Changes in lens connexin expression lead to increased gap junctional voltage dependence and conductance

1995 ◽  
Vol 269 (3) ◽  
pp. C590-C600 ◽  
Author(s):  
P. J. Donaldson ◽  
Y. Dong ◽  
M. Roos ◽  
C. Green ◽  
D. A. Goodenough ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Gap Junction ◽  
Voltage Dependence ◽  
Expression Patterns ◽  
Fiber Cell ◽  
Lens Epithelial Cells ◽  
Connexin Expression ◽  
Fiber Cells ◽  
Gap Junctional ◽  
Mouse Lens

The differentiation of mouse lens epithelial cells into fiber cells is a useful model for studying the changes of the electrical properties of gap junction (cell-to-cell) channels that are induced by an alteration in connexin expression patterns. In this model, cuboidal lens epithelial cells differentiate into elongated fiber cells, and the expression of connexin43 (Cx43) in the epithelial cells is replaced with the production of high levels of Cx50 and Cx46 in the fiber cells. We now report a new procedure to isolate mouse lens fiber cell pairs suitable for double whole cell patch-clamp analysis. Analysis was also performed for fiberlike cell pairs differentiated from epithelial cells in culture. Voltage dependence and unitary conductance of fiber cell gap junction channels were determined and compared with the corresponding values previously measured for the channels joining lens epithelial cells and for lens connexin channels formed in Xenopus oocyte pairs. Our results support a differentiation-induced shift toward stronger gap junctional voltage dependence and larger unitary conductances in the fiber cells. Our data further reflect a balanced functional contribution of Cx50 and Cx46 in the fiber cell-to-cell channels rather than a predominance of a single connexin.

Mitomycin C-Induced Cell Death in Mouse Lens Epithelial Cells

2002 ◽  
Vol 34 (4) ◽  
pp. 213-219 ◽  
Author(s):  
Hyun-Kyung Park ◽  
Kwang-Won Lee ◽  
Jun-Sub Choi ◽  
Choun-Ki Joo
Keyword(s):  
Cell Death ◽  
Epithelial Cells ◽  
Mitomycin C ◽  
Lens Epithelial Cells ◽  
Mouse Lens

Effect of exogenous stress on the tissue-cultured mouse lens epithelial cells

2002 ◽  
Vol 86 (2) ◽  
pp. 302-306 ◽  
Author(s):  
Mihir Bagchi ◽  
Malkhan Katar ◽  
H. Maisel
Keyword(s):  
Epithelial Cells ◽  
Lens Epithelial Cells ◽  
Exogenous Stress ◽  
Mouse Lens

scholarly journals Identification of Differential Gene Expression Pattern in Lens Epithelial Cells Derived from Cataractous and Noncataractous Lenses of Shumiya Cataract Rat

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Hidetoshi Ishida ◽  
Teppei Shibata ◽  
Yuka Nakamura ◽  
Yasuhito Ishigaki ◽  
Dhirendra P. Singh ◽  
...  
Keyword(s):  
Gene Expression ◽  
Epithelial Cells ◽  
Expression Patterns ◽  
Synergetic Effect ◽  
Gene Expression Pattern ◽  
Lens Opacity ◽  
Lens Epithelial Cells ◽  
Lens Fiber ◽  
Molecular Events ◽  
Old Rats

The Shumiya cataract rat (SCR) is a model for hereditary cataract. Two-thirds of these rats develop lens opacity within 10-11 weeks. Onset of cataract is attributed to the synergetic effect of lanosterol synthase (Lss) and farnesyl-diphosphate farnesyltransferase 1 (Fdft1) mutant alleles that lead to cholesterol deficiency in the lenses, which in turn adversely affects lens biology including the growth and differentiation of lens epithelial cells (LECs). Nevertheless, the molecular events and changes in gene expression associated with the onset of lens opacity in SCR are poorly understood. In the present study, a microarray-based approach was employed to analyze comparative gene expression changes in LECs isolated from the precataractous and cataractous stages of lenses of 5-week-old SCRs. The changes in gene expression observed in microarray results in the LECs were further validated using real-time reverse transcribed quantitative PCR (RT-qPCR) in 5-, 8-, and 10-week-old SCRs. A mild posterior and cortical opacity was observed in 5-week-old rats. Expressions of approximately 100 genes, including the major intrinsic protein of the lens fiber (Mip and Aquaporin 0), deoxyribonuclease II beta (Dnase2B), heat shock protein B1 (HspB1), and crystallin γ (γCry) B, C, and F, were found to be significantly downregulated (0.07-0.5-fold) in rat LECs derived from cataract lenses compared to that in noncataractous lenses (control). Thus, our study was aimed at identifying the gene expression patterns during cataract formation in SCRs, which may be responsible for cataractogenesis in SCR. We proposed that cataracts in SCR are associated with reduced expression of these lens genes that have been reported to be related with lens fiber differentiation. Our findings may have wider implications in understanding the effect of cholesterol deficiency and the role of cholesterol-lowering therapeutics on cataractogenesis.

Effects of melatonin on ionic currents in cultured ocular tissues

1999 ◽  
Vol 276 (4) ◽  
pp. C923-C929 ◽  
Author(s):  
Adam Rich ◽  
Gianrico Farrugia ◽  
James L. Rae
Keyword(s):  
Epithelial Cells ◽  
Trabecular Meshwork ◽  
Cell Voltage ◽  
Ionic Currents ◽  
Lens Epithelial Cells ◽  
Delayed Rectifier ◽  
Inactivation Kinetics ◽  
Epithelial Cell Line ◽  
Voltage Dependent ◽  
Mouse Lens

The effects of melatonin on ionic conductances in a cultured mouse lens epithelial cell line (α-TN4) and in cultured human trabecular meshwork (HTM) cells were measured using the amphotericin perforated patch whole cell voltage-clamp technique. Melatonin stimulated a voltage-dependent Na+-selective current in lens epithelial cells and trabecular meshwork cells. The effects of melatonin were observed at 50 pM and were maximal at 100 μM. Melatonin enhanced activation and inactivation kinetics, but no change was observed in the voltage dependence of activation. The results are consistent with an increase in the total number of ion channels available for activation by membrane depolarization. Melatonin was also found to stimulate a K+-selective current at high doses (1 mM). Melatonin did not affect the inwardly rectifying K+ current or the delayed rectifier type K+ current that has been described in cultured mouse lens epithelial cells. The results show that melatonin specifically stimulated the TTX-insensitive voltage-dependent Na+ current by an apparently novel mechanism.

scholarly journals Connexin Mutants Compromise the Lens Circulation and Cause Cataracts through Biomineralization

2020 ◽  
Vol 21 (16) ◽  
pp. 5822
Author(s):  
Viviana M. Berthoud ◽  
Junyuan Gao ◽  
Peter J. Minogue ◽  
Oscar Jara ◽  
Richard T. Mathias ◽  
...  
Keyword(s):  
Gap Junction ◽  
Lens Fiber ◽  
Lens Fiber Cell ◽  
Alizarin Red ◽  
General Process ◽  
Fiber Cells ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Gap Junctional ◽  
Junction Proteins

Gap junction-mediated intercellular communication facilitates the circulation of ions, small molecules, and metabolites in the avascular eye lens. Mutants of the lens fiber cell gap junction proteins, connexin46 (Cx46) and connexin50 (Cx50), cause cataracts in people and in mice. Studies in mouse models have begun to elucidate the mechanisms by which these mutants lead to cataracts. The expression of the dominant mutants causes severe decreases in connexin levels, reducing the gap junctional communication between lens fiber cells and compromising the lens circulation. The impairment of the lens circulation results in several changes, including the accumulation of Ca2+ in central lens regions, leading to the formation of precipitates that stain with Alizarin red. The cataract morphology and the distribution of Alizarin red-stained material are similar, suggesting that the cataracts result from biomineralization within the organ. In this review, we suggest that this may be a general process for the formation of cataracts of different etiologies.

Ca2+ regulation of gap junctional coupling in lens epithelial cells

2001 ◽  
Vol 281 (3) ◽  
pp. C972-C981 ◽  
Author(s):  
Grant C. Churchill ◽  
Monica M. Lurtz ◽  
Charles F. Louis
Keyword(s):  
Epithelial Cells ◽  
Gap Junctions ◽  
Direct Action ◽  
Hill Coefficient ◽  
Lens Epithelial Cells ◽  
Alexa Fluor ◽  
Agonist Stimulation ◽  
Junctional Coupling ◽  
Gap Junctional ◽  
Gap Junctional Coupling

The quantitative effects of Ca2+signaling on gap junctional coupling in lens epithelial cells have been determined using either the spread of Mn2+ that is imaged by its ability to quench the fluorescence of fura 2 or the spread of the fluorescent dye Alexa Fluor 594. Gap junctional coupling was unaffected by a mechanically stimulated cell-to-cell Ca2+wave. Furthermore, when cytosolic Ca2+ concentration (Ca[Formula: see text]) increased after the addition of the agonist ATP, coupling was unaffected during the period that Ca[Formula: see text] was maximal. However, coupling decreased transiently ∼5–10 min after agonist addition when Ca[Formula: see text] returned to resting levels, indicating that this transient decrease in coupling was unlikely due to a direct action of Ca[Formula: see text] on gap junctions. An increase in Ca[Formula: see text] mediated by the ionophore ionomycin that was sustained for several minutes resulted in a more rapid and sustained decrease in coupling (IC50 ∼300 nM Ca2+, Hill coefficient of 4), indicating that an increase in Ca[Formula: see text]alone could regulate gap junctions. Thus Ca[Formula: see text]increases that occurred during agonist stimulation and cell-to-cell Ca2+ waves were too transient to mediate a sustained uncoupling of lens epithelial cells.

Cell kinetic status of mouse lens epithelial cells lacking αA- and αB-crystallin

2004 ◽  
Vol 265 (1/2) ◽  
pp. 115-122 ◽  
Author(s):  
Fang Bai ◽  
Jinghua Xi ◽  
Ryuji Higashikubo ◽  
Usha P. Andley
Keyword(s):  
Epithelial Cells ◽  
Lens Epithelial Cells ◽  
Cell Kinetic ◽  
Αb Crystallin ◽  
Mouse Lens

scholarly journals Gating characteristics of a steeply voltage-dependent gap junction channel in rat Schwann cells.

1993 ◽  
Vol 102 (5) ◽  
pp. 925-946 ◽  
Author(s):  
M Chanson ◽  
K J Chandross ◽  
M B Rook ◽  
J A Kessler ◽  
D C Spray
Keyword(s):  
Steady State ◽  
Gap Junction ◽  
Schwann Cells ◽  
Voltage Dependence ◽  
Single Channel ◽  
Neonatal Rat ◽  
Order Kinetic ◽  
Patch Clamp Technique ◽  
Gap Junctional ◽  
Closing Rate

The gating properties of macroscopic and microscopic gap junctional currents were compared by applying the dual whole cell patch clamp technique to pairs of neonatal rat Schwann cells. In response to transjunctional voltage pulses (Vj), macroscopic gap junctional currents decayed exponentially with time constants ranging from < 1 to < 10 s before reaching steady-state levels. The relationship between normalized steady-state junctional conductance (Gss) and (Vj) was well described by a Boltzmann relationship with e-fold decay per 10.4 mV, representing an equivalent gating charge of 2.4. At Vj > 60 mV, Gss was virtually zero, a property that is unique among the gap junctions characterized to date. Determination of opening and closing rate constants for this process indicated that the voltage dependence of macroscopic conductance was governed predominantly by the closing rate constant. In 78% of the experiments, a single population of unitary junctional currents was detected corresponding to an unitary channel conductance of approximately 40 pS. The presence of only a limited number of junctional channels with identical unitary conductances made it possible to analyze their kinetics at the single channel level. Gating at the single channel level was further studied using a stochastic model to determine the open probability (Po) of individual channels in a multiple channel preparation. Po decreased with increasing Vj following a Boltzmann relationship similar to that describing the macroscopic Gss voltage dependence. These results indicate that, for Vj of a single polarity, the gating of the 40 pS gap junction channels expressed by Schwann cells can be described by a first order kinetic model of channel transitions between open and closed states.

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