title: Differential evolution of repetitive sequences in Cryptosporidium parvum and Cryptosporidium hominis.
abstract: Cryptosporidium parvum and Cryptosporidium hominis are two morphologically identical species of Apicomplexan protozoa infecting humans. Although the genomes of these species are 97% identical, their host range is strikingly different. C. parvum infects humans and animals and is primarily a zoonotic infection, whereas C. hominis is typically not detected in animals. The extent of genetic polymorphism in both species has been surveyed locally, but not on a larger geographical scale. Herein, a collection of unrelated C. parvum and C. hominis isolates was genotyped using multiple, randomly distributed micro- and minisatellites. In average, minisatellites, consisting of tandemly repeated sequence motifs of 6-24 basepair, were more polymorphic than microsatellites. When the average number of micro- and minisatellite alleles per locus was used as a measure of heterogeneity, no difference between C. parvum and C. hominis was found. However, the frequency distribution of alleles in both species was significantly different and in 6 of the 14 loci the size of the C. parvum and C. hominis repeats did not overlap. Assuming that C. parvum and C. hominis evolved from a common ancestor, these observations suggest a differential evolution of repeat length at these loci.
authors.affiliation: Tufts University School of Veterinary Medicine, Division of Infectious Diseases, 200 Westborough Road, North Grafton, MA 01536, USA.
authors.forename: Sultan
authors.initials: S
authors.lastname: Tanriverdi
authors.forename: Giovanni
authors.initials: G
authors.lastname: Widmer
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003458:Cryptosporidium / Q000235:genetics* / Q000302:isolation & purification; D016785:Cryptosporidium parvum / Q000235:genetics* / Q000302:isolation & purification; D016054:DNA, Protozoan / Q000032:analysis / Q000235:genetics*; D004586:Electrophoresis; D019143:Evolution, Molecular; D005787:Gene Frequency; D005819:Genetic Markers; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data; D033661:Oocysts / Q000235:genetics / Q000302:isolation & purification; D016366:Open Reading Frames; D010802:Phylogeny; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D013045:Species Specificity
chemical_list: D016054:DNA, Protozoan; D005819:Genetic Markers