Molecular Characterization and Expression of G q/11 Protein in Fishes
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Teleost fishes and lower vertebrates adjust to changing light conditions by diurnal movements of melanin pigment granules in their retinal pigment epithelium (RPE). RPE is not directly activated by light and several observations suggest that some extracellular signal from the retina may trigger the cascade of events leading to the granular movement in RPE. Findings by González et al. (2004) and Phatarpekar et al. (2005) suggest that pigment granule movements in fish RPE may be induced via G-protein coupled muscarinic receptors. Based on these findings, I hypothesize that bluegill (Lepomis macrochirus) RPE expresses at least one member of the Gq/11 family that mediates the signal from the activated muscarinic receptor to the effector. To test this hypothesis, I characterized cDNAs encoding two G-proteins from the Gq/11 family. The subtype identity of these novel cDNAs and the encoded G-protein fragments from bluegill were examined using phylogenetic analyses. Their expression was examined in adult bluegill and zebrafish eyes using RT-PCR and immuno-histochemistry. Immunolabeling was also used to study the ontogeny of Gaq/11 expression in zebrafish eyes. My results indicate that bluegill express both bona fide Gaq and a second member of the Gaq/11 family, but that only Gaq is expressed in eye. These findings imply that Gaq could play a specific role in pigment movement in fish eyes. It also lays the groundwork for the future elucidation of the function of these genes in carbachol-induced pigment granule dispersion.