title: Expression profile of genes during resistance reversal in a temephos selected strain of the dengue vector, Aedes aegypti.
abstract: BACKGROUND
  The mosquito Aedes aegypti is one of the most important disease vectors because it transmits two major arboviruses, dengue and yellow fever, which cause significant global morbidity and mortality. Chemical insecticides form the cornerstone of vector control. The organophosphate temephos a larvicide recommended by WHO for controlling Ae. aegypti, however, resistance to this compound has been reported in many countries, including Brazil.
  
  
  RESULTS
  The aim of this study was to identify genes implicated in metabolic resistance in an Ae. aegypti temephos resistant strain, named RecR, through microarray analysis. We utilized a custom 'Ae. aegypti detox chip' and validated microarray data through RT-PCR comparing susceptible and resistant individuals. In addition, we analyzed gene expression in 4(th) instar larvae from a reversed susceptible strain (RecRev), exposed and unexposed to temephos. The results obtained revealed a set of 13 and 6 genes significantly over expressed in resistant adult mosquitoes and larvae, respectively. One of these genes, the cytochrome P450 CYP6N12, was up-regulated in both stages. RT-PCR confirmed the microarray results and, additionally, showed no difference in gene expression between temephos exposed and unexposed RecRev mosquitoes. This suggested that the differences in the transcript profiles among the strains are heritable due to a selection process and are not caused by immediate insecticide exposure. Reversal of temephos resistance was demonstrated and, importantly, there was a positive correlation between a decrease in the resistance ratio and an accompanying decrease in the expression levels of previously over expressed genes. Some of the genes identified here have also been implicated in metabolic resistance in other mosquito species and insecticide resistant populations of Ae. aegypti.
  
  
  CONCLUSIONS
  The identification of gene expression signatures associated to insecticide resistance and their suppression could greatly aid the development of improved strategies of vector control.
authors.affiliation: Vector Group, Liverpool School of Tropical Medicine, Liverpool, United Kingdom. c.strode@liv.ac.uk
authors.forename: Clare
authors.initials: C
authors.lastname: Strode
authors.forename: Maria
authors.initials: M
authors.lastname: de Melo-Santos
authors.forename: Tereza
authors.initials: T
authors.lastname: Magalhães
authors.forename: Ana
authors.initials: A
authors.lastname: Araújo
authors.forename: Contancia
authors.initials: C
authors.lastname: Ayres
mesh_terms: D000330:Aedes / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001938:Brazil; D003715:Dengue; D003716:Dengue Virus; D004351:Drug Resistance; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D017344:Genes, Insect; D019476:Insect Proteins / Q000096:biosynthesis* / Q000235:genetics; D007303:Insect Vectors / Q000235:genetics / Q000378:metabolism*; D007306:Insecticides / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000002:Temefos / Q000494:pharmacology*
chemical_list: D019476:Insect Proteins; D007306:Insecticides; D000002:Temefos