Gap junctional coupling in lenses from alpha(8) connexin knockout mice

Area of Science:

• Ophthalmology
• Cell Biology
• Biophysics

Background:

• Lens fiber cells utilize gap junctions for communication.
• These gap junctions are primarily composed of alpha(3) (Cx46) and alpha(8) (Cx50) connexins.
• Understanding the distinct roles of these connexins is crucial for lens physiology.

Purpose of the Study:

• To investigate the specific functions of alpha(3) and alpha(8) connexins in mouse lens fiber cells.
• To determine the contribution of each connexin isoform to junctional conductance and its pH sensitivity.
• To elucidate the roles of these connexins in maintaining lens transparency and communication.

Main Methods:

• Genetic engineering of mice to create knockout models lacking either alpha(3) or alpha(8) connexin.
• Intracellular impedance studies to measure junctional conductance in lens fiber cells.
• Analysis of connexin contribution in distinct lens domains (differentiating fibers and mature fibers) and response to cytoplasmic pH changes.

Main Results:

• Alpha(3) connexin is solely responsible for communication in mature fiber cells (MF).
• Alpha(8) connexin is essential for the pH-sensitive gating of gap junctions in differentiating fiber cells (DF).
• Both connexins contribute to DF coupling, with alpha(3) providing approximately half the conductance.

Conclusions:

• Alpha(3) connexin ensures long-term communication in mature lens fiber cells.
• Alpha(8) connexin regulates the pH-dependent closure of gap junctions in differentiating fiber cells.
• Loss of either connexin leads to lens opacity, highlighting their critical importance for vision.