Saeij lab:Research: Difference between revisions

From OpenWetWare
Jump to navigationJump to search
Line 24: Line 24:




==Identification of Toxoplasma virulence genes==
 
Toxoplasma has a haploid genome with 14 chromosomes that total 65 Mbp in size, representing ~7900 genes (http://www.toxodb.org ). Classical genetic crosses can be performed in Toxoplasma and several experimental crosses have been used to generate genetic linkage maps. To identify the Toxoplasma loci involved in virulence, we mapped virulence in F1 progeny derived from crosses between type II and type III strains. Five virulence loci were thus identified, and for three of these, genetic complementation showed that protein kinases (ROP18 and ROP16, respectively) and pseudokinases (ROP5)  are the key molecules (Saeij et al. 2006, Saeij et al. 2007, Reese et al. 2011). These are hypervariable rhoptry proteins that are secreted into the host cell upon invasion.
We have also used linkage mapping to identify Toxoplasma loci involved in modulation of host gene expression. Our initial analysis of the data identified that most of the strain-specific differences in the modulation of host cell transcription are mediated by two genes ROP16 and GRA15. Upon invasion by the parasite, ROP16 is injected into the host cell, where it ultimately affects the activation of signal transducer and activator of transcription (STAT) signaling pathways (Saeij et al. 2007). GRA15, encodes a dense granule protein, which affects activation of NF-kB, a transcription factor involved in the activation of the inflammatory response (Rosowski et al. 2011). Different Toxoplasma strains (e.g. type I, II and III) have different alleles of ROP16 and GRA15. Our results showed that the precise allelic combination of ROP16 and GRA15 determines how distinct Toxoplasma strains modulate the host immune response (Jensen et al. 2011). For example, type II strains can kill susceptible mice because they induce a hyper-inflammatory response that damages host tissue (Jensen et al. 2011). We are now combining genetic and biochemical approaches to identify host factors that interact with GRA15. Furthermore, we are continuing to investigate the host genes and pathways that mediate ROP16’s strong anti-inflammatory effects.
Overall, these results suggest that analogous to bacterial pathogens and their secretion system, it seems that Toxoplasma can secrete effectors into host cells to subvert host-cell signaling pathways. ROP16, ROP18 and ROP5 are members of a large protein family suggesting that Toxoplasma has a wide arsenal of effectors to modulate diverse host cell signaling pathways. The detailed characterization of these effectors represents a major focus of the laboratory.


==Identification of host genes and pathways that influence resistance or susceptibility to ''Toxoplasma''==
==Identification of host genes and pathways that influence resistance or susceptibility to ''Toxoplasma''==

Revision as of 17:23, 4 January 2014

Home        Contact        Internal        Lab Members        Publications        Research        Opportunities        Protocols        Links       


Overview

Learn about our research at our website




Identification of host genes and pathways that influence resistance or susceptibility to Toxoplasma

In addition to parasite strain differences, host genetic differences also determine the outcome of toxoplasmosis. We found that inflammatory pathways are differentially regulated in macrophages from susceptible and resistant mice. Using a genetic approach we have identified the mouse genomic regions that determine these differences and we are now in the position to identify the exact causative genes.

Projects the lab is currently working on

   1. Pathogenesis: what properties make certain strains more virulent than others and what proteins are involved?
   2. How does Toxoplasma co-opt host-cell gene expression and how does this differ between strains?
   3. How does Toxoplasma modulate the NF-κB signaling pathway?
   4. How can we use Toxoplasma whole genome data to understand its population biology?
   5. What are the host genes and pathways that influence resistance or susceptibility to Toxoplasma?



Retrieved from "https://openwetware.org/mediawiki/index.php?title=Saeij_lab:Research&oldid=763131"