Genomic linkage map of the human blood fluke Schistosoma mansoni
Schistosoma mansoni is a blood fluke that infects ~90 million people. The complete life cycle can be maintained in the laboratory making this one of the few experimentally tractable human helminth infections and a rich literature reveals heritable variation in important biomedical traits such as virulence, host-specificity, transmission and drug resistance. However, there is a current lack of tools needed to study molecular, quantitative, and population genetics. Our goal was to construct genetic linkage map for S. mansoni, and thus provide a new resource that will help stimulate research on this neglected pathogen.
We genotyped grandparents, parents and 88 progeny to construct a 5.6cM linkage map containing 243 microsatellites positioned on 203 of the largest scaffolds in the genome sequence. The map allows 70% of the estimated 300Mb genome to be ordered on chromosomes, and highlights where scaffolds have been incorrectly assembled. The markers fall into 8 main linkage groups, consistent with 7 pairs of autosomes and one pair of sex chromosomes, and we were able to anchor linkage groups to chromosomes using fluorescent in situ hybridization (FISH). The genome measures 1228.6cM. Marker segregation reveals higher female recombination, confirms ZW inheritance patterns, and identifies recombination hotspots and regions of segregation distortion.
The genetic linkage map presented here is the first for S. mansoni and first for a species in the phylum Platyhelminthes. The map provides the critical tool necessary for quantitative genetic analysis, aids genome assembly, and furnishes a framework for comparative flatworm genomics and field-based molecular epidemiological studies.
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