Diagnosis of Methionine/Valine Variant Creutzfeldt-Jakob Disease by Protein Misfolding Cyclic Amplification

A patient with a heterozygous variant of Creutzfeldt-Jakob disease (CJD) with a methionine/valine genotype at codon 129 of the prion protein gene was recently reported. Using an ultrasensitive and specific protein misfolding cyclic amplification–based assay for detecting variant CJD prions in cerebrospinal fluid, we discriminated this heterozygous case of variant CJD from cases of sporadic CJD

Genetic Factors Contributing to the Susceptibility of Development of Prion Diseases

This paper won an honorable mention writing flag award in the research category. Claire Culbertson, writing for Katherine Bruner’s BIO 325L class, “Lab Experience in Genetics”.Bruner, KatherineUndergraduate Studie

Clinical Features of Rapidly Progressive Alzheimer's Disease

Objective: To characterize clinical features, CSF biomarkers and genetic polymorphisms of patients suffering from a rapidly progressing subtype of Alzheimer's dementia (rpAD). Methods: Retrospective analyses of 32 neuropathologically confirmed cases differentially diagnosed as AD out of a group with rapidly progressive dementia. CSF biomarkers (14-3-3, tau, beta-amyloid 1-42) and genetic markers (PRNP codon 129, apolipoprotein E, ApoE, polymorphism) were determined. Results: Median survival was 26 months, age at onset 73 years. Biomarkers: mean beta-amyloid 1-42: 266 pg/ml, median tau: 491 pg/ml, 14-3-3 positive: 31%. Genetic polymorphisms showed a predominance of methionine homozygosity at PRNP codon 129 and a low frequency of ApoE4 (38%, no homozygous patients). Thirty-five symptoms were studied. Frequent symptoms were myoclonus (75%), disturbed gait (66%) and rigidity (50%). Discussion: rpAD is associated with a diversity of neurological signs even able to mimic Creutz feldt-Jakob disease. Biomarkers and genetic profile differ from those seen in classical AD. The findings on biomarkers, symptomatology and genetics may aid the differential diagnostic process. Copyright (C) 2010 S. Karger AG, Base

Prion diseases are efficiently transmitted by blood transfusion in sheep

The emergence of variant Creutzfeld-Jakob disease, following on from the bovine spongiform encephalopathy (BSE) epidemic, led to concerns about the potential risk of iatrogenic transmission of disease by blood transfusion and the introduction of costly control measures to protect blood supplies. We previously reported preliminary data demonstrating the transmission of BSE and natural scrapie by blood transfusion in sheep. The final results of this experiment, reported here, give unexpectedly high transmission rates by transfusion of 36% for BSE and 43% for scrapie. A proportion of BSE-infected tranfusion recipients (3 of 8) survived for up to 7 years without showing clinical signs of disease. The majority of transmissions resulted from blood collected from donors at more than 50% of the estimated incubation period. The high transmission rates and relatively short and consistent incubation periods in clinically positive recipients suggest that infectivity titers in blood were substantial and/or that blood transfusion is an efficient method of transmission. This experiment has established the value of using sheep as a model for studying transmission of variant Creutzfeld-Jakob disease by blood products in humans. (Blood. 2008; 112: 4739-4745

Human stem cell-derived astrocytes replicate human prions in a PRNP genotype-dependent manner.

Prions are infectious agents that cause neurodegenerative diseases such as Creutzfeldt-Jakob disease (CJD). The absence of a human cell culture model that replicates human prions has hampered prion disease research for decades. In this paper, we show that astrocytes derived from human induced pluripotent stem cells (iPSCs) support the replication of prions from brain samples of CJD patients. For experimental exposure of astrocytes to variant CJD (vCJD), the kinetics of prion replication occur in a prion protein codon 129 genotype-dependent manner, reflecting the genotype-dependent susceptibility to clinical vCJD found in patients. Furthermore, iPSC-derived astrocytes can replicate prions associated with the major sporadic CJD strains found in human patients. Lastly, we demonstrate the subpassage of prions from infected to naive astrocyte cultures, indicating the generation of prion infectivity in vitro. Our study addresses a long-standing gap in the repertoire of human prion disease research, providing a new in vitro system for accelerated mechanistic studies and drug discovery

Prion infectivity in the spleen of a <em>PRNP</em> heterozygous individual with subclinical variant Creutzfeldt-Jakob disease

Blood transfusion has been identified as a source of human-to-human transmission of variant Creutzfeldt–Jakob disease. Three cases of variant Creutzfeldt–Jakob disease have been identified following red cell transfusions from donors who subsequently developed variant Creutzfeldt–Jakob disease and an asymptomatic red cell transfusion recipient, who did not die of variant Creutzfeldt–Jakob disease, has been identified with prion protein deposition in the spleen and a lymph node, but not the brain. This individual was heterozygous (MV) at codon 129 of the prion protein gene (PRNP), whereas all previous definite and probable cases of variant Creutzfeldt–Jakob disease have been methionine homozygotes (MM). A critical question for public health is whether the prion protein deposition reported in peripheral tissues from this MV individual correlates with infectivity. Additionally it is important to establish whether the PRNP codon 129 genotype has influenced the transmission characteristics of the infectious agent. Brain and spleen from the MV blood recipient were inoculated into murine strains that have consistently demonstrated transmission of the variant Creutzfeldt–Jakob disease agent. Mice were assessed for clinical and pathological signs of disease and transmission data were compared with other transmission studies in variant Creutzfeldt–Jakob disease, including those on the spleen and brain of the donor to the index case. Transmission of variant Creutzfeldt–Jakob disease was observed from the MV blood recipient spleen, but not from the brain, whereas there was transmission from both spleen and brain tissues from the red blood cell donor. Longer incubation times were observed for the blood donor spleen inoculum compared with the blood donor brain inoculum, suggesting lower titres of infectivity in the spleen. The distribution of vacuolar pathology and abnormal prion protein in infected mice were similar following inoculation with both donor and recipient spleen homogenates, providing initial evidence of similar transmission properties after propagation in PRNP codon 129 MV and MM individuals. These studies demonstrate that spleen tissue from a PRNP MV genotype individual can propagate the variant Creutzfeldt–Jakob disease agent and that the infectious agent can be present in the spleen without CNS involvement

Methionine 129 variant of human prion protein oligomerizes more rapidly than the valine 129 variant - Implications for disease susceptibility to Creutzfeldt-Jakob disease

The human PrP gene (PRNP) has two common alleles that encode either methionine or valine at codon 129. This polymorphism modulates disease susceptibility and phenotype of human transmissible spongiform encyphalopathies, but the molecular mechanism by which these effects are mediated remains unclear. Here, we compared the misfolding pathway that leads to the formation of beta-sheet-rich oligomeric isoforms of the methionine 129 variant of PrP to that of the valine 129 variant. We provide evidence for differences in the folding behavior between the two variants at the early stages of oligomer formation. We show that Met(129) has a higher propensity to form beta-sheet-rich oligomers, whereas Val(129) has a higher tendency to fold into alpha-helical-rich monomers. An equimolar mixture of both variants displayed an intermidate folding behavior. We show that the oligomers of both variants are initially a mixture of alpha- and beta-rich conformers that evolve with time to an increasingly homogeneous beta-rich form. This maturation process, which involves no further change in proteinase K resistance, occurs more rapidly in the Met(129) form than the Val(129) form. Although the involvement of such beta-rich oligomers in prion pathogenesis is speculative, the misfolding behavior could, in part, explain the higher susceptibility of individuals that are methionine homozygote to both sporadic and variant Creutzfeldt-Jakob disease.</p

High prevalence of scrapie in a dairy goat herd: tissue distribution of disease-associated PrP and effect of PRNP genotype and age

Following a severe outbreak of clinical scrapie in 2006–2007, a large dairy goat herd was culled and 200 animals were selected for post-mortem examinations in order to ascertain the prevalence of infection, the effect of age, breed and PRNP genotype on the susceptibility to scrapie, the tissue distribution of diseaseassociated PrP (PrP$^{\rm d}$), and the comparative efficiency of different diagnostic methods. As determined by immunohistochemical (IHC) examinations with Bar224 PrP antibody, the prevalence of preclinical infection was very high (72/200; 36.0%), with most infected animals being positive for PrP$^{\rm d}$ in lymphoreticular system (LRS) tissues (68/72; 94.4%) compared to those that were positive in brain samples (38/72; 52.8%). The retropharyngeal lymph node and the palatine tonsil showed the highest frequency of PrP$^{\rm d}$ accumulation (87.3% and 84.5%, respectively), while the recto-anal mucosa-associated lymphoid tissue (RAMALT) was positive in only 30 (41.7%) of the infected goats. However, the efficiency of rectal and palatine tonsil biopsies taken shortly before necropsy was similar. The probability of brain and RAMALT being positive directly correlated with the spread of PrP$^{\rm d}$ within the LRS. The prevalence of infection was influenced by PRNP genetics at codon 142 and by the age of the goats: methionine carriers older than 60 months showed a much lower prevalence of infection (12/78; 15.4%) than those younger than 60 months (20/42; 47.6%); these last showed prevalence values similar to isoleucine homozygotes of any age (40/80; 50.0%). Two of seven goats with definite signs of scrapie were negative for PrP$^{\rm d}$ in brain but positive in LRS tissues, and one goat showed biochemical and IHC features of PrP$^{\rm d}$ different from all other infected goats. The results of this study have implications for surveillance and control policies for scrapie in goats

Significant association of a M129V independent polymorphism in the 5\prime UTR of the PRNP gene with sporadic Creutzfeldt-Jakob disease in a large German case-control study

Background: A single nucleotide polymorphism (SNP) in the coding region of the prion protein gene (PRNP) at codon 129 has been repeatedly shown to be an associated factor to sporadic Creutzfeldt-Jakob disease (sCJD), but additional major predisposing DNA variants for sCJD are still unknown. Several previous studies focused on the characterisation of polymorphisms in PRNP and the prion-like doppel gene (PRND), generating contradictory results on relatively small sample sets. Thus, extensive studies are required for validation of the polymorphisms in PRNP and PRND.Methods: We evaluated a set of nine SNPs of PRNP and one SNP of PRND in 593 German sCJD patients and 748 German healthy controls. Genotyping was performed using MALDI-TOF mass spectrometry.Results: In addition to PRNP 129, we detected a significant association between sCJD and allele frequencies of six further PRNP SNPs. No significant association of PRND T174M with sCJD was shown. We observed strong linkage disequilibrium within eight adjacent PRNP SNPs, including PRNP 129. However, the association of sCJD with PRNP 1368 and PRNP 34296 appeared to be independent on the genotype of PRNP 129. We additionally identified the most common haplotypes of PRNP to be over-represented or under-represented in our cohort of patients with sCJD.Conclusion: Our study evaluated previous findings of the association of SNPs in the PRNP and PRND genes in the largest cohorts for association study in sCJD to date, and extends previous findings by defining for the first time the haplotypes associated with sCJD in a large population of the German CJD surveillance study

Transcobalamin C776G genotype modifies the association between vitamin B12 and homocysteine in older Hispanics.

Background/objectivesA common polymorphism, C776G, in the plasma B12 transport protein transcobalamin (TC), encodes for either proline or arginine at codon 259. This polymorphism may affect the affinity of TC for B12 and subsequent delivery of B12 to tissues.Subjects/methodsTC genotype and its associations with indicators of B12 status, including total B12, holotranscobalamin (holoTC), methylmalonic acid and homocysteine, were evaluated in a cohort of elderly Latinos (N=554, age 60-93 years) from the Sacramento Area Latino Study on Aging (SALSA).ResultsThe distribution of TC genotypes was 41.3% homozygous reference (776CC) and 11.6% homozygous variant (776GG). No differences between the homozygous genotypes were observed in total B12, holoTC, methylmalonic acid or homocysteine. The holoTC/total B12 ratio was lower in the 776GG group compared with the 776CC group (P=0.04). Significant interactions of TC genotype with total B12 (P=0.04) and with holoTC (P&lt; or =0.03) were observed such that mean homocysteine concentrations and the odds ratios for hyperhomocysteinemia (&gt;13 micromol/l) were higher in the 776CC subjects compared with all carriers of the G allele (776CG and 776GG combined) when total B12 (&lt;156 pmol/l) or holoTC (&lt;35 pmol/l) were low.ConclusionsThis population of older Latinos has a lower prevalence of the TC 776GG variant than reported for Caucasian populations. The association between vitamin B12 and homocysteine concentrations is modified by TC 776 genotype. It remains to be determined whether the TC C776G polymorphism has a significant effect on the hematological and neurological manifestations of B12 deficiency or on vascular and other morbidities associated with hyperhomocysteinemia