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PLOS Papers on Chagas Vector, Colorectal Cancer Locus, Schistosoma Hybrids

In PLOS Genetics, researchers from the UK, Ecuador, the US, and Sweden present findings from a genomics-based analysis of Chagas vector adaptations, focusing on the triatomine insect vector Rhodnius ecuadoriensis. Using 2b-RAD reduced representation sequencing, the team assessed 272 R. ecuadoriensis representatives from wild and domestic populations at more than two dozen sites in the southern Ecuador province of Loja, using clues at thousands of SNP marker sites and mixed modeling analyses to flag potential adaptations to insecticide-treated homes and to retrace gene flow between wild and domestic populations — findings shored up with insect morphology and genome scan data. "Our findings suggest frequent and spatially targeted interventions, to cope with high gene flow and fragmented populations, are necessary to suppress Chagas disease transmission in Loja," the authors report, noting that "the discovery of signatures of possible local adaptation shed the first light on the genomic basis of domestication in triatomines."

A team from Zhejiang University in China characterizes functional variants in and around a chromosome 18 locus implicated in colorectal cancer (CRC) susceptibility for another paper in PLOS Genetics. By digging into loci linked to CRC in past genome-wide association studies, the investigators focused in on an apparent regulatory chromosome 18 SNP in an intron of SMAD7, along with variants in linkage disequilibrium. With additional expression quantitative trait locus, Hi-C chromatin interaction, and cell line data, for example, they saw hints that enhancer activity by such variants may regulate CRC-related activity by a LIPG gene linked to poorer-than-usual outcomes. "Collectively, our data suggest that these functional variants at 18q21.1 are involved in the pathogenesis of CRC by modulating enhancer activity, and possibly LIPG expression, thus indicating a promising therapeutic target for CRC," they suggest.

For a paper appearing in PLOS Neglected Tropical Diseases, investigators in the UK and Cameroon consider between-species hybridization in schistosomiasis-related worms in West Africa and Central Africa. With restriction site-associated DNA sequencing on 20 Schistosoma haematobium, S. bovis, S. guineensis, and hybrid worms, the team characterized genomic introgression and hybridization patterns for Schistosoma worms in Mali, Niger, São Tomé, and Cameroon. "The resulting dataset was used to characterize patterns of genomic ancestry across Schistosoma isolates of hybrid ancestry," they write. "This analysis was coupled with the use of genomic clines to study patterns of introgression in hybrids to detect loci that deviate from the genome-wide expectation of introgression, highlighting regions and specific genes that would be beneficial to increased infection/immunomodulation of [the] infected host."

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