scholarly journals Dominant cataracts result from incongruous mixing of wild-type lens connexins

2003 ◽  
Vol 161 (5) ◽  
pp. 969-978 ◽  
Author(s):  
Francisco J. Martinez-Wittinghan ◽  
Caterina Sellitto ◽  
Leping Li ◽  
Xiaohua Gong ◽  
Peter R. Brink ◽  
...  
Keyword(s):  
Fluorescent Dyes ◽  
Normal Growth ◽  
Fiber Morphology ◽  
Gap Junction Channels ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Junctional Coupling ◽  
Lens Growth ◽  
Gap Junctional ◽  
Gap Junctional Coupling

Gap junctions are composed of proteins called connexins (Cx) and facilitate both ionic and biochemical modes of intercellular communication. In the lens, Cx46 and Cx50 provide the gap junctional coupling needed for homeostasis and growth. In mice, deletion of Cx46 produced severe cataracts, whereas knockout of Cx50 resulted in significantly reduced lens growth and milder cataracts. Genetic replacement of Cx50 with Cx46 by knockin rescued clarity but not growth. By mating knockin and knockout mice, we show that heterozygous replacement of Cx50 with Cx46 rescued growth but produced dominant cataracts that resulted from disruption of lens fiber morphology and crystallin precipitation. Impedance measurements revealed normal levels of ionic gap junctional coupling, whereas the passage of fluorescent dyes that mimic biochemical coupling was altered in heterozygous knockin lenses. In addition, double heterozygous knockout lenses retained normal growth and clarity, whereas knockover lenses, where native Cx46 was deleted and homozygously knocked into the Cx50 locus, displayed significantly deficient growth but maintained clarity. Together, these findings suggest that unique biochemical modes of gap junctional communication influence lens clarity and lens growth, and this biochemical coupling is modulated by the connexin composition of the gap junction channels.

scholarly journals Approaches to Study Gap Junctional Coupling

2021 ◽  
Vol 15 ◽  
Author(s):  
Jonathan Stephan ◽  
Sara Eitelmann ◽  
Min Zhou
Keyword(s):  
Cell Types ◽  
Cellular Heterogeneity ◽  
Wide Field ◽  
Tissue Slices ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Junctional Coupling ◽  
Gap Junctional ◽  
Gap Junctional Coupling ◽  
Different Cell Types

Astrocytes and oligodendrocytes are main players in the brain to ensure ion and neurotransmitter homeostasis, metabolic supply, and fast action potential propagation in axons. These functions are fostered by the formation of large syncytia in which mainly astrocytes and oligodendrocytes are directly coupled. Panglial networks constitute on connexin-based gap junctions in the membranes of neighboring cells that allow the passage of ions, metabolites, and currents. However, these networks are not uniform but exhibit a brain region-dependent heterogeneous connectivity influencing electrical communication and intercellular ion spread. Here, we describe different approaches to analyze gap junctional communication in acute tissue slices that can be implemented easily in most electrophysiology and imaging laboratories. These approaches include paired recordings, determination of syncytial isopotentiality, tracer coupling followed by analysis of network topography, and wide field imaging of ion sensitive dyes. These approaches are capable to reveal cellular heterogeneity causing electrical isolation of functional circuits, reduced ion-transfer between different cell types, and anisotropy of tracer coupling. With a selective or combinatory use of these methods, the results will shed light on cellular properties of glial cells and their contribution to neuronal function.

Gap junction-mediated transfer of left-right patterning signals in the early chick blastoderm is upstream of Shh asymmetry in the node

Development ◽  
1999 ◽  
Vol 126 (21) ◽  
pp. 4703-4714 ◽  
Author(s):  
M. Levin ◽  
M. Mercola
Keyword(s):  
Gene Expression ◽  
Gap Junction ◽  
Large Scale ◽  
Chick Blastoderm ◽  
Gap Junction Channels ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Left And Right ◽  
The Right ◽  
Gap Junctional

Invariant patterning of left-right asymmetry during embryogenesis depends upon a cascade of inductive and repressive interactions between asymmetrically expressed genes. Different cascades of asymmetric genes distinguish the left and right sides of the embryo and are maintained by a midline barrier. As such, the left and right sides of an embryo can be viewed as distinct and autonomous fields. Here we describe a series of experiments that indicate that the initiation of these programs requires communication between the two sides of the blastoderm. When deprived of either the left or the right lateral halves of the blastoderm, embryos are incapable of patterning normal left-right gene expression at Hensen's node. Not only are both flanks required, suggesting that there is no single signaling source for LR pattern, but the blastoderm must be intact. These results are consistent with our previously proposed model in which the orientation of LR asymmetry in the frog, Xenopus laevis, depends on large-scale partitioning of LR determinants through intercellular gap junction channels (M. Levin and M. Mercola (1998) Developmental Biology 203, 90–105). Here we evaluate whether gap junctional communication is required for the LR asymmetry in the chick, where it is possible to order early events relative to the well-characterized left and right hierarchies of gene expression. Treatment of cultured chick embryos with lindane, which diminishes gap junctional communication, frequently unbiased normal LR asymmetry of Shh and Nodal gene expression, causing the normally left-sided program to be recapitulated symmetrically on the right side of the embryo. A survey of early expression of connexin mRNAs revealed that Cx43 is present throughout the blastoderm at Hamburger-Hamilton stage 2–3, prior to known asymmetric gene expression. Application of antisense oligodeoxynucleotides or blocking antibody to cultured embryos also resulted in bilateral expression of Shh and Nodal transcripts. Importantly, the node and primitive streak at these stages lack Cx43 mRNA. This result, together with the requirement for an intact blastoderm, suggests that the path of communication through gap junction channels circumvents the node and streak. We propose that left-right information is transferred unidirectionally throughout the epiblast by gap junction channels in order to pattern left-sided Shh expression at Hensen's node.

scholarly journals Gap junctions and ovarian folliculogenesis

Reproduction ◽  
2002 ◽  
pp. 613-620 ◽  
Author(s):  
GM Kidder ◽  
AA Mhawi
Keyword(s):  
Gap Junctions ◽  
Small Molecules ◽  
Cell Function ◽  
Cumulus Cells ◽  
Follicle Cells ◽  
Gap Junction Channels ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Ovarian Folliculogenesis ◽  
Gap Junctional

Gap junctions are collections of intercellular membrane channels that allow adjacent cells to share small molecules (< 1 kDa). Gap junction channels are composed of connexins, a homologous family of more than 20 proteins. In developing follicles, gap junctions couple the growing oocyte and its surrounding follicle cells into a functional syncytium. This review summarizes evidence on the expression of various connexins in developing follicles and the likely roles that some of the connexins play, on the basis of findings from gene targeting experiments in mice. Gap junctions between cumulus cells contain predominantly connexin43, and this connexin has also been detected using immunoelectron microscopy in a small minority of gap junctions at the oocyte surface. The importance of connexin43 for granulosa cell function is demonstrated by the fact that follicles lacking this connexin arrest in early preantral stages and produce incompetent oocytes. Connexin37 appears to be the only connexin contributed by oocytes to the gap junctions coupling them with granulosa cells, and loss of this connexin interferes with the development of antral follicles. The expression of multiple connexins in developing follicles is thus likely to reflect the multiple functions served by gap junctional communication in folliculogenesis.

Manipulation of gap junctional communication during compaction of the mouse early embryo

Development ◽  
1986 ◽  
Vol 91 (1) ◽  
pp. 283-296
Author(s):  
Harry Goodall
Keyword(s):  
Cell Adhesion ◽  
Early Embryo ◽  
Embryonal Carcinoma Cell ◽  
Cell Coupling ◽  
Calcium Dependent ◽  
Gap Junctional Communication ◽  
Embryonal Carcinoma Cell Line ◽  
Junctional Communication ◽  
Junctional Coupling ◽  
Gap Junctional

Three treatments that prevent cell flattening during compaction of the mouse preimplantation embryo were assessed for their effects on the onset of gap junctional communication. Medium low in calcium (LCM) and an antiserum to an embryonal carcinoma cell line (anti-EC; Johnson et al. 1979) both prevented the establishment of coupling between blastomeres of the 8-cell embryo as assessed by transmission of carboxyfluorescein or by ionic coupling. Since neither of these agents prevents the contact-mediated induction of cell polarity that occurs at this stage, it is concluded that the induction of this process is not signalled via gap junctions. A monoclonal antibody (ECCD-1; Yoshida-Noro, Suzuki & Takeichi, 1984), that recognizes more specific components of the calcium-dependent cell adhesion system, failed to prevent the onset of junctional coupling. This suggests that the onset of junctional coupling is not dependent upon extensive cell apposition and that the requirement for extracellular Ca2+ resides at a level other than that of cell adhesion. Moreover, neither LCM nor anti-EC could reverse cell coupling once it had become established despite their complete reversal of cell flattening.

Normal development of preimplantation mouse embryos deficient in gap junctional coupling

1997 ◽  
Vol 110 (15) ◽  
pp. 1751-1758 ◽  
Author(s):  
P.A. De Sousa ◽  
S.C. Juneja ◽  
S. Caveney ◽  
F.D. Houghton ◽  
T.C. Davies ◽  
...  
Keyword(s):  
Gap Junction ◽  
Preimplantation Development ◽  
Null Mutation ◽  
Dye Coupling ◽  
Permeability Characteristics ◽  
Gap Junction Channels ◽  
Junctional Coupling ◽  
Preimplantation Mouse ◽  
Gap Junctional ◽  
Gap Junctional Coupling

The connexin multigene family (13 characterized members in rodents) encodes the subunits of gap junction channels. Gap junctional intercellular coupling, established during compaction of the preimplantation mouse embryo, is assumed to be necessary for development of the blastocyst. One member of the connexin family, connexin43, has been shown to contribute to the gap junctions that form during compaction, yet embryos homozygous for a connexin43 null mutation develop normally, at least until implantation. We show that this can be explained by contributions from one or more additional connexin genes that are normally expressed along with connexin43 in preimplantation development. Immunogold electron microscopy confirmed that roughly 30% of gap junctions in compacted morulae contain little or no connexin43 and therefore are likely to be composed of another connexin(s). Confocal immunofluorescence microscopy was then used to demonstrate that connexin45 is also assembled into membrane plaques, beginning at the time of compaction. Correspondingly, embryos homozygous for the connexin43 null mutation were found to retain the capacity for cell-to-cell transfer of fluorescent dye (dye coupling), but at a severely reduced level and with altered permeability characteristics. Whereas mutant morulae showed no evidence of dye coupling when tested with 6-carboxyfluorescein, dye coupling could be demonstrated using 2′,7′-dichlorofluorescein, revealing permeability characteristics previously established for connexin45 channels. We conclude that preimplantation development in the mouse can proceed normally even though both the extent and nature of gap junctional coupling have been perturbed. Despite the distinctive properties of connexin43 channels, their role in preimplantation development can be fulfilled by one or more other types of gap junction channels.

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