Transmission Electron Microscopy in the Study of Autophagy: Seeing is Not Always Believing

Abstract

Abstract Autophagy is a catabolic process involved in the maintenance of cellular homeostasis in which macromolecules and cytoplasmic organelles are sequestered within double membrane vesicles named autophagosomes, and delivered to lysosomes for fusion and degradation. There are several methods for monitoring autophagy including transmission electron microscopy (TEM), and the detection of molecules such as the autophagy-related 8vproteins, sequestosome-1 and the microtubule-associated protein 1 light chain 3. The use of these methods has overtaken TEM as the main procedure to study autophagy. Despite this, TEM is still a reliable method to detect autophagic cells due to the high resolution of electron microscopy images, which provide key information on the ultrastructural details of autophagic compartments that are not obtained by any other procedures. However, caution should be taken when electron micrographs of presumably autophagic cells are analyzed, as several diagnostic errors have been reported. It is essential to avoid mistakes when identifying autophagic compartments in order to get the most accurate data. This is especially important when results among laboratories are compared. The goal of this review is to show some mistakes in the identification of autophagic neuroblasts in the rat cerebellar external granular layer after hydroxyurea exposure. It is my hope that the ultrastructural micrographs shown here will be a reference for researchers involved in the study of autophagy.