Variation in Plasmodium falciparum Histidine-Rich Protein 2 (Pfhrp2) and Plasmodium falciparum Histidine-Rich Protein 3 (Pfhrp3) Gene Deletions in Guyana and Suriname

Guyana and Suriname have made important progress in reducing the burden of malaria. While both countries use microscopy as the primary tool for clinical diagnosis, malaria rapid diagnostic tests (RDTs) are useful in remote areas of the interior where laboratory support may be limited or unavailable. Recent reports indicate that histidine-rich protein 2 (PfHRP2)-based diagnostic tests specific for detection of P. falciparum may provide false negative results in some parts of South America due to the emergence of P. falciparum parasites that lack the pfhrp2 gene, and thus produce no PfHRP2 antigen. Pfhrp2 and pfhrp3 genes were amplified in parasite isolates collected from Guyana and Suriname to determine if there were circulating isolates with deletions in these genes. Pfhrp3 deletions were monitored because some monoclonal antibodies utilized in PfHRP2-based RDTs cross-react with the PfHRP3 protein. We found that all 97 isolates from Guyana that met the inclusion criteria were both pfhrp2- and pfhrp3-positive. In Suriname (N = 78), 14% of the samples tested were pfhrp2-negative while 4% were pfhrp3-negative. Furthermore, analysis of the genomic region proximal to pfhrp2 and pfhrp3 revealed that genomic deletions extended to the flanking genes. We also investigated the population substructure of the isolates collected to determine if the parasites that had deletions of pfhrp2 and pfhrp3 belonged to any genetic subtypes. Cluster analysis revealed that there was no predominant P. falciparum population substructure among the isolates from either country, an indication of genetic admixture among the parasite populations. Furthermore, the pfhrp2-deleted parasites from Suriname did not appear to share a single, unique genetic background.     

Functional Characterization of a Novel Class of Morantel-Sensitive Acetylcholine Receptors in Nematodes

Acetylcholine receptors are pentameric ligand–gated channels involved in excitatory neuro-transmission in both vertebrates and invertebrates. In nematodes, they represent major targets for cholinergic agonist or antagonist anthelmintic drugs. Despite the large diversity of acetylcholine-receptor subunit genes present in nematodes, only a few receptor subtypes have been characterized so far. Interestingly, parasitic nematodes affecting human or animal health possess two closely related members of this gene family, acr-26 and acr-27 that are essentially absent in free-living or plant parasitic species. Using the pathogenic parasitic nematode of ruminants, Haemonchus contortus, as a model, we found that Hco-ACR-26 and Hco-ACR-27 are co-expressed in body muscle cells. We demonstrated that co-expression of Hco-ACR-26 and Hco-ACR-27 in Xenopus laevis oocytes led to the functional expression of an acetylcholine-receptor highly sensitive to the anthelmintics morantel and pyrantel. Importantly we also reported that ACR-26 and ACR-27, from the distantly related parasitic nematode of horses, Parascaris equorum, also formed a functional acetylcholine-receptor highly sensitive to these two drugs. In Caenorhabditis elegans, a free-living model nematode, we demonstrated that heterologous expression of the H. contortus and P. equorum receptors drastically increased its sensitivity to morantel and pyrantel, mirroring the pharmacological properties observed in Xenopus oocytes. Our results are the first to describe significant molecular determinants of a novel class of nematode body wall muscle AChR.     

The MMS22L-TONSL complex mediates recovery from replication stress and homologous recombination

Genome integrity is jeopardized each time DNA replication forks stall or collapse. Here we report the identification of a complex composed of MMS22L (C6ORF167) and TONSL (NFKBIL2) that participates in the recovery from replication stress. MMS22L and TONSL are homologous to yeast Mms22 and plant Tonsoku/Brushy1, respectively. MMS22L-TONSL accumulates at regions of ssDNA associated with distressed replication forks or at processed DNA breaks, and its depletion results in high levels of endogenous DNA double-strand breaks caused by an inability to complete DNA synthesis after replication fork collapse. Moreover, cells depleted of MMS22L are highly sensitive to camptothecin,?a topoisomerase I poison that impairs DNA replication progression. Finally, MMS22L and TONSL are necessary for the efficient formation of RAD51 foci after DNA damage, and their depletion impairs homologous recombination. These results indicate that MMS22L and TONSL are genome caretakers that stimulate the recombination-dependent repair of stalled or collapsed replication forks.     

Improving water quality in polluated drains with free water surface constructed wetlands

In Egypt, disposing of partially treated or untreated domestic and industrial wastewater into agricultural drains deteriorates their water quality. A growing interest in effective low-cost treatment of polluted water and wastewater has resulted in many studies on constructed wetlands.This study evaluates free water surface constructed wetlands (by far the largest application project is named “Lake Manzala Engineered Wetland [Egypt]”) utilized to improve the water quality in Bahr El Baqar drain, which is located at the northeastern edge of the Nile Delta. This drain discharges its water into Manzala Lake, which in turn has many fishing activities and is connected to the Mediterranean Sea. The full capacity of the constructed wetland system is 25,000 m³/day. Three various flow rate wetlands were investigated; five wetland beds of high flow rate of 0.344 m³/m²-day, five wetland beds of low flow rate of 0.048 m³/m²-day and reciprocated cells of flow of 500 m³/day.The concentrations of different contaminants along the constructed wetlands system were measured to determine the treatment efficiency. The effluent was compared with the Egyptian standards of water quality in agricultural drains (Law 48/1982). Due to the high percentage of the agricultural water drain, the concentrations of contaminants in the influent were relatively low. The percentages of removal for the different contaminants were BOD₅: 52%, COD: 50%, TSS: 87%, TDS: 32%, NH₄-N: 66%, PO₄: 52%, Fe: 51%, Cu: 36%, Zn: 47% and Pb: 52%. The natural vegetation considerably increased the value of dissolved oxygen in the treated effluent. There were little differences in the removal efficiency between the high and low flow rates beds in the system.     

Escherichia coli HdeB is an acid stress chaperone

We cloned, expressed, and purified the hdeB gene product, which belongs to the hdeAB acid stress operon. We extracted HdeB from bacteria by the osmotic-shock procedure and purified it to homogeneity by ion-exchange chromatography and hydroxyapatite chromatography. Its identity was confirmed by mass spectrometry analysis. HdeB has a molecular mass of 10 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which matches its expected molecular mass. We purified the acid stress chaperone HdeA in parallel in order to compare the two chaperones. The hdeA and hdeB mutants both display reduced viability upon acid stress, and only the HdeA/HdeB expression plasmid can restore their viability to close to the wild-type level, suggesting that both proteins are required for optimal protection of the bacterial periplasm against acid stress. Periplasmic extracts from both mutants aggregate at acidic pH, suggesting that HdeA and HdeB are required for protein solubilization. At pH 2, the aggregation of periplasmic extracts is prevented by the addition of HdeA, as previously reported, but is only slightly reduced by HdeB. At pH 3, however, HdeB is more efficient than HdeA in preventing periplasmic-protein aggregation. The solubilization of several model substrate proteins at acidic pH supports the hypothesis that, in vitro, HdeA plays a major role in protein solubilization at pH 2 and that both proteins are involved in protein solubilization at pH 3. Like HdeA, HdeB exposes hydrophobic surfaces at acidic pH, in accordance with the appearance of its chaperone properties at acidic pH. HdeB, like HdeA, dissociates from dimers at neutral pH into monomers at acidic pHs, but its dissociation is complete at pH 3 whereas that of HdeA is complete at a more acidic pH. Thus, we can conclude that Escherichia coli possesses two acid stress chaperones that prevent periplasmic-protein aggregation at acidic pH.     

Heterooligomerization of human dopamine receptor 2 and somatostatin receptor 2 Co-immunoprecipitation and fluorescence resonance energy transfer analysis

Somatostatin and dopamine receptors are well expressed and co-localized in several brain regions, suggesting the possibility of functional interactions. In the present study we used a combination of pharmacological, biochemical and photobleaching fluorescence resonance energy transfer (pbFRET) to determine the functional interactions between human somatostatin receptor 2 (hSSTR2) and human dopamine receptor 2 (hD2R) in both co-transfected CHO-K1 or HEK-293 cells as well as in cultured neuronal cells which express both the receptors endogenously. In monotransfected CHO-K1 or HEK-293 cells, D2R exists as a preformed dimer which is insensitive to agonist or antagonist treatment. In control CHO-K1 cells stably co-transfected with hD2R and hSSTR2, relatively low FRET efficiency and weak expression in co-immunoprecipitate from HEK-293 cells suggest the absence of preformed heterooligomers. However, upon treatment with selective ligands, hD2R and hSSTR2 exhibit heterodimerization. Agonist-induced heterodimerization was accompanied by increased affinity for dopamine and augmented hD2R signalling as well as prolonged hSSTR2 internalization. In contrast, cultured striatal neurons display constitutive heterodimerization between D2R and SSTR2, which were agonist-independent. However, heterodimerization in neurons was completely abolished in the presence of the D2R antagonist eticlopride. These findings suggest that hD2R and hSSTR2 operate as functional heterodimers modulated by ligands in situ, which may prove to be a useful model in designing new therapeutic drugs.     

Decoding the genome beyond sequencing: the new phase of genomic research

While our understanding of gene-based biology has greatly improved, it is clear that the function of the genome and most diseases cannot be fully explained by genes and other regulatory elements. Genes and the genome represent distinct levels of genetic organization with their own coding systems; Genes code parts like protein and RNA, but the genome codes the structure of genetic networks, which are defined by the whole set of genes, chromosomes and their topological interactions within a cell. Accordingly, the genetic code of DNA offers limited understanding of genome functions. In this perspective, we introduce the genome theory which calls for the departure of gene-centric genomic research. To make this transition for the next phase of genomic research, it is essential to acknowledge the importance of new genome-based biological concepts and to establish new technology platforms to decode the genome beyond sequencing.