Cloning and characterization of cDNAs encoding putative CTCFs in the mosquitoes, Aedes aegypti and Anopheles gambiae.
BACKGROUND
One of the many ascribed functions of CCCTC-binding factor (CTCF) in vertebrates is insulation of genes via enhancer-blocking. Insulation allows genes to be shielded from "cross-talk" with neighboring regulatory elements. As such, endogenous insulator sequences would be valuable elements to enable stable transgene expression. Recently, CTCF joined Su(Hw), Zw5, BEAF32 and GAGA factor as a protein associated with insulator activity in the fruitfly, Drosophila melanogaster. To date, no known insulators have been described in mosquitoes.


RESULTS
We have identified and characterized putative CTCF homologs in the medically-important mosquitoes, Aedes aegypti and Anopheles gambiae. These genes encode polypeptides with eleven C2H2 zinc fingers that show significant similarity to those of vertebrate CTCFs, despite at least 500 million years of divergence. The mosquito CTCFs are constitutively expressed and are upregulated in early embryos and in the ovaries of blood-fed females. We have uncovered significant bioinformatics evidence that CTCF is widespread, at least among Drosophila species. Finally, we show that the An. gambiae CTCF binds two known insulator sequences.


CONCLUSIONS
Mosquito CTCFs are likely orthologous to the widely-characterized vertebrate CTCFs and potentially also serve an insulating function. As such, CTCF may provide a powerful tool for improving transgene expression in these mosquitoes through the identification of endogenous binding sites.
Department of Entomology, Texas A&M University, MS 2475, College Station, TX 77843-2475, USA. c-gray@tamu.edu
Christine E
CE
Gray
Craig J
CJ
Coates
D000330:Aedes / Q000235:genetics* / Q000254:growth & development; D000595:Amino Acid Sequence; D000818:Animals; D000852:Anopheles / Q000235:genetics* / Q000254:growth & development; D000076246:CCCTC-Binding Factor; D002478:Cells, Cultured / Q000276:immunology; D002645:Chickens / Q000235:genetics; D003001:Cloning, Molecular / Q000379:methods; D018076:DNA, Complementary / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D004330:Drosophila / Q000235:genetics; D005260:Female; D020869:Gene Expression Profiling; D007106:Immune Sera / Q000378:metabolism; D008969:Molecular Sequence Data; D010053:Ovary / Q000378:metabolism; D010802:Phylogeny; D012097:Repressor Proteins / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D015854:Up-Regulation / Q000235:genetics
D000076246:CCCTC-Binding Factor; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D007106:Immune Sera; D012097:Repressor Proteins