Electron microscopy of myelin: Structure preservation by high-pressure freezing

•Novel techniques improve visualization of myelin biogenesis, structure and pathology.•High-pressure freezing preserves myelin structure in terrestrial and aquatic species.•Electron microscopy is independent of sequence data, antibodies or transgenic lines.•Model species of myelin evolution can be analyzed using high-pressure freezing and EM.

Electron microscopic visualization of nervous tissue morphology is crucial when aiming to understand the biogenesis and structure of myelin in healthy and pathological conditions. However, accurate interpretation of electron micrographs requires excellent tissue preservation. In this short review we discuss the recent utilization of tissue fixation by high-pressure freezing and freeze-substitution, which now supplements aldehyde fixation in the preparation of samples for electron microscopy of myelin. Cryofixation has proven well suited to yield both, improved contrast and excellent preservation of structural detail of the axon/myelin-unit in healthy and mutant mice and can also be applied to other model organisms, including aquatic species.This article is part of a Special Issue entitled SI: Myelin Evolution.