Squirrel monkeys (Saimiri sciureus) infected with the agent of bovine spongiform encephalopathy develop tau pathology.

Squirrel monkeys (Saimiri sciureus) were infected experimentally with the agent of classical bovine spongiform encephalopathy (BSE). Two to four years later, six of the monkeys developed alterations in interactive behaviour and cognition and other neurological signs typical of transmissible spongiform encephalopathy (TSE). At necropsy examination, the brains from all of the monkeys showed pathological changes similar to those described in variant Creutzfeldt-Jakob disease (vCJD) of man, except that the squirrel monkey brains contained no PrP-amyloid plaques typical of that disease. Constant neuropathological features included spongiform degeneration, gliosis, deposition of abnormal prion protein (PrP(TSE)) and many deposits of abnormally phosphorylated tau protein (p-Tau) in several areas of the cerebrum and cerebellum. Western blots showed large amounts of proteinase K-resistant prion protein in the central nervous system. The striking absence of PrP plaques (prominent in brains of cynomolgus macaques [Macaca fascicularis] with experimentally-induced BSE and vCJD and in human patients with vCJD) reinforces the conclusion that the host plays a major role in determining the neuropathology of TSEs. Results of this study suggest that p-Tau, found in the brains of all BSE-infected monkeys, might play a role in the pathogenesis of TSEs. Whether p-Tau contributes to development of disease or appears as a secondary change late in the course of illness remains to be determined.

Proteasomal inhibition induced by manganese ethylene-bis-dithiocarbamate: relevance to Parkinson's disease.

Maneb, a widely used fungicide, has been associated with Parkinsonism in humans. In experimental models, maneb and its major active element, manganese ethylene-bis-dithiocarbamate (Mn-EBDC) cause selective nigrostriatal neurodegeneration in mice and in rats, respectively. To investigate the mechanisms underlying this neurodegeneration, we studied the effects of Mn-EBDC on proteasomal function, which is decreased in patients with Parkinson's disease (PD), in a dopaminergic neuronal cell line (MES 23.5 or MES). The results demonstrated that exposure of MES cells to 6 microM Mn-EBDC for 7 days produced not only significant neurotoxicity but also inhibition of proteasomal chymotrypsin-like and postglutamyl peptidase activities. Proteasomal dysfunction was accompanied by formation of cytoplasmic inclusions that were positive for alpha-synuclein immunostaining and significantly increased sodium dodecyl sulfate-insoluble alpha-synuclein aggregation seen by Western blot analysis. In addition, there was a significant increase in oxidative stress, evidenced by elevated total protein carbonyl content, in cells treated with Mn-EBDC. Manipulation of intracellular reduced glutathione levels with N-acetyl-L-cysteine or L-buthionine sulfoximine pretreatment to modulate Mn-EBDC-mediated oxidative stress altered Mn-EBDC-mediated neurotoxicity, proteasomal dysfunction, and alpha-synuclein aggregation in these cells. These data suggest that neurotoxicity-induced by Mn-EBDC is at least partially attributable to Mn-EBDC-mediated proteasomal inhibition, and that the proteasome may be an important target by which environmental exposure modifies the risk for developing PD in vulnerable populations.

Insomnia associated with thalamic involvement in E200K Creutzfeldt-Jakob disease.

BACKGROUND: Insomnia with predominant thalamic involvement and minor cortical and cerebellar pathologic changes is not characteristic of familial Creutzfeldt-Jakob disease (CJD) but is a hallmark of fatal familial insomnia. OBJECTIVE: To report a 53-year-old woman with intractable insomnia as her initial symptom of disease. METHODS: The authors characterized clinical, pathologic, and molecular features of the disease using EEG, polysomnography, neurohistology, Western blotting, protein sequencing, and prion protein (PrP) gene (PRNP) analysis. RESULTS: The patient developed dysgraphia, dysarthria, bulimia, myoclonus, memory loss, visual hallucinations, and opisthotonos, as well as pyramidal, extrapyramidal, and cerebellar signs. Polysomnographic studies showed an absence of stages 3 and 4, and REM. She died 8 months after onset. On neuropathologic examination, there was major thalamic involvement characterized by neuronal loss, spongiform changes, and prominent gliosis. The inferior olivary nuclei exhibited chromatolysis, neuronal loss, and gliosis. Spongiform changes were mild in the neocortex and not evident in the cerebellum. PrP immunopositivity was present in these areas as well as in the thalamus. PRNP analysis showed the haplotype E200K-129M. Western blot analysis showed the presence of proteinase K (PK)-resistant PrP (PrP(sc)) with the nonglycosylated isoform of approximately 21 kd, corresponding in size to that of type 1 PrP(sc). N-terminal protein sequencing demonstrated PK cleavage sites at glycine (G) 82 and G78, as previously reported in CJD with the E200K-129 M haplotype. CONCLUSIONS: Insomnia may be a prominent early symptom in cases of CJD linked to the E200K-129M haplotype in which the thalamus is severely affected.

A new PRNP mutation (G131V) associated with Gerstmann-Sträussler-Scheinker disease.

BACKGROUND: Gerstmann-Sträussler-Scheinker disease is a rare form of prion disease. OBJECTIVE: To determine the prion mutation in a 51-year-old man without a family history of neurologic disease who died from Gerstmann-Sträussler-Scheinker disease. PATIENT AND METHODS: The patient was a 51-year-old man who died after a 9-year illness characterized by dementia and eventually ataxia. Neuropathologic studies were performed, the results of which revealed abundant prion protein-immunopositive amyloid plaques in the cerebellum without spongiform degeneration. RESULTS: Genetic analysis of the prion protein gene showed a novel mutation at codon 131 that caused a valine-for-glycine substitution (G131V) and homozygosity at codon 129 (129M). Proteinase K-resistant prion protein was detected by Western blot analysis. CONCLUSIONS: This is the first mutation described in the short, antiparallel beta-sheet domain of the prion protein. This report highlights the importance of genetic analysis of patients with atypical dementia even in the absence of a family history.

Prion proteins with different conformations accumulate in Gerstmann-Sträussler-Scheinker disease caused by A117V and F198S mutations.

Gerstmann-Sträussler-Scheinker disease (GSS) is characterized by the accumulation of proteinase K (PK)-resistant prion protein fragments (PrP(sc)) of approximately 7 to 15 kd in the brain. Purified GSS amyloid is composed primarily of approximately 7-kd PrP peptides, whose N terminus corresponds to residues W(81) and G(88) to G(90) in patients with the A117V mutation and to residue W(81) in patients with the F198S mutation. The aim of this study was to characterize PrP in brain extracts, microsomal preparations, and purified fractions from A117V patients and to determine the N terminus of PrP(sc) species in both GSS A117V and F198S. In all GSS A117V patients, the approximately 7-kd PrP(sc) fragment isolated from nondigested and PK-digested samples had the major N terminus at residue G(88) and G(90), respectively. Conversely, in all patients with GSS F198S, an approximately 8-kd PrP(sc) fragment was isolated having the major N terminus start at residue G(74). It is possible that a further degradation of this fragment generates the amyloid subunit starting at W(81). The finding that patients with GSS A117V and F198S accumulate PrP(sc) fragments of different size and N-terminal sequence, suggests that these mutations generate two distinct PrP conformers.

Primary myopathy and accumulation of PrPSc-like molecules in peripheral tissues of transgenic mice expressing a prion protein insertional mutation.

A nine-octapeptide insertional mutation in the prion protein (PrP) gene is associated with an inherited variant of Creutzfeldt-Jakob disease in humans. Transgenic mice that express the mouse PrP homologue of this mutation (designated PG14) under control of a PrP promoter display a progressive neurological disorder characterized by ataxia, apoptosis of cerebellar granule cells, and accumulation in the brain of mutant PrP molecules that display the biochemical hallmarks of PrP(Sc), the pathogenic isoform of PrP. In this report, we have investigated the expression of PG14 PrP in the peripheral tissues of these mice. We found highest levels of mutant PrP in the brain and spinal cord, intermediate levels in skeletal muscle, heart, and testis and low levels in kidney, lung, spleen, intestine, and stomach. Up to 70% of the PG14 PrP expressed in peripheral tissues was detergent-insoluble, and digestion with low concentrations of proteinase K yielded a PrP 27-30 fragment. These results suggest that the mutant protein was converted to a physical state reminiscent of PrP(Sc), although its infectivity remains to be determined. Histological analysis of skeletal muscle, one of the peripheral tissues with the highest level of PG14 PrP, revealed features indicative of a progressive, primary myopathy, including central nuclei, necrotic and regenerating fibers, and variable fiber size. These results indicate that the PG14 mutation structurally alters the protein in a way that promotes conversion to a PrP(Sc)-like state, regardless of the tissue context, and suggest that accumulation of PrP(Sc) can have deleterious effects on skeletal muscle cells as well as on neurons.

Codeposition of cystatin C with amyloid-beta protein in the brain of Alzheimer disease patients.

Immunohistochemical analysis of brains of patients with Alzheimer disease (AD) revealed that the cysteine proteinase inhibitor cystatin C colocalizes with amyloid beta-protein (Abeta) in parenchymal and vascular amyloid deposits. No evidence of cerebral hemorrhage was observed in any of the brains studied. Immunoelectron microscopy demonstrated dual staining of amyloid fibrils with anti-Abeta and anti-cystatin C antibodies. Cystatin C immunoreactivity was also observed in amyloid deposits in the brain of transgenic mice overexpressing human beta amyloid precursor protein. Massive deposition of the variant cystatin C in the cerebral vessels of patients with the Icelandic form of hereditary cerebral hemorrhage with amyloidosis is thought to be responsible for the pathological processes leading to stroke. Anti-cystatin C antibodies strongly labeled pyramidal neurons within cortical layers most prone to amyloid deposition in the brains of AD patients. Immunohistochemistry with antibodies against the carboxyl-terminus of Abeta(x-42) showed intracellular immunoreactivity in the same neuronal subpopulation. It remains to be established whether the association of cystatin C to Abeta plays a primary role in amyloidogenesis of AD or is a late event in which the protein is bound to the previously formed Abeta amyloid fibrils.

Biochemical characterization of a neuroserpin variant associated with hereditary dementia.

Neuroserpin isolated from inclusion bodies in the brain of a patient with a neurodegenerative disease was characterized biochemically. The protein consisted of residues 20 to 410 of the neuroserpin precursor deduced from its cDNA sequence indicating the entire molecule was deposited. A minor amount started with residue 19 of the precursor, and the carboxyl terminus was heterogeneous ending at residues 405, 407, 409, and 410. Arg was present at position 52. No normal Ser52 was found indicating that only mutant neuroserpin was present in the inclusion bodies. The three potential Asn glycosylation sites all contained carbohydrate. DNA sequence analysis of exons 2 to 9 of the neuroserpin gene in the proband showed the published normal neuroserpin sequence except for the presence of both adenine and cytosine at the first position of codon 52, that indicates heterozygosity for both the normal Ser(AGT) and variant Arg(CGT) at this position in the expressed protein. Restriction fragment length polymorphism analysis of a polymerase chain reaction product from exon 2 revealed the propositus and his affected sibling both were heterozygous for the mutation whereas 100 unaffected controls were negative. Chemical characterization of the variant neuroserpin will significantly enhance the understanding of this protein in both normal physiology and neurodegenerative diseases.

A 7-kDa prion protein (PrP) fragment, an integral component of the PrP region required for infectivity, is the major amyloid protein in Gerstmann-Sträussler-Scheinker disease A117V.

Gerstmann-Sträussler-Scheinker disease (GSS) is a cerebral amyloidosis associated with mutations in the prion protein (PrP) gene (PRNP). The aim of this study was to characterize amyloid peptides purified from brain tissue of a patient with the A117V mutation who was Met/Val heterozygous at codon 129, Val(129) being in coupling phase with mutant Val117. The major peptide extracted from amyloid fibrils was a approximately 7-kDa PrP fragment. Sequence analysis and mass spectrometry showed that this fragment had ragged N and C termini, starting mainly at Gly88 and Gly90 and ending with Arg148, Glu152, or Asn153. Only Val was present at positions 117 and 129, indicating that the amyloid protein originated from mutant PrP molecules. In addition to the approximately 7-kDa peptides, the amyloid fraction contained N- and C-terminal PrP fragments corresponding to residues 23-41, 191-205, and 217-228. Fibrillogenesis in vitro with synthetic peptides corresponding to PrP fragments extracted from brain tissue showed that peptide PrP-(85-148) readily assembled into amyloid fibrils. Peptide PrP-(191-205) also formed fibrillary structures although with different morphology, whereas peptides PrP-(23-41) and PrP-(217-228) did not. These findings suggest that the processing of mutant PrP isoforms associated with Gerstmann-Sträussler-Scheinker disease may occur extracellularly. It is conceivable that full-length PrP and/or large PrP peptides are deposited in the extracellular compartment, partially degraded by proteases and further digested by tissue endopeptidases, originating a approximately 7-kDa protease-resistant core that is similar in patients with different mutations. Furthermore, the present data suggest that C-terminal fragments of PrP may participate in amyloid formation.

Ectopic white matter neurons, a developmental abnormality that may be caused by the PSEN1 S169L mutation in a case of familial AD with myoclonus and seizures.

We report clinical, neuropathologic and molecular genetic data from an individual affected by a familial Alzheimer disease (AD) variant. The proband had an onset of dementia at age 29 followed by generalized seizures a year later. He died at age 40. Neuropathologically, he had severe brain atrophy and characteristic histopathologic lesions of AD. Three additional neuropathologic features need to be emphasized: 1) severe deposition of Abeta in the form of diffuse deposits in the cerebral and cerebellar cortices, 2) numerous Abeta deposits in the subcortical white matter and in the centrum semiovale, and 3) numerous ectopic neurons, often containing tau-immunopositive neurofibrillary tangles, in the white maner of the frontal and temporal lobes. A molecular genetic analysis of DNA extracted from brain tissue of the proband revealed a S169L mutation in the Presenilin 1 (PSEN1) gene. The importance of this case lies in the presence of ectopic neurons in the white matter, early-onset seizures, and a PSEN1 mutation. We hypothesize that the PSEN1 mutation may have a causal relationship with an abnormality in neuronal development.

Cellular and transgenic models of familial prion diseases.

Prion diseases are fatal neurodegenerative disorders of humans and animals, which result from the conformational conversion of a normal, cell surface glycoprotein (PrP(C)) into a pathogenic isoform (PrP(Sc)) that is the main component of infectious prions (1,2) . Familial prion diseases, which include 10% of the cases of Creutzfeldt-Jakob disease and all cases of Gerstmann-Sträussler syndrome and fatal familial insomnia, are linked in an autosomal dominant fashion to point and insertional mutations in the PrP gene on chromosome 20 (3,4). These mutations are presumed to favor spontaneous conversion of PrP to the PrPSc state. One way to experimentally model familial prion diseases is to express PrP molecules carrying disease-associated mutations in either cultured mammalian cells or transgenic mice. The authors review their own work using these two kinds of model systems, which have provided complementary information about the PrPC?PrP(Sc) conversion process, and about the pathogenic effects of mutant PrP.

Senile dementia associated with amyloid beta protein angiopathy and tau perivascular pathology but not neuritic plaques in patients homozygous for the APOE-epsilon4 allele.

Amyloid beta protein deposition in cortical and leptomeningeal vessels, causing the most common type of cerebral amyloid angiopathy, is found in sporadic and familial Alzheimer's disease (AD) and is the principal feature in the hereditary cerebral hemorrhage with amyloidosis, Dutch type. The presence of the Apolipopriotein E (APOE)-epsilon4 allele has been implicated as a risk factor for AD and the development of cerebral amyloid angiopathy in AD. We report clinical, pathological and biochemical studies on two APOE-epsilon4 homozygous subjects, who had senile dementia and whose main neuropathological feature was a severe and diffuse amyloid angiopathy associated with perivascular tau neurofibrillary pathology. Amyloid beta protein and ApoE immunoreactivity were observed in leptomeningeal vessels as well as in medium-sized and small vessels and capillaries in the parenchyma of the neocortex, hippocampus, thalamus, cerebellum, midbrain, pons, and medulla. The predominant peptide form of amyloid beta protein was that terminating at residue Val40, as determined by immunohistochemistry, amino acid sequence and mass spectrometry analysis. A crown of tau-immunopositive cell processes was consistently present around blood vessels. DNA sequence analysis of the Amyloid Precursor Protein gene and Presenilin-1 (PS-1) gene revealed no mutations. In these APOE-epsilon4 homozygous patients, the pathological process differed from that typically seen in AD in that they showed a heavy burden of perivascular tau-immunopositive cell processes associated with severe amyloid beta protein angiopathy, neurofibrillary tangles, some cortical Lewy bodies and an absence of neuritic plaques. These cases emphasize the concept that tau deposits may be pathogenetically related to amyloid beta protein deposition.

Neuropathology of Gerstmann-Sträussler-Scheinker disease.

Gerstmann-Sträussler-Scheinker disease is a familial neurodegeneration characterized clinically by adult-onset ataxia, postural abnormalities, and cognitive decline, and pathologically by amyloid deposits mostly localized in the cerebral and cerebellar cortices and the basal ganglia. The disease is due to mutations in the prion protein gene. Processing of the mutant proteins originates the amyloidogenic fragments that accumulate in the tissue. PrP-immunoreactive amyloid deposits are the morphological hallmark of the disease. Hypertrophic astrocytes, activated microglia, and nerve cell loss are consistently associated with PrP-amyloid deposits, while spongiosis, diffuse PrP immunoreactivity, neurofibrillary tangles, Lewy bodies, and long fiber tracts degeneration are occasionally associated. The clinical and pathological variability observed in GSS families is related to both mutations and the M/V polymorphism at codon 129 of the mutated gene.

Accumulation of protease-resistant prion protein (PrP) and apoptosis of cerebellar granule cells in transgenic mice expressing a PrP insertional mutation.

We have generated lines of transgenic mice that express a mutant prion protein (PrP) containing 14 octapeptide repeats whose human homologue is associated with an inherited prion dementia. These mice develop a neurological illness with prominent ataxia at 65 or 240 days of age, depending on whether the transgene array is, respectively, homozygous or hemizygous. Starting from birth, mutant PrP is converted into a protease-resistant and detergent-insoluble form that resembles the scrapie isoform of PrP, and this form accumulates dramatically in many brain regions throughout the lifetime of the mice. As PrP accumulates, there is massive apoptosis of granule cells in the cerebellum. Our analysis provides important insights into the molecular pathogenesis of inherited prion disorders in humans.

A transgenic model of a familial prion disease.

We have generated lines of transgenic mice that express a mutant prion protein containing 14 octapeptide repeats whose human homologue is associated with an inherited prion dementia. These mice develop an ataxic illness that begins at 65 days of age when the transgene array is homozygous, and results in death by 115-138 days. Starting from birth, mutant PrP is converted into a protease-resistant and detergent-insoluble form that resembles PrP(Sc), and this form accumulates dramatically in many brain regions throughout the lifetime of the mice. As PrP accumulates, there is massive apoptosis of cerebellar granule cells, as well as astrocytosis and deposition of PrP in a punctate pattern. These results establish a new transgenic animal model of an inherited human prion disease, and provide important insights into the molecular pathogenesis of these disorders.

Neuroserpin mutation S52R causes neuroserpin accumulation in neurons and is associated with progressive myoclonus epilepsy.

Mutations in the Neuroserpin gene have been reported to cause familial presenile dementia. We describe a new family in which the S52R Neuroserpin mutation is associated with progressive myoclonus epilepsy in 2 siblings. The proband presented myoclonus and epilepsy at age 24, his brother and mother presented a similar disorder when they were 25. A clinical diagnosis of progressive myoclonus epilepsy was made on the proband and his brother. Skin and liver biopsies did not reveal the presence of cytological alterations in the proband. His neurological status worsened over the subsequent 19 yr during which he became demented and had uncontrollable seizures. He died at 43 yr of age from aspiration pneumonia. Neuropathologically, eosinophilic bodies, which were positive for periodic acid-Schiff and immunoreactive with antibodies against human neuroserpin, were present in the perikarya and cell processes of the neurons. They were found in large numbers in the cerebral cortex and substantia nigra and to a lesser extent, in most subcortical gray areas, spinal cord, and dorsal root ganglia. By electron microscopy, the intracytoplasmic bodies were contained within the membranes of the rough endoplasmic reticulum. Occasionally neuroserpin immunopositivity was seen throughout the cytoplasm, even without the presence of well-defined bodies. Our study characterizes for the first time the neuropathologic phenotype associated with hereditary progressive myoclonus epilepsy caused by the S52R Neuroserpin mutation.

Apolipoprotein E is essential for amyloid deposition in the APP(V717F) transgenic mouse model of Alzheimer's disease.

We quantified the amount of amyloid beta-peptide (Abeta) immunoreactivity as well as amyloid deposits in a large cohort of transgenic mice overexpressing the V717F human amyloid precursor protein (APP(V717F+/-) TG mice) with no, one, or two mouse apolipoprotein E (Apoe) alleles at various ages. Remarkably, no amyloid deposits were found in any brain region of APP(V717F+/-) Apoe(-/-) TG mice as old as 22 mo of age, whereas age-matched APP(V717F +/-) Apoe(+/-) and Apoe(+/+) TG mice display abundant amyloid deposition. The amount of Abeta immunoreactivity in the hippocampus was also markedly reduced in an Apoe gene dose-dependent manner (Apoe(+/+) > Apoe(+/-) >> Apoe(-/-)), and no Abeta immunoreactivity was detected in the cerebral cortex of APP(V717F+/-) Apoe(-/-) TG mice at any of the time points examined. The absence of apolipoprotein E protein (apoE) dramatically reduced the amount of both Abeta(1-40) and Abeta(1-42) immunoreactive deposits as well as the resulting astrogliosis and microgliosis normally observed in APP(V717F) TG mice. ApoE immunoreactivity was detected in a subset of Abeta immunoreactive deposits and in virtually all thioflavine-S-fluorescent amyloid deposits. Because the absence of apoE alters neither the transcription or translation of the APP(V717F) transgene nor its processing to Abeta peptide(s), we postulate that apoE promotes both the deposition and fibrillization of Abeta, ultimately affecting clearance of protease-resistant Abeta/apoE aggregates. ApoE appears to play an essential role in amyloid deposition in brain, one of the neuropathological hallmarks of Alzheimer's disease.

Classification of sporadic Creutzfeldt-Jakob disease based on molecular and phenotypic analysis of 300 subjects.

Phenotypic heterogeneity in sporadic Creutzfeldt-Jakob disease (sCJD) is well documented, but there is not yet a systematic classification of the disease variants. In a previous study, we showed that the polymorphic codon 129 of the prion protein gene (PRNP), and two types of protease-resistant prion protein (PrP(Sc)) with distinct physicochemical properties, are major determinants of these variants. To define the full spectrum of variants, we have examined a series of 300 sCJD patients. Clinical features, PRNP genotype, and PrP(Sc) properties were determined in all subjects. In 187, we also studied neuropathological features and immunohistochemical pattern of PrP(Sc) deposition. Seventy percent of subjects showed the classic CJD phenotype, PrP(Sc) type 1, and at least one methionine allele at codon 129; 25% of cases displayed the ataxic and kuru-plaque variants, associated to PrP(Sc) type 2, and valine homozygosity or heterozygosity at codon 129, respectively. Two additional variants, which included a thalamic form of CJD and a phenotype characterized by prominent dementia and cortical pathology, were linked to PrP(Sc) type 2 and methionine homozygosity. Finally, a rare phenotype characterized by progressive dementia was linked to PrP(Sc) type 1 and valine homozygosity. The present data demonstrate the existence of six phenotypic variants of sCJD. The physicochemical properties of PrP(Sc) in conjunction with the PRNP codon 129 genotype largely determine this phenotypic variability, and allow a molecular classification of the disease variants.

Endogenous proteolytic cleavage of normal and disease-associated isoforms of the human prion protein in neural and non-neural tissues.

We have investigated the proteolytic cleavage of the cellular (PrPC) and pathological (PrPSc) isoforms of the human prion protein (PrP) in normal and prion-affected brains and in tonsils and platelets from neurologically intact individuals. The various PrP species were resolved after deglycosylation according to their electrophoretic mobility, immunoreactivity, Sarkosyl solubility, and, as a novel approach, resistance to endogenous proteases. First, our data show that PrPC proteolysis in brain originates amino-truncated peptides of 21 to 22 and 18 (C1) kd that are similar in different regions and are not modified by the PrP codon 129 genotype, a polymorphism that affects the expression of prion disorders. Second, this proteolytic cleavage of PrPC in brain is blocked by inhibitors of metalloproteases. Third, differences in PrPC proteolysis, and probably in Asn glycosylation and glycosylphosphatidylinositol anchor composition, exist between neural and non-neural tissues. Fourth, protease-resistant PrPSc cores in sporadic Creutzfeldt-Jakob disease (CJD) and Gerstmann-Sträussler-Scheinker F198S disease brains all have an intact C1 cleavage site (Met111-His112), which precludes disruption of a domain associated with toxicity and fibrillogenesis. Fifth, the profile of endogenous proteolytic PrPSc peptides is characteristic of each disorder studied, thus permitting the molecular classification of these prion diseases without the use of proteinase K and even a recognition of PrPSc heterogeneity within type 2 CJD patients having different codon 129 genotype and neuropathological phenotype. This does not exclude the role of additional factors in phenotypic expression; in particular, differences in glycosylation that may be especially relevant in the new variant CJD. Proteolytic processing of PrP may play an important role in the neurotropism and phenotypic expression of prion diseases, but it does not appear to participate in disease susceptibility.

Phenotypic variability of Gerstmann-Sträussler-Scheinker disease is associated with prion protein heterogeneity.

Gerstmann-Sträussler-Scheinker disease (GSS), a cerebello-pyramidal syndrome associated with dementia and caused by mutations in the prion protein gene (PRNP), is phenotypically heterogeneous. The molecular mechanisms responsible for such heterogeneity are unknown. Since we hypothesize that prion protein (PrP) heterogeneity may be associated with clinico-pathologic heterogeneity, the aim of this study was to analyze PrP in several GSS variants. Among the pathologic phenotypes of GSS, we recognize those without and with marked spongiform degeneration. In the latter (i.e. a subset of GSS P102L patients) we observed 3 major proteinase-K resistant PrP (PrPres) isoforms of ca. 21-30 kDa, similar to those seen in Creutzfeldt-Jakob disease. In contrast, the 21-30 kDa isoforms were not prominent in GSS variants without spongiform changes, including GSS A117V, GSS D202N, GSS Q212P, GSS Q217R, and 2 cases of GSS P102L. This suggests that spongiform changes in GSS are related to the presence of high levels of these distinct 21-30 kDa isoforms. Variable amounts of smaller, distinct PrPres isoforms of ca. 7-15 kDa were seen in all GSS variants. This suggests that GSS is characterized by the presence PrP isoforms that can be partially cleaved to low molecular weight PrPres peptides.