Aedes aegypti: an emerging model for vector mosquito development

Abstract

Blood-feeding mosquitoes, including the dengue and yellow fever vector Aedes aegypti, transmit many of the world's deadliest diseases. Such diseases have resurged in developing countries and pose clear threats for epidemic outbreaks in developed countries. Recent mosquito genome projects have stimulated interest in the potential for arthropod-borne disease control by genetic manipulation of vector insects. Targets of particular interest include genes that regulate development. However, although the Ae. aegypti genome project uncovered homologs of many known developmental regulatory genes, little is known of the genetic regulation of development in Ae. aegypti or other vector mosquitoes. This article provides an overview of the background, husbandry, and potential uses of Ae. aegypti as a model species. Methods for culturing, collecting and fixing developing tissues, analyzing gene and protein expression, and knocking down genes are permitting detailed analyses of the functions of developmental regulatory genes and the selective inhibition of such genes during Ae. aegypti development. This methodology, much of which is applicable to other mosquito species, is useful to both the comparative development and vector research communities.

Figure 1

Adult Ae. aegypti female. Ae. aegypti adults have white scales on the dorsal surface of their thorax as well as a dark brown/black abdomen that may also possess white scales. The tarsal segments of the hind legs have white basal bands. Photo Credit: James Gathany, CDC.

Figure 2

Mosquito rearing cage. Methodology for culturing mosquitoes is described in Protocol 1. The cotton sleeve on the cage (seen in A) permits human access and manipulations within the cage. The netted top of the cage (top down view shown in B) allows for blood feeding prior to egg collections.

Figure 3

Dissection methodology for Ae. aegypti embryos. Methods for fixing and dissecting mosquito embryos are included in Protocol 2. The process of dissecting a fixed embryo is shown in A-F (see text for details). It is critical to remove the black endochorion (A-D) and transparent serosal cuticle (arrowhead in F) in order to successfully perform gene and protein expression assays.

Figure 4

Expression of axon guidance genes in Ae. aegypti embryos. (A) fra and casein kinase (B, C) are expressed ventrally in the developing nerve cord at 55 hrs. of development. Lateral views of whole-mount embryos stained with the accompanying in situ methodology (Protocol 3) are shown in A and B (anterior is oriented left). A filleted nerve cord is shown in C (anterior is oriented up).

Figure 5

Protein expression analysis in Ae. aegypti during embryonic development. (A,B) Acetylated tubulin expression labels the axons of the developing nerve cord. A lateral view of a 55 hr whole-mount embryo stained with the accompanying immunohistochemistry methodology (Protocol 4) is shown in A (anterior is oriented left). A filleted nerve cord from a 55 hr embryo is shown in B (anterior is oriented up).