Ana Castro and Joseph Giacalone to present at Genetics Student Seminar 3/10/2016
Ana Castro’s Abstract
The role of the anti-sigma factor RsiV in lysozyme sensing and stress response
A Castro1, Jessica Hastie1, Craig Ellermeier1
Microbiology Department, College of Medicine, University of Iowa
Bacteria respond to changes in their environment by altering gene expression. Understanding the mechanism by which information is transmitted from outside the cells across the membrane is critical, as it will provide insight into how cells regulate resistance mechanisms. The goal is to gain insight into stress response mechanisms that may contribute to microbial survival in rapidly changing conditions. Extra cytoplasmic function (ECF) s factors are a subset of s factors that allow many organisms to sense and respond to changes in the environment. Most ECF s factors are held in an inactive state by an anti-s factor that prevents the ECF s from interacting with RNA polymerase. Certain envelope stresses in bacteria include the regulated intramembrane proteolysis (RIP), a mechanisms which results in the sequential cleavage of membrane-bound proteins, including s factors. In Bacillus subtilis, the ECF s factor, sV, belongs to the ECF30 subfamily of ECF s factors, members which are primarily found in firmicutes.sV is activated specifically by lysozyme, a critical component of the host innate immune system. sV induces resistance to lysozyme in organisms such as Clostridium difficile. In the absence of lysozyme sV is inhibited by the anti-s factor RsiV. In response to lysozyme, RsiV is cleaved by signal peptidase at site-1 leading to the release and activation of sV. We have shown that RIP dependent mechanism of sV activation is dependent on the anti-s, RsiV, binding to the inducing signal, lysozyme. My project involves using B. subtilis as a model to determine RsiV factors that allow signal peptidase cleavage in the presence of lysozyme. We will determine how σV is important for pathogenesis and virulence in B. subtilis. The objective of this project is to determine the mechanisms by which RsiV binding to lysozyme allow for signal peptidase cleavage at site-1 in the extracellular domain.
Joseph Giacalone’s Abstract
Disease modeling using patient-specific photoreceptor precursor cells
Induced pluripotent stem cell (iPSC)-derived photoreceptor precursor cells can be used to study biological processes and have the potential to restore vision to patients with retinal degenerative diseases like retinitis pigmentosa. Biopsies were obtained from patients with inherited retinal degeneration and fibroblast lines were established. Patient-specific iPSCs were then generated, clonally expanded and validated. Post-mitotic photoreceptor precursor cells were generated using a stepwise 3D differentiation protocol. This method will serve as a platform for studying RPGR-associated XLRP.