PhD PROPOSAL FOR THE PASTEUR-PARIS UNIVERSITY INTERNATIONAL PROGRAM

 

Deadline for full application: December 15th, 2013

Interviews: March, 2014

Start of the Ph.D.: October 1st, 2014

 

 

 

Department: Parasitology and Mycology

Title of the PhD project: Epigenetics and susceptibility of the malaria vector Anopheles gambiae to Plasmodium falciparum

 

Name of the lab: Genetics and Genomics of Insect Vectors

Head of the lab: K.D. Vernick

PhD advisor: C. Bourgouin

Email address: cabourg@pasteur.fr

Web site address of the lab:

Doctoral school affiliation and University:

 

Compléxité du Vivant, Université Pierre et Marie Curie (UPMC)

 

 

Presentation of the laboratory and its research topics:

 

The research developed in the Unit aims at understanding the genetics and molecular basis of Anopheles mosquito’s receptivity to the human malaria parasite Plasmodium falciparum.

This includes genome wide association studies (GWAS), functional genomics of immune pathways and effectors, analyzing the trade off between nutrition and mosquito immune response. Many tools are routinely used as RNAi, An. gambiae transgenesis and mosquito infection with rodent Plasmodium and P. falciparum.

http://www.pasteur.fr/recherche/RAR/RAR2012/Vernick.pdf

 

Description of the project:

(1 page, Arial font size 11 : 600 words in total with at least 50% dedicated specifically to the proposed PhD project(s))

 

Malaria is still heavily impacting human health in many developing countries. Africa counts 90% of the 600,000 reported deaths/year, due to Plasmodium falciparum, which is mainly transmitted by Anopheles gambiae. The susceptibility/refractoriness of An.gambiae to Plasmodium has been extensively studied over the last decade leading to the identification of sets of immunity genes involved in controlling the development of the parasite in the mosquito [1]. In addition, genomic and genetic approaches led to the identification of several loci contributing to P. falciparum refractoriness in An.gambiae natural populations [2]. One locus contains several genes encoding putative immune effectors. Within this locus, we showed that APL1 orthologs protect differently An.gambiae from P. falciparum or rodent Plasmodium that have no co-evolution history with this mosquito [3].

We have discovered that An.gambiae susceptibility/refractoriness to P.falciparum is maternally controlled (Mitri et al, in preparation). Our results revealed that progenies from old females are more susceptible to the parasite than progenies from young females, while being overall better fitted. This constitutes the first report of such maternal effects in mosquitoes where the mother mosquitoes were never previously exposed to Plasmodium. This finding is likely to have consequences to both malaria transmission modeling and vector control, as mosquito population age structure is an essential parameter of malaria transmission.

 

Environmental epigenetics is currently one leading field in understanding the molecular basis of maternal effects in the susceptibility/resistance phenotype of progenies to diseases [4].

We are initiating the molecular analysis of the maternal effect observed in An.gambiae susceptibility to P. falciparum, and this project will constitute the core of a PhD program.

While epigenetics is a growing field of study in Drosophila and Caenorhabditis elegans, almost nothing is known in Anopheles mosquitoes. Epigenetic mechanisms include DNA methylation, histone modifications and small ncRNA (siRNA, piRNA, microRNA). As Drosophila, Anopheles and Aedes genomes contained only a single DNA methyltransferase (DNMT2), which in Drosophila has a low and randomly methylation activity. Therefore, DNA methylation in these insects is considered to be marginal. However, recent data showed that Aedes DNMT2 might methylate DNA non-randomly [5]

In this project, we will use standard high-throughput methods to analyze at genome scale DNA methylation and histone modifications in embryos collected from young and old Anopheles. In addition, we will focus on the promoter region of the APL1 genes and of other immune genes that encodes proteins known to interact with APL1 protein (TEP1, LRIM1 [6]).

To test whether the nutrition status of embryos from young and old female might contribute to the maternal effect, their protein and lipid composition will be compared.

Last, we want to determine whether the maternal effect observed with P.falciparum is also occurring with rodent parasites that have no evolutionary history with An.gambiae.

 

For the completion of this project, the PhD student will manipulate mosquitoes, isolate embryos from ovaries, determine the level of DNA methylation of target genes using bisulfite or MEDIP sequencing, determine levels of histone modifications (H3K9/K4/etc) using ChIP sequencing approaches.

Embryos protein content will used protein quantification and polyacrylamide gel (1D, even 2D). Relevant procedures for lipid content determination need to be established.

Evaluation of the maternal effect on P.berghei susceptibility will be conducted using the lab routine techniques for infecting mice and mosquitoes.

Depending upon the advancement of this project at the time the student joins, investigation on the role of small ncRNAs on the maternal effect could be envisaged.

Support will be provided by technological platforms from the Institute where necessary (ie 2D PAGE, mosquito production) and scientific advises from C. Antoniewski, specialist in Drosophila epigenetics

 

References:

 

1.  Yassine, H. and M.A. Osta, Anopheles gambiae innate immunity. Cellular Microbiology, 2010. 12(1): p. 1-9.

2.  Riehle, M.M., et al., Natural malaria infection in Anopheles gambiae is regulated by a single genomic control region. Science, 2006. 312(5773): p. 577-9.

3.  Mitri, C., et al., Fine pathogen discrimination within the APL1 gene family protects Anopheles gambiae against human and rodent malaria species. PLoS Pathog, 2009. 5(9): p. e1000576.

4.  Feil, R. and M.F. Fraga, Epigenetics and the environment: emerging patterns and implications. Nat Rev Genet, 2012. 13(2): p. 97-109.

5.  Ye, Y.H., et al., Infection with a Virulent Strain of Wolbachia Disrupts Genome Wide-Patterns of Cytosine Methylation in the Mosquito Aedes aegypti. PLoS ONE, 2013. 8(6): p. e66482.

 6. Povelones, M., et al., Structure-Function Analysis of the Anopheles gambiae LRIM1/APL1C Complex and its Interaction with Complement C3-Like Protein TEP1. PLoS Pathog, 2011. 7(4): p. e1002023.

 

Keywords:

 

Malaria transmission, Anopheles-plasmodium interaction, maternal effect, epigenetics

 

Expected profile of the candidate (optional):

 

Background in molecular biology and biochemistry, Strong Interest in vector borne diseases

 

Contact:

 

Catherine Bourgouin, Genetics and Genomics of Insect Vectors, cabourg@pasteur.fr, +33-1-45688224

Mis à jour le 16/09/2013