Plant, Animal & Microbe Genomes X Conference

January 12-16, 2002
Town & Country Convention Center
San Diego, CA

Poster: Microbial Genome Technology
            

DEVELOPMENT OF PCR-BASED GENETIC MARKERS FOR MAPPING AND LINKAGE ANALYSIS OF ACUTE VIRULENCE IN TOXOPLASMA GONDII

¹ Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110.

² Gluck Equine Research Center, University of Kentucky, Lexington, Kentucky 40546.

³ Parasite Biology and Epidemiology Laboratory, USDA, Beltsville, MD 20705.

⁴ Department of Pathology, Cambridge University, Cambridge, CB21QP UK.

Toxoplasma gondii strains from a variety of human and animal sources have been subtyped into three predominant clonal lineages by restriction fragment length polymorphism (RFLP) analysis of independent genetic markers. Acute virulence in mice is restricted to the type I lineage. To identify the acute virulence genes, a virulent type I strain was crossed with a non-virulent type III strain and 27 representative progeny were selected for genotyping and analysis of their virulence in mice. The virulence of selected progeny was compared to the parental strains to establish their phenotypes (virulent strains have a LD₁₀₀ = 1 and nonvirulent strains have a LD₁₀₀ greater than 10³). Since the recombination frequency in T. gondii is fairly low, with 1 cM (1% recombination frequency) corresponding to about 300 kb, it is practical to map a given trait to a specific chromosome using a simple set of PCR-based markers distributed among all the chromosomes. In this study, we have developed 45 PCR-based genetic markers for rapid genotyping the recombinant progeny and an updated version of genetic map is presented. Linkage analysis suggests that the acute virulence is located on chromosome VII. Further study will be carried out to refine the genetic map on chromosome VII and to isolate the gene(s) by positional cloning.