We recommend a new term, “primary age-related tauopathy” (PART), to describe a pathology that is commonly observed in the brains of aged individuals. Many autopsy studies have reported brains with neurofibrillary tangles (NFT) that are indistinguishable from those of Alzheimer's disease (AD), in the absence of amyloid (Aβ) plaques. For these “NFT+/Aβ−” brains, for which formal criteria for AD neuropathologic changes are not met, the NFT are mostly restricted to structures in the medial temporal lobe, basal forebrain, brainstem, and olfactory areas (bulb and cortex). Symptoms in persons with PART usually range from normal to amnestic cognitive changes, with only a minority exhibiting profound impairment. Because cognitive impairment is often mild, existing clinicopathologic designations, such as “tangle-only dementia” and “tangle-predominant senile dementia”, are imprecise and not appropriate for most subjects. PART is almost universally detectable at autopsy among elderly individuals, yet this pathological process cannot be specifically identified pre-mortem at the present time. Improved biomarkers and tau imaging may enable diagnosis of PART in clinical settings in the future. Indeed, recent studies have identified a common biomarker profile consisting of temporal lobe atrophy and tauopathy without evidence of Aβ accumulation. For both researchers and clinicians, a revised nomenclature will raise awareness of this extremely common pathologic change while providing a conceptual foundation for future studies. Prior reports that have elucidated features of the pathologic entity we refer to as PART are discussed, and working neuropathological diagnostic criteria are proposed.

Highlights d optoTDP43 is a light-inducible model of TDP-43 proteinopathy and is neurotoxic d RNA binding antagonizes aberrant liquid-liquid phase separation (LLPS) of TDP-43 d Acute recruitment to RNA-containing stress granules maintains TDP-43 solubility d TDP-43 targeting oligonucleotides prevent aberrant LLPS and rescues neurotoxicity

Background There exists great heterogeneity in patient survival and the time interval between motor symptom and dementia onset (MDI) across Lewy body spectrum disorders (LBSD). The goal of this study is to identify genetic and pathological findings that have the strongest association with these features of clinical heterogeneity in LBSD. Methods In this retrospective study, we examined symptom onset, and genetic and neuropathological data from a cohort of LBSD patients with autopsy-confirmed α-synucleinopathy (as of Oct 1, 2015) recruited from 5 clinical research centres in 5 cities in the USA. Using histopathology techniques and markers, we assessed the burden of tau neurofibrillary tangles, neuritic plaques, α-synuclein inclusions, and other pathologic changes in cortical regions using averaged ordinal scores and genotyped cases for variants associated with LBSD. We evaluated the time interval from onset of motor symptoms to dementia (MDI) and overall survival in groups with varying levels of co-morbid Alzheimer’s disease pathology (AD) according to current National Institute on Aging–Alzheimer’s Association neuropathological criteria and used multivariate regression to control for age at death and gender. Findings This study included 213 patients who had been followed to autopsy and met inclusion criteria of clinical LBSD with autopsy-confirmed α-synculeinopathy. Patient groups were characterized by no (n=49,23%), low-level (n=56,26%), intermediate-level (n=45,21%) or high-level (n=63,30%) AD neuropathology. Across groups of increasing levels of AD neuropathology, there were higher cerebral α-synuclein scores, shorter MDI, and shorter disease duration (p<0·0001 all). Multivariate regression found independent negative associations of cerebral tau score with MDI (β= −4·0, 95% CI −5·5 to −2·6; p<0·0001) (R2=0·22, p<0·0001) and with survival (β=−2·0, 95% CI −3·2 to −0·8; p<0·0001) (R2=0·15, p<0·0001) in models including age at death, gender, cerebral neuritic plaque scores, cerebral α-synuclein, presence of cerebrovascular disease, MAPT haplotype, and APOE genotype as covariates. Interpretation AD neuropathology is common in LBSD and confers a worse prognosis for each increasing level of neuropathological change. Cerebral neurofibrillary tau tangle burden, α-synuclein pathology, and amyloid plaque pathology are the strongest pathological predictors of a shorter MDI and survival in LBSD. In the future, clinical diagnostic criteria which use reliable biomarkers for AD neuropathology in LBSD should help identify the most appropriate patients for clinical trials of emerging therapies targeting tau, amyloid-beta or α-synuclein, and stratify them by level of AD neuropathology. Funding NIH (NIA/NINDS).

Missense mutations in leucine-rich repeat kinase 2 (LRRK2) cause familial Parkinson's disease (PD). However, a potential role of wild-type LRRK2 in idiopathic PD (iPD) remains unclear. Here, we developed proximity ligation assays to assess Ser1292 phosphorylation of LRRK2 and, separately, the dissociation of 14-3-3 proteins from LRRK2. Using these proximity ligation assays, we show that wild-type LRRK2 kinase activity was selectively enhanced in substantia nigra dopamine neurons in postmortem brain tissue from patients with iPD and in two different rat models of the disease. We show that this occurred through an oxidative mechanism, resulting in phosphorylation of the LRRK2 substrate Rab10 and other downstream consequences including abnormalities in mitochondrial protein import and lysosomal function. Our study suggests that, independent of mutations, wild-type LRRK2 plays a role in iPD. LRRK2 kinase inhibitors may therefore be useful for treating patients with iPD who do not carry LRRK2 mutations.

Pathological accumulation of abnormally phosphorylated tau protein in astrocytes is a frequent, but poorly characterized feature of the aging brain. Its etiology is uncertain, but its presence is sufficiently ubiquitous to merit further characterization and classification, which may stimulate clinicopathological studies and research into its pathobiology. This paper aims to harmonize evaluation and nomenclature of aging-related tau astrogliopathy (ARTAG), a term that refers to a morphological spectrum of astroglial pathology detected by tau immunohistochemistry, especially with phosphorylation-dependent and 4R isoform-specific antibodies. ARTAG occurs mainly, but not exclusively, in individuals over 60 years of age. Tau-immunoreactive astrocytes in ARTAG include thorn-shaped astrocytes at the glia limitans and in white matter, as well as solitary or clustered astrocytes with perinuclear cytoplasmic tau immunoreactivity that extends into the astroglial processes as fine fibrillar or granular immunopositivity, typically in gray matter. Various forms of ARTAG may coexist in the same brain and might reflect different pathogenic processes. Based on morphology and anatomical distribution, ARTAG can be distinguished from primary tauopathies, but may be concurrent with primary tauopathies or other disorders. We recommend four steps for evaluation of ARTAG: (1) identification of five types based on the location of either morphologies of tau astrogliopathy: subpial, subependymal, perivascular, white matter, gray matter; (2) documentation of the regional involvement: medial temporal lobe, lobar (frontal, parietal, occipital, lateral temporal), subcortical, brainstem; (3) documentation of the severity of tau astrogliopathy; and (4) description of subregional involvement. Some types of ARTAG may underlie neurological symptoms; however, the clinical significance of ARTAG is currently uncertain and awaits further studies. The goal of this proposal is to raise awareness of astroglial tau pathology in the aged brain, facilitating communication among neuropathologists and researchers, and informing interpretation of clinical biomarkers and imaging studies that focus on tau-related indicators.