Identification of three single nucleotide polymorphisms in Anopheles gambiae immune signaling genes that are associated with natural Plasmodium falciparum infection

Abstract

BackgroundLaboratory studies have demonstrated that a variety of immune signaling pathways regulate malaria parasite infection in Anopheles gambiae, the primary vector species in Africa.MethodsTo begin to understand the importance of these associations under natural conditions, an association mapping approach was adopted to determine whether single nucleotide polymorphisms (SNPs) in selected immune signaling genes in A. gambiae collected in Mali were associated with the phenotype of Plasmodium falciparum infection.ResultsThree SNPs were identified in field-collected mosquitoes that were associated with parasite infection in molecular form-dependent patterns: two were detected in the Toll5B gene and one was detected in the gene encoding insulin-like peptide 3 precursor. In addition, one infection-associated Toll5B SNP was in linkage disequilibrium with a SNP in sequence encoding a mitogen-activated protein kinase that has been associated with Toll signaling in mammalian cells. Both Toll5B SNPs showed divergence from Hardy-Weinberg equilibrium, suggesting that selection pressure(s) are acting on these loci.ConclusionsSeven of these eight infection-associated and linked SNPs alter codon frequency or introduce non-synonymous changes that would be predicted to alter protein structure and, hence, function, suggesting that these SNPs could alter immune signaling and responsiveness to parasite infection.

Plasmodium falciparum suppresses the host immune response by inducing the synthesis of insulin-like peptides (ILPs) in the mosquito Anopheles stephensi

“…AsILP4 expression is further restricted, with induction only in the midgut and only by P. falciparum infection (Marquez et al, 2011). In field-collected Anopheles gambiae , we identified coding sequence SNPs in AgILP3 (Horton et al, 2010) and AgILP4 (unpublished data) that are significantly associated with natural P. falciparum infection, suggesting functional involvement of these ILPs in the host response. To determine whether As ILP3 and 4 were functionally associated with P. falciparum infection in A. stephensi , we treated A. stephensi with translation blocking antisense morpholinos (Pietri et al, 2014) that repress As ILP3 and 4 peptide levels in vitro and in vivo (Cator et al, 2015).…”

“…In the mosquito midgut, ingested Plasmodium gametocytes undergo a series of developmental changes in the context of robust immune responses that contribute to marked losses in parasite numbers (Clayton et al, 2014; Yassine et al, 2010). This process is regulated in part by insulin/insulin-like growth factor signaling (IIS) and mitogen-activated protein kinase (MAPK) pathways (Corby-Harris et al, 2010; Drexler et al, 2013; Drexler et al, 2014; Hauck et al, 2013; Horton et al, 2010; Luckhart et al, 2013; Pakpour et al, 2012; Surachetpong et al, 2009; Surachetpong et al, 2010). …”

“…However, ingestion of a P. falciparum -infected blood meal profoundly increased expression of AsILP2 , 3 , 4 , and 5 in the head and midgut (Marquez et al, 2011). In support of a role for As ILPs in parasite infection, studies of field-collected A. gambiae from Mali identified a single nucleotide polymorphism (SNP) in AgILP3 that was significantly associated with natural P. falciparum infection (Horton et al, 2010). We have since identified additional infection-associated SNPs in AgILP3 and AgILP4 that are predicted to alter protein function (unpublished data).…”

Genetics and evolution of triatomines: from phylogeny to vector control

“…Whereas several microsatellite markers have been identified in major triatomine species such as T. infestans, T. dimidiata or R. prolixus, molecular markers are lacking for many other species. Also, genome-wide single-nucleotide polymorphism genotyping approaches, which are now popular in other insect vector species (Megy et al, 2009;Horton et al, 2010;Li et al, 2010), have not yet been developed in triatomines. In that respect, the ongoing sequencing of the R. prolixus genome (Megy et al, 2009) will provide a very valuable tool to further understand triatomine biology and genetics.…”

Single-Nucleotide Polymorphisms for High-Throughput Genotyping of Anopheles arabiensis in East and Southern Africa

“…Genes involved in the mosquito immune system have been intensively studied in efforts to understand interactions between the malaria parasite and mosquito vector and to manipulate vectors to reduce malaria transmission (Morlais et al 2004; Lim et al 2005; Riehle et al 2006; Obbard et al 2007; Cohuet et al 2008; Parmakelis et al 2008, 2010; Zou et al 2008; Cirimotich et al 2010; Horton et al 2010). Genetic markers such as single-nucleotide polymorphisms (SNPs) located in or near immune genes can facilitate the identification of genes associated with resistance or refractoriness to Plasmodium infection and contribute to assessing the relative importance of ecological and genetic determinants of this phenotype.…”