Event

Abstract: Cryptosporidium is a leading cause of diarrheal disease and infects millions of people worldwide each year. With no vaccine and inadequate treatment, a great need exists for new therapeutics. Transmission of the parasite occurs via the fecal-oral route, and the entire life cycle takes place in a single host. Cryptosporidium propagates in the intestinal epithelium through a programmed countdown to sexual commitment, with three asexual cycles followed by the production of male and female gametes. This makes both asexual and sexual replication essential for continuous infection and transmission. However, the molecular mechanisms governing these stage transitions remain unknown. This seminar will detail how we used single-cell RNA sequencing of infected cultures and mice to determine the complete life cycle transcriptome of Cryptosporidium parvum. The analysis of 9,310 individual parasite transcriptomes revealed a highly organized program for the assembly of components at each stage and showed an abrupt transcriptional switch from asexual to male or female fate, with no evidence for a pre-commitment stage. We identified transcription factor Myb-M as the earliest male fate determinant, in an organism that lacks genetic sex determination. Conditional ablation of Myb-M resulted in the loss of male gametes in culture while observed numbers of asexual and female parasites remained similar to control. In mice, conditional ablation of Myb-M led to a complete block of sex and oocyst production. Conditional overexpression of Myb-M induced the male pathway in all parasites, leading to the expression of male specific-genes and the formation of terminally differentiated males, ablating further parasite replication and growth. These findings demonstrate that Myb-M is necessary and sufficient to drive male fate. Overall, our work provides the first comprehensive view of C. parvum gene expression across the entire life cycle and identifies Myb-M as a master regulator of sex determination and prime drug target.