Types I GT1, II Me49, III CTGara strains - tachyzoite and Compound 1

Previous studies suggested that specific bradyzoite genes were differentially expressed in the three major lineages common to North America and Europe (Radke et al., 2006). In order to determine if these differences extended to the global transcriptome, we characterized whole-cell mRNA levels in both tachyzoite and bradyzoite populations from three primary strain isolates differentiated in vitro. It is well understood in the field that long passage history is associated with the loss of developmental competence (Frenkel et al., 1976). Therefore, the Type I-GT1, Type II-Me49B7 and Type III-CTG strains studied here were maintained at < 20 cell culture passages from the oocyst stage and are capable of completing both intermediate and definitive host life cycles. These experiments used newly constructed Affymetrix GeneChips that include probe sets for ~8000 genes, and we assessed the induction of bradyzoite genes using a strong inducer of bradyzoite differentiation, Compound 1 (Radke et al., 2006). Both tachyzoite and induced (Compound 1/48hrs - bradyzoite) RNA for strains representing the three major lineages of Toxoplasma gondii were hybridized .