MSc Exit Seminar- Alexa Chioran – Tuesday, November 14, 2017

MSc Exit Seminar

Tuesday November 14^th, 2:30 pm – Earth Sciences Centre, Rm. 3087

Alexa Chioran (Ringuette lab)

“SPARC promotes proper nucleation and assembly of collagen IV from Drosophila melanogaster embryonic haemocytes”

Abstract

Basement membranes (BMs) are a hallmark feature of all multicellular organisms in which they support essential developmental events. Collagen IV is the major structural component of the BM, however, its spatiotemporal assembly into stereotypic lattice networks is poorly understood. SPARC (Secreted Protein Acidic and Rich in Cysteine), a collagen IV-binding glycoprotein, is enriched in the BMs of Drosophila embryos and larvae. Fat body cells of Drosophila larvae and egg chamber follicular epithelial cells of the adult deficient in SPARC expression exhibit a fibrotic-like accumulation of collagen IV and other BM components in the pericellular space, resulting in larval lethality. Thus, SPARC is hypothesized to be an extracellular chaperone-like protein, whereby its association with collagen IV prevents aberrant collagen IV polymerization. In this study, I utilized molecular markers distinguishing secretory pathway compartments to demonstrate that SPARC and collagen IV co-localize primarily in the trans-Golgi network prior to secretion. Moreover, knockdown of SPARC expression in cultured embryonic haemocytes supports a role for SPARC in preventing premature nucleation of collagen IV molecules in embryonic haemocytes adherent to a laminin matrix. In order to gain further mechanistic insight on the functional relationship between SPARC and collagen IV, CRISPR gene editing technology was used to generate a sparc-null mutant. This genetic tool will be used in future experiments to unmask the structural domains of SPARC responsible for collagen IV assembly, maturation, and BM homeostasis.