C9orf72 intermediate repeats are associated with corticobasal degeneration, increased C9orf72 expression and disruption of autophagy.

Microsatellite repeat expansion disease loci can exhibit pleiotropic clinical and biological effects depending on repeat length. Large expansions in C9orf72 (100s-1000s of units) are the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal degeneration (FTD). However, whether intermediate expansions also contribute to neurodegenerative disease is not well understood. Several studies have identified intermediate repeats in Parkinson's disease patients, but the association was not found in autopsy-confirmed cases. We hypothesized that intermediate C9orf72 repeats are a genetic risk factor for corticobasal degeneration (CBD), a neurodegenerative disease that can be clinically similar to Parkinson's but has distinct tau protein pathology. Indeed, intermediate C9orf72 repeats were significantly enriched in autopsy-proven CBD (n = 354 cases, odds ratio = 3.59, p = 0.00024). While large C9orf72 repeat expansions are known to decrease C9orf72 expression, intermediate C9orf72 repeats result in increased C9orf72 expression in human brain tissue and CRISPR/cas9 knockin iPSC-derived neural progenitor cells. In contrast to cases of FTD/ALS with large C9orf72 expansions, CBD with intermediate C9orf72 repeats was not associated with pathologic RNA foci or dipeptide repeat protein aggregates. Knock-in cells with intermediate repeats exhibit numerous changes in gene expression pathways relating to vesicle trafficking and autophagy. Additionally, overexpression of C9orf72 without the repeat expansion leads to defects in autophagy under nutrient starvation conditions. These results raise the possibility that therapeutic strategies to reduce C9orf72 expression may be beneficial for the treatment of CBD.

MicroRNA-125b induces tau hyperphosphorylation and cognitive deficits in Alzheimer's disease.

Sporadic Alzheimer's disease (AD) is the most prevalent form of dementia, but no clear disease-initiating mechanism is known. Aß deposits and neuronal tangles composed of hyperphosphorylated tau are characteristic for AD. Here, we analyze the contribution of microRNA-125b (miR-125b), which is elevated in AD. In primary neurons, overexpression of miR-125b causes tau hyperphosphorylation and an upregulation of p35, cdk5, and p44/42-MAPK signaling. In parallel, the phosphatases DUSP6 and PPP1CA and the anti-apoptotic factor Bcl-W are downregulated as direct targets of miR-125b. Knockdown of these phosphatases induces tau hyperphosphorylation, and overexpression of PPP1CA and Bcl-W prevents miR-125b-induced tau phosphorylation, suggesting that they mediate the effects of miR-125b on tau. Conversely, suppression of miR-125b in neurons by tough decoys reduces tau phosphorylation and kinase expression/activity. Injecting miR-125b into the hippocampus of mice impairs associative learning and is accompanied by downregulation of Bcl-W, DUSP6, and PPP1CA, resulting in increased tau phosphorylation in vivo. Importantly, DUSP6 and PPP1CA are also reduced in AD brains. These data implicate miR-125b in the pathogenesis of AD by promoting pathological tau phosphorylation.

Profiling of methylation and demethylation pathways during brain development and ageing.

Numerous signal pathways are epigenetically controlled during brain development and ageing. Thereby, both 5-methylcytosine (5mC) and the newly described 5-hydroxymethylcytosine (5hmC) are highly exhibited in the brain. As there is an uneven distribution of 5hmC in the brain depending on age and region, there is the need to investigate the underlying mechanisms being responsible for 5hmC generation and decline. The aim of this study was to quantify expression levels of genes that are associated with DNA methylation/demethylation in different brain regions and at different ages. Therefore, we investigated frontal cortex and cerebellum of 40 mice (strain C57BL/6), each eight mice sacrificed at day 0, 7, 15, 30 and 120 after birth. We performed expression profiling of methylation/demethylation genes depending on age and brain region. Interestingly, we see significant expression differences of genes being responsible for methylation/demethylation with a significant reduction of expression levels during ageing. Validating selected expression data on protein level using immunohistochemistry verified the expression data. In conclusion, our findings demonstrate that the regulation of methylation/demethylation pathways is highly controlled depending on brain region and age. Thus our data will help to better understand the complexity and plasticity of the brain epigenome.

Clinical findings and diagnosis in genetic prion diseases in Germany.

To describe the clinical syndrome and diagnostic tests in patients with genetic prion diseases (gPD) in Germany. Clinical features, MRI, EEG, and CSF markers were studied in 91 patients (28 D178N, 20 E200K, 17 inserts, 13 V210I, 8 P102L, 5 E196K). Dementia (35 %) and ataxia (29 %) were the most common initial symptoms and signs. A wide variety and high frequency of neurological/psychiatric symptoms and signs was found during disease course in all patients independently of the type of the mutation. Psychiatric manifestations were frequent (87 %). Neuropsychological abnormalities were observed in 67 %, and aphasia was the most common disturbance (45 %). In E200K, V210I and D178N patients, visual/oculomotor deficits were followed by ataxia early in the disease. Dementia followed by ataxia at onset was common in patients with insert and E196K mutation. P102L patients had isolated ataxia over a longer time period followed by pyramidal signs. Dementia was present only late in the disease course. All clinical routine tests such as MRI, EEG and CSF tests were less sensitive than in sporadic CJD. We provide the first detailed analysis of clinical signs and symptoms in a large group of patients with gPD. Frequency of clinical symptoms and signs was similar in different mutations in a later disease course, but the sequence of occurrence may be of great diagnostic importance. CSF markers were shown to be more sensitive than MRI and EEG.

Dynamic 18F-FET PET in suspected WHO grade II gliomas defines distinct biological subgroups with different clinical courses.

In suspected grade II gliomas, three distinct patterns of time-activity curves (TAC) on O-(2-[(18)F]fluoroethyl)-1-tyrosine ((18)F-FET) positron emission tomography (PET) have been delineated (i) increasing TAC homogeneously throughout the tumor, and decreasing TAC, (ii) either homogeneously throughout the tumor or (iii) only focally within otherwise increasing TAC patterns. Increasing TAC was associated with low-grade histology and decreasing TAC with high-grade histology. This prospective study analyzed whether these patterns correlate with distinct biological tumor subtypes and differential outcome. (18)F-FET PET-guided biopsies were used for stepwise histopathological evaluation. Molecular-genetic evaluation included O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation, isocitrate dehydrogenase (IDH1/2) mutational and 1p/19q codeletion status. Progression-free survival (PFS) was estimated with the Kaplan-Meier method. Prognostic factors were obtained from multivariate regression models. 98 adult patients were included. Homogeneous increasing, focal decreasing and homogeneous decreasing TAC were seen in 51, 19 and 28 patients. The corresponding 1-year (2-years) PFS were 92% (85%), 89% (51%) and 50% (28%; p = 0.002). IDH1/2 mutations were more frequent in tumors with homogeneous increasing (90%) and focal decreasing (79%) TAC, but were rare in those exhibiting homogeneous decreasing TAC (25%; p < 0.001). Overall, TAC patterns, IDH1/2 mutational and 1p/19q codeletion status were powerful and independent prognostic factors. Dynamic (18)F-FET PET might be an important and independent imaging biomarker for patients with suspected WHO grade II gliomas and offers perspectives for stratified diagnostic and therapeutic strategies. Tumors with focal decreasing TAC need highly targeted surgical interventions to avoid undergrading and undertreatment.

The cellular prion protein mediates neurotoxic signalling of ß-sheet-rich conformers independent of prion replication.

Formation of aberrant protein conformers is a common pathological denominator of different neurodegenerative disorders, such as Alzheimer's disease or prion diseases. Moreover, increasing evidence indicates that soluble oligomers are associated with early pathological alterations and that oligomeric assemblies of different disease-associated proteins may share common structural features. Previous studies revealed that toxic effects of the scrapie prion protein (PrP(Sc)), a ß-sheet-rich isoform of the cellular PrP (PrP(C)), are dependent on neuronal expression of PrP(C). In this study, we demonstrate that PrP(C) has a more general effect in mediating neurotoxic signalling by sensitizing cells to toxic effects of various ß-sheet-rich (ß) conformers of completely different origins, formed by (i) heterologous PrP, (ii) amyloid ß-peptide, (iii) yeast prion proteins or (iv) designed ß-peptides. Toxic signalling via PrP(C) requires the intrinsically disordered N-terminal domain (N-PrP) and the GPI anchor of PrP. We found that the N-terminal domain is important for mediating the interaction of PrP(C) with ß-conformers. Interestingly, a secreted version of N-PrP associated with ß-conformers and antagonized their toxic signalling via PrP(C). Moreover, PrP(C)-mediated toxic signalling could be blocked by an NMDA receptor antagonist or an oligomer-specific antibody. Our study indicates that PrP(C) can mediate toxic signalling of various ß-sheet-rich conformers independent of infectious prion propagation, suggesting a pathophysiological role of the prion protein beyond of prion diseases.

Reducing tau aggregates with anle138b delays disease progression in a mouse model of tauopathies.

Pathological tau aggregation leads to filamentous tau inclusions and characterizes neurodegenerative tauopathies such as Alzheimer's disease and frontotemporal dementia and parkinsonism linked to chromosome 17. Tau aggregation coincides with clinical symptoms and is thought to mediate neurodegeneration. Transgenic mice overexpressing mutant human P301S tau exhibit many neuropathological features of human tauopathies including behavioral deficits and increased mortality. Here, we show that the di-phenyl-pyrazole anle138b binds to aggregated tau and inhibits tau aggregation in vitro and in vivo. Furthermore, anle138b treatment effectively ameliorates disease symptoms, increases survival time and improves cognition of tau transgenic PS19 mice. In addition, we found decreased synapse and neuron loss accompanied by a decreased gliosis in the hippocampus. Our results suggest that reducing tau aggregates with anle138b may represent an effective and promising approach for the treatment of human tauopathies.

Loss of 5-hydroxymethylcytosine and intratumoral heterogeneity as an epigenomic hallmark of glioblastoma.

Glioblastoma (GBM) is the most malignant neoplasm with predominant astrocytic differentiation and the most frequent primary brain tumor of the adult. Here, we investigated 170 human GBM specimens deriving from 162 patients, as well as 66 healthy control tissue specimens deriving from 27 patients, and analyzed the amount of 5-hydroxymethylcytosine (5hmC) in GBMs compared to normal brain and tumor infiltration zones. Additionally, we correlated the amount of 5hmC with two different proliferation markers, Ki67 and H3S10p. Genetic characterization of GBMs enabled us to analyze the effect of isocitrate dehydrogenase 1 (IDH1) mutations, O6-methylguanin-DNA-methyltransferase (MGMT) promoter methylation, and loss of heterozygosity of chromosome 1p and 19q (LOH1p/19q) on 5hmC amount. We found that GBMs show a tremendous loss of 5hmC, and we observed that even the infiltration zones show reduced amounts of 5hmC. Interestingly, the amount of 5hmC was inversely proportional to the two investigated proliferation markers, Ki67 and H3S10p. Correlation of 5hmC amount and molecular genetic markers of GBMs showed that there are no correlations of 5hmC amount and IDH1 mutations, MGMT promoter methylation, and LOH1p/19q. Furthermore, we evaluated the intratumoral distribution of 5hmC in compact and infiltrating areas and found that the quantification of the 5hmC amount is a useful tool in evaluation of tumor infiltration. In summary, our data emphasize that GBMs show a disturbed hydroxymethylome that is disrupted by IDH1 independent pathways, and that loss of 5hmC shows astonishing intratumoral heterogeneity.

5-Hydroxymethylcytosine, the "Sixth Base", during brain development and ageing.

The epigenome is of fundamental importance for development and ageing. The discovery of 5-hydroxymethylcytosine (5hmC), a further base modification of cytosine beyond 5-methylcytosine, might be of high relevance in understanding the complexity of the human brain, as 5hmC is found in great extent in brain tissue. The aim of this study was to investigate the quantity of 5hmC containing nuclei by immunohistochemistry in human and murine brains at several developmental stages. We performed immunohistochemical stainings on frontal cortex, white matter and cerebellar cortex of 15 healthy controls. Three cases each were assigned to five age groups (foetus, adolescent, adult, elderly, aged). Additionally, cortex and cerebellum of 15 mice sacrificed between day 0 and 120 after birth were investigated. We found marked alterations of 5hmC amount during ageing. In human cortex there was an increase of 5hmC of 50%, in white matter we found an increase of even 200% during ageing. In the cerebellum both internal granular cell layer and molecular cell layer showed a significant increase of 5hmC till adulthood. Purkinje cell nuclei showed constantly positive signals for 5hmC. These data were paralleled in murine brains. Co-labelling of 5hmC and markers for mature and immature cells in murine cerebellar cortex at the age of 7 days revealed that 5hmC was found in mature but not in immature cells. In conclusion, the findings described in this study emphasise the importance of 5hmC in brain development and ageing and will help to better understand the complexity and plasticity of the brain.

Long non-coding RNA normalisers in human brain tissue.

The family of long non-coding RNA (lncRNA) is of increasing scientific interest as there is emerging evidence, that lncRNAs are of essential importance for transcriptional and translational control, genomic imprinting and regulation of normal development as well as neuronal plasticity. As the generation of reliable expression profiles requires adequate normalisers, it is of fundamental importance to determine suitable references for lncRNA studies. However, to date no systematic analysis of potential lncRNA normalisers has been performed on human postmortem brain tissue samples. In this study, we investigated three different brain regions (cortex, white matter, and cerebellum) of human postmortem tissue and analysed the expression stability of 90 lncRNAs. Bioinformatical analysis was performed to identify stably expressed lncRNAs. Subsequently, lncRNAs were classified according to their stability values using the NormFinder algorithm. We identified 30 suitable normalisers in cortex, 22 in white matter, and 41 in cerebellum. In addition, there were 13 suitable normalisers for studies comparing cortex and white matter, 25 for studies comparing cortex and cerebellum and 7 for studies comparing white matter and cerebellum. 5 lncRNAs (LUST, IGF2AS (family), 7SK, HOXA6as, NDM29) showed stable expression in all investigated brain regions. A subsequent analysis of the influence of postmortem intervals (PMI) on expression of lncRNAs revealed that expression levels of the newly identified 5 universal lncRNA normalisers are stable within PMI of up to 27 h. Thus, these 5 lncRNAs may be applicable as references for accurate normalisation of lncRNA profiling in multiple brain regions during long PMI, enabling the generation of highly reproducible datasets in lncRNA studies of the human brain.

Three novel presenilin 1 mutations marking the wide spectrum of age at onset and clinical patterns in familial Alzheimer's disease.

Presenilin 1 (PSEN1) mutations are the major cause of autosomal dominant Alzheimer's disease (ADAD). Here we report three novel PSEN1 mutations: Ile238_Lys239insIle, Ala246Pro and Ala164Val from patients who manifested in their twenties, forties and seventies, respectively, with variant clinical presentations of dementia. These cases exemplify the tremendous heterogeneity of clinical phenotypes and age of onset associated with PSEN1 mutations. The possibility of ADAD--not previously suspected in two of our patients--should always be considered in neurodegenerative conditions albeit they might neither exhibit the typical clinical picture of Alzheimer's disease nor early onset dementia, which is regarded the primary clinical sign of hereditary neurodegeneration.

Common mechanisms in neurodegeneration and neuroinflammation: a BrainNet Europe gene expression microarray study.

Neurodegenerative diseases of the central nervous system are characterized by pathogenetic cellular and molecular changes in specific areas of the brain that lead to the dysfunction and/or loss of explicit neuronal populations. Despite exhibiting different clinical profiles and selective neuronal loss, common features such as abnormal protein deposition, dysfunctional cellular transport, mitochondrial deficits, glutamate excitotoxicity, iron accumulation and inflammation are observed in many neurodegenerative disorders, suggesting converging pathways of neurodegeneration. We have generated comparative genome-wide gene expression data, using the Illumina HumanRef 8 Beadchip, for Alzheimer's disease, amyotrophic lateral sclerosis, Huntington's disease, multiple sclerosis, Parkinson's disease, and schizophrenia using an extensive cohort (n = 113) of well-characterized post-mortem brain tissues. The analysis of whole-genome expression patterns across these major disorders offers an outstanding opportunity not only to look into exclusive disease-specific changes, but more importantly to look for potential common molecular pathogenic mechanisms. Surprisingly, no dysregulated gene that passed our selection criteria was found in common across all six diseases. However, 61 dysregulated genes were shared when comparing five and four diseases. The few genes highlighted by our direct gene comparison analysis hint toward common neuronal homeostatic, survival and synaptic plasticity pathways. In addition, we report changes to several inflammation-related genes in all diseases. This work is supportive of a general role of the innate immune system in the pathogenesis and/or response to neurodegeneration.

The workflow from post-mortem human brain sampling to cell microdissection: a Brain Net Europe study.

Brain banks manage and store fully clinically and pathologically characterised brains. The diversity of techniques used in research projects increases. These biological resource centres are made to adapt brain tissue processing. Furthermore, the development of more sensitive techniques to analyse nucleic acids and proteins offers new fields of exploration when combined with laser capture microdissection in order to decipher the physiopathology of diseases at the cell level. In this study, our goal was to evaluate procedures and set a workflow compatible with the constraints of brain banks, from brain sampling to laser capture microdissection and pre-analytical quality assessment. We compared various methods of freezing brain tissue, focused on morphological quality preservation of brain microscopical structures and on the quality of nucleic acid or protein yields. Staining protocols combined with strategies to lower neurones autofluorescence were adapted for the same purpose. Finally, we found that laser capture microdissection is possible in the setting of brain banks. However, the entire process has to be envisioned from the autopsy to the analysis. The impact on protein or nucleic acid quality is a limitation that restricts the amount of samples available for this purpose.

Neuropathological assessments of the pathology in frontotemporal lobar degeneration with TDP43-positive inclusions: an inter-laboratory study by the BrainNet Europe consortium.

The BrainNet Europe consortium assessed the reproducibility in the assignment of the type of frontotemporal lobar degeneration (FTLD) with TAR DNA-binding protein (TDP) 43 following current recommendations. The agreement rates were influenced by the immunohistochemical (IHC) method and by the classification strategy followed. p62-IHC staining yielded good uniform quality of stains, but the most reliable results were obtained implementing specific Abs directed against the hallmark protein TDP43. Both assessment of the type and the extent of lesions were influenced by the Abs and by the quality of stain. Assessment of the extent of the lesions yielded poor results repeatedly; thus, the extent of pathology should not be used in diagnostic consensus criteria. Whilst 31 neuropathologists typed 30 FTLD-TDP cases, inter-rater agreement ranged from 19 to 100 per cent, being highest when applying phosphorylated TDP43/IHC. The agreement was highest when designating Type C or Type A/B. In contrast, there was a poor agreement when attempting to separate Type A or Type B FTLD-TDP. In conclusion, we can expect that neuropathologist, independent of his/her familiarity with FTLD-TDP pathology, can identify a TDP43-positive FTLD case. The goal should be to state a Type (A, B, C, D) or a mixture of Types (A/B, A/C or B/C). Neuropathologists, other clinicians and researchers should be aware of the pitfalls whilst doing so. Agreement can be reached in an inter-laboratory setting regarding Type C cases with thick and long neurites, whereas the differentiation between Types A and B may be more troublesome.

Age-dependent levels of 5-methyl-, 5-hydroxymethyl-, and 5-formylcytosine in human and mouse brain tissues.

The absolute levels of 5-hydroxymethylcytosine (hmC) and 5-methylcytosine (mC) in human brain tissues at various ages were determined. Additionally, absolute levels of 5-formylcytosine (fC) in adult individuals and cytosine modification levels in sorted neurons were quantified. These data were compared with age-related fC, hmC, and mC levels in mouse brain samples. For hmC, an initial steady increase is observed, which levels off with age to a final steady-state value of 1.2 % in human brain tissue. This level is nearly twice as high as in mouse cerebral cortex. In contrast, fC declines rapidly with age during early developmental stages, thus suggesting that while hmC is a stable epigenetic mark, fC is more likely an intermediate of active DNA demethylation during early brain development. The trends in global cytosine modification dynamics during the lifespan of an organism are conserved between humans and mice and show similar patterns in different organs.

Constitutive activation of ß-catenin in neural progenitors results in disrupted proliferation and migration of neurons within the central nervous system.

Wnt signaling is known to play crucial roles in the development of multiple organs as well as in cancer. In particular, constitutive activation of Wnt/ß-Catenin signaling in distinct populations of forebrain or brainstem precursor cells has previously been shown to result in dramatic brain enlargement during embryonic stages of development as well as in the formation of medulloblastoma, a malignant brain tumor in childhood. In order to extend this knowledge to postnatal stages of both cerebral and cerebellar cortex development, we conditionally activated Wnt signaling by introducing a dominant active form of ß-catenin in hGFAP-positive neural precursors. Such mutant mice survived up to 21 days postnatally. While the mice revealed enlarged ventricles and an initial expansion of the Pax6-positive ventricular zone, Pax6 expression and proliferative activity in the ventricular zone was virtually lost by embryonic day 16.5. Loss of Pax6 expression was not followed by expression of the subventricular zone marker Tbr2, indicating insufficient neuronal differentiation. In support of this finding, cortical thickness was severely diminished in all analyzed stages from embryonic day 14.5 to postnatal day 12, and appropriate layering was not detectable. Similarly, cerebella of hGFAP-cre::Ctnnb1(ex3)(Fl/+) mice were hypoplastic and displayed severe lamination defects. Constitutively active ß-Catenin induced inappropriate proliferation of granule neurons and inadequate development of Bergmann glia, thereby preventing regular migration of granule cells and normal cortical layering. We conclude that Wnt signaling has divergent roles in the central nervous system and that Wnt needs to be tightly controlled in a time- and cell type-specific manner.

Analyses of protease resistance and aggregation state of abnormal prion protein across the spectrum of human prions.

Prion diseases are characterized by tissue accumulation of a misfolded, ß-sheet-enriched isoform (scrapie prion protein (PrP(Sc))) of the cellular prion protein (PrP(C)). At variance with PrP(C), PrP(Sc) shows a partial resistance to protease digestion and forms highly aggregated and detergent-insoluble polymers, two properties that have been consistently used to distinguish the two proteins. In recent years, however, the idea that PrP(Sc) itself comprises heterogeneous species has grown. Most importantly, a putative proteinase K (PK)-sensitive form of PrP(Sc) (sPrP(Sc)) is being increasingly investigated for its possible role in prion infectivity, neurotoxicity, and strain variability. The study of sPrP(Sc), however, remains technically challenging because of the need of separating it from PrP(C) without using proteases. In this study, we have systematically analyzed both PK resistance and the aggregation state of purified PrP(Sc) across the whole spectrum of the currently characterized human prion strains. The results show that PrP(Sc) isolates manifest significant strain-specific differences in their PK digestion profile that are only partially explained by differences in the size of aggregates, suggesting that other factors, likely acting on PrP(Sc) aggregate stability, determine its resistance to proteolysis. Fully protease-sensitive low molecular weight aggregates were detected in all isolates but in a limited proportion of the overall PrP(Sc) (i.e. <10%), arguing against a significant role of slowly sedimenting PK-sensitive PrP(Sc) in the biogenesis of prion strains. Finally, we highlight the limitations of current operational definitions of sPrP(Sc) and of the quantitative analytical measurements that are not based on the isolation of a fully PK-sensitive PrP(Sc) form.

Lack of Pur-alpha alters postnatal brain development and causes megalencephaly.

Pur-alpha (Purα) plays an important role in a variety of cellular processes including transcriptional regulation, cell proliferation and oncogenic transformation. To better understand the role of Purα in the developing and mature brain, we generated Purα-deficient mice, which we were able to raise to the age of six months. Purα(-/-) mice were born with no obvious pathological condition. We obtained convincing evidence that lack of Purα prolongs the postnatal proliferation of neuronal precursor cells both in the hippocampus and in the cerebellum, however, without affecting the overall number of postmitotic neurons. Independent of these findings, we observed alterations in the expression and distribution of the dendritic protein MAP2, the translation of which has been proposed previously to be Purα-dependent. At the age of 2 weeks, Purα(-/-) mice generated a continuous tremor which persisted throughout lifetime. Finally, adult Purα(-/-) mice displayed a megalencephaly and histopathological findings including axonal swellings and hyperphosphorylation of neurofilaments. Our studies underline the importance of Purα in the proliferation of neuronal precursor cells during postnatal brain development and suggest a role for Purα in the regulation of the expression and cellular distribution of dendritic and axonal proteins. Since recent studies implicate a link between Purα and the fragile X tremor/ataxia syndrome, our Purα(-/-) mouse model will provide new opportunities for understanding the mechanisms of neurodegeneration.

Genome-wide association study in multiple human prion diseases suggests genetic risk factors additional to PRNP.

Prion diseases are fatal neurodegenerative diseases of humans and animals caused by the misfolding and aggregation of prion protein (PrP). Mammalian prion diseases are under strong genetic control but few risk factors are known aside from the PrP gene locus (PRNP). No genome-wide association study (GWAS) has been done aside from a small sample of variant Creutzfeldt-Jakob disease (CJD). We conducted GWAS of sporadic CJD (sCJD), variant CJD (vCJD), iatrogenic CJD, inherited prion disease, kuru and resistance to kuru despite attendance at mortuary feasts. After quality control, we analysed 2000 samples and 6015 control individuals (provided by the Wellcome Trust Case Control Consortium and KORA-gen) for 491032-511862 SNPs in the European study. Association studies were done in each geographical and aetiological group followed by several combined analyses. The PRNP locus was highly associated with risk in all geographical and aetiological groups. This association was driven by the known coding variation at rs1799990 (PRNP codon 129). No non-PRNP loci achieved genome-wide significance in the meta-analysis of all human prion disease. SNPs at the ZBTB38-RASA2 locus were associated with CJD in the UK (rs295301, P = 3.13 × 10(-8); OR, 0.70) but these SNPs showed no replication evidence of association in German sCJD or in Papua New Guinea-based tests. A SNP in the CHN2 gene was associated with vCJD [P = 1.5 × 10(-7); odds ratio (OR), 2.36], but not in UK sCJD (P = 0.049; OR, 1.24), in German sCJD or in PNG groups. In the overall meta-analysis of CJD, 14 SNPs were associated (P < 10(-5); two at PRNP, three at ZBTB38-RASA2, nine at nine other independent non-PRNP loci), more than would be expected by chance. None of the loci recently identified as genome-wide significant in studies of other neurodegenerative diseases showed any clear evidence of association in prion diseases. Concerning common genetic variation, it is likely that the PRNP locus contains the only strong risk factors that act universally across human prion diseases. Our data are most consistent with several other risk loci of modest overall effects which will require further genetic association studies to provide definitive evidence.