Characterisation and prion transmission study in mice with genetic reduction of sporadic Creutzfeldt-Jakob disease risk gene Stx6.

Sporadic Creutzfeldt-Jakob disease (sCJD), the most common human prion disease, is thought to occur when the cellular prion protein (PrPC) spontaneously misfolds and assembles into prion fibrils, culminating in fatal neurodegeneration. In a genome-wide association study of sCJD, we recently identified risk variants in and around the gene STX6, with evidence to suggest a causal increase of STX6 expression in disease-relevant brain regions. STX6 encodes syntaxin-6, a SNARE protein primarily involved in early endosome to trans-Golgi network retrograde transport. Here we developed and characterised a mouse model with genetic depletion of Stx6 and investigated a causal role of Stx6 expression in mouse prion disease through a classical prion transmission study, assessing the impact of homozygous and heterozygous syntaxin-6 knockout on disease incubation periods and prion-related neuropathology. Following inoculation with RML prions, incubation periods in Stx6-/- and Stx6+/- mice differed by 12 days relative to wildtype. Similarly, in Stx6-/- mice, disease incubation periods following inoculation with ME7 prions also differed by 12 days. Histopathological analysis revealed a modest increase in astrogliosis in ME7-inoculated Stx6-/- animals and a variable effect of Stx6 expression on microglia activation, however no differences in neuronal loss, spongiform change or PrP deposition were observed at endpoint. Importantly, Stx6-/- mice are viable and fertile with no gross impairments on a range of neurological, biochemical, histological and skeletal structure tests. Our results provide some support for a pathological role of Stx6 expression in prion disease, which warrants further investigation in the context of prion disease but also other neurodegenerative diseases considering syntaxin-6 appears to have pleiotropic risk effects in progressive supranuclear palsy and Alzheimer's disease.

Humanized Transgenic Mice Are Resistant to Chronic Wasting Disease Prions From Norwegian Reindeer and Moose.

Chronic wasting disease (CWD) is the transmissible spongiform encephalopathy or prion disease affecting cervids. In 2016, the first cases of CWD were reported in Europe in Norwegian wild reindeer and moose. The origin and zoonotic potential of these new prion isolates remain unknown. In this study to investigate zoonotic potential we inoculated brain tissue from CWD-infected Norwegian reindeer and moose into transgenic mice overexpressing human prion protein. After prolonged postinoculation survival periods no evidence for prion transmission was seen, suggesting that the zoonotic potential of these isolates is low.

Highly infectious prions are not directly neurotoxic.

Prions are infectious agents which cause rapidly lethal neurodegenerative diseases in humans and animals following long, clinically silent incubation periods. They are composed of multichain assemblies of misfolded cellular prion protein. While it has long been assumed that prions are themselves neurotoxic, recent development of methods to obtain exceptionally pure prions from mouse brain with maintained strain characteristics, and in which defined structures-paired rod-like double helical fibers-can be definitively correlated with infectivity, allowed a direct test of this assertion. Here we report that while brain homogenates from symptomatic prion-infected mice are highly toxic to cultured neurons, exceptionally pure intact high-titer infectious prions are not directly neurotoxic. We further show that treatment of brain homogenates from prion-infected mice with sodium lauroylsarcosine destroys toxicity without diminishing infectivity. This is consistent with models in which prion propagation and toxicity can be mechanistically uncoupled.

Hereditary angioedema: the challenges of cross-border family investigation and treatment.

Hereditary angioedema (HAE) is a rare genetic disorder characterised by recurrent swellings involving subcutaneous and submucosal tissue that can be potentially life threatening in cases involving the upper airway. In this case report, we present a Syrian refugee family with HAE who have lived in Denmark since 2014. The index patient is an 8-year-old girl diagnosed with HAE after being hospitalised in Denmark with an angioedema attack. Her younger sister and father were diagnosed later, following investigation of the family. Exploring the family history, deaths due to suffocation were described in previous generations and other family members based in Sweden, Germany, Turkey, Saudi Arabia, USA and Syria could also potentially be affected. This highlights the need for a cross-border effort to diagnose and treat this inherited disorder.

Altered Gray Matter Structure and White Matter Microstructure in Patients with Congenital Adrenal Hyperplasia: Relevance for Working Memory Performance.

Congenital adrenal hyperplasia (CAH) has been associated with brain structure alterations, but systematic studies are lacking. We explore brain morphology in 37 (21 female) CAH patients and 43 (26 female) healthy controls, aged 16-33 years, using structural magnetic resonance imaging to estimate cortical thickness, surface area, volume, subcortical volumes, and white matter (WM) microstructure. We also report data on a small cohort of patients (n = 8) with CAH, who received prenatal dexamethasone (DEX). Patients with CAH had reduced whole brain volume (4.23%) and altered structure of the prefrontal, parietal, and superior occipital cortex. Patients had reduced mean FA, and reduced RD and MD, but not after correcting for brain volume. The observed regions are hubs of the visuospatial working memory and default mode (DMN) networks. Thickness of the left superior parietal and middle frontal gyri was associated with visuospatial working memory performance, and patients with CAH performed worse on this task. Prenatal treatment with DEX affected brain structures in the parietal and occipital cortex, but studies in larger cohorts are needed. In conclusion, our study suggests that CAH is associated with brain structure alterations, especially in the working memory network, which might underlie the cognitive outcome observed in patients.

Evaluation of behavioral problems after prenatal dexamethasone treatment in Swedish children and adolescents at risk of congenital adrenal hyperplasia.

Prenatal dexamethasone (DEX) treatment in congenital adrenal hyperplasia (CAH) is effective in reducing virilization in affected girls, but potential long-term adverse effects are largely unknown. In this report we intended to explore potential side effects of DEX therapy to enhance the adequacy of future risk benefit analyses of DEX treatment. We investigated the long-term effects of first trimester prenatal DEX treatment on behavioral problems and temperament in children and adolescents aged 7-17 years. The study included 34 children and adolescents, without CAH, who had been exposed to DEX during the first trimester and 67 untreated controls. Standardized parent-completed questionnaires were used to evaluate adaptive functioning and behavioral/emotional problems (CBCL), social anxiety (SPAI-C-P), and temperament (EAS) in the child. Self-reports were used to assess the children's perception of social anxiety (SASC-R). No statistically significant differences were found between DEX-treated and control children and adolescents, suggesting that, in general, healthy children treated with DEX during early fetal life are well adjusted.

Sex-Dimorphic Effects of Prenatal Treatment With Dexamethasone.

CONTEXT: Dexamethasone (DEX) is used to prevent virilization in female fetuses at risk of congenital adrenal hyperplasia (CAH). Given that treatment has to be started before the genotype is known, 7 out of 8 fetuses will be exposed to DEX without benefit. OBJECTIVE: To evaluate long-term cognitive effects of prenatal DEX therapy in healthy (non-CAH) DEX-treated children. DESIGN AND SETTING: Observational study with patient and control groups from a single research institute. PARTICIPANTS: Healthy (non-CAH) DEX-treated subjects (n = 34) and untreated population controls (n = 66) from Sweden, aged 7-17 years. INTERVENTION: DEX-treatment used in unborn children at risk of CAH, during first trimester of fetal life. MAIN OUTCOME MEASURES: Standardized neuropsychological tests and questionnaires were used. RESULTS: DEX treatment has widespread negative effects in girls. In Wechsler Intelligence Scales for Children-III scale subtests, we observed significant interactions between DEX and GENDER (coding, P = .044; block design, P = .013; vocabulary, P = .025) and a trend for the subtest digit span (P = .074). All interactions were driven by DEX effects in girls, but not boys, with DEX-treated females showing lower scores than female untreated controls (coding, P = .068, d = 0.66; block design, P = .021, d = 0.81; vocabulary, P = .014, d = 0.84; digit span, P = .001, d = 1.0). Likewise, DEX-treated girls tend to have poorer visual spatial working memory performance than controls (span board test forward: P = .065, d = .80). We observed no effects on long-term memory, handedness, speed of processing, nor self-perceived or parentally reported scholastic performance. CONCLUSIONS: Early prenatal DEX exposure affects cognitive functions in healthy girls, ie, children who do not benefit from the treatment. It can therefore not be considered safe to use this therapy in the context of CAH.

RETRACTED: Evaluation of behavioral problems after prenatal dexamethasone treatment in Swedish adolescents at risk of CAH.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the authors due to technical errors that have called into question the reliability of the data used to inform the author's conclusions. All data on cognitive and behavioral outcomes in CAH and non­CAH cases, treated or not treated with DEX prenatally, were put into a single Excel database. The authors had in total four different patient groups for each age group (5­6 y, 7­17 y and 18-35 y). The database consisted of 237 cases in total and there were multiple columns for the different outcome measures. When the behavioral data for the sub-cohort described in this paper (first trimester treated non-CAH cases and healthy population controls, age 7­17 y) were copied to another sheet and compressed/modified in preparation for statistical analysis in SPSS, an error occurred. This technological issue caused rows to shift and the data from the different groups got mixed up. In particular, the non­CAH group versus the control group were "contaminated" with cases from the wrong patient group. The authors discovered this mistake when they started to analyse the data from the other sub­groups of patients, the CAH cases and the adult cohort, which was after their original results had already been published in Hormones and Behavior in this manuscript "Evaluation of behavioral problems after prenatal dexamethasone treatment in Swedish adolescents at risk of CAH". It then became apparent that the entire data set was unreliable and needed to be re­analysed which is what has motivated the retraction of this article. The authors have recently completed this re­analysis and the results have been published here: https://www.sciencedirect.com/science/article/pii/S0018506X17300752

A systematic investigation of production of synthetic prions from recombinant prion protein.

According to the protein-only hypothesis, infectious mammalian prions, which exist as distinct strains with discrete biological properties, consist of multichain assemblies of misfolded cellular prion protein (PrP). A critical test would be to produce prion strains synthetically from defined components. Crucially, high-titre 'synthetic' prions could then be used to determine the structural basis of infectivity and strain diversity at the atomic level. While there have been multiple reports of production of prions from bacterially expressed recombinant PrP using various methods, systematic production of high-titre material in a form suitable for structural analysis remains a key goal. Here, we report a novel high-throughput strategy for exploring a matrix of conditions, additives and potential cofactors that might generate high-titre prions from recombinant mouse PrP, with screening for infectivity using a sensitive automated cell-based bioassay. Overall, approximately 20,000 unique conditions were examined. While some resulted in apparently infected cell cultures, this was transient and not reproducible. We also adapted published methods that reported production of synthetic prions from recombinant hamster PrP, but again did not find evidence of significant infectious titre when using recombinant mouse PrP as substrate. Collectively, our findings are consistent with the formation of prion infectivity from recombinant mouse PrP being a rare stochastic event and we conclude that systematic generation of prions from recombinant PrP may only become possible once the detailed structure of authentic ex vivo prions is solved.

N-terminal domain of prion protein directs its oligomeric association.

The self-association of prion protein (PrP) is a critical step in the pathology of prion diseases. It is increasingly recognized that small non-fibrillar ß-sheet-rich oligomers of PrP may be of crucial importance in the prion disease process. Here, we characterize the structure of a well defined ß-sheet-rich oligomer, containing ∼12 PrP molecules, and often enclosing a central cavity, formed using full-length recombinant PrP. The N-terminal region of prion protein (residues 23-90) is required for the formation of this distinct oligomer; a truncated form comprising residues 91-231 forms a broad distribution of aggregated species. No infectivity or toxicity was found using cell and animal model systems. This study demonstrates that examination of the full repertoire of conformers and assembly states that can be accessed by PrP under specific experimental conditions should ideally be done using the full-length protein.

Prion neuropathology follows the accumulation of alternate prion protein isoforms after infective titre has peaked.

Prions are lethal infectious agents thought to consist of multi-chain forms (PrP(Sc)) of misfolded cellular prion protein (PrP(C)). Prion propagation proceeds in two distinct mechanistic phases: an exponential phase 1, which rapidly reaches a fixed level of infectivity irrespective of PrP(C) expression level, and a plateau (phase 2), which continues until clinical onset with duration inversely proportional to PrP(C) expression level. We hypothesized that neurotoxicity relates to distinct neurotoxic species produced following a pathway switch when prion levels saturate. Here we show a linear increase of proteinase K-sensitive PrP isoforms distinct from classical PrP(Sc) at a rate proportional to PrP(C) concentration, commencing at the phase transition and rising until clinical onset. The unaltered level of total PrP during phase 1, when prion infectivity increases a million-fold, indicates that prions comprise a small minority of total PrP. This is consistent with PrP(C) concentration not being rate limiting to exponential prion propagation and neurotoxicity relating to critical concentrations of alternate PrP isoforms whose production is PrP(C) concentration dependent.

A novel prion disease associated with diarrhea and autonomic neuropathy.

BACKGROUND: Human prion diseases, although variable in clinicopathological phenotype, generally present as neurologic or neuropsychiatric conditions associated with rapid multifocal central nervous system degeneration that is usually dominated by dementia and cerebellar ataxia. Approximately 15% of cases of recognized prion disease are inherited and associated with coding mutations in the gene encoding prion protein (PRNP). The availability of genetic diagnosis has led to a progressive broadening of the recognized spectrum of disease. METHODS: We used longitudinal clinical assessments over a period of 20 years at one hospital combined with genealogical, neuropsychological, neurophysiological, neuroimaging, pathological, molecular genetic, and biochemical studies, as well as studies of animal transmission, to characterize a novel prion disease in a large British kindred. We studied 6 of 11 affected family members in detail, along with autopsy or biopsy samples obtained from 5 family members. RESULTS: We identified a PRNP Y163X truncation mutation and describe a distinct and consistent phenotype of chronic diarrhea with autonomic failure and a length-dependent axonal, predominantly sensory, peripheral polyneuropathy with an onset in early adulthood. Cognitive decline and seizures occurred when the patients were in their 40s or 50s. The deposition of prion protein amyloid was seen throughout peripheral organs, including the bowel and peripheral nerves. Neuropathological examination during end-stage disease showed the deposition of prion protein in the form of frequent cortical amyloid plaques, cerebral amyloid angiopathy, and tauopathy. A unique pattern of abnormal prion protein fragments was seen in brain tissue. Transmission studies in laboratory mice were negative. CONCLUSIONS: Abnormal forms of prion protein that were found in multiple peripheral tissues were associated with diarrhea, autonomic failure, and neuropathy. (Funded by the U.K. Medical Research Council and others.).

Prion propagation and toxicity in vivo occur in two distinct mechanistic phases.

Mammalian prions cause fatal neurodegenerative conditions including Creutzfeldt-Jakob disease in humans and scrapie and bovine spongiform encephalopathy in animals. Prion infections are typically associated with remarkably prolonged but highly consistent incubation periods followed by a rapid clinical phase. The relationship between prion propagation, generation of neurotoxic species and clinical onset has remained obscure. Prion incubation periods in experimental animals are known to vary inversely with expression level of cellular prion protein. Here we demonstrate that prion propagation in brain proceeds via two distinct phases: a clinically silent exponential phase not rate-limited by prion protein concentration which rapidly reaches a maximal prion titre, followed by a distinct switch to a plateau phase. The latter determines time to clinical onset in a manner inversely proportional to prion protein concentration. These findings demonstrate an uncoupling of infectivity and toxicity. We suggest that prions themselves are not neurotoxic but catalyse the formation of such species from PrP(C). Production of neurotoxic species is triggered when prion propagation saturates, leading to a switch from autocatalytic production of infectivity (phase 1) to a toxic (phase 2) pathway.

Chronic wasting disease prions are not transmissible to transgenic mice overexpressing human prion protein.

Chronic wasting disease (CWD) is a prion disease that affects free-ranging and captive cervids, including mule deer, white-tailed deer, Rocky Mountain elk and moose. CWD-infected cervids have been reported in 14 USA states, two Canadian provinces and in South Korea. The possibility of a zoonotic transmission of CWD prions via diet is of particular concern in North America where hunting of cervids is a popular sport. To investigate the potential public health risks posed by CWD prions, we have investigated whether intracerebral inoculation of brain and spinal cord from CWD-infected mule deer transmits prion infection to transgenic mice overexpressing human prion protein with methionine or valine at polymorphic residue 129. These transgenic mice have been utilized in extensive transmission studies of human and animal prion disease and are susceptible to BSE and vCJD prions, allowing comparison with CWD. Here, we show that these mice proved entirely resistant to infection with mule deer CWD prions arguing that the transmission barrier associated with this prion strain/host combination is greater than that observed with classical BSE prions. However, it is possible that CWD may be caused by multiple prion strains. Further studies will be required to evaluate the transmission properties of distinct cervid prion strains as they are characterized.

The otic ganglion in rats and its parotid connection: cholinergic pathways, reflex secretion and a secretory role for the facial nerve.

Otic ganglionectomy in rats was found to have affected the parotid gland more profoundly than section of the auriculotemporal nerve as assessed by reduction in gland weight (by 33 versus 20%) and total acetylcholine synthesizing capacity (by 88 versus 76%) 1 week postoperatively and, when assessed on the day of surgery under adrenoceptor blockade, by reflex secretion (by 99 versus 88%). The facial nerve contributed to the acetylcholine synthesizing capacity of the gland. Section of the nerve only, at the level of the stylomastoid foramen, reduced the acetylcholine synthesis by 15% and, combined with otic ganglionectomy, by 98% or, combined with section of the auriculotemporal nerve, by 82%. The facial nerve was secretory to the gland, and the response was of a cholinergic nature. The nerve conveyed reflex secretion of saliva and caused secretion of saliva upon stimulation. Most of the facial secretory nerve fibres originated from the otic ganglion, since after otic ganglionectomy (and allowing for nerve degeneration) the secretory response to facial nerve stimulation was markedly reduced (from 23 to 4 microl (5 min)(-1)). The persisting secretory response after otic ganglionectomy, exaggerated due to sensitization, and the residual acetylcholine synthesizing capacity (mainly depending on the facial nerve) showed that a minor proportion of pre- and postganglionic nerve fibres relay outside the otic ganglion. The great auricular nerve, which like the facial nerve penetrates the gland, caused no secretion of saliva upon stimulation. Avulsion of the auriculotemporal nerve was more effective than otic ganglionectomy in reducing the acetylcholine synthesizing capacity (by 94 versus 88%) and as effective as otic ganglionectomy in abolishing reflex secretion (by 99%). When aiming at parasympathetic denervation, avulsion may be the preferable choice, since it is technically easier to perform than otic ganglionectomy.

Altered interaction and expression of proteins involved in neurosecretion in scrapie-infected GT1-1 cells.

Prions cause transmissible and fatal diseases that are associated with spongiform degeneration, astrogliosis, and loss of axon terminals in the brains. To determine the expression of proteins involved in neurosecretion and synaptic functions after prion infection, gonadotropin-releasing hormone neuronal cell line subclone (GT1-1) was infected with the RML scrapie strain and analyzed by Western blotting, real time PCR, and immunohistochemistry. As revealed by Western blotting of lysates exposed to different temperatures, the levels of complexed SNAP-25, syntaxin 1A, and synaptophysin were decreased in scrapie-infected GT1-1 cells (ScGT1-1), whereas the level of monomeric forms of these proteins was increased and correlated to the level of scrapie prion protein (PrPSc). However, when complex formation was prevented by prolonged heating of samples in SDS, the levels of monomeric SNAP-25, syntaxin 1A and synaptophysin in ScGT1-1 cells were decreased in comparison to GT1-1 cells. The reduced level of SNAP-25 was observed as early as 32 days postinfection. Increased mRNA levels of both splice variants SNAP-25a and -b in ScGT1-1 cells were seen. No difference in the morphology, neuritic outgrowth or distribution of SNAP-25, syntaxin 1A, or synaptophysin could be observed in ScGT1-1 cells. Treatment with quinacrine or pentosan polysulfate cleared the PrPSc from the ScGT1-1 cell cultures, and the increase in levels of monomeric SNAP-25 and synaptophysin was reversible. These results indicate that a scrapie infection can cause changes in the expression of proteins involved in neuronal secretion, which may be of pathogenetic relevance for the axon terminal changes seen in prion-infected brains.

Scrapie-infected GT1-1 cells show impaired function of voltage-gated N-type calcium channels (Ca(v) 2.2) which is ameliorated by quinacrine treatment.

Prions are transmissible pathogens that cause neurodegenerative diseases, although the mechanisms behind the nervous system dysfunctions are unclear. To study the effects of a prion infection on voltage-gated calcium channels, scrapie-infected gonadotropin-releasing hormone neuronal cells (ScGT1-1) in culture were depolarized by KCl and calcium responses recorded. Lower calcium responses were observed in infected compared to uninfected cells. This effect was still observed when L-type calcium channels were blocked by nimodipine. After inhibition of N-type calcium channels with omega-conotoxin GVIA, there was no difference in calcium responses. The calcium responses after nimodipine treatment became progressively lower during infection, but there was no major loss of the cellular prion protein (PrP(C)) or marked increase in accumulation of the abnormal prion protein (PrP(Sc)) in the cultures. These results indicate that scrapie infection causes a dysfunction of voltage-gated N-type calcium channels, which is exacerbated slowly over time. Quinacrine treatment cleared PrP(Sc) and restored calcium responses in the ScGT1-1 cultures.