(2007) and Gubbels et al. (2008) provide a detailed mechanistic Lumacaftor mouse and structural outline of the apicomplexan cell cycle and cell division as it pertains to the different developmental stages (44,49). The genomic revolution has ushered the study of parasite biology into an era where it is now possible to apply high-throughput functional genomics techniques to address pertinent questions regarding the variation in modes of cell cycle and its regulatory mechanisms at different developmental stages, and how these relate to the success of the parasite in the host cell environment. Analyses of global changes in gene expression

have been carried out to define more complex networks of gene interactions on a functional level. It is now beginning to emerge that there are extensive dynamic changes in parasite gene expression that mark the progression through different phases of the replication cycle as well as during transition between host cells (41,50,51). The temporal ordering of global gene expression during the course of the tachyzoite replication cycle has been mapped out using microarray analysis (50). This study measured gene expression at hourly time points during the full replication cycle of synchronized tachyzoites. Over

35% of all Toxoplasma genes were identified to exhibit cyclic expression patterns that are coordinated with the parasite replication cycle. These dynamic expression patterns reflect a functional diversification of gene expression that allows for rapid Vitamin B12 and efficient ‘just-in-time’ transcription of genes that are functionally MG132 relevant for the different phases of the cycle. There is a coordinated progression from the G1-phase transcription of genes with metabolic and biosynthetic functions to the S/M-phase induction of genes involved in daughter cell maturation and infectivity (50). The transition from one host cell to

another is also marked by a similar pattern of gene expression changes, which is additionally coupled to the parasite cell cycle (51). Parasites in G1 phase of the cell cycle exhibit the highest capacity for egress and reinvasion. Approximately 16% of T. gondii genes are differentially expressed between extracellular and intracellular parasites. The differential expression profiles of extracellular and intracellular parasites reflect their respective biological needs for motility and invasion in the extracellular environment and growth and replication in the intracellular environment. An emerging theme from these studies is the functional diversification of the transcription and translation machinery to temporally coordinate gene expression with parasite cell cycle (50,51). During the asexual phase of its life cycle, T. gondii transitions between two main developmental forms: the actively dividing tachyzoites and the essentially dormant bradyzoites that may persist for the life of the host. Tachyzoite-to-bradyzoite interconversion is important on two levels.