Assessment of Genetic Variability of Citrus tristeza virus by SSCP and CE-SSCP.

Single-strand conformation polymorphism (SSCP) is a popular method used to study the genetic heterogeneity and population variability of Citrus tristeza virus (CTV) isolates. It is a simple, low-cost, and highly specific method for mutation detection of specific genes, mostly of the CTV major coat protein gene (p25). The technique is based on a comparison on polyacrylamide gel of electrophoretic profiles of single-stranded (ss) DNA sequences in terms of their spatial conformation. SSCP involves cDNA synthesis and amplification of the target gene, denaturation of single strands, and electrophoresis in non-denaturing conditions. The ssDNAs can be afterward visualized by staining the polyacrylamide gel. Alternatively, using fluorescently labeled primers, the procedure can be performed in automated sequencers equipped with an appropriate capillary (CE-SSCP), which increases the potential of high-throughput analysis, precision, and the reproducibility of results. CE-SSCP can be also directly applied to the virus particles obtained by elution from ELISA plates or tissue-print membranes.

SNaPshot and CE-SSCP: Two Simple and Cost-Effective Methods to Reveal Genetic Variability Within a Virus Species.

The multiplex SNaPshot and the capillary electrophoresis-single-strand conformation polymorphism (CE-SSCP) procedures are here used for rapid and high-throughput description of the molecular variability of viral populations. Both approaches are based on (1) standard amplification of genomic sequence(s), (2) labeled primers or labeled single-stranded DNA, and (3) migration of fluorescent-labeled molecules in capillary electrophoresis system. The SNaPshot technology was used to describe the diversity of 20 targeted single nucleotide polymorphisms (SNPs) selected from alignment of viral genomic sequences retrieved from public database. The CE-SSCP procedure was applied to identify the polymorphisms of two small (<500 bases in length) genomic regions of viral genomes. The different steps of SNaPshot and CE-SSCP setup procedures are presented using Potato virus Y (PVY, Potyvirus) and Plum pox virus (PPV, Potyvirus) RNA viruses as molecular targets, respectively.

Assessment of sequence variability in a p23 gene region within and among three genotypes of the Theileria orientalis complex from south-eastern Australia.

Oriental theileriosis is a tick-borne, protozoan disease of cattle caused by one or more genotypes of Theileria orientalis complex. In this study, we assessed sequence variability in a region of the 23kDa piroplasm membrane protein (p23) gene within and among three T. orientalis genotypes (designated buffeli, chitose and ikeda) in south-eastern Australia. Genomic DNA (n=100) was extracted from blood of infected cattle from various locations endemic for oriental theileriosis and tested by polymerase chain reaction (PCR)-coupled mutation scanning (single-strand conformation polymorphism (SSCP)) and targeted sequencing analysis. Eight distinct sequences represented all DNA samples, and three genotypes were found: buffeli (n=3), chitose (3) and ikeda (2). Nucleotide pairwise comparisons among these eight sequences revealed considerably higher variability among the genotypes (6.6-11.7%) than within them (0-1.9%), indicating that the p23 gene region allows the accurate identification of T. orientalis genotypes. In the future, we will combine this gene with other molecular markers to study the genetic structure of T. orientalis populations in Australasia, which will pave the way to establish a highly sensitive and specific PCR-based assay for genotypic diagnosis of infection and for assessing levels of parasitaemia in cattle.

An initial assessment of correlations between host- and virus-related factors affecting analogues antiviral therapy in HBV chronically infected patients.

BACKGROUND: Success in treating hepatitis B virus (HBV) infection with nucleoside analogues drugs is limited by the emergence of drug-resistant viral strains upon prolonged therapy. In addition to mutation patterns in the viral polymerase gene, host factors are assumed to contribute to failure of treatment in chronic HBV infections. The aim of this study was to analyze the correlation between efficacy of antiviral therapy and the prevalence of HBV pretreatment drug-resistant variants. We also analyzed the role of heterogeneity in the promoter region of the IL-10 on the HBV pol/s gene polymorphisms and efficacy of analogues-driven therapy. MATERIAL AND METHODS: HBV DNA was extracted from 54 serum samples from chronic hepatitis B (CHB) patients. Drug-resistance mutations were analyzed using MALDI-TOF mass spectrometry technology (MALDI-TOF MS) and Multi-temperature single-strand conformation polymorphism (MSSCP). IL-10 gene promoter region polymorphisms at positions -1082, -819, and -592 were determined in allele-specific PCR reactions (AS-PCR). RESULTS: Drug-resistance mutations were detected in 74% of naïve and 93% of experienced patients, but the effect of pre-existence of drug-resistant HBV variants on antiviral therapy was not statistically significant (p=0.86). The role of polymorphisms at positions -1082 (p=0.88), -819 (p=0.26), and -592 (p=0.26) of IL-10 promoter region polymorphisms was excluded from the response-predicting factors. The main host factors predicting successful response to antiviral therapy were female sex (p=0.007) and young age (p=0.013). CONCLUSIONS: The presence of drug-resistant HBV variants in baseline is not a viral predictor of good response to nucleoside/nucleotide analogues therapy. Only low HBV viral load predicted positive response to antiviral therapy. The ideal candidate for antiviral therapy is an immunocompetent, young female with low HBV viral load and elevated ALT activity.

Assessment of the efficacy of 8 weeks of primaquine for the prevention of relapse in vivax malaria patients using SSCP-PCR and sequencing in South and South-East Iran, 2008-2011.

BACKGROUND: Treatment of vivax malaria with primaquine prevents the risk of relapse. This study was designed to assess the efficacy of 8 weeks of primaquine treatment in prevention of relapse in patients with vivax malaria in south and south-east Iran by SSCP-PCR and sequencing. METHODS: A total of 163 symptomatic vivax malaria cases were followed up in Hormozgan and Sistan, Baluchestan provinces in south and south-east Iran between December 2008 and December 2011. DNA was extracted from primary and secondary positive samples. A variation region of PvMSP-1 gene was selected and amplified by PCR. The obtained fragments were processed in polyacrylamide gel for single-strand conformational polymorphism (SSCP) and then sequenced. RESULTS: Among 145 patients treated with chloroquine plus primaquine who completed the study period, two patients (1.4%) experienced a secondary infection after the initial episode of Plasmodium vivax. The comparison between primary and secondary isolates by SSCP indicated different banding patterns and electrophoretic mobility. Alignment of nucleotide sequences between pair primary and secondary isolates revealed dissimilar homology. Secondary isolates of both patients were considered as reinfection. Five of the 18 cases (28%) treated with chloroquine only revealed secondary infection. Analysis of nucleotide sequences and SSCP patterns indicated the relapse in all of them. CONCLUSION: This survey indicates that intake of primaquine, 0.75 mg/kg, weekly for 8 consecutive weeks, is effective for the prevention of relapse in vivax cases in Iran.

Asymmetric single-strand conformation polymorphism: an accurate and cost-effective method to amplify and sequence allelic variants.

PREMISE OF THE STUDY: An efficient alternative strategy to conventional cloning was needed to generate high-quality DNA sequences from a variety of nuclear orthologs for phylogenetic studies. This method would facilitate studies and minimize technical problems typically encountered in cloning methodologies. METHODS: We tested a variety of single-strand conformation polymorphism (SSCP) protocols including purified and unpurified symmetric and asymmetric PCR, loading buffers, and electrophoresis conditions (buffers, matrix, running time, temperature). Results obtained from direct SSCP band sequencing were compared to those obtained from cloning. KEY RESULTS: Our optimized protocol uses asymmetric PCR, with the majority of the samples run in polyacrylamide gel electrophoresis (PAGE). It consistently separated PCR products from 450 to 1200 bp. CONCLUSIONS: Asymmetric PCR single-strand conformation polymorphism is an efficient alternative technique for isolating allelic variants of highly heterozygous individuals, with its greatest applications in sequencing allopolyploids. It eliminates two common problems encountered in cloning: PCR recombination and heteroduplex fixation. In addition, our protocol greatly lowers costs and time associated with procedures.

Screening and cell-based assessment of mutations in the Aristaless-related homeobox (ARX) gene.

ARX mutations cause a diverse spectrum of human disorders, ranging from severe brain and genital malformations to non-syndromic intellectual disability (ID). ARX is a transcription factor with multiple domains that include four polyalanine (pA) tracts, the first two of which are frequently expanded by mutations. We progressively screened DNA samples from 613 individuals with ID initially for the most frequent ARX mutations (c.304ins(GCG)(7)'expansion' of pA1 and c.429_452dup 'dup24bp' of pA2). Five hundred samples without pA1 or pA2 mutations had the entire ARX ORF screened by single stranded polymorphism conformation (SSCP) and/or denaturing high pressure liquid chromatography (dHPLC) analysis. Overall, eight families with six mutations in ARX were identified (1.31%): five duplication mutations in pA2 (0.82%) with three new clinical reports of families with the dup24bp and two duplications larger than the dup24bp mutation discovered (dup27bp, dup33bp); and three point mutations (0.6%), including one novel mutation in the homeodomain (c.1074G>T). Four ultraconserved regions distal to ARX (uc466-469) were also screened in a subset of 94 patients, with three unique nucleotide changes identified in two (uc466, uc467). The subcellular localization of full length ARX proteins was assessed for 11 variants. Protein mislocalization increased as a function of pA2 tract length and phenotypic severity, as has been previously suggested for pA1. Similarly, protein mislocalization of the homeodomain mutations also correlated with clinical severity, suggesting an emerging genotype vs cellular phenotype correlation.

Novel SNPs of the bovine CACNA2D1 gene and their association with carcass and meat quality traits.

Calcium channel, voltage-dependent, alpha-2/delta subunit 1 (CACNA2D1) gene encodes a member of the alpha-2/delta subunit family, proteins are accessory molecules associated with voltage-gated calcium channels, and increase the density at the plasma membrane of calcium channels activated by high voltage. The main objective of the present study was to identify polymorphisms of CACNA2D1 gene, and to analyze associations between these polymorphisms and carcass and meat quality traits in cattle. In this study, through PCR-SSCP and DNA sequencing methods, two new allelic variant corresponding to the C→G and G→T mutations at positions 526740 and 537917 in the exon25 and exon35 of bovine CACNA2D1 gene, respectively, could be detected. SNP C526740G is a nonsynonymous mutation, resulting in a Cysteine (Cys) to Tryptophan (Trp) amino acid replacement and SNP G537917T resulting in an Aspartic (Asp) to Tyrosine (Tyr) amino acid replacement. The gene-specific SNP markers association analysis was investigated. The C526740G was significantly associated with Meat color (MC) (P=0.0297) and Backfat thickness (BF) (P<0.001). The G537917A indicated significant association with Dressing percentage (DP) (P=0.0485). No significant association, however, was detected between any of the marker genotype and other traits measured in this study. Results from this study initially suggested that CACNA2D1 gene is one of the potential candidate genes influencing carcass and meat quality traits and gene-specific SNPs may be a useful marker for MAS programs in cattle breeding.

Economical protocol for combined single-strand conformation polymorphism and heteroduplex analysis on a standard capillary electrophoresis apparatus.

Combined single-strand conformational polymorphism (SSCP) and heteroduplex (HD) analysis (SSCP-HD) take advantage of parallel mutation detection in single-strand and duplex fraction during the single capillary electrophoresis (CE) run. The high mutation detection rate of individual SSCP and HD in CE guarantees almost a 100% success rate of combined SSCP-HD. Described here, the protocol for SSCP-HD-CE does not require dedicated instrumentation but can be applied for any commonly available CE DNA analyzer. We focused mostly on the sample preparation step that is critical for the stability of generated fractions and reproducibility of a generated result. The application of universal primer for fluorescent labeling and omitting the PCR purification step also greatly reduce the cost of mutation detection by SSCP-HD-CE.

Instantaneous normal modes as an unforced reaction coordinate for protein conformational transitions.

We present a novel sampling approach to explore large protein conformational transitions by determining unique substates from instantaneous normal modes calculated from an elastic network model, and applied to a progression of atomistic molecular dynamics snapshots. This unbiased sampling scheme allows us to direct the path sampling between the conformational end states over simulation timescales that are greatly reduced relative to the known experimental timescales. We use adenylate kinase as a test system to show that instantaneous normal modes can be used to identify substates that drive the structural fluctuations of adenylate kinase from its closed to open conformations, in which we observe 16 complete transitions in 4 mus of simulation time, reducing the timescale over conventional simulation timescales by two orders of magnitude. Analysis shows that the unbiased determination of substates is consistent with known pathways determined experimentally.

E6/E7 mRNA expression analysis: a test for the objective assessment of cervical adenocarcinoma in clinical prognostic procedure.

Detection of E6/E7 mRNA expression using the real-time nucleic acid sequence-based amplification assay (NASBA) PreTect HPV-Proofer was compared with results of human papillomavirus (HPV) DNA detection in 98 paraffin-embedded samples from patients with cervical adenocarcinoma. HR-HPV DNA was detected in 61 (62%), while HR-HPV E6/E7 mRNA was detected in 63 (64%) of the samples. Correlation between results from DNA analyses and the E6/E7 mRNA assay showed consistent results in 87% of samples (47 of 54). The results from these two methods in detecting presence of HPV infection of any type agreed in 77%. Overall agreement between the methods was seen in 82 of the 98 cases (84%). When evaluating change in sensitivity for detection of HPV positives by adding more HPV types to the HPV DNA assay, maximum sensitivity was reached by targeting four HPV types. The coverage of HPV DNA presence was 76.9%, while the E6/E7 mRNA assay achieved a maximum coverage of 80.8% using only three HPV types. Thus, E6/E7 oncogene expression analysis may provide a more objective test for assessment of neoplastic glandular cells. Further studies may reveal whether the clinical performance of the E6/E7 mRNA assay will be of prognostic value in management of cervical adenocarcinoma.

Mutations of MC4R gene and its association with economic traits in Qinchuan cattle.

MC4R belongs to a seven-transmembrane G-protein-coupled receptor which may regulate body composition and insulin action. Many mutations in the MC4R gene are associated with obesity, energy expenditure and serum triglyceride levels in human and animals. Six mutations in the MC4R gene were identified in our study (-293C>G, -193A>T, -192T>G, -129A>G, -84T>C and 1,069C>G). The -129A>G was significantly associated with live weight (LW) (P < 0.05), Cattle with the genotypes AG and GG had higher LW than genotype AA. The 1,069C>G was significantly associated with LW, carcass weight (CW), backfat thickness and marbling score (MS). Cattle with the genotype GG had higher LW, CW and MS than genotype CC; Cattle with the genotypes GG and CG had higher MS than CC. The results suggested that -129A>G and 1,069C>G SNP of the MC4R gene may be useful as a genetic marker for carcass and meat quality traits in Qinchuan cattle.

Sexual conflict inhibits female mate choice for major histocompatibility complex dissimilarity in Chinook salmon.

In many species females prefer major histocompatibility complex (MHC) dissimilar mates, which may improve offspring resistance to pathogens. However, sexual conflict may interfere with female preference when males attempt to mate with all females, regardless of compatibility. Here we used semi-natural spawning channels to examine how mating behaviour and genetic similarity at the MHC class II peptide binding region affected parentage patterns in Chinook salmon (Oncorhynchus tshawytscha). We found that females directed aggression at more MHC-similar males than expected by chance, providing a possible mechanism of female MHC choice in salmon. Males also directed aggression towards MHC-similar females, which was consistent with males harassing unreceptive mates. Males' aggression was positively correlated with their reproductive success, and it appeared to overcome female aversion to mating with MHC-similar males, as females who were the target of high levels of male aggression had lower than expected MHC divergence in their offspring. Indeed, offspring MHC divergence was highest when the sex ratio was female-biased and male harassment was likely to be less intense. These data suggest that male harassment can reduce female effectiveness in selecting MHC-compatible mates, and sexual conflict can thus have an indirect cost to females.

Assessment of the microbial diversity at the surface of Livarot cheese using culture-dependent and independent approaches.

The microbial diversity of the surface of a commercial red-smear cheese, Livarot cheese, sold on the retail market was studied using culture-dependent and independent approaches. Forty yeasts and 40 bacteria from the cheese surface were collected, dereplicated using single-strand conformation polymorphism (SSCP) analysis and identified using rRNA gene sequencing for the culture-dependent approach. The culture-independent approach involved cloning and sequencing of the 16S rRNA gene and SSCP analysis from total DNA extracted from the cheese. The most dominant bacteria were Microbacterium gubbeenense, Leucobacter komagatae and Gram-negative bacteria from the Gamma-Proteobacteria class. Fluorescence in situ hybridization (FISH) analysis was also used to study the cheese microbial diversity with class-level and specific rRNA-targeted probes for bacteria and yeasts, respectively. FISH analysis confirmed that Gamma-Proteobacteria were important microorganisms in this cheese. Four specific FISH probes targeting the dominant yeasts present in the cheese, Candida catenulata, Candida intermedia, Geotrichum spp. and Yarrowia lipolytica, were also designed and evaluated. These probes allowed the detection of these yeasts directly in cheese. The use of the rRNA gene-based approach combined with FISH analysis was useful to investigate the diversity of a surface microbial consortium from cheese.

Sputum PCR-single-strand conformational polymorphism test for same-day detection of pyrazinamide resistance in tuberculosis patients.

Pyrazinamide is a first-line drug for treating tuberculosis, but pyrazinamide resistance testing is usually too slow to guide initial therapy, so some patients receive inappropriate therapy. We therefore aimed to optimize and evaluate a rapid molecular test for tuberculosis drug resistance to pyrazinamide. Tuberculosis PCR-single-strand conformational polymorphism (PCR-SSCP) was optimized to test for mutations causing pyrazinamide resistance directly from sputum samples and Mycobacterium tuberculosis isolates. The reliability of PCR-SSCP tests for sputum samples (n = 65) and Mycobacterium tuberculosis isolates (n = 185) from 147 patients was compared with four tests for pyrazinamide resistance: Bactec-460 automated culture, the Wayne biochemical test, DNA sequencing for pncA mutations, and traditional microbiological broth culture. PCR-SSCP provided interpretable results for 96% (46/48) of microscopy-positive sputum samples, 76% (13/17) of microscopy-negative sputum samples, and 100% of Mycobacterium tuberculosis isolates. There was 100% agreement between PCR-SSCP results from sputum samples and Mycobacterium tuberculosis isolates and 100% concordance between 50 blinded PCR-SSCP rereadings by three observers. PCR-SSCP agreement with the four other tests for pyrazinamide resistance varied from 89 to 97%. This was similar to how frequently the four other tests for pyrazinamide resistance agreed with each other: 90 to 94% for Bactec-460, 90 to 95% for Wayne, 92 to 95% for sequencing, and 91 to 95% for broth culture. PCR-SSCP took less than 24 hours and cost approximately $3 to $6, in contrast with the other assays, which took 3 to 14 weeks and cost $7 to $47. In conclusion, PCR-SSCP is a relatively reliable, rapid, and inexpensive test for pyrazinamide resistance that indicates which patients should receive pyrazinamide from the start of therapy, potentially preventing months of inappropriate treatment.

A duplex allele-specific amplification PCR to detect SMN1 deletion.

Spinal muscular atrophy (SMA), the leading genetic cause of death in childhood, is an autosomal recessive neuromuscular disorder characterized by progressive muscle weakness, associated with deletions of the survival motor neuron (SMN) gene identified and mapped to chromosome 5q13. SMN is present in two highly homologous copies (SMN1 and SMN2). In the general population, normal individuals (noncarriers) have at least one telomeric (SMN1) copy, and 5% of them have no copies of SMN2. Approximately 95% of SMA patients carry homologous deletions of SMN1 exon(s) 7 (and 8). SMN1 and SMN2 exons 7 and 8 differ only by 1 bp each, and SMA diagnosis might be performed by single-strand conformational polymorphism, PCR amplification followed by restriction fragment length polymorphism (RFLP), multiple ligation-dependent probe amplification, or realtime PCR of SMNs exons 7 and 8. We developed a simpler and cost-effective method to detect SMN1 exon 7 deletion based on allele-specific amplification PCR.

Rapid detection of deletions in hotspot C-terminal segment region of MECP2 by routine PCR method: report of two classical Rett syndrome patients of Indian origin.

Rett syndrome (RS) is an X-linked dominant neurodevelopment disorder with normal prenatal and postnatal development till 6-18 months, followed by stagnation and regression of acquired skills. RS primarily manifests in females, and there are a few reports with males having RS. Sporadic or de novo mutations of the methyl CpG binding protein 2 (MECP2) gene have been reported in 70-90% of affected girls. Conventional methods such as fluorescence in situ hybridization, real-time PCR, southern blotting, multiplex ligation-dependent probe amplification, and DNA sequencing have been previously reported for the detection of insertions or deletions in the MECP2 gene. Here, we report detection of two deletions of 44 bp (c.1157_1200del44 or p.L386fs) and 38 bp (c.1151_1188del38 or p.P384fs) in exon 4 or C-terminal segment (CTS) region of MECP2 using a simple PCR technique that is rapid, accurate, and cost effective as compared to other techniques. The deletions were detected by routine PCR amplification followed by 2% agarose gel electrophoresis. We suggest that a simple PCR can easily detect deletions in the hotspot CTS region of the MECP2 gene and can be used for routine molecular diagnostics of RS.

The use of SSCP analysis in the assessment of phytoplasma gene variability.

Single-strand conformation polymorphism (SSCP) analysis is a broadly used technique for detecting mutations. The aim of this work was to assess the applicability of SSCP as a new tool for the detection of the molecular variability of uncultivable mollicutes - phytoplasmas. Three phytoplasma regions were investigated: 16S rDNA, tuf gene, and dnaB gene. Fragments amplified by PCR were subjected to SSCP under conditions optimized for each fragment length. In all of the analyzed regions, SSCP revealed the presence of polymorphism undetected by routine RFLP analyses. Reliability of the method was confirmed by the multiple alignments and phylogenetic analyses of representative sequences showing different SSCP profiles.

[Correlations between SNP of LALBA gene and economic traits in Inner Mongolian white cashmere goat].

PCR-SSCP and DNA sequencing methods were conducted to detect single nucleotide polymorphism of alpha-lactalbumin (LALBA) gene in 452 Inner Mongolian white cashmere goats (IMWC). Correlations between SNP of goat LALBA gene and economic traits, e.g., cashmere yield, cashmere thickness, length and weight, were analyzed. The SSCP in P2 primer locus, which was caused by the point mutation M63868:g.1897T>C in the exon 3 of LALBA gene was detected. At this locus, the genotype TT and allele T were predominant in the IMWC population, which agreed with Hardy-Weinberg equilibrium. Moreover, there was a significant correlation between polymorphism of goat M63868:g.1897 locus and cashmere yield of IMWC (P=0.017). The individuals with genotype TC had more cashmere yield than those with geontype TT. Hence, genotype TC of LALBA gene can be used as a molecular marker for breeding superior cashmere yield in goat marker-assisted selection.