The immunocytochemical localization of connexin 36 at rod and cone gap junctions in the guinea pig retina

Abstract

Connexin 36 (Cx36) is a channel-forming protein found in the membranes of apposed cells, forming the hexameric hemichannels of intercellular gap junction channels. It localizes to certain neurons in various regions of the brain including the retina. We characterized the expression pattern of neuronal Cx36 in the guinea pig retina by immunocytochemistry using specific antisera against Cx36 and green/red cone opsin or recoverin. Strong Cx36 immunoreactivity was visible in the ON sublamina of the inner plexiform layer and in the outer plexiform layer, as punctate labelling patterns. Double-labelling experiments with antibody directed against Cx36 and green/red cone opsin or recoverin showed that strong clustered Cx36 immunoreactivity localized to the axon terminals of cone or close to rod photoreceptors. By electron microscopy, Cx36 immunoreactivity was visible in the gap junctions as well as in the cytoplasmic matrices of both sides of cone photoreceptors. In the gap junctions between cone and rod photoreceptors, Cx36 immunoreactivity was only visible in the cytoplasmic matrices of cone photoreceptors. These results clearly indicate that Cx36 forms homologous gap junctions between neighbouring cone photoreceptors, and forms heterologous gap junctions between cone and rod photoreceptors in guinea pig retina. This focal location of Cx36 at the terminals of the photoreceptor suggests that rod photoreceptors can transmit rod signals to the pedicle of a neighbouring cone photoreceptor via Cx36, and that the cone in turn signals to corresponding ganglion cells via ON and OFF cone bipolar cells.

Identification of myopia-associated WNT7B polymorphisms provides insights into the mechanism underlying the development of myopia

“…Nevertheless, the precise mechanisms mediating the transduction of this defocus signal leading to myopia are still unclear. GJD2 is reportedly localized at the synapses between alpha-ganglion cells, AII amacrine cells, cone bipolar cells and photoreceptor cells [42][43][44][45][46][47][48][49][50][51] . Of all the interactions between these cells, the coupling between the amacrine cells and ganglion cells has been reported to be dramatically reduced in GJD2 knockout mice 52 .…”

Connexin and pannexin hemichannels of neurons and astrocytes

“…15,16 This channel is highly expressed in the retina, with localization in AII amacrine cells (the interneurons of the retina), 17 cone photoreceptors, and OFF cone bipolar cells. 18,19 It is thought that Cx36 gap junctions play critical roles in coordinating network properties such as spike synchronization 15 and electrical coupling of hippocampal interneurons, 20 amacrine cells, 21 and striatal medium spiny neurons. 22 The importance of Cx36 as gap junctions of interneurons is well established and has been reviewed elsewhere.…”

Modulation of rod photoreceptor output by HCN1 channels is essential for regular mesopic cone vision

“…On the basis of a previous work 14 (and our unpublished data with this protocol in nob mice, N.T. and M.W.S), we knew that responses to low temporal frequency stimulation (0-3 Hz) are dominated by rod system activity, those to intermediate frequency stimulation (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) by cone ON system activity, and those to high-frequency stimulation (≥15 Hz) by cone OFF system activity 15,16 . The ERG data in Figure 3a,b show that low frequency stimuli were well resolved in HCN1 − / − mice despite considerably prolonged responses, whereas, to our surprise, response amplitudes decreased dramatically with increasing frequency, and essentially no responses were observable above 5 Hz.…”