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Human prion diseases are rare, transmissible and often rapidly progressive dementias. The most common type, sporadic Creutzfeldt-Jakob disease (sCJD), is highly variable in clinical duration and age at onset. Genetic determinants of late onset or slower progression might suggest new targets for research and therapeutics. We assembled and array genotyped sCJD cases diagnosed in life or at autopsy. Clinical duration (median:4, interquartile range (IQR):2.5-9 (months)) was available in 3,773 and age at onset (median:67, IQR:61-73 (years)) in 3,767 cases. Phenotypes were successfully transformed to approximate normal distributions allowing genome-wide analysis without statistical inflation. 53 SNPs achieved genome-wide significance for the clinical duration phenotype; all of which were located at chromosome 20 (top SNP rs1799990, pvalue = 3.45x10-36, beta = 0.34 for an additive model; rs1799990, pvalue = 9.92x10-67, beta = 0.84 for a heterozygous model). Fine mapping, conditional and expression analysis suggests that the well-known non-synonymous variant at codon 129 is the obvious outstanding genome-wide determinant of clinical duration. Pathway analysis and suggestive loci are described. No genome-wide significant SNP determinants of age at onset were found, but the HS6ST3 gene was significant (pvalue = 1.93 x 10-6) in a gene-based test. We found no evidence of genome-wide genetic correlation between case-control (disease risk factors) and case-only (determinants of phenotypes) studies. Relative to other common genetic variants, PRNP codon 129 is by far the outstanding modifier of CJD survival suggesting only modest or rare variant effects at other genetic loci., Competing Interests: Stéphane Haik reports grants from Santé Publique France, during the conduct of the study; grants from LFB Biomedicaments, grants from Institut de Recherche Servier, grants from MedDay Pharmaceuticals, outside the submitted work; In addition, Stéphane Haik has a patent Method for treating prion diseases (PCT/EP2019/070457) pending. Brian Appleby has received funding from CDC, NIH, CJD Foundation, Alector, and Ionis. He has served as a consultant for Ionis, Sangamo, and Gate Biosciences. He has received royalties from Wolter Kluwers. Karl Fronztek reports grants from Ono Pharmaceuticals outside the submitted work. Simon Mead reports grants from Medical Research Council (UK) and grants from National Institute of Health Research’s Biomedical Research Centre at University College London Hospitals NHS Foundation Trust during the conduct of the study. Gabor G Kovacs reports personal fees from Biogen, outside the submitted work. John Collinge reports grants from Medical Research Council, grants from NIHR UCLH Biomedical Research Centre, during the conduct of the study; and is a Director and shareholder of D-Gen Limited, an academic spinout in the field of prion disease diagnostics, decontamination and therapeutics. Inga Zerr reports grants from the Bundesministerium für Gesundheit via Robert Koch institute, JPND and personal fees (not related to the content of the manuscript) from Ferring Pharmaceuticals and IONIS, speaking honoraria for medical lectures from Lilly, Biogen, Medfora, DGLN (German Society for cerebrospinal fluid diagnostics in Neurology). Maurizio Pocchiari reports personal fees from Ferring Pharmaceuticals, personal fees from CNCCS (Collection of National Chemical Compounds and Screening Center), non-financial support from Fondazione Cellule Staminali, outside the submitted work. Michael D Geschwind has consulted for3D Communications, Adept Field Consulting, Advanced Medical Inc., Best Doctors Inc., Second Opinion Inc., Gerson Lehrman Group Inc., Guidepoint Global LLC, InThought Consulting Inc., Market Plus, Trinity Partners LLC, Biohaven Pharmaceuticals, Quest Diagnostics and various medical-legal consulting. He has received speaking honoraria for various medical center lectures and from Oakstone publishing. He has received past research support from Alliance Biosecure, CurePSP, the Tau Consortium, and Quest Diagnostics. Michael D Geschwind serves on the board of directors for San Francisco Bay Area Physicians for Social Responsibility and on the editorial board of Dementia & Neuropsychologia., (Copyright: © 2024 Hummerich et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Definitive diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD) relies on the examination of brain tissues for the pathological prion protein (PrP Sc ). Our previous study revealed that PrP Sc -seeding activity (PrP Sc -SA) is detectable in skin of sCJD patients by an ultrasensitive PrP Sc seed amplification assay (PrP Sc -SAA) known as real-time quaking-induced conversion (RT-QuIC). A total of 875 skin samples were collected from 2 cohorts (1 and 2) at autopsy from 2-3 body areas of 339 cases with neuropathologically confirmed prion diseases and non-sCJD controls. The skin samples were analyzed for PrP Sc -SA by RT-QuIC assay. The results were compared with demographic information, clinical manifestations, cerebrospinal fluid (CSF) PrP Sc -SA, other laboratory tests, subtypes of prion diseases defined by the methionine (M) or valine (V) polymorphism at residue 129 of PrP, PrP Sc types (#1 or #2), and gene mutations in deceased patients. RT-QuIC assays of the cohort #1 by two independent laboratories gave 87.3% or 91.3% sensitivity and 94.7% or 100% specificity, respectively. The cohort #2 showed sensitivity of 89.4% and specificity of 95.5%. RT-QuIC of CSF available from 212 cases gave 89.7% sensitivity and 94.1% specificity. The sensitivity of skin RT-QuIC was subtype dependent, being highest in sCJDVV1-2 subtype, followed by VV2, MV1-2, MV1, MV2, MM1, MM1-2, MM2, and VV1. The skin area next to the ear gave highest sensitivity, followed by lower back and apex of the head. Although no difference in brain PrP Sc -SA was detected between the cases with false negative and true positive skin RT-QuIC results, the disease duration was significantly longer with the false negatives [12.0 ± 13.3 (months, SD) vs. 6.5 ± 6.4, p < 0.001]. Our study validates skin PrP Sc -SA as a biomarker for the detection of prion diseases, which is influenced by the PrP Sc types, PRNP 129 polymorphisms, dermatome sampled, and disease duration., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Alzheimer's disease (AD) is characterized by the prion-like propagation of amyloid-β (Aβ). However, the role of Aβ in cognitive impairment is still unclear. To determine the causal role of Aβ in AD, we intracerebrally seeded the entorhinal cortex of a 2-month-old App NL - G - F mouse model with an Aβ peptide derived from patients who died from rapidly progressing AD. When the mice were 3 months of age or 1 month following seeding, spatial learning and memory were tested using the Morris water task. Immunohistochemical labeling showed seeding with the Aβ was found accelerate Aβ plaque deposition and microgliosis in the App NL - G - F mice, but this was dependent on the presence of the knocked-in genes. However, we found no correlation between pathology and spatial performance. The results of the present study show the seeding effects in the App NL - G - F knock-in model, and how these are dependent on the presence of a humanized App gene. But these pathological changes were not initially causal in memory impairment., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Lacoursiere, Safar, Westaway, Mohajerani and Sutherland.)

Variably protease-sensitive prionopathy (VPSPr) is a recently described sporadic prion disease with distinctive clinical and histopathological features. We report the clinical, imaging, and neuropathological features of VPSPr in a 46-year-old right-handed man who presented with progressive cognitive decline, behavior disturbances, and a 50-pound weight loss over 6 months. The initial evaluation revealed severe cognitive impairment with no focal neurologic deficits. His cognitive, psychiatric, and behavior symptoms progressed rapidly, and he died 12 months after the initial visit. Throughout his disease course, workup for rapid progressive dementia was unremarkable except that brain MRI diffusion-weighted imaging showed persistent diffuse cortical and thalamic signal abnormalities. Sporadic Creutzfeldt-Jakob disease was highly suspected; however, two EEGs (8 months apart) demonstrated only nonspecific cerebral dysfunction. The patient's CSF 14-3-3 protein was negative at the initial visit and again 8 months later. His CSF real-time quaking-induced conversion and total tau level were normal. An autopsy of his brain was performed, and the neuropathological findings confirmed VPSPr. Our case underlines the importance of considering VPSPr in the spectrum of prion disease phenotypes when evaluating individuals with rapidly progressive dementia., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Recent studies in animal models demonstrate that certain misfolded proteins associated with neurodegenerative diseases can support templated misfolding of cognate native proteins, to propagate across neural systems, and to therefore have some of the properties of classical prion diseases like Creutzfeldt-Jakob disease. The National Institute of Aging convened a meeting to discuss the implications of these observations for research priorities. A summary of the discussion is presented here, with a focus on limitations of current knowledge, highlighting areas that appear to require further investigation in order to guide scientific practice while minimizing potential exposure or risk in the laboratory setting. The committee concluded that, based on all currently available data, although neurodegenerative disease-associated aggregates of several different non-prion proteins can be propagated from humans to experimental animals, there is currently insufficient evidence to suggest more than a negligible risk, if any, of a direct infectious etiology for the human neurodegenerative disorders defined in part by these proteins. Given the importance of this question, the potential for noninvasive human transmission of proteopathic disorders is deserving of further investigation., (© 2020 American Association of Neuropathologists, Inc.)

Background: Human prion diseases are rare and usually rapidly fatal neurodegenerative disorders, the most common being sporadic Creutzfeldt-Jakob disease (sCJD). Variants in the PRNP gene that encodes prion protein are strong risk factors for sCJD but, although the condition has similar heritability to other neurodegenerative disorders, no other genetic risk loci have been confirmed. We aimed to discover new genetic risk factors for sCJD, and their causal mechanisms., Methods: We did a genome-wide association study of sCJD in European ancestry populations (patients diagnosed with probable or definite sCJD identified at national CJD referral centres) with a two-stage study design using genotyping arrays and exome sequencing. Conditional, transcriptional, and histological analyses of implicated genes and proteins in brain tissues, and tests of the effects of risk variants on clinical phenotypes, were done using deep longitudinal clinical cohort data. Control data from healthy individuals were obtained from publicly available datasets matched for country., Findings: Samples from 5208 cases were obtained between 1990 and 2014. We found 41 genome-wide significant single nucleotide polymorphisms (SNPs) and independently replicated findings at three loci associated with sCJD risk; within PRNP (rs1799990; additive model odds ratio [OR] 1·23 [95% CI 1·17-1·30], p=2·68 × 10 -15 ; heterozygous model p=1·01 × 10 -135 ), STX6 (rs3747957; OR 1·16 [1·10-1·22], p=9·74 × 10 -9 ), and GAL3ST1 (rs2267161; OR 1·18 [1·12-1·25], p=8·60 × 10 -10 ). Follow-up analyses showed that associations at PRNP and GAL3ST1 are likely to be caused by common variants that alter the protein sequence, whereas risk variants in STX6 are associated with increased expression of the major transcripts in disease-relevant brain regions., Interpretation: We present, to our knowledge, the first evidence of statistically robust genetic associations in sporadic human prion disease that implicate intracellular trafficking and sphingolipid metabolism as molecular causal mechanisms. Risk SNPs in STX6 are shared with progressive supranuclear palsy, a neurodegenerative disease associated with misfolding of protein tau, indicating that sCJD might share the same causal mechanisms as prion-like disorders., Funding: Medical Research Council and the UK National Institute of Health Research in part through the Biomedical Research Centre at University College London Hospitals National Health Service Foundation Trust., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Accumulation of phosphorylated tau is a key pathological feature of Alzheimer's disease. Phosphorylated tau accumulation causes synaptic impairment, neuronal dysfunction and formation of neurofibrillary tangles. The pathological actions of phosphorylated tau are mediated by surrounding neuronal proteins; however, a comprehensive understanding of the proteins that phosphorylated tau interacts with in Alzheimer's disease is surprisingly limited. Therefore, the aim of this study was to determine the phosphorylated tau interactome. To this end, we used two complementary proteomics approaches: (i) quantitative proteomics was performed on neurofibrillary tangles microdissected from patients with advanced Alzheimer's disease; and (ii) affinity purification-mass spectrometry was used to identify which of these proteins specifically bound to phosphorylated tau. We identified 542 proteins in neurofibrillary tangles. This included the abundant detection of many proteins known to be present in neurofibrillary tangles such as tau, ubiquitin, neurofilament proteins and apolipoprotein E. Affinity purification-mass spectrometry confirmed that 75 proteins present in neurofibrillary tangles interacted with PHF1-immunoreactive phosphorylated tau. Twenty-nine of these proteins have been previously associated with phosphorylated tau, therefore validating our proteomic approach. More importantly, 34 proteins had previously been associated with total tau, but not yet linked directly to phosphorylated tau (e.g. synaptic protein VAMP2, vacuolar-ATPase subunit ATP6V0D1); therefore, we provide new evidence that they directly interact with phosphorylated tau in Alzheimer's disease. In addition, we also identified 12 novel proteins, not previously known to be physiologically or pathologically associated with tau (e.g. RNA binding protein HNRNPA1). Network analysis showed that the phosphorylated tau interactome was enriched in proteins involved in the protein ubiquitination pathway and phagosome maturation. Importantly, we were able to pinpoint specific proteins that phosphorylated tau interacts with in these pathways for the first time, therefore providing novel potential pathogenic mechanisms that can be explored in future studies. Combined, our results reveal new potential drug targets for the treatment of tauopathies and provide insight into how phosphorylated tau mediates its toxicity in Alzheimer's disease., (© The Author(s) (2020). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Objective: To determine whether preventive trials in genetic prion disease could be designed to follow presymptomatic mutation carriers to onset of disease., Methods: We assembled age at onset or death data from 1,094 individuals with high penetrance mutations in the prion protein gene ( PRNP ) in order to generate survival and hazard curves and test for genetic modifiers of age at onset. We used formulae and simulations to estimate statistical power for clinical trials., Results: Genetic prion disease age at onset varies over several decades for the most common mutations and neither sex, parent's age at onset, nor PRNP codon 129 genotype provided additional explanatory power to stratify trials. Randomized preventive trials would require hundreds or thousands of at-risk individuals in order to be statistically powered for an endpoint of clinical onset, posing prohibitive cost and delay and likely exceeding the number of individuals available for such trials., Conclusion: The characterization of biomarkers suitable to serve as surrogate endpoints will be essential for the prevention of genetic prion disease. Parameters such as longer trial duration, increased enrollment, and the use of historical controls in a postmarketing study could provide opportunities for subsequent determination of clinical benefit., (© 2019 American Academy of Neurology.)

Switches in heterogamety are known to occur in both animals and plants. Although plant sex determination systems probably often evolved more recently than those in several well-studied animals, including mammals, and have had less time for switches to occur, we previously detected a switch in heterogamety in the plant genus Silene: section Otites has both female and male heterogamety, whereas S. latifolia and its close relatives, in a different section of the genus, Melandrium (subgenus Behenantha), all have male heterogamety. Here we analyse the evolution of sex chromosomes in section Otites, which is estimated to have evolved only about 0.55 MYA. Our study confirms female heterogamety in S. otites and newly reveals female heterogamety in S. borysthenica. Sequence analyses and genetic mapping show that the sex-linked regions of these two species are the same, but the region in S. colpophylla, a close relative with male heterogamety, is different. The sex chromosome pairs of S. colpophylla and S. otites each correspond to an autosome of the other species, and both differ from the XY pair in S. latifolia. Silene section Otites species are suitable for detailed studies of the events involved in such changes, and our phylogenetic analysis suggests a possible change from female to male heterogamety within this section. Our analyses suggest a possibility that has so far not been considered, change in heterogamety through hybridization, in which a male-determining chromosome from one species is introgressed into another one, and over-rides its previous sex-determining system.

Background: Cerebrospinal fluid (CSF) levels of total tau (t-tau) protein are thought to reflect the intensity of the neuronal damage in neurodegeneration, including Alzheimer's disease (AD). The recent link of CSF t-tau to rapidly progressive AD raises the question among other AD clinical variants regarding CSF t-tau. We investigated the clinical phenotypes of AD patients with varying CSF t-tau levels., Objective: We tested the hypothesis that highly elevated CSF t-tau level would have a higher likelihood of presenting with atypical non-amnestic variants of AD., Methods: Retrospective comparative case study of 97 patients evaluated in a memory clinic with clinical presentation and CSF biomarkers consistent with AD. We compared the age, sex, education, APOEɛ4 status, Montreal Cognitive Assessment (MoCA) score, clinical phenotype, and MRI volumetric measures by CSF t-tau quartile at baseline. Multivariable logistic regression models were used to evaluate if CSF t-tau levels predict non-amnestic presentations controlling for covariates., Results: Non-amnestic AD had a higher median CSF t-tau level compared to amnestic-AD (p = 0.014). Each 50 pg/ml increase in CSF t-tau was associated with an increase in the odds of having a non-amnestic presentation (7.4%) and aphasia (10.6 %) as the initial presenting symptom even after taking into account; age, sex, education, APOEɛ4, MoCA, and CSF Aβ42. Logopenic AD had higher t-tau and p-tau levels compared to other variants., Conclusions: Highly elevated CSF t-tau levels could indicate more cortical involvement presenting with early non-amnestic symptoms in atypical AD subtypes, particularly in the logopenic variant.

The diagnosis and treatment of synucleinopathies such as Parkinson disease and dementia with Lewy bodies would be aided by the availability of assays for the pathogenic disease-associated forms of α-synuclein (αSyn D ) that are sufficiently sensitive, specific, and practical for analysis of accessible diagnostic specimens. Two recent αSyn D seed amplification tests have provided the first prototypes for ultrasensitive and specific detection of αSyn D in patients' cerebrospinal fluid. These prototypic assays require 5-13 days to perform. Here, we describe an improved α-synuclein real time quaking-induced conversion (αSyn RT-QuIC) assay that has similar sensitivity and specificity to the prior assays, but can be performed in 1-2 days with quantitation. Blinded analysis of cerebrospinal fluid from 29 synucleinopathy cases [12 Parkinson's and 17 dementia with Lewy bodies] and 31 non-synucleinopathy controls, including 16 Alzheimer's cases, yielded 93% diagnostic sensitivity and 100% specificity for this test so far. End-point dilution analyses allowed quantitation of relative amounts of αSyn D seeding activity in cerebrospinal fluid samples, and detection in as little as 0.2 μL. These results confirm that αSyn D seeding activity is present in cerebrospinal fluid. We also demonstrate that it can be rapidly detected, and quantitated, even in early symptomatic stages of synucleinopathy.

Background: A rapidly progressive phenotype of Alzheimer's disease (AD) has been described in some prion disease cohorts. Limited information regarding rapidly progressive AD (rpAD) is available from longitudinal national cohorts., Objective: To compare the clinical characteristics of rpAD in two different national cohorts., Methods: A retrospective analysis was performed on AD subjects with available neuropathology in the National Alzheimer's Coordinating Center (NACC) database and among neuropathologically characterized AD cases from the National Prion Disease Pathology Surveillance Center (NPDPSC) that were evaluated for suspected prion disease. In the NACC cohort, rpAD was delineated by the lower 10th percentile of follow up duration from pre-dementia to death duration among subjects meeting pathological diagnosis of AD., Results: rpAD from the NPDPSC had a shorter mean symptom duration than the NACC identified rpAD cases (11.6 months versus 62.4 months) and were also younger at the time of their death (60.0 versus 81.8 years). NACC identified rpAD subjects, beginning from a predementia stage, had slower rate of MMSE change per year than NPDPSC cases (2.5 versus 6.0 points)., Conclusions: rpAD constitute an important subset of AD subjects in whom a rapid course of symptomatic clinical decline is noted, as confirmed in both national cohorts. rpAD was best characterized by survival time (≤3 years), as there were clear differences between the rpAD cohorts in terms of symptom duration, age at death, and MMSE change per year, likely due to the strong selection biases. rpAD could shed light on the biology of rate of progression in AD.

The term "brain health" integrates general health and well-being with cognitive fitness, in the context of an environment that includes the spectrum of positive and negative factors affecting the individual. Brain health incorporates the effects of neurodegeneration in an ecological sense and the effects of environment and health practices on brain function. It also provides a framework for understanding and maximizing cognitive function across the lifespan. Despite decades of research into the pathogenesis of neurodegenerative disorders, our understanding of how to treat them is relatively rudimentary. Unidimensional approaches, such as medication monotherapies, have generally produced negative results in treatment trials. New integrative paradigms that cut across the molecular and cellular level to the individual and societal level may provide new approaches to understand and treat these disorders. This report on proceedings of a multi-disciplinary conference held in Cleveland, Ohio, in October 2013 summarizes research progress in understanding neurodegenerative disorders in a brain health context. A new "brain health" paradigm is essential to finally understand neurodegenerative disorders such as Alzheimer's disease and overcome the relative stand-still in therapeutics research that has characterized the last decade. The authors summarize progress in these emerging areas with the aim of producing new integrated scientific models for understanding brain health, potentially modifying disease course and advancing care for individuals and families affected by neurodegenerative conditions.

Metallothioneins (MTs) were identified as important players in metal metabolism. MT3 gene presents a key metallothionein controlling copper homeostasis in plants. We have selected one cupricolous and one non-cupricolous ecotype to isolate and analyse the MT3 gene in Silene vulgaris. For expression data comparison, we have also included other metal-tolerant ecotypes. Based on a S. vulgaris BAC library screening, we have identified and sequenced a genomic clone containing MT3 gene (SvMT3). We found that SvMT3 gene has been locally duplicated in a tandem arrangement. Expression analysis and complementation studies using yeast mutants showed that both copies of the SvMT3 gene were functional. Moreover, we examined the expression of MT3 gene(s) in selected ecotypes under different copper treatments to show the tissue-specific expression response to copper stress. We demonstrated that higher copper concentrations specifically affected MT3 expression among ecotypes. Our analysis shows that MT3a has similar expression pattern in cupricolous ecotypes while MT3b has common expression features shared by all metallophyte S. vulgaris ecotypes. Our data indicate that down-regulation of MT3b root expression in higher copper concentrations is associated with copper stress. We propose that there might be a specific regulation of SvMT3s transcription depending on the type of heavy metal tolerance.

We produced a reference sequence of the 1-gigabase chromosome 3B of hexaploid bread wheat. By sequencing 8452 bacterial artificial chromosomes in pools, we assembled a sequence of 774 megabases carrying 5326 protein-coding genes, 1938 pseudogenes, and 85% of transposable elements. The distribution of structural and functional features along the chromosome revealed partitioning correlated with meiotic recombination. Comparative analyses indicated high wheat-specific inter- and intrachromosomal gene duplication activities that are potential sources of variability for adaption. In addition to providing a better understanding of the organization, function, and evolution of a large and polyploid genome, the availability of a high-quality sequence anchored to genetic maps will accelerate the identification of genes underlying important agronomic traits., (Copyright © 2014, American Association for the Advancement of Science.)

Prion diseases are fatal, neurodegenerative illnesses caused by the accumulation of PrP(Sc), an aberrantly folded isoform of the normal, cellular prion protein. Detection of PrP(Sc) commonly relies on immunochemical methods, a strategy hampered by the lack of Abs specific for this disease-causing isoform. In this article, we report the generation of eight mAbs against prion protein (PrP) following immunization of Prnp-null mice with rPrP. The eight mAbs exhibited distinct differential binding to cellular prion protein and PrP(Sc) from different species as well as PrP-derived synthetic peptides. Five of the eight mAbs exhibited binding to discontinuous PrP epitopes, all of which were disrupted by the addition of 2-ME or DTT, which reduced the single disulfide bond found in PrP. One mAb F20-29 reacted only with human PrP, whereas the F4-31 mAb bound bovine PrP; the K(D) values for mAbs F4-31 and F20-29 were ~500 pM. Binding of all five conformation-dependent mAbs to PrP was inhibited by 2-ME in ELISA, Western blots, and histoblots. One conformation-dependent mAb F4-31 increased the sensitivity of an ELISA-based test by nearly 500-fold when it was used as the capture Ab. These new conformation-dependent mAbs were found to be particularly useful in histoblotting studies, in which the low backgrounds after treatment with 2-ME created unusually high signal-to-noise ratios.

As the staple food for 35% of the world's population, wheat is one of the most important crop species. To date, sequence-based tools to accelerate wheat improvement are lacking. As part of the international effort to sequence the 17-billion-base-pair hexaploid bread wheat genome (2n = 6x = 42 chromosomes), we constructed a bacterial artificial chromosome (BAC)-based integrated physical map of the largest chromosome, 3B, that alone is 995 megabases. A chromosome-specific BAC library was used to assemble 82% of the chromosome into 1036 contigs that were anchored with 1443 molecular markers, providing a major resource for genetic and genomic studies. This physical map establishes a template for the remaining wheat chromosomes and demonstrates the feasibility of constructing physical maps in large, complex, polyploid genomes with a chromosome-based approach.

Quinacrine and related 9-aminoacridine compounds are effective in eliminating the alternatively folded prion protein, termed PrP(Sc), from scrapie-infected cultured cells. Clinical evaluations of quinacrine for the treatment of human prion diseases are progressing in the absence of a clear understanding of the molecular mechanism by which prion replication is blocked. Here, insight into the mode of action of 9-aminoacridine compounds was sought by using a chemical proteomics approach to target identification. Cellular macromolecules that bind 9-aminoacridine ligands were affinity-purified from tissue lysates by using a 9-aminoacridine-functionalized solid-phase matrix. Although the 9-aminoacridine matrix was conformationally selective for PrP(Sc), it was inefficient: approximately 5 % of PrP(Sc) was bound under conditions that did not support binding of the cellular isoform, PrP(C). Our findings suggest that 9-aminoacridine compounds may reduce the PrP(Sc) burden either by occluding epitopes necessary for templating on the surface of PrP(Sc) or by altering the stability of PrP(Sc) oligomers, where a one-to-one stoichiometry is not necessary.

Chronic wasting disease (CWD) is a fatal prion disease in deer and elk. Unique among the prion diseases, it is transmitted among captive and free-ranging animals. To facilitate studies of the biology of CWD prions, we generated five lines of transgenic (Tg) mice expressing prion protein (PrP) from Rocky Mountain elk (Cervus elaphus nelsoni), denoted Tg(ElkPrP), and two lines of Tg mice expressing PrP common to white-tailed deer (Odocoileus virginianus) and mule deer (Odocoileus hemionus), denoted Tg(DePrP). None of the Tg(ElkPrP) or Tg(DePrP) mice exhibited spontaneous neurologic dysfunction at more than 600 days of age. Brain samples from CWD-positive elk, white-tailed deer, and mule deer produced disease in Tg(ElkPrP) mice between 180 and 200 days after inoculation and in Tg(DePrP) mice between 300 and 400 days. One of eight cervid brain inocula transmitted disease to Tg(MoPrP)4053 mice overexpressing wild-type mouse PrP-A in approximately 540 days. Neuropathologic analysis revealed abundant PrP amyloid plaques in the brains of ill mice. Brain homogenates from symptomatic Tg(ElkPrP) mice produced disease in 120 to 190 days in Tg(ElkPrP) mice. In contrast to the Tg(ElkPrP) and Tg(DePrP) mice, Tg mice overexpressing human, bovine, or ovine PrP did not develop prion disease after inoculation with CWD prions from among nine different isolates after >500 days. These findings suggest that CWD prions from elk, mule deer, and white-tailed deer can be readily transmitted among these three cervid species.

The aim of this work was to isolate new DNA markers linked to the Silene latifolia Y chromosome. To do this we created a chromosome-specific plasmid library after DOP-PCR amplification of laser-microdissected Y-chromosomes. The library screening led to the isolation of several clones yielding mostly to exclusive male specific hybridization signals. Subsequent PCR confirmed the Y-unique linkage for one of the sequences. This DNA sequence called MK17 has no homology to any known DNA sequence and it is not expressed. Based on PCR and Southern analyses, MK17 is present only in dioecious species of the Elisanthe section of the genus Silene (S. latifolia, S. dioica, and S. diclinis) and it is absent in related gynodioecious and hermaphroditic species. The mapping analysis using a panel of deletion mutants showed that MK17 is closely linked to the region controlling suppression of gynoecium development. Hence MK17 represents a valuable marker to isolate genes controlling the gynoecium development suppression on the Y chromosome of S. latifolia.

Loss of the GABAergic system of neurons has been reported to be the first detectable neuropathological change in prion diseases, which features the accumulation of an aberrant isoform of the prion protein (PrP(Sc)). To determine the timing of GABAergic system dysfunction and degeneration and its relationship to PrP(Sc) accumulation during the course of prion disease in Syrian hamsters, we applied 3 approaches: i) quantifying GABA-immunopositive neurons and their processes by light and electron microscopy to test for selective loss; ii) measuring evoked [3H]-GABA release from synaptosomes to test for functional abnormalities; and iii) determining the kinetics of PrP(Sc) accumulation in subcellular fractions to correlate it with GABAergic dysfunction. At the terminal stages of disease, we found a significant increase in the number of GABA-positive and -negative presynaptic boutons with abnormally aggregated synaptic vesicles. At the same stage, we also found an equal degree of GABA-immunopositive and -immunonegative presynaptic bouton loss. In contrast, GABA-positive neocortical cell bodies increased, based on stereologic estimates in the terminal stage of scrapie. In the context of these abnormalities, evoked release of [3H]-GABA from cortical and thalamic synaptosomes was significantly decreased, which correlated well with the accumulation of PrP(Sc) in synaptosomes and cell membrane fractions.

Background: Approximately 2% of Alzheimer disease cases and 10% to 15% of prion disease cases are due to mutations in autosomal dominant genes. Mutations have been found in patients without family histories of neurological disease., Objectives: To emphasize the need for consideration of a genetic etiology of prion disease and early-onset Alzheimer disease, regardless of the absence of a significant family history, as well as the need for pretest genetic counseling of all patients or their families., Design: Three case reports., Patients and Results: Patient 1, a 53-year-old man with possible Creutzfeldt-Jakob disease, was enrolled in a research study that included sequencing of the prion protein gene. Although there was no family history of neurological disease, an E200K mutation was found. This unexpected result caused the family significant distress. Patient 2, a 55-year-old woman with biopsy-proven Creutzfeldt-Jakob disease, participated in a prion disease research study. Her family was counseled about the possibility of hereditary Creutzfeldt-Jakob disease, despite the lack of family history. After assessing the ramifications, the family decided not to learn about the patient's genetic test results. Patient 3 was a 54-year-old man with a 6-year history of memory loss. A diagnosis of probable Alzheimer disease was given, and the patient and his family were counseled on the availability of presenilin 1 testing, although there was no known family history of dementia. The family agreed to testing, and a presenilin 1 mutation was identified., Conclusions: Certain neurodegenerative diseases may have a genetic etiology, despite the lack of a positive family history. Revealing a newly discovered hereditary cause of Creutzfeldt-Jakob disease or Alzheimer disease can have a profound effect on families. Pretest counseling on genetic issues is essential to better prepare families and to allow them to make an informed choice about learning genetic test results.

We have investigated the conformation of Syrian hamster PrP(C) on the surface of transfected CHO cells by performing cross-competition experiments between a set of nine monoclonal antibody fragments (Fab) directed to defined epitopes throughout the protein. No competition was observed between antibodies recognizing epitopes located within the unstructured N-terminal portion of PrP(C) and those recognizing epitopes located within the ordered C-terminal half of the molecule. However, competition was observed between antibodies recognizing overlapping epitopes and between antibodies recognizing epitopes lying adjacent to one another in the PrP sequence. Titrating the reactivity of each Fab against cell-surface PrP(C) revealed a clear heterogeneity in the accessibility of different specific epitopes. Fab D18, recognizing sequence incorporating the first alpha-helix of PrP(C), bound the largest fraction of the cell-surface PrP population. In contrast, Fab E123, binding an epitope at the extreme N terminus of PrP, and Fab 13A5, binding an epitope in the central region of PrP, were able to recognize fewer than half the number of PrP(C) molecules bound by Fab D18. The pattern of antibody reactivity we observed may, in part, result from N-terminal truncation of a proportion of PrP(C) molecules found at the cell surface. However, truncation cannot account for the marked disparity between exposure of the Fab D18 and 13A5 epitopes, which lie adjacent in the PrP sequence. The relative inaccessibility of the 13A5 epitope likely reflects either PrP(C)-PrP(C) interaction, interaction between PrP(C) and other constituents on the cell membrane, or the existence of PrP(C) subspecies with distinct conformations.

Our discovery of dominant-negative inhibition of prion formation in cultured cells provided an explanation for the resistance of some sheep to scrapie and humans to Creutzfeldt-Jakob disease. To determine whether dominant-negative inhibition occurs in vivo, we produced transgenic (Tg) mice expressing prion protein (PrP) with either the Q167R or Q218K mutation alone or in combination with wild-type (wt) PrP. Tg(MoPrP,Q167R)Prnp(0/0) mice expressing mutant PrP at levels equal to non-Tg mice remained healthy for >550 days, indicating that inoculation with prions did not cause disease. Immunoblots of brain homogenates and histologic analysis did not reveal abnormalities. Tg(MoPrP,Q167R)Prnp(+/+) mice expressing both mutant and wt PrP did not exhibit neurologic dysfunction, but their brains revealed low levels of the PrP pathogenic isoform (PrP(Sc)), and sections showed numerous vacuoles and severe astrocytic gliosis at 300 days after inoculation. Both Tg(MoPrP,Q218K)Prnp(0/0) and Tg(MoPrP,Q218K)Prnp(+/+) mice expressing high levels of the transgene product remained healthy for >300 days after inoculation. Neither PrP(Sc) nor neuropathologic changes were found. Our studies demonstrate that although dominant-negative inhibition of wt PrP(Sc) formation occurs, expression of the dominant-negative PrP at the same level as wt PrP does not prevent prion formation completely. However, expression of dominant-negative PrP alone had no deleterious effects on the mice and did not support prion propagation.

Branched polyamines, including polyamidoamine and polypropyleneimine (PPI) dendrimers, are able to purge PrP(Sc), the disease-causing isoform of the prion protein, from scrapie-infected neuroblastoma (ScN2a) cells in culture (S. Supattapone, H.-O. B. Nguyen, F. E. Cohen, S. B. Prusiner, and M. R. Scott, Proc. Natl. Acad. Sci. USA 96:14529-14534, 1999). We now demonstrate that exposure of ScN2a cells to 3 microg of PPI generation 4.0/ml for 4 weeks not only reduced PrP(Sc) to a level undetectable by Western blot but also eradicated prion infectivity as determined by a bioassay in mice. Exposure of purified RML prions to branched polyamines in vitro disaggregated the prion rods, reduced the beta-sheet content of PrP 27-30, and rendered PrP 27-30 susceptible to proteolysis. The susceptibility of PrP(Sc) to proteolytic digestion induced by branched polyamines in vitro was strain dependent. Notably, PrP(Sc) from bovine spongiform encephalopathy-infected brain was susceptible to PPI-mediated denaturation in vitro, whereas PrP(Sc) from natural sheep scrapie-infected brain was resistant. Fluorescein-labeled PPI accumulated specifically in lysosomes, suggesting that branched polyamines act within this acidic compartment to mediate PrP(Sc) clearance. Branched polyamines are the first class of compounds shown to cure prion infection in living cells and may prove useful as therapeutic, disinfecting, and strain-typing reagents for prion diseases.

Recent progress determining the structure of the host-encoded prion protein (PrP(C)) and the role of auxiliary molecules in prion replication permits a more rational approach in the development of therapeutic interventions. Our objective is to identify a new class of lead compounds that mimic the dominant negative PrP(C) mutants, which inhibit an abnormal isoform (PrP(Sc)) formation. A computational search was conducted on the Available Chemicals Directory for molecules that mimic both the spatial orientation and basic polymorphism of PrP residues 168, 172, 215, and 219, which confer dominant negative inhibition. The search revealed 1,000 potential candidates that were visually analyzed with respect to the structure of this four-residue epitope on PrP(C). Sixty-three compounds were tested for inhibition of PrP(Sc) formation in scrapie-infected mouse neuroblastoma cells (ScN2a). Two compounds, Cp-60 (2-amino-6-[(2-aminophenyl)thio]-4-(2-furyl)pyridine-3, 5-dicarbonitrile) and Cp-62 (N'1-(¿5-[(4, 5-dichloro-1H-imidazol-1-yl)methyl]-2-furyl¿carbonyl)-4 methoxybenzene-1-sulfonohydrazide), inhibited PrP(Sc) formation in a dose-dependent manner and demonstrated low levels of toxicity. A substructure search of the Available Chemicals Directory based on Cp-60 identified five related molecules, three of which exhibited activities comparable to Cp-60. Mimicking dominant negative inhibition in the design of drugs that inhibit prion replication may provide a more general approach to developing therapeutics for deleterious protein-protein interactions.

The molecular basis of the infectious, inherited and sporadic forms of prion diseases is best explained by a conformationally dimorphic protein that can exist in distinct normal and disease-causing isoforms. We identified a 55-residue peptide of a mutant prion protein that can be refolded into at least two distinct conformations. When inoculated intracerebrally into the appropriate transgenic mouse host, 20 of 20 mice receiving the beta-form of this peptide developed signs of central nervous system dysfunction at approximately 360 days, with neurohistologic changes that are pathognomonic of Gerstmann-Sträussler-Scheinker disease. By contrast, eight of eight mice receiving a non-beta-form of the peptide failed to develop any neuropathologic changes more than 600 days after the peptide injections. We conclude that a chemically synthesized peptide refolded into the appropriate conformation can accelerate or possibly initiate prion disease., (Copyright 2000 Academic Press.)

A redacted prion protein (PrP) of 106 amino acids with two large deletions was expressed in transgenic (Tg) mice deficient for wild-type (wt) PrP (Prnp0/0) and supported prion propagation. RML prions containing full-length PrP(Sc)produced disease in Tg(PrP106)Prnp0/0 mice after approximately 300 days, while transmission of RML106 prions containing PrP(Sc)106 created disease in Tg(PrP106) Prnp0/0 mice after only approximately 66 days on repeated passage. This artificial transmission barrier for the passage of RML prions was diminished by the coexpression of wt MoPrPc in Tg(PrP106)Prnp+/0 mice that developed scrapie in approximately 165 days, suggesting that wt MoPrP acts in trans to accelerate replication of RML106 prions. Purified PrP(Sc)106 was protease resistant, formed filaments, and was insoluble in nondenaturing detergents. The unique features of RML106 prions offer insights into the mechanism of prion replication, and the small size of PrP(Sc)106 should facilitate structural analysis.

Variations in prions, which cause different incubation times and deposition patterns of the prion protein isoform called PrP(Sc), are often referred to as 'strains'. We report here a highly sensitive, conformation-dependent immunoassay that discriminates PrP(Sc) molecules among eight different prion strains propagated in Syrian hamsters. This immunoassay quantifies PrP isoforms by simultaneously following antibody binding to the denatured and native forms of a protein. In a plot of the ratio of antibody binding to denatured/native PrP graphed as a function of the concentration of PrP(Sc), each strain occupies a unique position, indicative of a particular PrP(Sc) conformation. This conclusion is supported by a unique pattern of equilibrium unfolding of PrP(Sc) found with each strain. Our findings indicate that each of the eight prion strains has a PrP(Sc) molecule with a unique conformation and, in accordance with earlier results, indicate the biological properties of prion strains are 'enciphered' in the conformation of PrP(Sc) and that the variation in incubation times is related to the relative protease sensitivity of PrP(Sc) in each strain.

The infectious isoform of the prion protein (PrPSc) is derived from cellular PrP (PrPC) in a conversion reaction involving a dramatic reorganization of secondary and tertiary structure. While our understanding of the pathogenic role of PrPSc has grown, the normal physiologic function of PrPC still remains unclear. Using recombinant Syrian hamster prion protein [SHaPrP(29-231)], we investigated metal ions as possible ligands of PrP. Near-UV circular dichroism spectroscopy (CD) indicates that the conformation of SHaPrP(29-231) resembles PrPC purified from hamster brain. Here we demonstrate by CD and tryptophan (Trp) fluorescence spectroscopy that copper induces changes to the tertiary structure of SHaPrP(29-231). Binding of copper quenches the Trp fluorescence emission significantly, shifts the emission spectrum to shorter wavelengths, and also induces changes in the near-UV CD spectrum of SHaPrP(29-231). The binding sites are highly specific for Cu2+, as indicated by the lack of a change in Trp fluorescence emission with Ca2+, Co2+, Mg2+, Mn2+, Ni2+, and Zn2+. Binding of Cu2+ also promotes the conformational shift from a predominantly alpha-helical to a beta-sheet structure. Equilibrium dialysis experiments indicate a binding stoichiometry of approximately 2 copper molecules per PrP molecule at physiologically relevant concentrations, and pH titration of Cu2+ binding suggests a role for histidine as a chelating ligand. NMR spectroscopy has recently demonstrated that the octarepeats (PHGGGWGQ) in SHaPrP(29-231) lack secondary or tertiary structure in the absence of Cu2+. Our results suggest that each Cu2+ binds to a structure defined by two octarepeats (PHGGGWGQ) with one histidine and perhaps one glycine carbonyl chelating the ion. We propose that the binding of two copper ions to four octarepeats induces a more defined structure to this region.

There is considerable concern that bovine prions from cattle with bovine spongiform encephalopathy (BSE) may have been passed to humans (Hu), resulting in a new form of Creutzfeldt-Jakob disease (CJD). We report here the transmission of bovine (Bo) prions to transgenic (Tg) mice expressing BoPrP; one Tg line exhibited incubation times of approximately 200 days. Like most cattle with BSE, vacuolation and astrocytic gliosis were confined in the brainstems of these Tg mice. Unexpectedly, mice expressing a chimeric Bo/Mo PrP transgene were resistant to BSE prions whereas mice expressing Hu or Hu/Mo PrP transgenes were susceptible to Hu prions. A comparison of differences in Mo, Bo, and Hu residues within the C terminus of PrP defines an epitope that modulates conversion of PrPC into PrPSc and, as such, controls prion transmission across species. Development of susceptible Tg(BoPrP) mice provides a means of measuring bovine prions that may prove critical in minimizing future human exposure.

A fundamental step in the pathogenesis of spongiform encephalopathies (prion diseases) is the conversion of the cellular isoform of prion protein (PrPC) into the infectious form (scrapie isoform, PrPSc), apparently by a conformational mechanism. Comparison of the native secondary and tertiary structures of both proteins is essential to elucidate the molecular basis of this transformation. To obtain sufficient quantities of native-like PrPC, we have developed a semipreparative method to purify PrPC from hamster brains. PrPC was solubilized from purified synaptosomal and microsomal membranes by the nonionic detergent n-octyl- beta-glucopyranoside; the soluble fraction was loaded at pH 7.5 onto a semipreparative cation-exchange TSK-SP-5PW (HPLC) column. The fractions eluted by linear NaCl gradient and enriched for PrPC were sequentially purified using an immobilized ion-affinity HPLC column charged by Co2+, followed by wheat germ agglutinin (WGA)-affinity HPLC or size-exclusion HPLC (SE-HPLC) using a TSK G3000SW column. More than 95% purity was achieved after SE-HPLC as estimated by quantitative densitometry of the silver-stained SDS-PAGE gel; the recovery of total brain PrPC was >/=8%. The purified PrPC was a monomer with an intact N-terminus, and with a Stoke's radius of 26 A, corresponding to that expected from the molecular weight for a native protein. The presence of the native-like conformation was further verified by peptide mapping after limited trypsin proteolysis, and by the apparent unfolding in guanidine hydrochloride, as detected by SE-HPLC.

We studied the regional distribution of infectious amyloid protein by western immunoblots of brain tissue extracts from 37 patients with different forms of spongiform encephalopathy, i.e., 16 sporadic cases, 18 familial cases with a variety of mutations, and 3 iatrogenic cases. In sporadic and familial Creutzfeldt-Jakob disease, amyloid protein concentrations were usually highest in the frontotemporal regions of the cerebral cortex, whereas iatrogenic Creutzfeldt-Jakob disease and Gerstmann-Sträussler-Scheinker syndrome had as high or higher concentrations in the deep cerebral nuclei and cerebellum. As a group, familial cases had lower amyloid protein concentrations than either sporadic or iatrogenic cases, and fatal familial insomnia patients had the lowest concentrations found in any form of disease. This hierarchy of amyloid protein concentrations corresponds to the experimental transmission rates observed for each form of disease and is consistent with the concept that the protein molecule is an integral component of the infectious agent. Regional amyloid protein pattern analysis of brain and spinal cord may help to distinguish sporadic from environmentally acquired infections, as for example, cases of human disease suspected to have arisen from exposure to sheep or cows infected with scrapie or bovine spongiform encephalopathy.

The scrapie amyloid (prion) protein (PrP27-30) is a host-derived component of the infectious scrapie agent; the potential to replicate, propagate, and form amyloid is a result of the posttranslational event or conformational abnormality. In low concentrations of guanidine hydrochloride (Gdn.HCl), PrP27-30 dissociates into a compact equilibrium intermediate with a substantial portion of secondary structure, partially denatured tertiary structure, and tryptophan residues in an apolar environment [Safar, J., Roller, P. P., Gajdusek, D. C., & Gibbs, C. J., Jr. (1993) J. Biol. Chem. 27, 20276-20284]. Here we describe the characteristics of this metastable form as monitored by 8-anilino-1-naphthalenesulfonate (ANS) fluorescence spectroscopy and circular dichroism (CD) spectroscopy, and we propose a mechanism for scrapie amyloid association. The Gdn.HCl-induced equilibrium intermediate of PrP27-30 had multiple high-affinity hydrophobic binding sites for ANS, some close to the Trp residues. The amide CD spectrum of an acid-induced intermediate (A-form), in equilibrium at pH < 2.0, was similar to the Gdn.HCl-induced intermediate and suggested the presence of a significant portion of an alpha-helical or beta-turn secondary structure. In contrast, the PrP27-30 associated into aggregates in an all beta-sheet conformation with less ordered and more exposed hydrophobic side chains. The noncooperative unfolding of the Gdn.HCl-induced intermediate at high temperature was irreversible and correlated with the loss of infectivity. The results demonstrate that PrP27-30 associates through a compact, metastable hydrophobic intermediate with an nonnative, nondenatured secondary structure and a tertiary structure close to the unfolded form.(ABSTRACT TRUNCATED AT 250 WORDS)

The scrapie amyloid (prion) protein (PrP27-30) is the protease-resistant core of a larger precursor (PrPSc) and a component of the infectious scrapie agent; the potential to form amyloid is a result of posttranslational event or conformational abnormality. The conformation, heat stability, and solvent-induced conformational transitions of PrP27-30 were studied in the solid state in films by CD spectroscopy and correlated with the infectivity of rehydrated and equilibrated films. The exposure of PrP27-30 in films to 60 degrees C, 100 degrees C, and 132 degrees C for 30 min did not change the beta-sheet secondary structure; the infectivity slightly diminished at 132 degrees C and correlated with a decreased solubility of PrP27-30 in sodium dodecyl sulfate (SDS), probably due to cross-linking. Exposing PrP27-30 films to formic acid (FA), trifluoroacetic acid (TFA), trifluoroethanol (TFE), hexafluoro-2-propanol (HFIP), and SDS transformed the amide CD band, diminished the mean residue ellipticity of aromatic bands, and inactivated scrapie infectivity. The convex constraint algorithm (CAA) deconvolution of the CD spectra of the solvent-exposed and rehydrated solid state PrP27-30 identified five common spectral components. The loss of infectivity quantitatively correlated with a decreasing proportion of native, beta-pleated sheet-like secondary structure component, an increasing amount of alpha-helical component, and an increasingly disordered tertiary structure. The results demonstrate the unusual thermal stability of the beta-sheet secondary structure of PrP27-30 protein in the solid state. The conformational perturbations of PrP27-30 parallel the changes in infectivity and suggest that the beta-sheet structure plays a key role in the physical stability of scrapie amyloid and in the ability to propagate and replicate scrapie.

The solid state secondary structure of myoglobin, RNase A, concanavalin A (Con A), poly(L-lysine), and two linear heterooligomeric peptides were examined by both far-uv CD spectroscopy1 and by ir spectroscopy. The proteins associated from water solution on glass and mica surfaces into noncrystalline, amorphous films, as judged by transmission electron microscopy of carbon-platinum replicas of surface and cross-fractured layer. The association into the solid state induced insignificant changes in the amide CD spectra of all alpha-helical myoglobin, decreased the molar ellipticity of the alpha/beta RNase A, and increased the molar ellipticity of all-beta Con A with no change in the positions of the bands' maxima. High-temperature exposure of the films induced permanent changes in the conformation of all proteins, resulting in less alpha-helix and more beta-sheet structure. The results suggest that the protein alpha-helices are less stable in films and that the secondary structure may rearrange into beta-sheets at high temperature. Two heterooligomeric peptides and poly(L-lysine), all in solution at neutral pH with "random coil" conformation, formed films with variable degrees of their secondary structure in beta-sheets or beta-turns. The result corresponded to the protein-derived Chou-Fasman amino acid propensities, and depended on both temperature and solvent used. The ir and CD spectra correlations of the peptides in the solid state indicate that the CD spectrum of a "random" structure in films differs from random coil in solution. Formic acid treatment transformed the secondary structure of the protein and peptide films into a stable alpha-helix or beta-sheet conformations. The results indicate that the proteins aggregate into a noncrystalline, glass-like state with preserved secondary structure. The solid state secondary structure may undergo further irreversible transformations induced by heat or solvent.

Ganglioside composition in brains of terminally ill LVG/LAK golden Syrian hamsters infected with the 263K strain of the scrapie agent was analyzed. Results were compared to those obtained from noninfected animals matched by age, sex, and strain. Gangliosides extracted from scrapie-infected animals showed little change in major components, while an increased number of new alkali-labile species appeared. Additionally, the animal strain employed demonstrated a significant polymorphism in brain ganglioside composition. No significant changes in incubation time, clinical development or pathologic features of scrapie were associated with this polymorphism.