Neuronal loss in familial frontotemporal dementia with ubiquitin-positive, tau-negative inclusions

Altered Levels of Visinin-Like Protein 1 Correspond to Regional Neuronal Loss in Alzheimer Disease and Frontotemporal Lobar Degeneration

Recent studies have implicated the neuronal calcium-sensing protein visinin-like 1 protein (Vilip-1) as a peripheral biomarker in Alzheimer disease (AD), but little is known about expression of Vilip-1 in the brains of patients with AD. We used targeted and quantitative mass spectrometry to measure Vilip-1 peptide levels in the entorhinal cortex (ERC) and the superior frontal gyrus (SF) from cases with early to moderate stage AD, frontotemporal lobar degeneration (FTLD), and cognitively and neuropathologically normal elderly controls. We found that Vilip-1 levels were significantly lower in the ERC, but not in SF, of AD subjects compared to normal controls. In FTLD cases, Vilip-1 levels in the SF were significantly lower than in normal controls. These findings suggest a unique role for cerebrospinal fluid Vilip-1 as a biomarker of ERC neuron loss in AD.

Asymmetric pathology in primary progressive aphasia with progranulin mutations and TDP inclusions

OBJECTIVE

To investigate quantitative regional distribution and hemispheric asymmetry of TDP-43 (TAR DNA-binding protein 43) inclusions, neurons, and activated microglia in primary progressive aphasia (PPA) with progranulin (GRN) mutations, and to determine concordance between distribution of pathology, clinical phenotype, and known atrophy patterns.

METHODS

Antibodies to phospho-TDP-43, NeuN (neuronal nuclei), and HLA-DR were used to visualize inclusions, neurons, and activated microglia in paraffin-embedded tissue sections from 4 participants with PPA: 2 of the agrammatic and 2 of the logopenic subtype. Unbiased stereological counting techniques were used for quantitation of immunoreactive profiles in language- and memory-related cortical areas bilaterally. Patterns of pathology across cortical areas and hemispheres were compared and their relationships with known patterns of atrophy investigated.

RESULTS

Numerical densities of TDP-43 inclusions, and less so of activated microglia, were greater in language-related areas compared with memory-related areas. In language areas, neuronal density displayed a pattern opposite to inclusions and activated microglia. Densities of inclusions and microglia were greater (p < 0.05), and densities of neurons were lower (p < 0.005), in the left hemisphere compared with the right. In agrammatic PPA, the highest densities of TDP-43 inclusions were observed in left inferior or middle frontal gyri, and in logopenic participants, the highest density of inclusions was seen in left inferior parietal lobule. This distribution is consistent with subtype-specific peak atrophy sites.

CONCLUSIONS

Distribution of TDP-43 inclusions and neurons, and to a smaller extent of activated microglia, show a regional and hemispheric pattern consistent with disease phenotype and known patterns of atrophy in PPA with GRN mutations.

Stereological approaches to dementia research using human brain tissue

The relationship between the clinical features of dementia disorders and the resultant changes in underlying neuropathological mechanisms has long been of interest to researchers working in the field of neurodegenerative disorders. The majority of neuropathological research in dementia has utilized semi-quantitative analysis of protein inclusions, which have defined the hallmark histological features of the conditions. However, the advent of three-dimensional stereological techniques has enabled unbiased and fully quantitative assessment of brain tissue. The present review focuses on studies that have used these techniques to elucidate important relationships between neuropathological changes and clinical features and, in doing so, revealed important mechanistic insights into the pathophysiology of dementia disorders.

Neuropathologic heterogeneity in HDDD1: a familial frontotemporal lobar degeneration with ubiquitin-positive inclusions and progranulin mutation

Hereditary dysphasic disinhibition dementia (HDDD) describes a familial disorder characterized by personality changes, and language and memory deficits. The neuropathology includes frontotemporal lobar atrophy, neuronal loss and gliosis and, in most cases, abundant Abeta plaques and neurofibrillary tangles (NFTs). A Pick/Alzheimer's spectrum was proposed for the original family (HDDD1). Here we report the clinicopathologic case of an HDDD1 individual using modern immunohistochemical methods, contemporary neuropathologic diagnostic criteria to distinguish different frontotemporal lobar degenerations (FTLDs), and progranulin (PRGN) mutation analysis. Clinical onset was at age 62 years with personality changes and disinhibition, followed by nonfluent dysphasia, and memory loss that progressed to muteness and total dependence with death at age 84 years. There was severe generalized brain atrophy (weight=570 g). Histopathology showed superficial microvacuolation, marked neuronal loss, gliosis, and ubiquitin-positive, tau-negative cytoplasmic and intranuclear neuronal inclusions in frontal, temporal, and parietal cortices. There were also frequent neuritic plaques and NFTs in parietal and occipital cortices. The case met neuropathologic criteria for both FTLD with ubiquitin-positive, tau-negative inclusions (FTLD-U), and Alzheimer disease (Braak NFT stage V). We discovered a novel pathogenic PGRN mutation c.5913 A>G (IVS6-2 A>G) segregating with FTLD-U in this kindred. In conclusion, HDDD1 is an FTLD-U caused by a PGRN mutation and is neuropathologically heterogeneous with Alzheimer disease as a common comorbidity.