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PubMed2025

A comprehensive phylogeny of mammalian PRNP gene reveals no influence of prion misfolding propensity on the evolution of this gene.

Prion diseases are invariably fatal neurodegenerative diseases that affect some mammalian species, including humans. These diseases are caused by the misfolding of the cellular prion protein (PrPC) into a pathologic isoform (PrPSc). The prion protein is highly conserved across mammals. However, some species present lower susceptibility to prion diseases than others. This behavior is likely explained by the resistance of these animal species' prion proteins to acquire a pathological conformation. Therefore, the tertiary structure and interspecific variations encoded in the primary structure determine a PrP proneness to misfolding. For this reason, we studied the PRNP gene from a phylogenetic perspective, potentially unveiling evolutionary events related to prion diseases. We generated a database of mammalian PRNP sequences and constructed phylogenetic trees based on nucleotide sequence variations. We aligned 1146 PRNP gene sequences from 901 different mammalian species and built a PRNP gene-based phylogenetic tree. Classical phylogenetic orders tend to maintain their clustering in the PRNP gene tree. Nonetheless, the few differences found may shed some light on potential evolutionary constraints posed by prion disorders. Moreover, this phylogenetic study was combined with an in vitro misfolding study. Protein Misfolding Shaking Amplification (PMSA) was used to evaluate the tendency of many of these proteins to misfold. This comprehensive analysis spanned a wide range of mammalian prion protein sequences and included analysis of different variants with a focus on the human rs1799990 locus (c.385A > G, p.Met129Val). This variant, widely linked to prion disease susceptibility in humans, is explored in the context of its evolutionary origins. All in all, our PRNP gene-based tree, despite showing some topological differences with the reference species tree that could be in some cases related to prion disease susceptibility, is not significantly distinct. Indicating that the proneness of a PrP variant to misfold spontaneously has not shaped the evolution of this gene.

Phylogeny↗
PubMed2025

Isolation of a novel human prion strain from a PRNP codon 129 heterozygous vCJD patient.

The epizootic prion disease of cattle, bovine spongiform encephalopathy (BSE), caused variant Creutzfeldt-Jakob disease (vCJD) in humans following dietary exposure. Codon 129 polymorphism of the human prion protein gene (PRNP), encoding either methionine (M) or valine (V), dictates the propagation of distinct human prion strains and up to now all but one neuropathologically confirmed vCJD patients have had a 129MM genotype. Concordant with this genetic association, transgenic modelling has established that human PrP 129V is incompatible with the vCJD prion strain and that depending on codon 129 genotype, primary human infection with BSE prions may, in addition to vCJD, result in sporadic CJD-like or novel phenotypes. In 2016 we saw the first neuropathologically confirmed case of vCJD in a patient with a codon 129MV genotype. This patient's neuropathology and molecular strain type were pathognomonic of vCJD but their clinical presentation and neuroradiological features were more typical of sporadic CJD, suggestive of possible co-propagation of another prion strain. Here we report the transmission properties of prions from the brain and lymphoreticular tissues of the 129MV vCJD patient. Primary transmissions into transgenic mice expressing human PrP with different codon 129 genotypes mainly produced neuropathological and molecular phenotypes congruent to those observed in the same lines of mice challenged with prions from 129MM vCJD patient brain, indicative that the vCJD prion strain was the dominant propagating prion strain in the patient's brain. Remarkably however, some transgenic mice challenged with 129MV vCJD patient brain propagated a novel prion strain type which at secondary passage was uniformly lethal in mice of all three PRNP codon 129 genotypes after similar short mean incubation periods. These findings establish that cattle BSE prions can trigger the co-propagation of distinct prion strains in humans.

Animals↗
PubMed2026

Prion-Like Protein LENG8-Mediated Nucleation Drives Stress Granule Assembly.

Stress granules (SGs) are highly dynamic and reversible cytoplasmic biomolecular condensates formed via liquid-liquid phase separation (LLPS) under various stresses. As inherently heterogeneous assemblies, SGs possess distinct stable cores (initial nucleation seeds), substructures, or microphases. However, the mechanisms governing the formation and heterogeneity of SG nucleation seeds, and their dynamic integration, remain largely unclear. Here, we demonstrate that LENG8 is recruited to SGs under multiple stress conditions and is indispensable for SG assembly. Upon stress exposure, nuclear LENG8 granules disassemble, enabling LENG8 to translocate into the cytoplasm and undergo LLPS to form independent initial nucleation foci distinct from canonical G3BP1/TIA1-dependent seeds. Subsequently, these LENG8-initiated foci merge into growing SGs through a direct interaction between the prion-like domain of LENG8 and TIA1, facilitating SG expansion and maturation. Depletion of LENG8 or disruption of the LENG8-TIA1 interaction markedly impairs SG formation. Using conditional Leng8 knockout mice, we further establish that LENG8 deficiency attenuates stress-induced SG assembly and increases cellular apoptosis in germ cells. Collectively, our study identifies LENG8 as a previously unrecognized SG nucleator, revealing the hierarchical assembly and integration mechanism of distinct nucleation modules during early SG biogenesis.

LENG8↗
PubMed2025

Pedigree analysis and genetic inheritance of fatal familial insomnia (FFI) in a Portuguese multigenerational family.

Fatal familial insomnia (FFI) is a rare, autosomal dominant prion disease caused by a mutation in the PRNP gene, leading to the misfolding of the cellular prion protein (PrPC) into its pathogenic form (PrPSc). This results in neurodegeneration, particularly in the thalamus, a key region regulating sleep-wake cycles, which underlies the hallmark symptoms of FFI, including insomnia, autonomic dysfunctions, motor disturbances and cognitive decline. This study focuses on a Portuguese family with FFI, providing a detailed pedigree analysis spanning five generations and comprising 134 individuals, to elucidate inheritance patterns, disease onset, and clinical progression. The findings confirm the autosomal-dominant inheritance pattern and a strong familial clustering of the disease with age of onset in the late 50s (mean 57 years). Although 67% of affected individuals succumbing to the disease within months to 1.5 years, a notably 33% exhibited prolonged survival beyond the typical disease duration, exceeding proportions reported in the literature. Family members retrospectively reported prodromal symptoms, including generalized pain, headaches, tinnitus, pruritus, and behavioral changes, occurring up to five years before diagnosis. In several cases, reportedly, disease onset was associated with major phycological stressors (e.g., emotional stress or mourning). While the significance of these observations remains uncertain, they may provide insights into potential early features in this kindred. Further research integrating genomic sequencing, biomarkers, and longitudinal clinical assessments are needed to better understand the mechanisms underlying the heterogeneity of FFI and to explore potential therapeutic interventions.

Humans↗
PubMed1976

Properties of the scrapie agent-endomembrane complex from hamster brain.

Subcellular fractionation of scrapie-infected hamster brain indicated the association of the scrapie agent with a component of the endomembrane system. Characterization by equilibrium density gradient centrifugation, electron microscopy, and marker enzymes suggested a primary association with rough and smooth endoplasmic reticulum and a possible incorporation into the plasma membrane. DNA polymerase activity demonstrated a direct correlation with regions of scrapie activity from the gradient fractions. A scrapie-related product was detected after (3H)TMP incorporation and analysis on 2.2% polyacrylamide gels. Analysis of nucleic acid species extracted from subcellular fractions resulted in a greater quantity from healthy brain; however, no qualitative distinctions were detected.

Adenosine Triphosphatases↗
PubMed2026

Prion disease mimicking rapidly progressive Alzheimer disease: case series and systematic review.

BACKGROUND: Prion disease and Alzheimer disease (AD) are common causes of rapidly progressive dementia (RPD). Although most patients with prion disease are distinguished by MRI and CSF findings, selected cases mimic rapidly progressive AD. We characterized AD-prion disease mimics within a prospective cohort and the extant literature to identify the clinical features and tests that support accurate diagnoses in these patients. METHODS: Patients with prion disease initially diagnosed as rapidly progressive AD were identified from a prospective cohort study at Mayo Clinic (February 2020-June 2026) and through systematic review of MEDLINE and Embase. RESULTS: Of 204 patients with RPD, five (2.5%) were initially diagnosed with clinically probable AD but ultimately determined to have prion disease. Systematic review identified 10 additional cases (n=15, median age-at-onset, 59 years; 67% male). Presentations reproduced amnestic (53%), dysexecutive (27%), primary progressive aphasia (13%), and posterior cortical atrophy (7%) AD phenotypes; median time from AD diagnosis to consideration of prion disease was 2 months. Diffusion-weighted MRI abnormalities were absent in Mayo Clinic cases and absent/equivocal (n=2) or overlooked (n=8) in published cases. CSF biomarkers were consistent with AD in 6/9 tested patients, with elevated total tau levels in 11/13 patients and total-tau/p hosphorylated-tau181 ratios in 5/9 patients. Real-time quaking-induced conversion assays for prions were positive in the CSF of 9/12 patients. Prion disease was confirmed by neuropathology (n=7), genetics (n=2), or real-time quaking-induced conversion (n=6) assays. CONCLUSIONS: Prion disease may rarely mimic rapidly progressive AD. Disproportionate elevations in CSF total-tau levels or total-tau/p hosphorylated-tau181 ratios should prompt consideration of prion disease.

Humans↗
PubMed1978

Partial purification and evidence for multiple molecular forms of the scrapie agent.

A procedure for the partial purification of the scrapie agent from mouse spleen was developed based on its sedimentation profile. Differential centrifugation and detergent treatment with sodium deoxycholate yielded a fraction designated "P5" which was enriched for scrapie infectivity approximately 20-fold with respect to cellular protein. The P5 fraction was devoid of cellular membranes but heavily contaminated with ribosomes as judged by electron microscopy. On centrifugation of the fraction P5 to near equilibrium in a sucrose gradient scrapie infectivity was distributed over a range of densities from 1.08 to 1.30 g/cm3. Parallel rate-zonal analysis showed that the infectivity was distributed over a range of particle sizes with s20.w values from approximately 40 S to greater than 500 S. Incubation of P5 at 37 or 80 degrees C, under conditions that disrupt ribosomes, dramatically altered the rate-zonal gradient profile of the agent. Under these conditions, the agent sedimented as particles with s20.w greater than 500 S. The apparent heterogeneity of the scrapie agent with respect to both size and density and its ability to shift from one form to another suggest that the agent may contain hydrophobic domains on its surface.

Animals↗
PubMed1978

The scrapie agent: evidence against its dependence for replication on intrinsic nucleic acid.

Exposure of the scrapie agent to u.v. light at various wavelengths has shown that light of 237 nm is 4 to 5 times as effective in inactivating it as 'germicidal' wavelengths (250 to 270 nm); whereas with systems that depend on RNA or DNA for function, inactivation is most effective by wavelengths in the germicidal range and there is a minimum of response in the wavelength region round 240 nm. The action spectrum for the scrapie agent is reminiscent of the absorption spectrum for purified bacterial endotoxin, identified as a lipopolysaccharide complex. Dilute aqueous suspensions of scrapie agent were exposed to ionizing radiations in the presence or absence of oxygen. In dilute suspensions of test systems depending on the integrity of nucleic acid or protein, oxygen is almost invariably protective, but it was extremely sensitizing for inactivation of the scrapie agent, to an extent approached only in the case of membranous systems like lysosomes. Results of these two methods argue against dependence of the scrapie agent on an intrinsic nucleic acid moiety for ability to replicate. They suggest that a lipid fraction is an important component and to that extent provide additional support for the 'membrane hypothesis'.

Animals↗