Validation and calibration of a novel GEM biosensor for specific detection of Cd2+, Zn2+, and Pb2.

BACKGROUND: In this study, we designed a novel genetic circuit sensitive to Cd2+, Zn2+ and Pb2+ by mimicking the CadA/CadR operon system mediated heavy metal homeostasis mechanism of Pseudomonas aeruginosa. The regular DNA motifs on natural operon were reconfigured and coupled with the enhanced Green Fluorescent Protein (eGFP) reporter to develop a novel basic NOT type logic gate CadA/CadR-eGFP to respond metal ions mentioned above. A Genetically Engineered Microbial (GEM)-based biosensor (E.coli-BL21:pJET1.2-CadA/CadR-eGFP) was developed by cloning the chemically synthesised CadA/CadR-eGFP gene circuit into pJET1.2-plasmid and transforming into Escherichia coli (E. coli)-BL21 bacterial cells. RESULTS: The GEM-based biosensor cells indicated the reporter gene expression in the presence of Cd2+, Zn2+ and Pb2+ either singly or in combination. Further, the same biosensor cells calibrated for fluorescent intensity against heavy metal concentration generated linear graphs for Cd2+, Zn2+ and Pb2+ with the R2 values of 0.9809, 0.9761 and 0.9758, respectively as compared to non-specific metals, Fe3+ (0.0373), AsO43- (0.3825) and Ni2+ (0.8498) making our biosensor suitable for the detection of low concentration of the former metal ions in the range of 1-6 ppb. Furthermore, the GEM based biosensor cells were growing naturally within the concentration range of heavy metals, at 37 °C and optimum pH = 7.0 in the medium, resembling the characteristics of wildtype E.coli. CONCLUSION: Finally, the novel GEM based biosensor cells developed in this study can be applied for detection of targeted heavy metals in low concentration ranges (1-6 ppb) at normal bacterial physiological conditions.

Could quantitative real-time polymerase chain reaction assay serve as an alternative test method to evaluate human epidermal growth factor receptor 2 status of gastric carcinoma in the South Asian setting?

BACKGROUND: Human epidermal growth factor receptor 2 (HER2) protein overexpression and/or HER2 gene amplification are/is linked to a dismal outcome of gastric carcinoma (GCa). Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) are key methods to identify patients for HER2 targeted therapy. Drawbacks of both the methods warrant novel tests. Hence, we evaluated the value of quantitative real-time polymerase chain reaction (qPCR) as an alternative test method, relative to IHC to detect HER2 status of GCa and to find relationship between these  results with demographic/clinicopathological data. METHOD: Twenty GCa patients with known IHC HER2 scores were evaluated. qPCR was performed for the HER2 gene and amyloid precursor protein (reference gene) in formalin-fixed paraffin-embedded GCa tissue. Cycle threshold values (Ct) were analyzed using the Pfaffl method to detect HER2 gene amplification. RESULTS: HER2 positivity rates by IHC and qPCR were 20% and 35%, respectively. The sensitivity and specificity of qPCR were 67% and 76%, respectively, relative to IHC. qPCR results were reproducible. The diagnostic consistency between IHC and qPCR (κ = 0.146) was slightly agreeable (0.01 < k < 0.20), with a 65% concordance. Based on McNemar's test, there was no significant difference between the results of the two tests. IHC HER2 protein expression had relationship with the tumor (TNM) stage and Lauren histological type (p < 0.05). Positive HER2 gene expression by qPCR showed relationship with depth of invasion, lymph node involvement, and degree of differentiation (p < 0.05). CONCLUSION: Cost-effective qPCR could serve as an alternative test method for detection of HER2 status of GCa. Both HER2 overexpression by IHC and gene amplification by qPCR are associated with adverse clinicopathological features.

An ARV1 homologue from a filarial nematode is functional in yeast.

The transmembrane protein, ARV1, plays a key role in intracellular sterol homeostasis by controlling sterol distribution and cellular uptake. To date, only the ARV1s from yeast and humans have been characterized to some extent. In this study, the ARV1 of an animal filarial parasite, Setaria digitata (SdARV1), was characterized; its cDNA was 761 bp and encoded a protein of 217 amino acids, with a predicted molecular weight of 25 kDa, containing a highly conserved ARV1 homology domain and three transmembrane domains in the bioinformatic analyses. Information required to cluster members belonging to a particular taxon has been revealed in phylogenetic analyses of ARV1 sequences derived from different organisms. Reverse transcription-polymerase chain reaction (RT-PCR) analyses indicated that SdARV1 was expressed in different developmental stages - microfilariae and adult male and female worms. Experiments carried out with a single copy of the SdARV1 under the control of the PMA-1 promoter in a temperature-sensitive Saccharomyces cerevisiae mutant strain indicated full complementation of the mutant phenotype, with growth at a non-permissive temperature (37°C). Microscopic observations of cellular morphology with Gram staining revealed alteration of the shape from shrunken to oval, in mutant and complemented strains, respectively. Assessment of free sterol levels extracted from mutant yeast and complemented strains indicated that the level of sterol was significantly higher in the former compared to the latter, which had sterol levels similar to those of the wild type. Thus, the results of the current study suggest that SdARV1 is ubiquitously expressed in different developmental stages of S. digitata, and that it is a true functional homologue of mammalian and yeast ARV1s, which have crucial phylogenetic information that follows classical evolutionary trends. Finally, this is the first study to report the biological function of nematode ARV1.

Prevalence of human papilloma virus and their high-risk genotypes in Sri Lankan women.

Human papilloma virus (HPV) causes cervical cancer in women and approximately 700 deaths have been reported annually in Sri Lanka due to this cancer. Despite, attempts have not been made to investigate the prevalence of HPV amongst Sri Lankan women with normal cytology. In this study, a polymerase chain reaction based assay was set up to detect HPV in both normal and abnormal cytology and the positive samples were then tested for the genotypes, HPV 16 and HPV 18 as they have been identified as the high-risk types associating with cervical cancer. Eighty-four (number = 84) clinical samples (age range 27-69) analyzed in this study indicated that the prevalence of HPV, regardless of cytological abnormalities was 15.5%, (n = 13, 95% class interval ± 7.7) while it was 100% (n = 3) for those with abnormal cytology. Association of HPV 16 and HPV 18 among the abnormal cytology was 0 and 50% (n = 1), respectively and further, the prevalence of HPV 16 and HPV 18 in women was found to be 3.6% (n = 3, 95% CI ± 4.0) and 2.4% (n = 2, 95% CI ± 3.3), respectively. Moreover, age wise prevalence analysis revealed women of the age of 35-years or more to have higher HPV prevalence. The prevalence of HPV among normal cytology is 12.3% (n = 10, 95% CI ± 7.2) which is similar to the rates in other regions of Asia (China 15.4%; India 10.43%). Finally, higher prevalence of HPV in women of the age of 35-years or more in Sri Lanka, especially with malignant types call for such age group to be screened for proper clinical intervention to be made in reducing the incident of cervical cancers. This is the first report of prevalence of HPV among women with normal cytology in Sri Lanka.

Development of siRNA mediated RNA interference and functional analysis of novel parasitic nematode-specific protein of Setaria digitata.

Despite the differences of the host, parasitic nematodes may share commonalities in their parasitizing genes. Setaria digitata novel protein (SDNP) is such an entity which is parasitic nematode-specific and having sequence similarities with those of W. bancrofti, B. malayi, Loa loa and Onchocerca volvulus. Post-transcriptional gene silencing by siRNA mediated RNA interference (RNAi) is a widely used technique in functional genomics. Though the technique has been used in several free-living, plant and animal parasitic nematodes, it has not yet been tried out for the filarial worm S. digitata. In this study, we developed an effective siRNA delivery method by microinjection and utilized the siRNAi tool to knockdown SDNP to study the phenotypic and cellular changes associated with the interference. qPCR analysis revealed, a significant reduction of SDNP transcript levels following siRNA microinjection into S. digitata adult worms. Similarly, immunohistochemical staining indicated a reduction of SDNP protein expression. Furthermore, worms treated with siRNA showed a significant reduction of microfilariae release together with embryonic lethality by arresting an early developmental stage compared to non-treated worms. A distinct motility reduction was also observed in treated worms compared to non-treated counterparts. This is the first report of the amenability of S. digitata to the siRNA induced RNAi. The presence of inter-domain linkers of muscle-specific twitchin kinase and calcium-dependent protein kinase isoform CDPK1 together with what our results revealed suggest that SDNP is most likely a protein involved in muscle movement and growth and development of the nematode. Hence SDNP has the characteristics of a potential drug target.

Setaria digitata in advancing our knowledge of human lymphatic filariasis.

Setaria digitata is a filarial parasite that causes fatal cerebrospinal nematodiasis in goats, sheep and horses, resulting in substantial economic losses in animal husbandry in the tropics. Due to its close resemblance to Wuchereria bancrofti, this nematode is also frequently used as a model organism to study human lymphatic filariasis. This review highlights numerous insights into the morphological, histological, biochemical, immunological and genetic aspects of S. digitata that have broadened our understanding towards the control and eradication of filarial diseases.

Development of single-strand conformational polymorphism to screen for mutations in hotspot regions of beta-globin gene of beta-thalassemia patients of Sri Lanka.

Beta-thalassemia is prevalent in Sri Lanka and imposes a heavy economic and social burden in the country due to the patients' life-long need for regular blood transfusion and treatment with iron chelation therapy. Thus, there is a need to develop a rapid, reliable and effective population-based presymptomatic and prenatal screening method for beta-thalassemia. Single-strand conformational polymorphism (SSCP) technique was developed as an adjunct for the previously developed allele-specific PCR (ASP) technique to screen the presence of mutations in beta-globin gene. A hotspot region of beta-globin gene containing 98% of known beta-thalassemia mutations was amplified from 24 clinically diagnosed beta-thalassemia patients and two normal individuals. Two overlapping amplicons of 238 bp and 268 bp were subjected to SSCP analysis. The SSCP banding patterns of these two fragments from beta-thalassemia patients were different from the corresponding regions of normal individuals. Sequence analysis of these regions revealed the presence of 4 mutations in the form of deletion and substitution that have not been reported previously from Sri Lanka. Therefore, the SSCP protocol developed in this study together with ASP should provide an appropriate screening approach for presymptomatic and parental diagnosis of beta-thalassemia in the Sri Lankan population.