Christine E. Gray, Ph.D.

“Cytoplasmic incompatibility in Drosophila and CTCF-dependent insulators in insects”

I am a geneticist with an interest in gene expression and how it varies with genomic environment. I currently am engaged in two projects. The first of these projects is investigating a potential mechanism to explain a phenomenon known as cytoplasmic incompatibility (CI). CI results in arrested cell division immediately after fertilization and occurs as a direct consequence of infection with a bacterium (Wolbachia). The end result is infertility. The phenomenon is directional. It only occurs when Wolbachia-infected males mate with uninfected females. Understanding just how Wolbachia causes CI in insects may allow other researchers to utilize Wolbachia in efforts to control populations of important insect disease vectors. This project is being done in the fruit fly, Drosophila melanogaster.

image alternate text Figure 1. Assessing Wolbachia infection status in experimental and control Drosophila lines. The 16S rDNA gene from Wolbachia (936 bp) and the 12S rDNA gene from Drosophila mitochondria (400 bp) were amplified by PCR with gene-specific primers. Samples in lanes 2-4 and lane 6 are infected, while the sample in lane 5 is uninfected. Lane 7 is a control with no input DNA. Lane 8 is a control with no Taq DNA polymerase.

The second project involves assessing several CTCF-binding sites from the malaria mosquito vector, Anopheles gambiae, for insulator activity in cell culture. CTCF is a well-characterized DNA binding protein that has been shown to be a potent insulator for gene expression in vertebrate systems. Insulators act as a type of “bookend” for genes and keep regulatory sequences that promote or repress gene expression from interacting with neighboring genes and affecting their expression simply because they are close by. A CTCF-like protein has been identified in fruit flies and in two species of mosquitoes that vector human pathogens. Identification of specific DNA sequences with CTCF-dependent insulator activity would be advantageous in protecting the expression of transgenes which reduce mosquito fertility and/or block expression of key genes required for pathogen replication or transmission.

Current research students:
Tiffany Brown, senior biology major (Biaggini)
Audiel Espitia, senior biology major (SURF)
John Fedorick, senior biology major
Sierra Tamez, senior biology major (Biaggini)
Melissa Valdes, junior biochemistry major (MARC)

Recent publication:
Gray, C.E. and Coates, C.J. (2005) Cloning and characterization of cDNAs encoding putative CTCFs in the mosquitoes, Aedes aegypti and Anopheles gambiaeBMC Molecular Biology 6:16.