Abstract
Gβ5 interacts with and stabilizes the R7 members of the regulators of G-protein signaling, which is important for G-protein signaling regulation in photoreceptors and ON-bipolar cells. In addition, it has been found that the dendritic morphology and the number of synaptic triads in the outer plexiform layer (OPL) are significantly altered in the Gβ5-/- mice. However, Gβ5 is also expressed in the inner plexiform layer (IPL) and the ganglion cell layer (GCL). In the present study, we examined the potential role of Gβ5 on dendritic morphology and synaptic distribution of retinal ganglion cells (RGCs). Gβ5 was conditionally knockout (cKO) in the Grik4-cre mice, which selectively label a subset of RGCs. The particle-mediated gene transfer technique was used to transfect RGCs of Gβ5floxed/floxed and Gβ5floxed/+ mice with PSD95-GFP plasmids. The dendritic morphology and the spatial distribution pattern of excitatory synapses of the cKO Gβ5 RGCs were visualized and compared with their littermate controls. Total of 5 RGC types (G2, G6, G12, G17, and G18) were analyzed in the present study. Their dendritic stratifications were normal in the absence of Gβ5, though the dendritic patterns of some RGCs were slightly altered. The PSD95 puncta were regularly spaced (in 1-2 μm interval) on local dendritic segments in both cKO Gβ5 RGCs and their littermate controls. However, the density of excitatory synapses along the dendrites was slightly reduced in G2, G6, and G12 cells of cKO Gβ5 mice compared with their littermate controls. Overall, our results showed that the morphological features of RGCs are only slightly changed when their Gβ5 is conditionally deleted. These findings suggest that, unlike the role of Gβ5 in the OPL (i.e., dramatically affecting the morphology and synapses of ON-bipolar cells), Gβ5 is apparently not essential for the development of dendritic morphology and synaptic distribution in RGCs. The functional significance of Gβ5 expression in the IPL and GCL thus remains to be studied in the future. Keywords: Gβ5, conditional knockout, dendritic morphology, synaptic distribution, retinal ganglion cell