October 17th, 2012

Speaker: Wen-Han Yu
Adviser: James Galagan
Title: Exploring temporal dynamics of transcriptional regulatory networks in Mycobacterium Tuberculosis by using synthetic genetic clock

ABTRACT
M. tuberculosis is known as a primary pathogen in the mammalian respiratory system and kills two million people every year. One-third of the world’s population harbors latent M. tuberculosis causing chronic, asymptomatic infections and reducing its susceptibility in drug treatment. In this study, we explore how M. tuberculosis activates dormancy in response of the environmental stimulus at gene-regulatory level and, more specifically, parameterize the dynamic gene-expression functions of regulators to target genes on either direct or indirect connections in the network. To do so, we constructed a synthetic self-sustaining oscillator-driving system with tunable period and amplitude in Mycobacteria, which provides a long-period dynamic perturbation of input regulators. The system in advance improves the ability for system identification of kinetic network model. We applied it into two simple networks, including single-edge, and feed-forward loop network motif. The temporal dynamics of each individual gene expression represented in fluorescent reporters in vivo were profiled by the time-lapse microscopy at single-cell level. By probing different pairs of regulators and targets as well as FFLs in the network, we will reveal the relationship of the regulator binding affinity and temporal regulation, and combinatorial effects when multiple regulators occur to a single target. The refined regulatory network model will be able to delineate all downstream target gene temporal expressions given a regulator condition over time. In addition, by single-cell measurement, we can also probe the initiation of cell-to-cell variability at regulatory network level. Overall, the network model will provide insight into M. tuberculosis responses to the environmental changes during dormancy.