The effects of development and virulence on gene expression in the protozoan parasite Neospora caninum



Unjit, KITTICHAI
(2018) The effects of development and virulence on gene expression in the protozoan parasite Neospora caninum. PhD thesis, University of Liverpool.

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Abstract

Neospora caninum is an obligate intracellular protozoan parasite which causes abortion in cattle and neuromuscular disease in dogs. Neosporosis causes substantial economic losses in both dairy and beef cattle industries worldwide. This thesis explores changes in genes and proteins expression associated with development and virulence of N. caninum in order to gain more biological information in this parasite. To achieve the global quantification of genes and proteins expression under different phenotypic conditions, transcriptomics and proteomics approaches are used to investigate these phenomenons. Chapter 2 examines the differential protein expression during tachyzoites-bradyzoites stage conversion using a label-free proteomics approach and finds that the differential protein expression of most apical secretory proteins decrease in abundance in bradyzoites stage. In addition, most of proteins associated with parasite motility were also reduced in abundance in bradyzoites. This indicates that proteins associated with host cell adhesion, invasion and gliding motility are down-regulated in the quiescent cyst-forming stage. Chapter 3 compares the transcriptomic profiles of low- and high-virulence N. caninum using RNA-Seq and finds that protein phosphatase 2C (PP2C) was preferentially expressed in the high-virulence strain, while a group of SRS family proteins was preferentially expressed in low-virulence conditions. This finding suggests that PP2C might play a role in virulence, while a group of SRS proteins might be associated with to limiting N. caninum virulence. Chapter 4 compares protein expression in low- and high-virulence N. caninum strains at three different time points using a label-free quantitative proteomic approach and finds that Rop24 was preferentially expressed in high-virulence N. caninum at all time points. Proteins associated with host cell attachment such as SAG3, TgSRS35A and cathepsin C2 also showed preferentially expression throughout the time course. This finding indicates that Rop24 might be associated with the N. caninum virulence, while the discovery of proteins associated with host cell attachment in low-virulence conditions might suggest that such strains are more efficient in invading host cells than high-virulence strains. Overall, this thesis identifies genes and proteins such as the rhoptry associated proteins PP2C and Rop24, which might be associated with virulence in neosporosis. It also shows that many proteins involved in host cell adhesion, invasion and parasite movement decrease in abundance in the cyst-forming bradyzoite stage. These discoveries enhance our understanding of parasite biology, providing a basis for future research into novel ways to prevent and control the disease by inhibiting parasite survival and transmission.

Item Type: Thesis (PhD)
Divisions: Fac of Health & Life Sciences > Institute of Veterinary Science
Depositing User: Symplectic Admin
Date Deposited: 20 Aug 2018 10:15
Last Modified: 23 Jan 2021 08:18
DOI: 10.17638/03023149
Supervisors:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3023149