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BMC Genomics  2010 

The Giardia lamblia vsp gene repertoire: characteristics, genomic organization, and evolution

DOI: 10.1186/1471-2164-11-424

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Abstract:

The WB Giardia 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 vsp repertoire. We have identified 228 complete and 75 partial vsp gene sequences for an estimated repertoire of 270 to 303, making up about 4% of the genome. The vsp gene diversity includes 30 genes containing tandem repeats, and 14 vsp 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 vsp repertoire is present in the form of linear gene arrays that can contain up to 10 vsp gene members. Lastly, evidence for recombination within and across minor clades of vsp genes is provided.The data we present here is the first comprehensive analysis of the vsp gene family from the Genotype A1 WB isolate with an emphasis on vsp characterization, function, evolution and contributions to pathogenesis of this important pathogen.Giardia lamblia (syn. G. duodenalis, G. intestinalis) is an anaerobic protist that is medically important as a common cause of intestinal infection and diarrhea [1]. Humans and other susceptible mammals become infected when cysts are ingested from contaminated water or food and excyst into trophozoites in the proximal small intestine. These trophozoites replicate and cause the symptoms of diarrhea. Infections with Giardia are frequently prolonged and malabsorption with weight loss may last for months in the absence of treatment, despite an immune response that would be expected to eradicate the infection. One of the possible reasons for the persistence of infection is antigenic variation of the variant-specific surface proteins (VSPs).A single trophozoite expresses only a single member of this protein family at any one time [2], but may switch expression from one VSP to another in vitro at a r

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