High capacity and low cost detection of prion protein gene variant alleles by denaturing HPLC

In Silico Selection and Evaluation of Pugnins with Antibacterial and Anticancer Activity Using Skin Transcriptome of Treefrog (Boana pugnax)

In order to combat bacterial and cancer resistance, we identified peptides (pugnins) with dual antibacterial l-anticancer activity from the Boana pugnax (B. pugnax) skin transcriptome through in silico analysis. Pugnins A and B were selected owing to their high similarity to the DS4.3 peptide, which served as a template for their alignment to the B. pugnax transcriptome, as well as their function as part of a voltage-dependent potassium channel protein. The secondary peptide structure stability in aqueous medium was evaluated as well, and after interaction with the Escherichia coli (E. coli) membrane model using molecular dynamics. These pugnins were synthesized via solid-phase synthesis strategy and verified by Reverse phase high-performance liquid chromatography (RP-HPLC) and mass spectrometry. Subsequently, their alpha-helix structure was determined by circular dichroism, after which antibacterial tests were then performed to evaluate their antimicrobial activity. Cytotoxicity tests against cancer cells also showed selectivity of pugnin A toward breast cancer (MFC7) cells, and pugnin B toward prostate cancer (PC3) cells. Alternatively, flow cytometry revealed necrotic cell damage with a major cytotoxic effect on human keratinocytes (HaCaT) control cells. Therefore, the pugnins found in the transcriptome of B. pugnax present dual antibacterial-anticancer activity with reduced selectivity to normal eukaryotic cells.

Second-Generation RT-QuIC Assay for the Diagnosis of Creutzfeldt-Jakob Disease Patients in Brazil

The recent development of IQ-CSF, the second generation of real-time quaking-induced conversion (RT-QuIC) using cerebrospinal fluid (CSF), for the diagnosis of Creutzfeldt-Jakob Disease (CJD) represents a major diagnostic advance in the field. Highly accurate results have been reported with encouraging reproducibility among different centers. However, availability is still insufficient, and only a few research centers have access to the method in developing countries. In Brazil, we have had 603 suspected cases of CJD since 2005, when surveillance started. Of these, 404 were undiagnosed. This lack of diagnosis is due, among other factors, to the lack of a reference center for the diagnosis of these diseases in Brazil, resulting in some of these samples being sent abroad for analysis. The aim of this research study is to report the pilot use of IQ-CSF in a small cohort of Brazilian patients with possible or probable CJD, implementing a reference center in the country. We stored CSF samples from patients with possible, probable or genetic CJD (one case) during the time frame of December 2016 through June 2018. All CSF samples were processed according to standardized protocols without access to the clinical data. Eight patients presented to our team with rapidly progressive dementia and typical neurological signs of CJD. We used CSF samples from seven patients with other neurological conditions as negative controls. Five out of seven suspected cases had positive tests; two cases showed inconclusive results. Among controls, there was one false-positive (a CSF sample from a 5-year-old child with leukemia under treatment). The occurrence of a false positive in one of the negative control samples raises the possibility of the presence of interfering components in the CSF sample from patients with non-neurodegenerative pathologies. Our pilot results illustrate the feasibility of having CJD CSF samples tested in Brazilian centers and highlight the importance of interinstitutional collaboration to pursue a higher diagnostic accuracy in CJD in Brazil and Latin America.

High phenotypic variability in Gerstmann-Sträussler-Scheinker disease

Gerstmann-Sträussler-Scheinker is a genetic prion disease and the most common mutation is p.Pro102Leu. We report clinical, molecular and neuropathological data of seven individuals, belonging to two unrelated Brazilian kindreds, carrying the p.Pro102Leu. Marked differences among patients were observed regarding age at onset, disease duration and clinical presentation. In the first kindred, two patients had rapidly progressive dementia and three exhibited predominantly ataxic phenotypes with variable ages of onset and disease duration. In this family, age at disease onset in the mother and daughter differed by 39 years. In the second kindred, different phenotypes were also reported and earlier ages of onset were associated with 129 heterozygosis. No differences were associated with apoE genotype. In these kindreds, the codon 129 polymorphism could not explain the clinical variability and 129 heterozygosis was associated with earlier disease onset. Neuropathological examination in two patients confirmed the presence of typical plaques and PrPsc immunopositivity.

Codon 129 polymorphism of prion protein gene in is not a risk factor for Alzheimer's disease

Interaction of prion protein and amyloid-b oligomers has been demonstrated recently. Homozygosity at prion protein gene (PRNP) codon 129 is associated with higher risk for Creutzfeldt-Jakob disease. This polymorphism has been addressed as a possible risk factor in Alzheimer disease (AD).ObjectiveTo describe the association between codon 129 polymorphisms and AD.MethodsWe investigated the association of codon 129 polymorphism of PRNP in 99 AD patients and 111 controls, and the association between this polymorphism and cognitive performance. Other polymorphisms of PRNP and additive effect of apolipoprotein E gene (ApoE) were evaluated.ResultsCodon 129 genotype distribution in AD 45.5% methionine (MM), 42.2% methionine valine (MV), 12.1% valine (VV); and 39.6% MM, 50.5% MV, 9.9% VV among controls (p>0.05). There were no differences of cognitive performance concerning codon 129. Stratification according to ApoE genotype did not reveal difference between groups.ConclusionCodon 129 polymorphism is not a risk factor for AD in Brazilian patients.

Simple detection of large InDeLS by DHPLC: the ACE gene as a model

Insertion-deletion polymorphism (InDeL) is the second most frequent type of genetic variation in the human genome. For the detection of large InDeLs, researchers usually resort to either PCR gel analysis or RFLP, but these are time consuming and dependent on human interpretation. Therefore, a more efficient method for genotyping this kind of genetic variation is needed. In this report, we describe a method that can detect large InDeLs by DHPLC (denaturating high-performance liquid chromatography) using the angiotensin-converting enzyme (ACE) gene I/D polymorphism as a model. The InDeL targeted in this study is characterized by a 288 bp Alu element insertion (I). We used DHPLC at nondenaturating conditions to analyze the PCR product with a flow through the chromatographic column under two different gradients based on the differences between D and I sequences. The analysis described is quick and easy, making this technique a suitable and efficient means for DHPLC users to screen InDeLs in genetic epidemiological studies.

Prion diseases are undercompulsory notification in Brazil: Surveillance of cases evaluated by biochemicaland/or genetic markers from 2005 to 2007

The emergence of the new variant of Creutzfeldt-Jakob disease (vCJD) in the United Kingdom has raised concerns over the risks of this prion disease in other parts of the world. Since 2005, human prion diseases have been under compulsory notification in Brazil. It is well known that some polymorphisms within the cellular prion gene (PRNP) have been associated to a higher susceptibility to sporadic CJD (sCJD) and vCJD.

Objectives

To describe the first notified cases and to evaluate the presence of mutations and polymorphisms of the PRNP in these cases.

Methods

Thirty-five notified cases were evaluated by clinical, auxiliary exams and biochemical and/or genetic tests and classified according to the World Health Organization criteria for CJD. A control group (N=202) was included for the purpose of comparing the genetic analyses.

Results

Twenty seven cases (74%) were classified as possible sCJD while 51% fulfilled the criteria for probable sCJD. Brain tissue analysis was available in three cases, where two were classified as definite sCJD and one as unconfirmed sCJD. Mutation of the PRNP was not found, and regarding the codon 129 polymorphism, valine in both alleles (Val129Val) was more frequent in patients than in the control group (OR=4.98; 1.55-15.96; p=0.007) when all possible cases were included, but not when only probable cases were considered.

Conclusions

Our data did not show correlation of PRNP polymorphisms with probable sCJD cases. It is necessary to work toward notification of all cases of possible CJD in Brazil and to increase the rate of definitive diagnoses.

Association between the M129V variant allele of PRNP gene and mild temporal lobe epilepsy in women

Specific variations in the prion protein gene (PRNP) are associated with, and prevalent in patients with intractable temporal lobe epilepsy (TLE) and influence the surgical outcome. We investigated whether or not the PRNP gene is a susceptibility gene in temporal lobe epileptic patients with mild epilepsy. We systematically screened the entire open reading frame of the PRNP gene and evaluated the genetic contribution of the functional PRNP M129V polymorphism in 289 patients with mild TLE compared with a neurologically unaffected age and sex matched control group (n=272). Statistical analysis revealed a moderate difference in the distribution at codon 129 of the PRNP gene between sporadic mild TLE patients and healthy controls (p=0.036; OR=1.30; 95% CI=1.01-1.68). Although, there was no statistically significant difference in the genotype distribution within the study groups (p=0.101), a further analysis showed that the 129V allele was highly represented only in women with TLE compared with control group (p=0.006, OR=1.632; 95%CI=1.15-2.31). This is the first publication of data that support the hypothesis that the common methionine/valine polymorphism at codon 129 of the PRNP gene may modify the susceptibility of women to mild TLE.

Cognitive performance of patients with mesial temporal lobe epilepsy is not associated with human prion protein gene variant allele at codons 129 and 171

Cognitive impairment has long been recognized in people with medically refractory epilepsies. Mesial temporal lobe epilepsy related to hippocampal sclerosis (MTLE-HS), the most common surgically remediable epileptic syndrome, has been associated with a cellular prion protein (PrPc) gene (Prnp) variant allele at codon 171. The polymorphism consisting of a methionine-for-valine substitution at codon 129 has been associated with early cognitive deterioration in elderly people and patients with Down syndrome. The same variant allele in homozygosis (V129V) has been associated to a lower long-term memory in healthy humans. PrPc mediates several processes related to neuroplasticity, and its role in cognitive processes remains unknown. In this study, we evaluated the genetic contribution of Prnp alleles to cognitive performance in patients with MTLE-HS. Cognitive performance, measured with 19 neuropsychological tests, of patients with refractory MTLE-HS with the normal Prnp genotypes was compared with that of patients with the variant alleles at codons 129 and 171. With the effects of clinical, demographic, electrophysiological, and neuroimaging variable interactions controlled by multiple linear regression analysis and adjustment for multiple test comparisons, the presence of Prnp variant alleles was found not to be significantly associated to cognitive performance of patients with MTLE-HS. The presence of variant alleles at codons 129 and 171 is not associated to cognitive performance of patients with refractory MTLE-HS.