLD-TDP through a genome-wide association study of 515 individuals with FTLD-TDP. We found that FTLD-TDP associates with multiple SNPs mapping to a single linkage disequilibrium block on 7p21 that contains TMEM106B. Three SNPs retained genome-wide significance following Bonferroni correction (top SNP rs1990622, P = 1.08 x 10(-11); odds ratio, minor allele (C) 0.61, 95% CI 0.53-0.71). The association replicated in 89 FTLD-TDP cases (rs1990622; P = 2 x 10(-4)). TMEM106B variants may confer risk of FTLD-TDP by increasing TMEM106B expression. TMEM106B variants also contribute to genetic risk for FTLD-TDP in individuals with mutations in GRN. Our data implicate variants in TMEM106B as a strong risk factor for FTLD-TDP, suggesting an underlying pathogenic mechanism.

From the Departments of Neurology (S.D.B., K.S.K.), Neuro-Ophthalmology (M.J.D.), Neurosurgery (Z.W.), Radiology (W.A.C.), and Pathology (S.H.F.), Massachusetts General Hospital; and the Departments of Neurology (S.D.B., K.S.K.), Neurology (M.J.D.), Surgery (Z.W.), Radiology (W.A.C.), and Pathology (S.H.F.), Harvard Medical School.

The aim of this thesis was to identify genetic factors involved in frontotemporal lobar degeneration (FTLD), a neurodegenerative disorder clinically characterised by a progressive change in personality, behaviour and language. FTLD is a genetically complex disorder and a positive family history is found in up to 40% of the cases.In 10-20% of the familial cases the disease can be explained by mutations in the gene encoding the microtubule associated protein tau (MAPT). In the first study we describe the clinical and neuropathological features of a Finnish family with FTLD caused by a mutation in MAPT. We also provide evidence that the pathogenic mechanism of this mutation is through altered splicing of MAPT transcripts.Recently, mutations in the gene encoding progranulin (PGRN) were identified as a major cause of FTLD. In the second study we describe a Swedish family with FTLD caused by a frameshift mutation in PGRN. We provide a clinical and neuropathological description of the family, as well as evidence that the pathogenicity of this mutation is through nonsense-mediated decay of the mutant mRNA transcripts and PGRN haploinsufficiency.In the third study we describe a novel PGRN splice site mutation and a previously described PGRN frameshift mutation, found in a mutation screen of 51 FTLD patients. We describe the clinical and neuropathological characteristics of the mutation carriers and demonstrate that haploinsufficiency is the pathogenic mechanism of the two mutations.In the fourth study we investigate the prevalence of PGRN and MAPT gene dosage alterations in 39 patients with FTLD. No gene dosage alterations were identified, indicating that variations in copy number of the PGRN and MAPT genes are not a common cause of disease, at least not in this FTLD patient collection.

Background/Aims: Alterations in gene dosage have recently been associated with neurodegenerative disorders, such as Alzheimer’s disease and Parkinson’s disease, and deletions of the progranulin (PGRN) locus were recently described in patients with frontotemporal lobar degeneration (FTLD). FTLD is a genetically complex neurodegenerative disorder with mutations in the PGRN and the microtubule-associated protein tau (MAPT) genes being the most common known causes of familial FTLD. In this study, we investigated 39 patients with FTLD, previously found negative for mutations in PGRN and MAPT, for copy number alterations of these 2 genes. Methods: Gene dosage analysis of PGRN and MAPT was performed using multiplex ligation-dependent probe amplification. Results: We did not identify any PGRN or MAPT gene dosage variations in the 39 FTLD patients investigated. Conclusion: We therefore conclude that alterations in gene copy number of PGRN and MAPT are not a cause of disease in this collection of FTLD patients.

Pigmented orthochromatic leukodystrophy and hereditary diffuse leukoencephalopathy with spheroids are two adult onset leukodystrophies with neuroaxonal spheroids presenting with prominent neurobehavioral, cognitive and motor symptoms. These are familial or sporadic disorders characterized by cerebral white matter degeneration including myelin and axonal loss, gliosis, macrophages and axonal spheroids. We report clinical, neuroimaging and pathological correlations of four women ages 34-50 years with adult onset leukodystrophy. Their disease course ranged from 1.5-8 years. Three patients had progressive cognitive and behavioral changes; however, one had acute onset. Neuroimaging revealed white matter abnormalities characterized by symmetric, bilateral, T2 hyperintense and T1 hypointense Magnetic Resonance Imaging signal involving frontal lobe white matter in all patients. Extensive laboratory investigations were negative apart from abnormalities in some mitochondrial enzymes and immunologic parameters. Autopsies demonstrated severe leukodystrophy with myelin and axonal loss, axonal spheroids and macrophages with early and severe frontal white matter involvement. The extent and degree of changes outside the frontal lobe appeared to correlate with disease duration. The prominent neurobehavioral deficits and frontal white matter disease provide clinical-pathologic support for association pathways linking distributed neural circuits sub-serving cognition. These observations lend further support to the notion that white matter disease alone can account for dementia.

Cerebral volume loss has long been associated with normal aging, but whether this is due to aging itself or to age-related diseases, including incipient Alzheimer disease, is uncertain. To understand the changes that occur in the aging brain, we examined the cerebral cortex of 27 normal individuals ranging in age from 56 to 103 years. None fulfilled the criteria for the neuropathologic diagnosis of Alzheimer disease or other neurodegenerative disease. Seventeen of the elderly participants had cognitive testing an average of 6.7 months prior to death. We used quantitative approaches to analyze cortical thickness, neuronal number, and density. Frontal and temporal neocortical regions had clear evidence of cortical thinning with age, but total neuronal numbers in frontal and temporal neocortical regions remained relatively constant during a 50-year age range. These data suggest that loss of neuronal and dendritic architecture, rather than loss of neurons, underlies neocortical volume loss with increasing age in the absence of Alzheimer disease.

Cerebral volume loss has been associated with normal aging but whether this is due to the aging process or to age-related diseases including incipient Alzheimer disease is uncertain. In order to understand the aging brain we examined the cerebral cortex of 27 individuals ranging in age from 56 through >90 years. None fulfilled the criteria for the neuropathological diagnosis of Alzheimer disease or other neurodegenerative diseases. Seventeen of the elderly participants had cognitive testing prior to death. Since the volume of the cerebral cortex reflects the sum of input fibers, neuronal cell bodies, dendritic arbors, and output fibers, we used two different quantitative approaches to analyze overall cortical thickness, neuronal number, neuronal size distribution and changes within the neuropil. Both frontal and temporal neocortical regions (BA 8, 9, and 17) had clear evidence of cortical thinning with age. In these same anatomic regions, neuronal density calculated for the entire cortical thickness revealed an increase in both frontal and temporal cortex, while the total neuronal number remained relatively constant over a 50-year age range. Measurements of neuronal size in the frontal, but not temporal cortex demonstrated decreasing perikaryal size with age. The combination of these changes suggests that loss of dendritic structures, rather than loss of neurons, underlies neocortical volume loss with increasing age.

Pick disease (PiD) is a frontotemporal dementia characterized by frontal and temporal atrophy, neuronal loss, gliosis, ballooned neurons that are positive for &agr;-B crystallin and neurofilament, and the presence of tau- and ubiquitin-positive Pick bodies. TAR-DNA binding protein 43 (TDP-43) has been found to be a component of ubiquitinated inclusions in other neurodegenerative diseases, including frontotemporal lobar degeneration with ubiquitinated inclusions and amyotrophic lateral sclerosis. Fifteen cases of PiD were examined using immunohistochemical methods, and 5 cases with both Pick bodies and smaller intracytoplasmic inclusions that showed staining for ubiquitin, tau, and TDP-43 were observed. The presence of TDP-43 inclusions in PiD suggests that TDP-43 accumulation may be an important component of many neurodegenerative diseases, and that its presence in only some cases of PiD may indicate different pathways of disease development.

Primary Progressive Aphasia (PPA) corresponds to a syndrome characterized by an isolated and progressive alteration of language function not associated with dementia. Since this syndrome is defined and diagnosed by clinical symptoms, its neuropathological diagnosis can include Pick's disease, frontotemporal dementia and Alzheimer's disease. However, it is still unclear what causes the focal neuropathological changes in PPA. To address this question, we performed microarray study on four PPA cases with FTD and three aged control cases. RNA samples were extracted and purified from homogenate of one-side angular gyrus and occipital lobe from each case using Absolutely RNA RT-PCR Miniprep Kit (Stratagene), then were hybridized to the GeneChip Human Whole Genome U133 plus 2.0 Array (Affymetrix). Results were screened for probes that were significantly different from one group to another with p-value less than 0.05 for intensities over background level, high signal/noise ratio and a fold change more than 2. Among 47,000 available probes, 118 probes were upregulated and 44 were downregulated in angular gyrus of PPA compared to that of control cases, and 91 upregulated and 24 downregulated genes are selected in angular gyrus compared to occipital lobes in PPA. Functional analysis of both data sets showed that complement pathways were significantly upregulated in angular gyrus of PPA cases. Gene set enrichment analysis supported this expression change of complement pathways. To further examine this upregulation in angular gyrus, we immunostained paraffin sections of identical cases with antibodies against C1q, showing that C1q-immunoreactivites were detected dominantly in angular gyrus of PPA cases comparing to that of control cases or occipital lobe of PPA. Three of four PPA cases had a lot of C1q-positive spiral structures in white matter of angular, which were never seen in control cases or Alzheimer disease cases. Our study suggests that significant upregulation of complement pathways in angular gyrus, especially in white matter, is strongly related to PPA. We postulate that suppression of upregulated complement pathways may lead to the therapy of PPA.

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.

Case presentation: A 47-year-old right-handed man presented with acute onset of right face, arm, and leg weakness; word-finding difficulties; and bifrontal headache.His medical history was remarkable for hyperlipidemia and spontaneous dissection of a distal coronary artery a year and a half previously.On examination, he had right lower face weakness, a plegic right arm, and distal greater than proximal right leg weakness.His speech was mildly dysarthric with word-finding difficulty.Comprehension was intact.Cardiac auscultation was normal.Results of laboratory investigations, including complete blood count, electrolytes, renal function, liver function, prothrombin time, partial thromboplastin time, cardiac enzymes, antinuclear antibody test, erythrocyte sedimentation rate, and urine toxicology screen, were all normal or negative.Initial noncontrast CT brain revealed a 3 ϫ 3.5 ϫ 3.5-cm left frontal subcortical intracerebral hemorrhage with surrounding edema, but no appreciable underlying mass (figure 1).

Cerebral accumulation of amyloid beta protein (Abeta) is characteristic of Alzheimer disease (AD). Abeta can be detected in cerebrospinal fluid and in plasma. Although plasma Abeta has been proposed as a marker of risk of AD, it is unknown how plasma levels relate to neuropathologic levels. We compared plasma levels of Abeta40 and Abeta42 obtained during life with biochemical and pathologic levels in frontal and temporal neocortex in 25 individuals (17 AD, 3 control, and 5 non-AD dementia) who died a median of 1 year after blood collection. Plasma levels of Abeta40 and Abeta42 were not associated with any of the brain measures, even after adjusting for age and interval between plasma collection and death. The APOE epsilon4 allele may modify the relationship between plasma Abeta42 and formic acid-extractable Abeta42, with an inverse correlation in APOE epsilon4 carriers and a positive correlation in those lacking APOE epsilon4. We conclude that plasma levels of Abeta40 and Abeta42 are not robust correlates of histologic or biochemically assessed amyloid burdens in brain, although the influence of the APOE genotype should be further explored.

OBJECTIVE:To determine the correspondence between uptake of Pittsburgh Compound B (PiB) in life and measures of beta-amyloid (Abeta) in postmortem tissue analysis. Patient A 76-year-old man with a clinical diagnosis of dementia with Lewy bodies underwent fluorodeoxyglucose (18)F and PiB positron emission tomographic brain scans. Imaging revealed marked region specific binding of PiB and abnormal fluorodeoxyglucose uptake. Intervention Autopsy was performed 3 months after the PiB scan.RESULTS:Autopsy confirmed the clinical diagnosis; in addition, there was severe cerebral amyloid angiopathy and only moderate numbers of parenchymal Abeta plaques. Biochemical measures revealed a positive correlation between Abeta levels and regional PiB binding.CONCLUSION:This report confirms that PiB detects Abeta in the living patient and demonstrates that amyloid deposited as cerebral amyloid angiopathy can be the dominant source of signal.

Ubiquitinated cytoplasmic inclusions (Ub-CIs) in superficial frontal cortex and dentate gyrus neurons are the hallmark of frontotemporal degeneration of the motor neuron disease-type (FTD-MND-type). To date, 2 reports have described intranuclear ubiquitinated inclusions (Ub-INIs) in 9 cases of familial FTD-MND-type (without clinical or pathologic motor neuron disease, MND). In the current study we found an additional 11 cases with Ub-INIs. We have identified for the first time among these cases 2 with a negative family history and 3 that have concomitant amyotrophic lateral sclerosis (ALS). The results of the present study i) confirm a previous report of significantly lower average brain weight and longer duration in cases with Ub-INIs, ii) reveal significantly greater striatal neuronal loss and gliosis in cases with intranuclear inclusions, and iii) demonstrate that intranuclear inclusions correlate with cytoplasmic inclusions and dystrophic neurites in frontal cortex and striatum but not in dentate gyrus. In addition, the current study confirms that Ub-INIs are found in familial FTD-MND-type, but also extends the presence of Ub-INIs to familial FTD-MND (with concomitant ALS), and probably also to non-familial FTD-MND-type.