| Summary: | <p>Abstract</p> <p>Background</p> <p><it>Giardia lamblia </it>trophozoites colonize the intestines of susceptible mammals and cause diarrhea, which can be prolonged despite an intestinal immune response. The variable expression of the variant-specific surface protein (VSP) genes may contribute to this prolonged infection. Only one is expressed at a time, and switching expression from one gene to another occurs by an epigenetic mechanism.</p> <p>Results</p> <p>The WB <it>Giardia </it>isolate has been sequenced at 10× coverage and assembled into 306 contigs as large as 870 kb in size. We have used this assembly to evaluate the genomic organization and evolution of the <it>vsp </it>repertoire. We have identified 228 complete and 75 partial <it>vsp </it>gene sequences for an estimated repertoire of 270 to 303, making up about 4% of the genome. The <it>vsp </it>gene diversity includes 30 genes containing tandem repeats, and 14 <it>vsp </it>pairs of identical genes present in either head to head or tail to tail configurations (designated as inverted pairs), where the two genes are separated by 2 to 4 kb of non-coding DNA. Interestingly, over half the total <it>vsp </it>repertoire is present in the form of linear gene arrays that can contain up to 10 <it>vsp </it>gene members. Lastly, evidence for recombination within and across minor clades of <it>vsp </it>genes is provided.</p> <p>Conclusions</p> <p>The data we present here is the first comprehensive analysis of the <it>vsp </it>gene family from the Genotype A1 WB isolate with an emphasis on <it>vsp </it>characterization, function, evolution and contributions to pathogenesis of this important pathogen.</p>
|
|---|