scholarly journals Targeted Ablation of Connexin50 in Mice Results in Microphthalmia and Zonular Pulverulent Cataracts

1998 ◽  
Vol 143 (3) ◽  
pp. 815-825 ◽  
Author(s):  
Thomas W. White ◽  
Daniel A. Goodenough ◽  
David L. Paul
Keyword(s):  
Cell Types ◽  
Targeted Deletion ◽  
Gap Junctional Communication ◽  
Eye Growth ◽  
Lens Fibers ◽  
Lens Transparency ◽  
Junctional Communication ◽  
Epithelial Junctions ◽  
Gap Junctional ◽  
Intercellular Channel

In the ocular lens, gap junctional communication is a key component of homeostatic mechanisms preventing cataract formation. Gap junctions in rodent lens fibers contain two known intercellular channel-forming proteins, connexin50 (Cx50) and Cx46. Since targeted ablation of Cx46 has been shown to cause senile-type nuclear opacities, it appears that Cx50 alone cannot meet homeostatic requirements. To determine if lens pathology arises from a reduction in levels of communication or the loss of a connexin-specific function, we have generated mice with a targeted deletion of the Cx50 gene. Cx50-null mice exhibited microphthalmia and nuclear cataracts. At postnatal day 14 (P14), Cx50-knockout eyes weighed 32% less than controls, whereas lens mass was reduced by 46%. Cx50-knockout lenses also developed zonular pulverulent cataracts, and lens abnormalities were detected by P7. Deletion of Cx50 did not alter the amounts or distributions of Cx46 or Cx43, a component of lens epithelial junctions. In addition, intercellular passage of tracers revealed the persistence of communication between all cell types in the Cx50-knockout lens. These results demonstrate that Cx50 is required not only for maintenance of lens transparency but also for normal eye growth. Furthermore, these data indicate that unique functional properties of both Cx46 and Cx50 are required for proper lens development.

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.

scholarly journals Dynamics of connexin43 phosphorylation in pp60v-src-transformed cells

1993 ◽  
Vol 295 (3) ◽  
pp. 735-742 ◽  
Author(s):  
G S Goldberg ◽  
A F Lau
Keyword(s):  
Cell Types ◽  
Serine Phosphorylation ◽  
Transformed Cells ◽  
Phosphoamino Acid ◽  
Gap Junctional Communication ◽  
Data Support ◽  
Junctional Communication ◽  
Gap Junctional

Connexin43 phosphorylation was analysed in non-transformed and pp60v-src-transformed Rat-1 fibroblasts. Connexin43 appeared to be the primary connexin expressed in these cells. Although gap-junctional communication was disrupted in pp60v-src-transformed cells, they contained more connexin43 protein and RNA than their non-transformed counterpart. Connexin43 was phosphorylated within minutes of its synthesis in both cell types and appeared to be degraded while in the phosphorylated state. Phosphopeptide and phosphoamino acid analyses suggested that connexin43 in both cell types contained at least five fragments with serine phosphorylation. The major difference in connexin43 phosphorylation between the pp60v-src-transformed and non-transformed cells was that, whereas approx. 70% of the phosphorylated connexin43 in the former contained phosphotyrosine, this phosphoamino acid was not detected in connexin43 isolated from the latter cells. These data support the hypothesis that phosphorylation of connexin43 on tyrosine is critical for the blockade of gap-junctional communication which occurs concomitantly with transformation by the pp60v-src oncogene.

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.

Syncytial organization of cultured rat mesangial cells

1991 ◽  
Vol 260 (6) ◽  
pp. F848-F855 ◽  
Author(s):  
K. Iijima ◽  
L. C. Moore ◽  
M. S. Goligorsky
Keyword(s):  
Calcium Channels ◽  
Mesangial Cells ◽  
Calcium Waves ◽  
Oxygen Intermediates ◽  
Voltage Gated ◽  
Fura 2 ◽  
Gap Junctional Communication ◽  
Voltage Gated Calcium Channels ◽  
Junctional Communication ◽  
Gap Junctional

To investigate communication competence of cultured rat mesangial cells, Lucifer yellow transfer was studied using microinjection and scrape-loading techniques. Both methods yielded results indicating considerable gap junctional communication between cultured mesangial cells. Gap junctional communication between mesangial cells was upregulated by adenosine 3',5'-cyclic monophosphate (cAMP). Conversely, cell-to-cell communication was attenuated by exposure to the tumor promoter phorbol myristate acetate, the Ca ionophore ionomycin, reduced oxygen intermediates, and cell acidification. Expression of voltage gated calcium channels by mesangial cells was studied microspectrofluorimetrically using fura-2 fluorescence. KCl-induced depolarization, BAY-K 8644, and readdition of calcium to Ca-free depolarizing medium all produced a nifedipine-inhibitable increase in cytosolic calcium concentration. The existence of voltage-gated calcium channels in communication-competent cells suggests the possibility of propagation of depolarizing signals across the syncytium. This was studied by microapplication of KCl to the microenvironment of a single cell and monitoring fura-2 fluorescence in remote cells. This maneuver resulted in propagating calcium waves in communication-competent monolayers; calcium waves could not be evoked in monolayers exposed to an alkanol-type gap junction uncoupler, octanol. It is concluded that cultured rat mesangial cells form a syncytium capable of propagating calcium transients from a single depolarized cell to its coupled neighbors.

scholarly journals Hyperglycaemia and Diabetes Impair Gap Junctional Communication among Astrocytes

ASN NEURO ◽  
2010 ◽  
Vol 2 (2) ◽  
pp. AN20090048 ◽  
Author(s):  
Gautam K Gandhi ◽  
Kelly K Ball ◽  
Nancy F Cruz ◽  
Gerald A Dienel
Keyword(s):  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Gap Junctional
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