Computational prediction and characterisation of miRNAs and their pathway genes in human schistosomiasis caused by Schistosoma haematobium

BACKGROUND Key genes control the infectivity of the Schistosoma haematobium causing schistosomiasis. A method for understanding the regulation of these genes might help in developing new disease strategies to control schistosomiasis, such as the silencing mediated by microRNAs (miRNAs). The miRNAs have been studied in schistosome species and they play important roles in the post-transcriptional regulation of genes, and in parasite-host interactions. However, genome-wide identification and characterisation of novel miRNAs and their pathway genes and their gene expression have not been explored deeply in the genome and transcriptome of S. haematobium. OBJECTIVES Identify and characterise mature and precursor miRNAs and their pathway genes in the S. haematobium genome. METHODS Computational prediction and characterisation of miRNAs and genes involved in miRNA pathway from S. haematobium genome on SchistoDB. Conserved domain analysis was performed using PFAM and CDD databases. A robust algorithm was applied to identify mature miRNAs and their precursors. The characterisation of the precursor miRNAs was performed using RNAfold, RNAalifold and Perl scripts. FINDINGS We identified and characterised 14 putative proteins involved in miRNA pathway including ARGONAUTE and DICER in S. haematobium. Besides that, 149 mature miRNAs and 131 precursor miRNAs were identified in the genome including novel miRNAs. MAIN CONCLUSIONS miRNA pathway occurs in the S. haematobium, including endogenous miRNAs and miRNA pathway components, suggesting a role of this type of non-coding RNAs in gene regulation in the parasite. The results found in this work will open up a new avenue for studying miRNAs in the S. haematobium biology in helping to understand the mechanism of gene silencing in the human parasite Schistosome.

Genetic Diversity of Schistosoma haematobium Eggs Isolated from Human Urine in Sudan

The genetic diversity of Schistosoma haematobium remains largely unstudied in comparison to that of Schistosoma mansoni. To characterize the extent of genetic diversity in S. haematobium among its definitive host (humans), we collected S. haematobium eggs from the urine of 73 infected schoolchildren at 5 primary schools in White Nile State, Sudan, and then performed a randomly amplified polymorphic DNA marker ITS2 by PCR-RFLP analysis. Among 73 S. haematobium egg-positive cases, 13 were selected based on the presence of the S. haematobium satellite markers A4 and B2 in their genomic DNA, and used for RFLP analysis. The 13 samples were subjected to an RFLP analysis of the S. haematobium ITS2 region; however, there was no variation in size among the fragments. Compared to the ITS2 sequences obtained for S. haematobium from Kenya, the nucleotide sequences of the ITS2 regions of S. haematobium from 4 areas in Sudan were consistent with those from Kenya (> 99%). In this study, we demonstrate for the first time that most of the S. haematobium population in Sudan consists of a pan-African S. haematobium genotype; however, we also report the discovery of Kenyan strain inflow into White Nile, Sudan.

Identification of the Boudicca and Sinbad retrotransposons in the genome of the human blood fluke Schistosoma haematobium

Schistosomes have a comparatively large genome, estimated for Schistosoma mansoni to be about 270 megabase pairs (haploid genome). Recent findings have shown that mobile genetic elements constitute significant proportions of the genomes of S. mansoni and S. japonicum. Much less information is available on the genome of the third major human schistosome, S. haematobium. In order to investigate the possible evolutionary origins of the S. mansoni long terminal repeat retrotransposons Boudicca and Sinbad, several genomes were searched by Southern blot for the presence of these retrotransposons. These included three species of schistosomes, S. mansoni, S. japonicum, and S. haematobium, and three related platyhelminth genomes, the liver flukes Fasciola hepatica and Fascioloides magna and the planarian, Dugesia dorotocephala. In addition, Homo sapiens and three snail host genomes, Biomphalaria glabrata, Oncomelania hupensis, and Bulinus truncatus, were examined for possible indications of a horizontal origin for these retrotransposons. Southern hybridization analysis indicated that both Boudicca and Sinbad were present in the genome of S. haematobium. Furthermore, low stringency Southern hybridization analyses suggested that a Boudicca-like retrotransposon was present in the genome of B. truncatus, the snail host of S. haematobium.

Recent studies on Schistosoma intercalatum: taxonomic status, puzzling distribution and transmission foci revisited

Schistosoma intercalatum, which causes human rectal schistosomiasis in Africa, still presents a great interest for its imprecise taxonomic status and its puzzling distribution in Africa. Two geographically isolated strains of S. intercalatum are recognized, the Lower Guinea strain and the Congo strain, which differ from each other in a number of morphological, biological and biochemical characteristics. Recent molecular data using RAPD markers indicate high divergence between the two strains, with values of Nei and Li's similarity indice allowing recognition of two genetically distinct taxa: experiments on pre- and post-isolating mechanisms are in progress in order to re-evaluate the taxonomic status of this polytypic species. With regard to its geographical distribution, S. intercalatum is characterized by the existence of two stable endemic areas (localized in Lower Guinea and North East of Democratic Republic of Congo) which correspond to the historical areas of species discovery, and the emergence during the last 15 years of new foci of the Lower Guinea strain outside previously known endemic areas. The absence of local adaptation of the Lower Guinea strain to its intermediate host, supported by experimental studies, may help to facilitate the spread of this strain. Nevertheless, the present restricted distribution of this species remains puzzling, because its potential snail hosts (bulinids) are widely distributed throughout much of Africa. Recent experimental and epidemiological studies suggest that interspecific sexual interactions between human schistosomes could have a role in limiting the distribution of S. intercalatum: the competitive sexual processes acting among human schistosomes show that S. haematobium and S. mansoni are always competitively dominant over S. intercalatum. These epidemiological observations lead the authors to distinguish three kinds of transmission foci for S. intercalatum

Infección por Schistosoma intercalatum y probable hibridización con Schistosoma haematobium en el este de Africa. Reporte de un caso / Infection caused by Schistosoma intercalatum and probable hybridization with Schistosoma haematobium in the eastern region of Africa. A case report

Se reporta la infección por Schistosoma intercalatum y probable hibridización con Schistosoma haematobium en un paciente procedente del este de Africa, área donde hasta la fecha no había sido demostrada. Las manifestaciones clínicas fundamentales consistieron en dolores abdominales y diarreas con sangre. El diagnóstico se realizó por el hallazgo en el examen microscópico de los huevos característicos de Schistosoma intercalatum en heces y orina, mediante la técnica de Ziehl-Neelsen modificada