Abstract
Purpose: :
Upon stimulation of G protein coupled receptors (GPCRs), including rhodopsin, G proteins are released as second messenger to activate their effectors. The family of regulators of G protein signaling (RGS) is known to be pivotal molecule for signal deactivation. While RGS9 which regulates rhodopsin signaling pathway in photoreceptor cells is extensively studied, the importance of other RGS members in the retina is poorly understood. We detected significant RGS16 mRNA in adult mouse retina by expression analysis. To understand the potential role of RGS16 in retinal function we systematically examined its expression pattern in the eye of a transgenic mouse expressing enhanced green fluorescent protein (eGFP) under the transcriptional control of RGS16 promoter.
Methods: :
A mouse line from the GENSAT bacterial artificial chromosome (BAC) project were characterized by immunohistological examination. The BAC transgenic approach has proven to be highly reliable to obtain accurate transgene expression in vivo. The principles of BAC transgenesis are homologous recombination of the translation start site of the BAC RGS16 gene with an eGFP expression cassette and introduction of the recombinated BAC into fertilized eggs.
Results: :
The eGFP positive cells were localized in the inner nuclear layer where nuclei of horizontal cells, bipolar cells, amacrine cells, and Müller cells reside and were identified as rod ON bipolar cells based on the results of immunostaining with each cell marker. In addition, the eGFP positive cells also express Gαo, a second messenger of glutamate receptor.
Conclusions: :
It is suggested that RGS16 would be a constituent of the signaling pathway of glutamate receptor, one of the GPCRs, in rod ON bipolar cells. This in vivo marking technology enables direct electrophysiological recording and/or isolation of the specific cell type. Purification of the eGFP positive cells and subsequent mRNA or protein analysis will unravel the molecular bases of rod ON bipolar cell function.
Keywords: bipolar cells • signal transduction • genetics