Genome-wide association study and functional validation implicates JADE1 in tauopathy

Primary age-related tauopathy (PART) is a neurodegenerative pathology with features distinct from but also overlapping with Alzheimer disease (AD). While both exhibit Alzheimer-type temporal lobe neurofibrillary degeneration alongside amnestic cognitive impairment, PART develops independently of amyloid-β (Aβ) plaques. The pathogenesis of PART is not known, but evidence suggests an association with genes that promote tau pathology and others that protect from Aβ toxicity. Here, we performed a genetic association study in an autopsy cohort of individuals with PART (n = 647) using Braak neurofibrillary tangle stage as a quantitative trait. We found some significant associations with candidate loci associated with AD (SLC24A4, MS4A6A, HS3ST1) and progressive supranuclear palsy (MAPT and EIF2AK3). Genome-wide association analysis revealed a novel significant association with a single nucleotide polymorphism on chromosome 4 (rs56405341) in a locus containing three genes, including JADE1 which was significantly upregulated in tangle-bearing neurons by single-soma RNA-seq. Immunohistochemical studies using antisera targeting JADE1 protein revealed localization within tau aggregates in autopsy brains with four microtubule-binding domain repeats (4R) isoforms and mixed 3R/4R, but not with 3R exclusively. Co-immunoprecipitation in post-mortem human PART brain tissue revealed a specific binding of JADE1 protein to four repeat tau lacking N-terminal inserts (0N4R). Finally, knockdown of the Drosophila JADE1 homolog rhinoceros (rno) enhanced tau-induced toxicity and apoptosis in vivo in a humanized 0N4R mutant tau knock-in model, as quantified by rough eye phenotype and terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) in the fly brain. Together, these findings indicate that PART has a genetic architecture that partially overlaps with AD and other tauopathies and suggests a novel role for JADE1 as a modifier of neurofibrillary degeneration.

Variable expression of mitochondrial complex IV in the course of nigral intracellular accumulation of α-synuclein

INTRODUCTION

Parkinson's disease (PD) is a neurodegenerative disease characterized by the deposition of disease-associated α-synuclein, which is thought to follow a sequential distribution in the human brain. Accordingly, α-Synuclein pathology affects the substantia nigra (SN) only in Braak stage 3 out of 6. Moreover, intracellular accumulation of α-synuclein follows maturation from non-ubiquitinated (p62 negative) to ubiquitinated (p62 positive) forms (Lewy bodies). Mitochondrial dysfunction is thought to be a central player in the pathogenesis of PD. It is not clear whether the nigral neurons already show mitochondrial alterations in stages preceding the deposition of α-synuclein in the SN, and how deposition of pre-aggregates or ubiquitinated mature inclusions relate to this.

METHODS

Using cell-based morphometric immunohistochemistry we evaluated the volume density of mitochondrial complex-IV (COX-IV) immunoreactivity in SN neurons lacking or showing α-synuclein deposits in non-diseased individuals and those with Lewy body pathology Braak stage <3 lacking nigral α-synuclein pathology and Braak stage >3 with prominent nigral α-synuclein deposition.

RESULTS

Increased volume density of COX-IV immunoreactivity appears before detectable pathological α-synuclein in nigral neurons. The volume density decreases significantly as pathological pre-aggregates of α-synuclein accumulates in the neurons and remains at a low level in neurons with p62 positive Lewy bodies.

CONCLUSIONS

COX-IV expression shows a change before and during accumulation of α-synuclein in the SN underpinning the role of early mitochondrio protective therapy strategies in PD.

Early Selective Vulnerability of the CA2 Hippocampal Subfield in Primary Age-Related Tauopathy

Primary age-related tauopathy (PART) is a neurodegenerative entity defined as Alzheimer-type neurofibrillary degeneration primarily affecting the medial temporal lobe with minimal to absent amyloid-β (Aβ) plaque deposition. The extent to which PART can be differentiated pathoanatomically from Alzheimer disease (AD) is unclear. Here, we examined the regional distribution of tau pathology in a large cohort of postmortem brains (n = 914). We found an early vulnerability of the CA2 subregion of the hippocampus to neurofibrillary degeneration in PART, and semiquantitative assessment of neurofibrillary degeneration in CA2 was significantly greater than in CA1 in PART. In contrast, subjects harboring intermediate-to-high AD neuropathologic change (ADNC) displayed relative sparing of CA2 until later stages of their disease course. In addition, the CA2/CA1 ratio of neurofibrillary degeneration in PART was significantly higher than in subjects with intermediate-to-high ADNC burden. Furthermore, the distribution of tau pathology in PART diverges from the Braak NFT staging system and Braak stage does not correlate with cognitive function in PART as it does in individuals with intermediate-to-high ADNC. These findings highlight the need for a better understanding of the contribution of PART to cognitive impairment and how neurofibrillary degeneration interacts with Aβ pathology in AD and PART.

GPR55 controls functional differentiation of self-renewing epithelial progenitors for salivation

GPR55, a lipid-sensing receptor, is implicated in cell cycle control, malignant cell mobilization, and tissue invasion in cancer. However, a physiological role for GPR55 is virtually unknown for any tissue type. Here, we localize GPR55 to self-renewing ductal epithelial cells and their terminally differentiated progeny in both human and mouse salivary glands. Moreover, we find GPR55 expression downregulated in salivary gland mucoepidermoid carcinomas and GPR55 reinstatement by antitumor irradiation, suggesting that GPR55 controls renegade proliferation. Indeed, GPR55 antagonism increases cell proliferation and function determination in quasiphysiological systems. In addition, Gpr55-/- mice present ~50% enlarged submandibular glands with many more granulated ducts, as well as disordered endoplasmic reticuli and with glycoprotein content. Next, we hypothesized that GPR55 could also modulate salivation and glycoprotein content by entraining differentiated excretory progeny. Accordingly, GPR55 activation facilitated glycoprotein release by itself, inducing low-amplitude Ca2+ oscillations, as well as enhancing acetylcholine-induced Ca2+ responses. Topical application of GPR55 agonists, which are ineffective in Gpr55-/- mice, into adult rodent submandibular glands increased salivation and saliva glycoprotein content. Overall, we propose that GPR55 signaling in epithelial cells ensures both the life-long renewal of ductal cells and the continuous availability of saliva and glycoproteins for oral health and food intake.

Plasma and cerebrospinal fluid tau and neurofilament concentrations in rapidly progressive neurological syndromes: a neuropathology-based cohort

BACKGROUND AND PURPOSE

Cerebrospinal fluid (CSF) tau and neurofilament light chain (NF-L) proteins have proved to be reliable biomarkers for neuronal damage; however, there is a strong need for blood-based tests.

METHODS

The present study included 132 autopsy cases with rapidly progressive neurological syndromes, including Alzheimer disease (AD) (21), sporadic (65) and genetic (21) Creutzfeldt-Jakob disease (CJD), 25 cases with vascular, neoplastic and inflammatory alterations, and additionally 18 healthy control individuals. CSF tau and NF-L concentrations were measured by enzyme-linked immunosorbent assay. Plasma tau and NF-L concentrations were measured using ultra-sensitive single molecule array technology.

RESULTS

Plasma and CSF tau (R = 0.59, P < 0.001) and NF-L (R = 0.69, P < 0.001) levels correlated significantly (Spearman test). Plasma tau and NF-L levels were significantly higher in all disease groups compared to healthy controls (P < 0.001). Receiver operating characteristic curves were used and area under the curve values for comparisons with controls were 0.82 (AD), 0.94 (sporadic CJD), 0.92 (genetic CJD) and 0.83 (other neurological disorders) for plasma tau and 0.99, 0.99, 1.00 and 0.96 for plasma NF-L, respectively. Molecular subtyping of sporadic CJD showed a strong effect (linear logistic regression) on plasma tau (P < 0.001) but not NF-L levels (P = 0.19).

CONCLUSION

Plasma tau and NF-L concentrations are strongly increased in CJD and show similar diagnostic performance to the corresponding CSF measure. Molecular subtypes of sporadic CJD show different levels of plasma tau. Although not disease-specific, these findings support the use of plasma tau and NF-L as tools to identify, or to rule out, neurodegeneration.

Tau pathology in Creutzfeldt-Jakob disease revisited

Creutzfeldt-Jakob disease (CJD) is a human prion disease with different etiologies. To determine the spectrum of tau pathologies in CJD, we assessed phospho-Tau (pTau) immunoreactivities in 75 sporadic CJD cases including an evaluation of the entorhinal cortex and six hippocampal subregions. Twelve cases (16%) showed only small tau-immunoreactive neuritic profiles. Fifty-two (69.3%) showed additional tau pathology in the medial temporal lobe compatible with primary age related tauopathy (PART). In 22/52 cases the lower pTau immunoreactivity load in the entorhinal cortex as compared to subiculum, dentate gyrus or CA4 region of the hippocampus was significantly different from the typical distribution of the Braak staging. A further 11 cases (14.7%) showed widespread tau pathologies compatible with features of primary tauopathies or the gray matter type of ageing-related tau astrogliopathy (ARTAG). Prominent gray matter ARTAG was also observed in two out of three additionally examined V203I genetic CJD cases. Analysis of cerebrospinal fluid revealed prominent increase of total tau protein in cases with widespread tau pathology, while pTau (T181) level was increased only in four. This correlated with immunohistochemical observations showing less pathology with anti-pTau T181 antibody when compared to anti-pTau S202/T205, T212/S214 and T231. The frequency of tau pathologies is not unusually high in sporadic CJD and does not precisely relate to PrP deposition. However, the pattern of hippocampal tau pathology often deviates from the stages of Braak. Currently applied examination of cerebrospinal fluid pTau (T181) level does not reliably reflect primary tauopathies, PART and ARTAG seen in CJD brains.

Dura mater is a potential source of Aβ seeds

Deposition of amyloid-β (Aβ) in the brain parenchyma and vessels is one of the hallmarks of Alzheimer disease (AD). Recent observations of Aβ deposition in iatrogenic Creutzfeldt-Jakob disease (iCJD) after dural grafting or treatment with pituitary extracts raised concerns whether Aβ is capable of transmitting disease as seen in prion diseases by the disease-associated prion protein. To address this issue, we re-sampled and re-evaluated archival material, including the grafted dura mater of two cases with iCJD (28 and 33-years-old) without mutations in the AβPP, PSEN1 and PSEN2 genes, and carrying ε3/ε3 alleles of the APOE gene. In addition, we evaluated 84 dura mater samples obtained at autopsy (mean age 84.9 ± 0.3) in the community-based VITA study for the presence of Aβ deposition. We show that the dura mater may harbor Aβ deposits (13 %) in the form of cerebral amyloid angiopathy or amorphous aggregates. In both iCJD cases, the grafted dura mater had accumulated Aβ. The morphology and distribution pattern of cerebral Aβ deposition together with the lack of tau pathology distinguishes the Aβ proteinopathy in iCJD from AD, from that seen in young individuals without cognitive decline carrying one or two APOE4 alleles, and from that related to traumatic brain injury. Our novel findings of Aβ deposits in the dura mater, including the grafted dura, and the distinct cerebral Aβ distribution in iCJD support the seeding properties of Aβ. However, in contrast to prion diseases, our study suggests that such Aβ seeding is unable to reproduce the full clinicopathological phenotype of AD.

Familial early-onset dementia with complex neuropathologic phenotype and genomic background

Despite significant progress in our understanding of hereditary neurodegenerative diseases, the list of genes associated with early-onset dementia is not yet complete. In the present study, we describe a familial neurodegenerative disorder characterized clinically as the behavioral and/or dysexecutive variant of Alzheimer's disease with neuroradiologic features of Alzheimer's disease, however, lacking amyloid-β deposits in the brain. Instead, we observed a complex, 4 repeat predominant, tauopathy, together with a TAR DNA-binding protein of 43 kDa proteinopathy. Whole-exome sequencing on 2 affected siblings and 1 unaffected aunt uncovered a large number of candidate genes, including LRRK2 and SYNE2. In addition, DDI1, KRBA1, and TOR1A genes possessed novel stop-gain mutations only in the patients. Pathway, gene ontology, and network interaction analysis indicated the involvement of pathways related to neurodegeneration but revealed novel aspects also. This condition does not fit into any well-characterized category of neurodegenerative disorders. Exome sequencing did not disclose a single disease-specific gene mutation suggesting that a set of genes working together in different pathways may contribute to the etiology of the complex phenotype.

The role of proto-oncogene GLI1 in pituitary adenoma formation and cell survival regulation

The Hedgehog (Hh) pathway is an important regulator of early tissue patterning and stem cell propagation. It was found to be aberrantly activated in numerous types of human cancer and might be relevant in cancer stem cells. The identification of adult stem cells in the pituitary raised the question if tumor-initiating cells and Hh signaling are involved in pituitary adenoma formation. The present study aimed at the evaluation of Hh signaling in relation to stem cell and cell cycle markers in 30 human pituitary adenomas and in cultured murine adenoma cells. Therefore, expression levels of components of the Hh pathway, stem cell marker SOX2, cell cycle regulator tumor-protein 53 (TP53), proliferation marker Ki67 (MKI67) and superoxide dismutase 1 (SOD1) were evaluated in 30 human pituitary adenomas in comparison to control tissue. Modulation of cell function and target gene expression by the inhibition and activation of the Hh pathway were studied in murine adenoma cells. We show that transcription factor glioma-associated oncogene 1 (GLI1) is overexpressed in 87% of all pituitary adenomas. The expression of GLI1 significantly correlated with that of SOX2, TP53, MKI67 and SOD1. Inhibition of GLI1 resulted in the downregulation of the above genes and severe cell death in mouse adenoma cells. On the other hand, activation of the Hh pathway increased cell viability and target gene expression. In conclusion, our findings point toward an alternative, ligand-independent Hh pathway activation with GLI1 playing a major role in the cell survival of pituitary adenoma cells.

Heroin abuse exaggerates age-related deposition of hyperphosphorylated tau and p62-positive inclusions

The observation of increased hyperphosphorylated tau levels correlating with microglial activation in opiate abusers has been interpreted as predisposition to accelerated Alzheimer disease-related changes. The present study focused on evaluating additional neurodegeneration-related proteins, including α-synuclein and TDP-43, and p62-positive deposits. We performed a systematic mapping of protein deposits in the brains of 27 individuals with documented heroin addiction (age: 19-40 years) and compared with 11 controls (age: 15-40 years). We confirm previous findings that heroin addiction associates with tau hyperphosphorylation in predilection brain areas for aging and Alzheimer disease. Furthermore, we show that this occurs also in areas implicated in the molecular disturbances and in vivo neuronal networks related to heroin abuse. There was, however, no presence of amyloid-beta deposits. We extend previous findings by showing the lack of TDP-43 or α-synuclein pathology and emphasize the independent effect of the duration of drug use on the appearance of age-related p62-positive neuritic profiles. These observations provide unique insights about neuropathological alterations in the brains of young heroin addicts and have implications about brain aging and the influences of environmental and toxic factors.