Profile
Educational Background
Postdoc, Molecular Parasitology, University of Pennsylvania, 2025
Ph.D., Genetics and Genomics, Duke University, 2018
B.S., Biological Sciences and English Writing, University of Pittsburgh, 2011
Research Interests
For over fifteen years, Dr. Walzer has studied the genetics and genomics of apicomplexan parasites, including Toxoplasma gondii, Plasmodium falciparum, and now Cryptosporidium parvum. She is determined to understand what makes these parasites tick and was particularly drawn to Cryptosporidium and its single-host model. Cryptosporidium is transmitted via the fecal-oral route and invades the epithelial cells of the small intestine, ultimately causing diarrheal disease. It propagates via a programmed countdown to sex, 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.
During her postdoctoral fellowship, Dr. Walzer determined the complete life cycle transcriptome of C. parvum through single-cell RNA sequencing (scRNA-seq) of 9,098 individual parasites. This single-cell atlas provides a roadmap of gene expression across parasite development and has enabled her to pinpoint the timing of important regulators of cell cycle progression and fate. These regulators include AP2 and Myb transcription factors. The Walzer Lab will define the regulatory networks of these transcription factors, with an initial focus on those expressed in males: Myb-M, AP2-M1, and AP2-M. Dr. Walzer discovered that Myb-M alone is necessary and sufficient to drive male fate. Now, her lab will identify the targets of Myb-M and unravel the transcriptional switch that leads to male. The Walzer Lab will prioritize the study of male-specific RNA-binding proteins as they share a similar expression profile to Myb-M and may coordinate its expression. The lab will also define the largely uncharacterized machinery involved in male egress, motility, attachment, and fusion. This will enable the Walzer Lab to figure out how a male traverses the harsh conditions of the gut to find and fertilize a female. As there is no vaccine and only limited treatment for cryptosporidiosis, this work will directly contribute to new and better therapeutics as the ability to disrupt Cryptosporidium sexual reproduction will stop continuous infection and transmission.
Selected Publications
Walzer KA, Tandel J, Byerly JH, Daniels AM, Gullicksrud JA, Whelan EC, Carro SD, Krespan E, Beiting DP, and Striepen B. (2024). Transcriptional control of the Cryptosporidium life cycle. Nature. 630, 174-180.
Pardy RD, Walzer KA, Wallbank BA, Byerly JH, O’Dea KM, Cohn IS, Haskins BE, Roncaioli JL, Smith EJ, Buenconsejo GY, Striepen B, and Hunter CA. (2024). Analysis of intestinal epithelial cell responses to Cryptosporidium highlights the temporal effects of IFN-gamma on parasite restriction. PLoS Pathogens. 20(5): e1011820.
Tandel J, Walzer KA, Byerly JH, Pinkston B, Beiting DP, and Striepen B. (2023). Genetic ablation of a female-specific Apetala 2 transcription factor blocks oocyst shedding in Cryptosporidium parvum. mBio. 14(2):e0326122.
Full publication list: https://www.ncbi.nlm.nih.gov/myncbi/katelyn.walzer.1/bibliography/public/
