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Faculty
J. Aaron Cassill, Ph.D. Research Interests My laboratory is interested in the mechanism of signal transduction in the Drosophila visual system. We are specifically pursuing two areas, that of attenuation of signal response and retinal degeneration caused by mutation of members of the signal pathway. There are two projects in the first area - the isolation of retina-specific serine/theonine protein kinases and characterization of a mutant line which appears to be defective in signal attenuation. We have synthesized two degenerate oligonucleotides which encode conserved domains in protein kinases and used these with PCR to amplify kinases from a library of Drosophila retinal cDNAs. Thus far, we have isolated 21 novel kinases and are characterizing these as well as screening for additional kinases. We are also characterizing a mutant Drosophila isolated from an enhancer trap screen which has a phenotype of responding with twice the normal level of activity to light pulses. We have isolated the genomic region containing the mutation and are characterizing the transcripts in this region to identify the affected gene. Mutations in the visual cascade can lead to retinal degeneration. We have screened 70,000 flies and isolated 14 mutants which undergo dominant retinal degeneration. Thirteen of these mutations are in the light receptor rhodopsin. Interestingly, four of these are the same as mutations occurring in human rhodopsin which cause the disease retinitis pigmentosa (RP). The last mutation does not map to any known members of the visual cascade and may represent a new member of the path. We are currently screening for additional mutants, creating mutations in Drosophila rhodopsin which correspond to other human RP mutations, and attempting to isolate the gene responsible for the degeneration in our non-rhodopsin mutant. Recent Publications Guntur KV, Velasquez D, Chadwell L, Carroll C, Weintraub S, Cassill JA, Renthal R. Apolipophorin-III-like protein expressed in the antenna of the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae). Arch Insect Biochem Physiol. 2004 Nov;57(3):101-10. Brunel CA, Madigan SJ, Cassill JA, Edeen PT, McKeown M. pcdr, a novel gene with sexually dimorphic expression in the pigment cells of the Drosophila eye. Dev Genes Evol. 1998 Aug;208(6):327-35.
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