title: Forward genetic analysis of the apicomplexan cell division cycle in Toxoplasma gondii.
abstract: Apicomplexa are obligate intracellular pathogens that have fine-tuned their proliferative strategies to match a large variety of host cells. A critical aspect of this adaptation is a flexible cell cycle that remains poorly understood at the mechanistic level. Here we describe a forward genetic dissection of the apicomplexan cell cycle using the Toxoplasma model. By high-throughput screening, we have isolated 165 temperature sensitive parasite growth mutants. Phenotypic analysis of these mutants suggests regulated progression through the parasite cell cycle with defined phases and checkpoints. These analyses also highlight the critical importance of the peculiar intranuclear spindle as the physical hub of cell cycle regulation. To link these phenotypes to parasite genes, we have developed a robust complementation system based on a genomic cosmid library. Using this approach, we have so far complemented 22 temperature sensitive mutants and identified 18 candidate loci, eight of which were independently confirmed using a set of sequenced and arrayed cosmids. For three of these loci we have identified the mutant allele. The genes identified include regulators of spindle formation, nuclear trafficking, and protein degradation. The genetic approach described here should be widely applicable to numerous essential aspects of parasite biology.
authors.affiliation: Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America.
authors.forename: Marc-Jan
authors.initials: MJ
authors.lastname: Gubbels
authors.forename: Margaret
authors.initials: M
authors.lastname: Lehmann
authors.forename: Mani
authors.initials: M
authors.lastname: Muthalagi
authors.forename: Maria E
authors.initials: ME
authors.lastname: Jerome
authors.forename: Carrie F
authors.initials: CF
authors.lastname: Brooks
authors.forename: Tomasz
authors.initials: T
authors.lastname: Szatanek
authors.forename: Jayme
authors.initials: J
authors.lastname: Flynn
authors.forename: Ben
authors.initials: B
authors.lastname: Parrot
authors.forename: Josh
authors.initials: J
authors.lastname: Radke
authors.forename: Boris
authors.initials: B
authors.lastname: Striepen
authors.forename: Michael W
authors.initials: MW
authors.lastname: White
mesh_terms: D000818:Animals; D002455:Cell Division / Q000235:genetics*; D002467:Cell Nucleus / Q000187:drug effects; D002478:Cells, Cultured; D003360:Cosmids / Q000235:genetics; D004252:DNA Mutational Analysis; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D016054:DNA, Protozoan / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts; D017125:Genes, Protozoan; D005816:Genetic Complementation Test; D015698:Genomic Library; D006801:Humans; D008957:Models, Genetic; D009154:Mutation; D010641:Phenotype; D011995:Recombination, Genetic; D014122:Toxoplasma / Q000166:cytology* / Q000235:genetics* / Q000472:pathogenicity; D014123:Toxoplasmosis; D014162:Transfection
chemical_list: D018076:DNA, Complementary; D016054:DNA, Protozoan