Giardia is a widespread zoonotic intestinal parasite and is one of the ten major parasites of humans, causing significant acute and chronic diarrheal disease. Due to the lack of concerted research efforts, giardiasis has been designated a World Health Organization (WHO) neglected disease. To proliferate and colonize the small intestine, trophozoites first find suitable sites for attachment using flagellar motility, and then avoid peristaltic flow by attaching to the villi with the ventral disc, a unique microtubule structure. Te ventral disc is critical for pathogenesis in that it mediates reversible attachment to the intestinl microvilli via an undefined mechanism. Our primary focus is to evaluate the functions of ventral disc substructures that are required for overall disc conformational changes leading to parasite attachment in vivo and in vitro. We will first determine the contributions of flagellar motility an lateral crest (LC) contact to early stages of attachment (Aim 1). We will then correlate the various disc conformational states occurring in late stage attachment with movements of substructures (Aim 2), and determine the contributions of these substructures to generating disc conformations required for attachment (Aim 2). Finally, we will define the stages disc biogenesis with respect to the assembly of disc substructures after mitosis, when two dorsal daughter discs are assembled and the parental ventral disc is disassembled, and during excystation, when two new daughter discs are rapidly formed. This work will inform our analyses of disc structure and function (Aims 1-2). We will also test the role of posttranslational tubulin modifications in sequentially recruiting disc-associated proteins to the assembling disc (Aim 3). Drugs affecting flagellar motility, ventral disc structure, disc biogenesis, or disc conformational dynamics may directly or indirectly decrease trophozoite attachment in the host, and thus limit the initiation o extent of infection.

Public Health Relevance

Giardia is a widespread intestinal parasite, and colonization of the host gut is a critical part of Giardia's life cycle. Parasite colonization is initiated when cels attach to the intestinal wall via a specialized suction cup-like structure, the ventral disc. This research into basic aspects of the attachment mechanism could provide targets for drugs that affect the functioning or assembly of the disc, preventing or leading to lower rates of infection.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Pathogenic Eukaryotes Study Section (PTHE)
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Mcgugan, Glen C
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University of California Davis
Schools of Medicine
United States
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Barash, N R; Maloney, J G; Singer, S M et al. (2017) Giardia Alters Commensal Microbial Diversity throughout the Murine Gut. Infect Immun 85:
Pham, Jonathan K; Nosala, Christopher; Scott, Erica Y et al. (2017) Transcriptomic Profiling of High-Density Giardia Foci Encysting in the Murine Proximal Intestine. Front Cell Infect Microbiol 7:227
McInally, Shane G; Dawson, Scott C (2016) Eight unique basal bodies in the multi-flagellated diplomonad Giardia lamblia. Cilia 5:21
Brown, Joanna R; Schwartz, Cindi L; Heumann, John M et al. (2016) A detailed look at the cytoskeletal architecture of the Giardia lamblia ventral disc. J Struct Biol 194:38-48
Nosala, Christopher; Dawson, Scott C (2015) The Critical Role of the Cytoskeleton in the Pathogenesis of Giardia. Curr Clin Microbiol Rep 2:155-162
Vicente, Juan-Jesus; Cande, W Zacheus (2014) Mad2, Bub3, and Mps1 regulate chromosome segregation and mitotic synchrony in Giardia intestinalis, a binucleate protist lacking an anaphase-promoting complex. Mol Biol Cell 25:2774-87
Dawson, Scott C; Paredez, Alexander R (2013) Alternative cytoskeletal landscapes: cytoskeletal novelty and evolution in basal excavate protists. Curr Opin Cell Biol 25:134-41
Wilson, Katherine L; Dawson, Scott C (2011) Evolution: functional evolution of nuclear structure. J Cell Biol 195:171-81
Hirst, Marissa B; Kita, Kelley N; Dawson, Scott C (2011) Uncultivated microbial eukaryotic diversity: a method to link ssu rRNA gene sequences with morphology. PLoS One 6:e28158
Hagen, Kari D; Hirakawa, Matthew P; House, Susan A et al. (2011) Novel structural components of the ventral disc and lateral crest in Giardia intestinalis. PLoS Negl Trop Dis 5:e1442

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