Intrafamilial clinical phenotypic heterogeneity with MAPT gene splice site IVS10+16C>T mutation

Elevated 4R-tau in astrocytes from asymptomatic carriers of the MAPT 10+16 intronic mutation

The microtubule-associated protein tau gene (MAPT) 10+16 intronic mutation causes frontotemporal lobar degeneration (FTLD) by increasing expression of four-repeat (4R)-tau isoforms. We investigated the potential role for astrocytes in the pathogenesis of FTLD by studying the expression of 4R-tau. We derived astrocytes and neurons from induced pluripotent stem cells from two asymptomatic 10+16 carriers which, compared to controls, showed persistently increased 4R:3R-tau transcript and protein ratios in both cell types. However, beyond 300 days culture, 10+16 neurons showed less marked increase of this 4R:3R-tau transcript ratio compared to astrocytes. Interestingly, throughout maturation, both 10+16 carriers consistently displayed different 4R:3R-tau transcript and protein ratios. These elevated levels of 4R-tau in astrocytes implicate glial cells in the pathogenic process and also suggests a cell-type-specific regulation and may inform and help on treatment of pre-clinical tauopathies.

GRN and MAPT Mutations in 2 Frontotemporal Dementia Research Centers in Brazil

BACKGROUND

Mutations in GRN (progranulin) and MAPT (microtubule-associated protein tau) are among the most frequent causes of monogenic frontotemporal dementia (FTD), but data on the frequency of these mutations in regions such as Latin America are still lacking.

OBJECTIVE

We aimed to investigate the frequencies of GRN and MAPT mutations in FTD cohorts from 2 Brazilian dementia research centers, the University of Sao Paulo and the Federal University of Minas Gerais medical schools.

METHODS

We included 76 probands diagnosed with behavioral-variant FTD (n=55), semantic-variant Primary Progressive Aphasia (PPA) (n=11), or nonfluent-variant PPA (n=10). Twenty-five percent of the cohort had at least 1 relative affected with FTD.

RESULTS

Mutations in GRN were identified in 7 probands, and in MAPT, in 2 probands. We identified 3 novel GRN mutations (p.Q130X, p.317Afs*12, and p.K259Afs*23) in patients diagnosed with nonfluent-variant PPA or behavioral-variant FTD. Plasma progranulin levels were measured and a cutoff value of 70 ng/mL was found, with 100% sensitivity and specificity to detect null GRN mutations.

CONCLUSIONS

The frequency of GRN mutations was 9.6% and that of MAPT mutations was 7.1%. Among familial cases of FTD, the frequency of GRN mutations was 31.5% and that of MAPT mutations was 10.5%.

Intrafamilial clinical phenotypic heterogeneity with progranulin gene p.Glu498fs mutation

A patient with a progressive aphasia syndrome underwent progranulin gene (GRN) testing in light of a family history of early-onset dementia in two of her brothers, one of whom had been previously examined and had the phenotype of frontal variant frontotemporal dementia. The proband was found to have the p.Glu498fs mutation. This is only the second English family, and the fifth family overall, to be described with this GRN mutation. There was marked intrafamilial phenotypic heterogeneity with respect to age at onset and clinical presentation. The mechanisms underpinning this heterogeneity, as seen with other GRN mutations, are currently unknown. Since all GRN mutations lead to progranulin haploinsufficiency, other modifying factors, possibly genetic, are implicated.

Tau and neurodegenerative disorders

The mechanisms that render tau a toxic agent are still unclear, although increasing evidence supports the assertion that alterations of tau can directly cause neuronal degeneration. In addition, it is unclear whether neurodegeneration in various tauopathies occurs via a common mechanism or that specific differences exist. The aim of this review is to provide an overview of tauopathies from bench to bedside. The review begins with clinicopathological findings of familial and sporadic tauopathies. It includes a discussion of the similarities and differences between these two conditions. The second part concentrates on biochemical alterations of tau such as phosphorylation, truncation and acetylation. Although pathological phosphorylation of tau has been studied for many years, recently researchers have focused on the physiological role of tau during development. Finally, the review contains a summary of the significance of tauopathy model mice for research on neurofibrillary tangles, axonopathies, and synaptic alteration.

Frontotemporal dementias: development of an integrated care pathway through an experiential survey of patients and carers

The frontotemporal lobar degenerations (FTLDs) constitute one form of neurodegenerative dementia, which presents with behavioural or linguistic symptoms which often elude precise diagnosis in the early stages of disease, to the frustration of both patients and carers. Based on experiential data from patients and carers seen in both the voluntary care sector (the Alzheimer's Society) and a dedicated Cognitive Function Clinic over periods of 3 to 4 years, a provisional integrated care pathway for FTLDs has been developed which seeks to ensure timely diagnosis and access to appropriate care needs.