Characterization of cytokinesis and ventrolateral flange dynamics in Giardia lamblia

Abstract

Giardia lamblia is recognized as one of the most common protozoan causes of diarrheal diseases worldwide. Giardia is an extracellular parasite that colonizes the intestine using its cytoskeleton to attach to the host intestine. The cytoskeleton is additionally involved in cell motility, membrane trafficking, mitosis, and cytokinesis. Although the actin-cytoskeleton is central for cell survival, Giardia does not have any canonical actin-binding proteins. Despite the number of processes the cytoskeleton contributes and having the most divergent actin-cytoskeleton of any eukaryote identified, very little is understood about the cellular and cytoskeletal dynamics during these events. The technical difficulties of performing live cell imaging in Giardia have hampered the understanding of these life-cycle events. This study developed live cell imaging and then used this tool to explore the cellular dynamics and molecular underpinnings of cytokinesis and the ventrolateral flange, a lamellipodia-like structure. Cytokinesis is completed in a myosin-independent manner that uses flagella to coordinate force generation and direct membrane trafficking. The ventrolateral flange is an enigmatic structure that reportedly aids in cell attachment. The first ventrolateral flange components were identified, actin, GlRac, and Flangin and found to be critical for its assembly. Taken together, live cell imaging was developed as a novel tool for giardial research that lead to new insights into cytokinesis and ventrolateral flange dynamics in the evolutionarily distant disease causing protist Giardia.