A Correlative Immunoconfocal and Electron Microscopic Study of Gap Junctions in Interlocking Domains of the Lens

Ball-and-sockets and protrusions are specialized interlocking membrane domains between fiber cells of the avascular lenses in all species studied [1, 2]. Although both domains are similar in their shape, surface morphology and are highly enriched with aquaporin-0 water channel protein, our previous studies reveal that ball-and-sockets and protrusions possess important structural and functional differences during fiber cell differentiation and maturation [2, 3]. Specifically, gap junctions are regularly associated with all ball-and-sockets examined in metabolically active young cortical fibers, but not with protrusions. Also, while many ball-and-sockets are distributed primarily on the broad and narrow surfaces of young hexagonal fiber cells, numerous protrusions are located along the angles of the cells throughout the entire lens. It was proposed that the unique ball-and-socket-associated gap junctions may significantly facilitate cell-to-cell communication between young cortical fiber cells since they often protrude deeply into neighboring cells to increase membrane surface areas [2]. In contrast, protrusions are shown to play important interlocking role in maintaining fiber-to-fiber stability during visual accommodation [3].