Assembly of gap junctions during amphibian neurulation

Area of Science:

• Developmental Biology
• Cell Biology
• Neuroscience

Background:

• Gap junctions are crucial for intercellular communication during development.
• Neurulation, the formation of the neural tube, involves dynamic cell rearrangements and junctional modifications.

Purpose of the Study:

• To elucidate the sequential steps of gap junction assembly during neurulation in Rana pipiens.
• To investigate the relationship between tight junctions and gap junction formation.

Main Methods:

• Sequential thin-section electron microscopy.
• Tracer studies using K-pyroantimonate, lanthanum, ruthenium red, and horseradish peroxidase.
• Freeze-fracture electron microscopy.

Main Results:

• Tight junctions (zonulae occludentes) fragment during neural groove deepening and become permeable.
• Gap junctions form at sites where tight junctional remnants intersect, with particles aggregating.
• Macular gap junctions replace tight junctional elements during neural fold closure.
• Independent formation of gap junctions occurs in basal regions, characterized by particle cluster assembly.

Conclusions:

• Gap junction assembly during neurulation involves the fragmentation and disappearance of tight junctions.
• The process suggests translational movement of particles within a fluid plasma membrane.
• Gap junctions can form independently of pre-existing structures in specific cellular domains.