Intracellular inclusions composed of hyperphosphorylated filamentous tau are a hallmark of Alzheimer’s disease, progressive supranuclear palsy, Pick’s disease and other sporadic neurodegenerative tauopathies. Recent in vitro and in vivo studies have shown that tau aggregates do not only seed further tau aggregation within neurons, but can also spread to neighbouring cells and functionally connected brain regions. This process is referred to as ‘tau propagation’ and may explain the stereotypic progression of tau pathology in the brains of Alzheimer’s disease patients. Here, we describe a novel in vivo model of tau propagation using human P301S tau transgenic mice infused unilaterally with brain extract containing tau aggregates. Infusion-related neurofibrillary tangle pathology was first observed 2 weeks post-infusion and increased in a stereotypic, time-dependent manner. Contralateral and anterior/posterior spread of tau pathology was also evident in nuclei with strong synaptic connections (efferent and afferent) to the site of infusion, indicating that spread was dependent on synaptic connectivity rather than spatial proximity. This notion was further supported by infusion-related tau pathology in white matter tracts that interconnect these regions. The rapid and robust propagation of tau pathology in this model will be valuable for both basic research and the drug discovery process.Electronic supplementary materialThe online version of this article (doi:10.1007/s00401-014-1254-6) contains supplementary material, which is available to authorized users.

Significance Understanding loci nominated by genome-wide association studies (GWASs) is challenging. Here, we show, using the specific example of Parkinson disease, that identification of protein–protein interactions can help determine the most likely candidate for several GWAS loci. This result illustrates a significant general principle that will likely apply across multiple diseases.

The interneuronal propagation of aggregated tau is believed to play an important role in the pathogenesis of human tauopathies. It requires the uptake of seed-competent tau into cells, seeding of soluble tau in recipient neurons and release of seeded tau into the extracellular space to complete the cycle. At present, it is not known which tau species are seed-competent. Here, we have dissected the molecular characteristics of seed-competent tau species from the TgP301S tau mouse model using various biochemical techniques and assessed their seeding ability in cell and animal models. We found that sucrose gradient fractions from brain lysates seeded cellular tau aggregation only when large (Ͼ10 mer) aggregated, hyperphosphorylated (AT8-and AT100-positive) and nitrated tau was present. In contrast, there was no detectable seeding by fractions containing small, oligomeric (Ͻ6 mer) tau. Immunodepletion of the large aggregated AT8-positive tau strongly reduced seeding; moreover, fractions containing these species initiated the formation and spreading of filamentous tau pathology in vivo, whereas fractions containing tau monomers and small oligomeric assemblies did not. By electron microscopy, seed-competent sucrose gradient fractions contained aggregated tau species ranging from ring-like structures to small filaments. Together, these findings indicate that a range of filamentous tau aggregates are the major species that underlie the spreading of tau pathology in the P301S transgenic model.

A previous genome-wide association (GWA) meta-analysis of 12,386 PD cases and 21,026 controls conducted by the International Parkinson's Disease Genomics Consortium (IPDGC) discovered or confirmed 11 Parkinson's disease (PD) loci. This first analysis of the two-stage IPDGC study focused on the set of loci that passed genome-wide significance in the first stage GWA scan. However, the second stage genotyping array, the ImmunoChip, included a larger set of 1,920 SNPs selected on the basis of the GWA analysis. Here, we analyzed this set of 1,920 SNPs, and we identified five additional PD risk loci (combined p<5×10−10, PARK16/1q32, STX1B/16p11, FGF20/8p22, STBD1/4q21, and GPNMB/7p15). Two of these five loci have been suggested by previous association studies (PARK16/1q32, FGF20/8p22), and this study provides further support for these findings. Using a dataset of post-mortem brain samples assayed for gene expression (n = 399) and methylation (n = 292), we identified methylation and expression changes associated with PD risk variants in PARK16/1q32, GPNMB/7p15, and STX1B/16p11 loci, hence suggesting potential molecular mechanisms and candidate genes at these risk loci.

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms show that miR-7 is decreased in the substantia nigra of patients with PD and therefore may play an essential role in the regulation of α-synuclein expression. Furthermore, we have found that lentiviral mediated expression of miR-7 complementary binding sites to stably induce a loss of miR-7 function results in an increase in α-synuclein expression in vitro and in vivo. We have also shown that depletion of miR-7 using a miR-decoy produces a loss of nigral dopaminergic neurons accompanied by a reduction of striatal dopamine content. These data suggest that miR-7 has an important role in the regulation of α-synuclein and dopamine physiology and may provide a new paradigm to study the pathology of PD.3

Because the power of our analyses within strata of lifetime smoking history was limited, larger studies will be needed to confirm these findings.

Some previous studies have suggested that the fast phenotype of the N-acetyltransferase NAT2 may confer susceptibility to colorectal cancer because of greater activation of dietary heterocyclic amines, particularly in individuals who also consume well-done red meat, but other studies have not supported this. We describe a large case-control study examining the interaction between dietary, smoking and drinking habits, and acetylation genotype in relation to susceptibility to colorectal cancer. One-hundred-and-seventy-four incident cases and 174 matched controls were recruited. Genotyping for polymorphisms in NAT2 was performed using a method that detects >95% of slow alleles and data on personal habits were collected using a standardized questionnaire. We found no difference in the frequency of the fast acetylator genotype between cases and controls [odds ratio = 0.95 (95% CI 0.61-1.49)], and analysis by sex, age and site also revealed no difference in acetylator genotype. There was, however, considerable heterogeneity in dietary risk factors between fast and slow acetylators. Analysis by acetylator type shows that recent smoking was more frequent in slow acetylator cases than matched controls [OR = 2.31 (1.16-4.6)] and that heavy alcohol consumption was also more frequent in the slow acetylator cases than controls [OR = 2.5 (1.02-7.29)]. In contrast, frequent fried meat intake was seen more frequently in fast acetylator cases than matched controls [OR = 6.0 (1.34-55)]. The odds ratio for the combination of fast acetylator status and frequent fried meat consumption in cases was 6.04 (1.6-26). Our study suggests that there may be different risk factors for colorectal cancer in slow and fast acetylators, and reveals a new observation that slow acetylators may be at risk of colon cancer from smoking. In our community, the overall effect of acetylator status on colorectal cancer risk is neutral.

The catechol-O-methyltranferase (COMT) is one of the main enzymes that metabolise dopamine in the brain. The Val158Met polymorphism in the COMT gene (rs4680) causes a trimodal distribution of high (Val/Val), intermediate (Val/Met) and low (Met/Met) enzyme activity. We tested whether the Val158Met polymorphism is a modifier of the age at onset (AAO) in Parkinson's disease (PD). The rs4680 was genotyped in a total of 16 609 subjects from five independent cohorts of European and North American origin (5886 patients with PD and 10 723 healthy controls). The multivariate analysis for comparing PD and control groups was based on a stepwise logistic regression, with gender, age and cohort origin included in the initial model. The multivariate analysis of the AAO was a mixed linear model, with COMT genotype and gender considered as fixed effects and cohort and cohort-gender interaction as random effects. COMT genotype was coded as a quantitative variable, assuming a codominant genetic effect. The distribution of the COMT polymorphism was not significantly different in patients and controls (p=0.22). The Val allele had a significant effect on the AAO with a younger AAO in patients with the Val/Val (57.1±13.9, p=0.03) than the Val/Met (57.4±13.9) and the Met/Met genotypes (58.3±13.5). The difference was greater in men (1.9 years between Val/Val and Met/Met, p=0.007) than in women (0.2 years, p=0.81). Thus, the Val158Met COMT polymorphism is not associated with PD in the Caucasian population but acts as a modifier of the AAO in PD with a sexual dimorphism: the Val allele is associated with a younger AAO in men with idiopathic PD.