Ontogeny of Muscarinic Acetylcholine Receptor Expression in the Eyes of Zebrafish
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The vertebrate eye exhibits a stage-dependent array of gene expression and physiological activity, making it an amenable model to further our understanding of development of the central nervous system and the associated signaling cascades. Muscarinic acetylcholine receptors are important neurotransmitter receptors, and their localization in the eyes of higher vertebrates has been well documented as has their role in normal ocular development and numerous eye diseases and disorders. Only limited work has been done to show the existence, localization, or functionality of these receptors in lower vertebrates. Zebrafish are a popular model for genetics, development, and evolutionary adaptations. Although zebrafish are widely divergent from mammals, I hypothesize that zebrafish have genes for the 5 muscarinic receptors previously identified. Here, I identify the putative M-odd subtypes of muscarinic receptors and show that they are expressed at specific developmental ages in the eyes of the zebrafish Danio rerio. In addition, I identify two possibly duplicated subtypes of muscarinic receptors. My results suggest that all the receptors examined are expressed in the eyes of developing zebrafish, but with different time courses. Differences between the expressions of ostensibly duplicated genes raise the possibility that subtle differences between the duplicates may enable refined regulation of specific developmental events. This manuscript was submitted on November 14, 2006.