Characterization of the tg(rgs4:mCherry) zebrafish line
Cell-to-cell communication is one of the fundamental requisites of making multicellular organisms. G protein-coupled receptors (GPCRs) are one of the most abundant receptor-types within vertebrates. They canonically mediate their signal via hetrotrimeric G proteins, and G protein signaling is regulated by regulators of G protein-signaling (RGS). One of these RGS proteins, RGS4, is preferentially expressed in the central nervous system of humans and has been strongly connected to dopaminergic signaling, along with a number of severe neuronal diseases. rgs4 is not well studied in the model organism Danio rerio, the zebrafish, with only two publications. In this project, a newly constructed transgenic line, tg(rgs4:mCherry), with the fluorophore mCherry regulated by the promoter element of rgs4 was characterized in order to investigate fidelity to endogenous rgs4 expression and the utility of the transgenic line. The mCherry expression is apparent by 48 hours post fertilization, and expression is found mainly in neuronal tissue. Cell bodies are visible only in some labeled areas, while other areas show a more diffuse signal indicative of projections. There is only one transgenically labeled area that also unambiguously expresses rgs4; the pronephric tubule. This line is therefore not particularly well suited for rgs4-specifc studies, but this does not discredit the fidelity of the construct. A transgenic line made with a site-directed technique would most likely confer the fidelity of the promoter to the expression of the fluorophore. A way of increasing the labeling resolution includes exchanging the mCherry fluorophore for one with stronger signal and a lower tendency to aggregate, e.g. eGFP. Increasing the resolution of the characterization, e.g. to the level of sub-nuclei or neuronal types, would serve to enhance the utility of the line. As it is, the tg(rgs4:mCherry) zebrafish line has limited uses, and yet it is not without them.
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