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Ribelayga CP, O’Brien J. When microscopy and electrophysiology meet connectomics-Steve Massey's contribution to unraveling the structure and function of the rod/cone gap junction. FRONTIERS IN OPHTHALMOLOGY 2023; 3:1305131. [PMID: 38983007 PMCID: PMC11182179 DOI: 10.3389/fopht.2023.1305131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Accepted: 10/31/2023] [Indexed: 07/11/2024]
Abstract
Electrical synapses, formed of gap junctions, are ubiquitous components of the central nervous system (CNS) that shape neuronal circuit connectivity and dynamics. In the retina, electrical synapses can create a circuit, control the signal-to-noise ratio in individual neurons, and support the coordinated neuronal firing of ganglion cells, hence, regulating signal processing at the network, single-cell, and dendritic level. We, the authors, and Steve Massey have had a long interest in gap junctions in retinal circuits, in general, and in the network of photoreceptors, in particular. Our combined efforts, based on a wide array of techniques of molecular biology, microscopy, and electrophysiology, have provided fundamental insights into the molecular structure and properties of the rod/cone gap junction. Yet, a full understanding of how rod/cone coupling controls circuit dynamics necessitates knowing its operating range. It is well established that rod/cone coupling can be greatly reduced or eliminated by bright-light adaptation or pharmacological treatment; however, the upper end of its dynamic range has long remained elusive. This held true until Steve Massey's recent interest for connectomics led to the development of a new strategy to assess this issue. The effort proved effective in establishing, with precision, the connectivity rules between rods and cones and estimating the theoretical upper limit of rod/cone electrical coupling. Comparing electrophysiological measurements and morphological data indicates that under pharmacological manipulation, rod/cone coupling can reach the theoretical maximum of its operating range, implying that, under these conditions, all the gap junction channels present at the junctions are open. As such, channel open probability is likely the main determinant of rod/cone coupling that can change momentarily in a time-of-day- and light-dependent manner. In this article we briefly review our current knowledge of the molecular structure of the rod/cone gap junction and of the mechanisms behind its modulation, and we highlight the recent work led by Steve Massey. Steve's contribution has been critical toward asserting the modulation depth of rod/cone coupling as well as elevating the rod/cone gap junction as one of the most suitable models to examine the role of electrical synapses and their plasticity in neural processing.
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Affiliation(s)
- Christophe P. Ribelayga
- Department of Vision Sciences, University of Houston College of Optometry, Houston, TX, United States
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Jin N, Zhang Z, Keung J, Youn SB, Ishibashi M, Tian LM, Marshak DW, Solessio E, Umino Y, Fahrenfort I, Kiyama T, Mao CA, You Y, Wei H, Wu J, Postma F, Paul DL, Massey SC, Ribelayga CP. Molecular and functional architecture of the mouse photoreceptor network. SCIENCE ADVANCES 2020; 6:eaba7232. [PMID: 32832605 PMCID: PMC7439306 DOI: 10.1126/sciadv.aba7232] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2019] [Accepted: 04/21/2020] [Indexed: 06/11/2023]
Abstract
Mouse photoreceptors are electrically coupled via gap junctions, but the relative importance of rod/rod, cone/cone, or rod/cone coupling is unknown. Furthermore, while connexin36 (Cx36) is expressed by cones, the identity of the rod connexin has been controversial. We report that FACS-sorted rods and cones both express Cx36 but no other connexins. We created rod- and cone-specific Cx36 knockout mice to dissect the photoreceptor network. In the wild type, Cx36 plaques at rod/cone contacts accounted for more than 95% of photoreceptor labeling and paired recordings showed the transjunctional conductance between rods and cones was ~300 pS. When Cx36 was eliminated on one side of the gap junction, in either conditional knockout, Cx36 labeling and rod/cone coupling were almost abolished. We could not detect direct rod/rod coupling, and cone/cone coupling was minor. Rod/cone coupling is so prevalent that indirect rod/cone/rod coupling via the network may account for previous reports of rod coupling.
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Affiliation(s)
- Nange Jin
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Zhijing Zhang
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Joyce Keung
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Sean B. Youn
- Summer Research Program, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Undergraduate Program, William Marsh Rice University, Houston, TX, USA
| | - Munenori Ishibashi
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Lian-Ming Tian
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - David W. Marshak
- Department of Neurobiology and Anatomy, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Neuroscience Research Center, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Program in Neuroscience, Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Eduardo Solessio
- Center for Vision Research and SUNY Eye Institute, Department of Ophthalmology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Yumiko Umino
- Center for Vision Research and SUNY Eye Institute, Department of Ophthalmology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Iris Fahrenfort
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Takae Kiyama
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Chai-An Mao
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Neuroscience Research Center, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Program in Neuroscience, Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Yanan You
- The Vivian L. Smith Department of Neurosurgery, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, USA
- Center for Stem Cell and Regenerative Medicine, The University of Texas Brown Foundation Institute of Molecular Medicine, Houston, TX, USA
| | - Haichao Wei
- The Vivian L. Smith Department of Neurosurgery, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, USA
- Center for Stem Cell and Regenerative Medicine, The University of Texas Brown Foundation Institute of Molecular Medicine, Houston, TX, USA
| | - Jiaqian Wu
- Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Program in Neuroscience, Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- The Vivian L. Smith Department of Neurosurgery, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, USA
- Center for Stem Cell and Regenerative Medicine, The University of Texas Brown Foundation Institute of Molecular Medicine, Houston, TX, USA
| | - Friso Postma
- Department of Neurobiology, Medical School, Harvard University, Boston, MA, USA
| | - David L. Paul
- Department of Neurobiology, Medical School, Harvard University, Boston, MA, USA
| | - Stephen C. Massey
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Summer Research Program, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Neuroscience Research Center, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Program in Neuroscience, Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Elizabeth Morford Distinguished Chair in Ophthalmology and Research Director, Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Christophe P. Ribelayga
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Summer Research Program, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Neuroscience Research Center, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Program in Neuroscience, Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Program in Biochemistry and Cellular Biology, Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Bernice Weingarten Chair in Ophthalmology, Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
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