The phylogeny of the genus Indoplanorbis (Gastropoda,Planorbidae) from Africa and the French West Indies

Indoplanorbis exustus is a freshwater snail known as the intermediate host of various trematode parasites, including different species of the genus Schistosoma. Although its genetic diversity is well described in Asia, the phylogenetic diversity of strains from Africa and Guadeloupe (French West Indies) and their relationship to Asian and South‐East Asian strains remain unknown. To tackle this issue, we sampled individuals from Africa and Guadeloupe, and we computed phylogenetic reconstructions using five molecular markers: partial sequences of two mitochondrial genes, cox1 and 16S, and three nuclear markers, ITS1, ITS2 (Internal Transcribed Spacer 1 and 2) and 5.8S. Our results suggest that strains in Africa and Guadeloupe come from Asia and that they all belong to a single clade that is widespread around the globe.     

Comparative analysis of the rhythm of cercariae emergence in three strains of Schistosoma bovis (trematoda: Schistosomatidae)

A comparative experimental study of the rhythmic shedding of three geographic strains of Schistosoma bovis cercariae (Sardinian, Sudanese and Spanish) by Bulinus truncatus showed a significant difference in the emergence patterns. The results support the existence of a genetic variability of the emergence rhythms. The origin of the variability is discussed and could be found in the pastoral practice and the ecological characteristics of the different transmission foci.     

High-throughput genotyping assays for identification of glycophorin B deletion variants in population studies

Glycophorins are the most abundant sialoglycoproteins on the surface of human erythrocyte membranes. Genetic variation in glycophorin region of human chromosome 4 (containing GYPA, GYPB, and GYPE genes) is of interest because the gene products serve as receptors for pathogens of major public health interest, including Plasmodium sp., Babesia sp., Influenza virus, Vibrio cholerae El Tor Hemolysin, and Escherichia coli. A large structural rearrangement and hybrid glycophorin variant, known as Dantu, which was identified in East African populations, has been linked with a 40% reduction in risk for severe malaria. Apart from Dantu, other large structural variants exist, with the most common being deletion of the whole GYPB gene and its surrounding region, resulting in multiple different deletion forms. In West Africa particularly, these deletions are estimated to account for between 5 and 15% of the variation in different populations, mostly attributed to the forms known as DEL1 and DEL2. Due to the lack of specific variant assays, little is known of the distribution of these variants. Here, we report a modification of a previous GYPB DEL1 assay and the development of a novel GYPB DEL2 assay as high-throughput PCR-RFLP assays, as well as the identification of the crossover/breakpoint for GYPB DEL2. Using 393 samples from three study sites in Ghana as well as samples from HapMap and 1000 G projects for validation, we show that our assays are sensitive and reliable for genotyping GYPB DEL1 and DEL2. To the best of our knowledge, this is the first report of such high-throughput genotyping assays by PCR-RFLP for identifying specific GYPB deletion types in populations. These assays will enable better identification of GYPB deletions for large genetic association studies and functional experiments to understand the role of this gene cluster region in susceptibility to malaria and other diseases.