The absence of Complexin 3 and Complexin 4 differentially impacts the ON and OFF pathways in mouse retina.
Complexins (Cplxs) regulate the speed and Ca(2+)-sensitivity of synaptic vesicle fusion. It has been shown that all four known Cplxs are present at mouse retinal synapses--at conventional amacrine cell synapses (Cplx 1 to Cplx 3) and at photoreceptor and bipolar cell ribbon synapses (Cplx 3 and Cplx 4) [K. Reim et al. (2005) J. Cell Biol., 169, 669-680]. Electroretinographic recordings in Cplx 3/Cplx 4 double-knockout (DKO) mice showed perturbed transmission in the outer plexiform layer, and possible changes in the inner plexiform layer [K. Reim et al. (2009) J. Cell Sci., 122, 1352-1361]. In the present study, we examined the effects of the absence of Cplx 3 and Cplx 4 on ganglion cell responses. We report that the lack of Cplx 3 and Cplx 4 differentially impacts the ON and OFF pathways. Under photopic conditions, the responses in the cone OFF pathway are largely unaffected, whereas the responses in the cone ON pathway are diminished in Cplx 3/Cplx 4 DKO mice. Under scotopic conditions, both ON and OFF response rates are reduced and high-sensitivity OFF responses are missing in Cplx 3/Cplx 4 DKO mice. The electrophysiological findings are corroborated by new immunocytochemical findings. We now show that rod spherules contain only Cplx 4. However, both Cplx 3 and Cplx 4 co-localize in cone pedicles. In the inner plexiform layer, Cplx 3 is present in rod bipolar cell terminals and in amacrine cell processes. Most importantly, Cplx 3 is localized in the lobular appendages of AII amacrine cells, the sites of signal transmission from the primary rod pathway into the OFF pathway in the inner plexiform layer.
Department of Biology and Environmental Sciences, Neurobiology, University of Oldenburg, 26111 Oldenburg, Germany.
Immanuel
I
Landgraf
Johanna
J
Mühlhans
Karin
K
Dedek
Kerstin
K
Reim
Johann H
JH
Brandstätter
Josef
J
Ammermüller
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010775:Photic Stimulation; D055351:Retinal Neurons / Q000378:metabolism / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology*
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; C529624:Cplx3 protein, mouse; C543115:Cplx4 protein, mouse; D005136:Eye Proteins; D009419:Nerve Tissue Proteins