A Historical and Evolutionary View of Tight Junctions

Abstract

The essential functions of a polarized epithelium are to separate the spaces between tissues and regulate the exchange of materials between them, functioning as an interface with the external environment. Tight junctions (TJ) are the anatomical structures responsible for creating this barrier. These cell junctions are regulated and selective, and vary depending on the tissue in which they are found. However, for many years it was considered that TJ were at the border of cells and their function was limited to blocking the passage of substances between cells, so it is understandable that they received names as “terminal bar.” It was not until the arrival of electron microscopy that it was possible to resolve that these “terminal bars” are, in fact, a complex of cell junctions. In this chapter, we will see the history and how the concept of tight junctions evolved. We will discuss the main functions of this type of cellular contacts and the experiments that allowed to study their structure and biology.