Tight Junctions in Arthropod Tissues

Abstract

This chapter describes the tight junctions in the arthropod tissues. The tight junctional particles are aligned in ridges shared by fusion of the plasma membranes of adjacent cells, thereby leading to closure of the intercellular space. Tight junctions or zonulae occludentes provide a seal among the epithelial cells, thereby creating a diffusion barrier to the intercellular movement of ions and molecules. The en face views of membranes are revealed, and then the intramembranous patterns assumed by junctional particles may be studied using the freeze-cleaved replicas. The plasma membrane of vertebrate cells is divided by circumferential junctions that establish and maintain cellular polarity. Tight tight junctions have a complex reticulum of tight junctional ridges, while leaky tight junctions have fewer strands and a less complex network. In the arthropods, which exhibit many physiological differences from vertebrate species, there has been a search for tight junctions in tissues known to possess permeability barriers. Analysis of the development of tight junctions can occur in vivo only during embryonic and very early hatchling stages in arthropods or possibly during the regeneration of injured tissues. The chapter also summarizes the features that various junctions share with tight junctions, together with the respects in which they differ.