Emily Dwosh

Mutations in progranulin cause tau-negative frontotemporal dementia linked to chromosome 17.

Frontotemporal dementia (FTD) is the second most common cause of dementia in people under the age of 65 years. A large proportion of FTD patients (35–50%) have a family history of dementia, consistent with a strong genetic component to the disease. In 1998, mutations in the gene encoding the microtubule-associated protein tau (MAPT) were shown to cause familial FTD with parkinsonism linked to chromosome 17q21 (FTDP-17). The neuropathology of patients with defined MAPT mutations is characterized by cytoplasmic neurofibrillary inclusions composed of hyperphosphorylated tau. However, in multiple FTD families with significant evidence for linkage to the same region on chromosome 17q21 (D17S1787–D17S806), mutations in MAPT have not been found and the patients consistently lack tau-immunoreactive inclusion pathology. In contrast, these patients have ubiquitin (ub)-immunoreactive neuronal cytoplasmic inclusions and characteristic lentiform ub-immunoreactive neuronal intranuclear inclusions. Here we demonstrate that in these families, FTD is caused by mutations in progranulin (PGRN) that are likely to create null alleles. PGRN is located 1.7 Mb centromeric of MAPT on chromosome 17q21.31 and encodes a 68.5-kDa secreted growth factor involved in the regulation of multiple processes including development, wound repair and inflammation. PGRN has also been strongly linked to tumorigenesis. Moreover, PGRN expression is increased in activated microglia in many neurodegenerative diseases including Creutzfeldt–Jakob disease, motor neuron disease and Alzheimers disease. Our results identify mutations in PGRN as a cause of neurodegenerative disease and indicate the importance of PGRN function for neuronal survival.

Clinical and pathological features of familial frontotemporal dementia caused by C9ORF72 mutation on chromosome 9p

Frontotemporal dementia and amyotrophic lateral sclerosis are closely related clinical syndromes with overlapping molecular pathogenesis. Several families have been reported with members affected by frontotemporal dementia, amyotrophic lateral sclerosis or both, which show genetic linkage to a region on chromosome 9p21. Recently, two studies identified the FTD/ALS gene defect on chromosome 9p as an expanded GGGGCC hexanucleotide repeat in a non-coding region of the chromosome 9 open reading frame 72 gene (C9ORF72). In the present study, we provide detailed analysis of the clinical features and neuropathology for 16 unrelated families with frontotemporal dementia caused by the C9ORF72 mutation. All had an autosomal dominant pattern of inheritance. Eight families had a combination of frontotemporal dementia and amyotrophic lateral sclerosis while the other eight had a pure frontotemporal dementia phenotype. Clinical information was available for 30 affected members of the 16 families. There was wide variation in age of onset (mean = 54.3, range = 34-74 years) and disease duration (mean = 5.3, range = 1-16 years). Early diagnoses included behavioural variant frontotemporal dementia (n = 15), progressive non-fluent aphasia (n = 5), amyotrophic lateral sclerosis (n = 9) and progressive non-fluent aphasia-amyotrophic lateral sclerosis (n = 1). Heterogeneity in clinical presentation was also common within families. However, there was a tendency for the phenotypes to converge with disease progression; seven subjects had final clinical diagnoses of both frontotemporal dementia and amyotrophic lateral sclerosis and all of those with an initial progressive non-fluent aphasia diagnosis subsequently developed significant behavioural abnormalities. Twenty-one affected family members came to autopsy and all were found to have transactive response DNA binding protein with M(r) 43 kD (TDP-43) pathology in a wide neuroanatomical distribution. All had involvement of the extramotor neocortex and hippocampus (frontotemporal lobar degeneration-TDP) and all but one case (clinically pure frontotemporal dementia) had involvement of lower motor neurons, characteristic of amyotrophic lateral sclerosis. In addition, a consistent and relatively specific pathological finding was the presence of neuronal inclusions in the cerebellar cortex that were ubiquitin/p62-positive but TDP-43-negative. Our findings indicate that the C9ORF72 mutation is a major cause of familial frontotemporal dementia with TDP-43 pathology, that likely accounts for the majority of families with combined frontotemporal dementia/amyotrophic lateral sclerosis presentation, and further support the concept that frontotemporal dementia and amyotrophic lateral sclerosis represent a clinicopathological spectrum of disease with overlapping molecular pathogenesis.

Genetic Counseling for Early-onset Familial Alzheimer Disease in Large Aboriginal Kindred from a Remote Community in British Columbia: Unique Challenges and Possible Solutions

A novel, pathogenic presenilin 1 (PS1) mutation has recently been identified in a large Aboriginal kindred living in dispersed communities throughout British Columbia, Canada. Disseminating genetic information and ensuring that appropriate genetic counseling services are provided to all concerned relatives have posed several unique challenges. These challenges include knowledge exchange and continuity of care in a geographically remote and culturally distinct community. To our knowledge, this is the first time a specific genetic counseling approach has been needed for early-onset familial Alzheimer disease (EOFAD) in a North American Aboriginal community.

A Novel PS1 Gene Mutation in a Large Aboriginal Kindred

BACKGROUND There is currently little information on the genetic epidemiology of Alzheimer disease (AD) among North American Aboriginal populations. No cases of familial AD (FAD) in these populations have been published to date. METHODS Here, we describe a large North American Aboriginal kindred with early onset FAD (EOFAD) in which genetic testing was done. RESULTS AND CONCLUSIONS A novel Presenilin 1 (PS1) gene mutation (L250F) has been identified. In contrast to the three previously reported families with PS1 codon 250 mutations, affected members of this kindred demonstrate neither myoclonus nor seizures. Furthermore, the identification of a PS1 mutation in a North American Aboriginal kindred presents several unique challenges with respect to knowledge transfer and continuity of care in a geographically remote and culturally distinct community.

Neuroethics, confidentiality, and a cultural imperative in early onset Alzheimer disease: a case study with a First Nation population

The meaningful consideration of cultural practices, values and beliefs is a necessary component in the effective translation of advancements in neuroscience to clinical practice and public discourse. Society’s immense investment in biomedical science and technology, in conjunction with an increasingly diverse socio-cultural landscape, necessitates the study of how potential discoveries in neurodegenerative diseases such as Alzheimer disease are perceived and utilized across cultures. Building on the work of neuroscientists, ethicists and philosophers, we argue that the growing field of neuroethics provides a pragmatic and constructive pathway to guide advancements in neuroscience in a manner that is culturally nuanced and relevant. Here we review a case study of one issue in culturally oriented neuroscience research where it is evident that traditional research ethics must be broadened and the values and needs of diverse populations considered for meaningful and relevant research practices. A global approach to neuroethics has the potential to furnish critical engagement with cultural considerations of advancements in neuroscience.

Familial frontotemporal dementia with neuronal intranuclear inclusions is not a polyglutamine expansion disease.

BackgroundMany cases of frontotemporal dementia (FTD) are familial, often with an autosomal dominant pattern of inheritance. Some are due to a mutation in the tau- encoding gene, on chromosome 17, and show an accumulation of abnormal tau in brain tissue (FTDP-17T). Most of the remaining familial cases do not exhibit tau pathology, but display neuropathology similar to patients with dementia and motor neuron disease, characterized by the presence of ubiquitin-immunoreactive (ub-ir), dystrophic neurites and neuronal cytoplasmic inclusions in the neocortex and hippocampus (FTLD-U). Recently, we described a subset of patients with familial FTD with autopsy-proven FTLD-U pathology and with the additional finding of ub-ir neuronal intranuclear inclusions (NII). NII are a characteristic feature of several other neurodegenerative conditions for which the genetic basis is abnormal expansion of a polyglutamine-encoding trinucleotide repeat region. The genetic basis of familial FTLD-U is currently not known, however the presence of NII suggests that a subset of cases may represent a polyglutamine expansion disease.MethodsWe studied DNA and post mortem brain tissue from 5 affected members of 4 different families with NII and one affected individual with familial FTLD-U without NII. Patient DNA was screened for CAA/CAG trinucleotide expansion in a set of candidate genes identified using a genome-wide computational approach. Genes containing CAA/CAG trinucleotide repeats encoding at least five glutamines were examined (n = 63), including the nine genes currently known to be associated with human disease. CAA/CAG tract sizes were compared with published normal values (where available) and with those of healthy controls (n = 94). High-resolution agarose gel electrophoresis was used to measure allele size (number of CAA/CAG repeats). For any alleles estimated to be equal to or larger than the maximum measured in the control population, the CAA/CAG tract length was confirmed by capillary electrophoresis. In addition, immunohistochemistry using a monoclonal antibody that recognizes proteins containing expanded polyglutamines (1C2) was performed on sections of post mortem brain tissue from subjects with NII.ResultsNo significant polyglutamine-encoding repeat expansions were identified in the DNA from any of our FTLD-U patients. NII in the FTLD-U cases showed no 1C2 immunoreactivity.ConclusionWe find no evidence to suggest that autosomal dominant FTLD-U with NII is a polyglutamine expansion disease.

Converging approaches to understanding early onset familial Alzheimer disease: A First Nation study.

Objectives: In 2007, a novel pathogenic genetic mutation associated with early onset familial Alzheimer disease was identified in a large First Nation family living in communities across British Columbia, Canada. Building on a community-based participatory study with members of the Nation, we sought to explore the impact and interplay of medicalization with the Nation’s knowledge and approaches to wellness in relation to early onset familial Alzheimer disease. Methods: We performed a secondary content analysis of focus group discussions and interviews with 48 members of the Nation between 2012 and 2013. The analysis focused specifically on geneticization, medicalization, and traditional knowledge of early onset familial Alzheimer disease, as these themes were prominent in the primary analysis. Results: We found that while biomedical explanations of disease permeate the knowledge and understanding of early onset familial Alzheimer disease, traditional concepts about wellness are upheld simultaneously. Conclusion: The analysis brings the theoretical framework of “two-eyed seeing” to the case of early onset familial Alzheimer disease for which the contributions of different ways of knowing are embraced, and in which traditional and western ways complement each other on the path of maintaining wellness in the face of progressive neurologic disease.

Neurobehavioral characterization of adult-onset Alexander disease A family study

Alexander disease is a clinically heterogeneous condition associated with glial fibrillary acidic protein ( GFAP ) gene mutations initially described in infants, but juvenile and adult forms exist. Adult-onset Alexander disease (AOAD) has an insidious onset of symptoms localized largely to brainstem, but may also include cognitive dysfunction.

Neurobehavioral characterization of adult-onset alexander's disease: A family study

MiDD was 9.90% in NCD, 16.89% in MCI, and 19.51% in ADD. The frequency of NIMH-dAD was 26.23%, 33.56%, and 40.24%, respectively. While the frequency of MaDD did not show any significant difference among cognitive subgroups, those of MiDD and NIMH-dAD, i.e., relatively milder depression syndromes, had significant group difference with gradual increase from NCD to ADD. Conclusions: The current findings obtained from a large number of cognitively diverse elderly individuals who visited a memory clinic indicated that mild depressive conditions are highly prevalent in general and more common in individuals with poorer cognitive condition, while the frequency of severe depressive disorder like MaDD is not related to cognitive status.

Early-onset familial Alzheimer's disease and the definition of family: Experience with an indigenous community

genotype. Conclusions: The CNR-MAJ has confirmed the molecular diagnosis in 9% of patients with sporadic early-onset AD. Moreover, the APOE4/E4 genotype could also explain additional 9% of patients. For the remaining cases, we have not found any genetical abnormality. Among them, 3 cases whose both parents are still alive and without dementia are currently enrolled in a research program to identify new genetic de novo causes involved in early-onset AD.