Ablation of gap junctional communication in hepatocytes of transgenic mice does not lead to disrupted cellular homeostasis or increased spontaneous tumourigenesis

2006 ◽  
Vol 85 (8) ◽  
pp. 717-728 ◽  
Author(s):  
Thomas Ott ◽  
Melanie Jokwitz ◽  
Diana Lenhard ◽  
Alessandro Romualdi ◽  
Frank Dombrowski ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
Cellular Homeostasis ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Gap Junctional

Heart and neural tube defects in transgenic mice overexpressing the Cx43 gap junction gene

Development ◽  
1997 ◽  
Vol 124 (7) ◽  
pp. 1281-1292 ◽  
Author(s):  
J.L. Ewart ◽  
M.F. Cohen ◽  
R.A. Meyer ◽  
G.Y. Huang ◽  
A. Wessels ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
Neural Crest ◽  
Gap Junction ◽  
Neural Tube ◽  
Neural Tube Defects ◽  
Transgene Expression ◽  
Cell Populations ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Gap Junctional

Transgenic mice were generated containing a cytomegaloviral promoter driven construct (CMV43) expressing the gap junction polylpeptide connexin 43. RNA and protein analysis confirmed that the transgene was being expressed. In situ hybridization analysis of embryo sections revealed that transgene expression was targeted to the dorsal neural tube and in subpopulations of neural crest cells. This expression pattern was identical to that seen in transgenic mice harboring other constructs driven by the cytomegaloviral promoter (Kothary, R., Barton, S. C., Franz, T., Norris, M. L., Hettle, S. and Surani, M. A. H. (1991) Mech. Develop. 35, 25–31; Koedood, M., Fitchel, A., Meier, P. and Mitchell, P. (1995) J. Virol. 69, 2194–2207), and corresponded to a subset of the endogenous Cx43 expression domains. Significantly, dye injection studies showed that transgene expression resulted in an increase in gap junctional communication. Though viable and fertile, these transgenic mice exhibited reduced postnatal viability. Examination of embryos at various stages of development revealed developmental perturbations consisting of cranial neural tube defects (NTD) and heart malformations. Interestingly, breeding of the CMV43 transgene into the Cx43 knockout mice extended postnatal viability of mice homozygote for the Cx43 knockout allele, indicating that the CMV43 trangsene may partially complement the Cx43 deletion. Both the Cx43 knockout and the CMV43 transgenic mice exhibit heart defects associated with malformations in the conotruncus, a region of the heart in which neural crest derivatives are known to have important roles during development. Together with our results indicating neural-crest-specific expression of the transgene in our CMV-based constructs, these observations strongly suggest a role for Cx43-mediated gap junctional communication in neural crest development. Furthermore, these observations indicate that the precise level of Cx43 function may be of critical importance in downstream events involving these migratory cell populations. As such, the CMV43 mouse may represent a powerful new model system for examining the role of extracardiac cell populations in cardiac morphogenesis and other developmental processes.

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.

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