Electron microscopy of the mouse central nervous system.

The high degree of similarity between mouse and human physiology and genomes makes mice the animal model of choice to study the functions and dysfunctions of the central nervous system (CNS). The considerable knowledge accumulated in the past decades and the steadily growing number of genetically modified mouse lines allow for the increasingly accurate understanding of biological circuits. Electron microscopy (EM) contributes to unravel the biology of neuronal networks and the myelinating glia by allowing a fine morphological scrutiny of the nervous tissue. We provide detailed descriptions of the conventional processing as well as cryopreparation methods such as high-pressure freezing (HPF), freeze-substitution (FS), and SDS-digested freeze-fracture replica labeling (SDS-FRL) on selected CNS regions such as the retina, optic nerve, and cerebellum. By taking example of the ribbon synapse in the retina and myelinated retinal ganglion cell axons of the optic nerve, we discuss the advantages and drawbacks of these methods in a comparative way.