title: Construction of a genetic map for Theileria parva: identification of hotspots of recombination.
abstract: The tick-borne protozoan parasite Theileria parva is the causal agent of East Coast Fever (ECF), a severe lymphoproliferative disease of cattle in eastern, central and southern Africa. The life cycle of T. parva is predominantly haploid, with a brief diploid stage occurring in the tick vector that involves meiotic recombination. Resolved genetic studies of T. parva are currently constrained by the lack of a genome-wide high-definition genetic map of the parasite. We undertook a genetic cross of two cloned isolates of T. parva to construct such a map from 35 recombinant progeny, using a genome-wide panel of 79 variable number of tandem repeat markers. Progeny were established by in vitro cloning of cattle lymphocytes after infection with sporozoites prepared from Rhipicephalus appendiculatus ticks fed on a calf undergoing a dual infection with the two clonal parental stocks. The genetic map was determined by assigning individual markers to the four chromosome genome, whose physical length is approximately 8309 kilobasepairs (Kb). Segregation analysis of the markers among the progeny revealed a total genetic size of 1683.8 centiMorgans (cM), covering a physical distance of 7737.62 Kb (∼93% of the genome). The average genome-wide recombination rate observed for T. parva was relatively high, at 0.22 cM Kb(-1) per meiotic generation. Recombination hot-spots and cold-spots were identified for each of the chromosomes. A panel of 27 loci encoding determinants previously identified as immunorelevant or likely to be under selection were positioned on the linkage map. We believe this to be the first genetic linkage map for T. parva. This resource, with the availability of the genome sequence of T. parva, will promote improved understanding of the pathogen by facilitating the use of genetic analysis for identification of loci responsible for variable phenotypic traits exhibited by individual parasite stocks.
authors.affiliation: Moredun Research Institute, Pentlands Science Park, Penicuik, Midlothian, UK.
authors.forename: Frank
authors.initials: F
authors.lastname: Katzer
authors.forename: Regina
authors.initials: R
authors.lastname: Lizundia
authors.forename: Daniel
authors.initials: D
authors.lastname: Ngugi
authors.forename: Damer
authors.initials: D
authors.lastname: Blake
authors.forename: Declan
authors.initials: D
authors.lastname: McKeever
mesh_terms: D000818:Animals; D002417:Cattle; D002874:Chromosome Mapping / Q000379:methods*; D003433:Crosses, Genetic; D016054:DNA, Protozoan / Q000235:genetics*; D008297:Male; D018598:Minisatellite Repeats; D011995:Recombination, Genetic; D048494:Rhipicephalus / Q000469:parasitology; D016797:Theileria parva / Q000235:genetics*
chemical_list: D016054:DNA, Protozoan