Myelin vesicles: What we know and what we do not know

Abstract

In the following review, we address difficulties that have arisen when attempting to convert the myelin multilayers into vesicles. The emphasis is on CNS myelin of adult mammals although both central nervous system (CNS) and peripheral nervous system (PNS) myelin are considered. The ability to prepare vesicle of myelin membrane has yet not been feasible. We hope to clarify some aspect of this problem and offer some possible approaches. Special attention is paid to myelin swelling phenomena because these indicate ways in which the myelin multilayer can break down. Images of isolated myelin are reviewed with special attention to the ways in which the multilayer actually breaks down. Attempts at reproducing a procedure for vesiculating myelin are summarized, and a critique is given to account for the inability to reproduce the published results. Finally, novel approaches for vesiculating myelin are proposed, which are based on well-characterized swelling phenomena.

Equivalent Aqueous Phase Modulation of Domain Segregation in Myelin Monolayers and Bilayer Vesicles

“…The myelin monolayer on water shows homogeneity at high surface pressure, similar to our isolated myelin vesicles, showing a single spacing (155 Å ) consistent with the 150-160 Å found in nerve CNS myelin in physiological conditions (1,13), and the 150 Å found in water as well in isolated CNS myelin in water (148-151 Å ) (26). This value is roughly twice the value found for reconstituted lipid/protein bilayers and is due to the double bilayer asymmetric cell unit of myelin, which, in turn, is due to the bilayer asymmetry.…”

“…An intermediate system between myelin in vivo and its monolayer is represented by the isolated myelin in the form of multi-or oligolamellar membranes, a material from which the monolayer can be prepared (7). Knowledge of the vesicle structure is relevant (13) because they constitute the starting material for many biochemical and topological studies. It has been established that the isolated CNS myelin membrane structure does not differ significantly from that of nerve myelin in vivo (14).…”

TREM2 sustains microglial expansion during aging and response to demyelination

“…A monoclonal antimurine TREM2 antibody (13) was used to block TREM2 signaling. To extract myelin lipids, myelin vesicles were generated as previously described (57). Briefly, brain from a WT mouse was homogenized with a Dounce homogenizer and resuspended in 0.25 M sucrose solution, followed by centrifugation onto a sucrose gradient.…”

Preparation of Giant Myelin Vesicles and Proteoliposomes to Register Ionic Channels

“…, and in periaxolemmal myelin (Sapirstein et al, 1992;Cherksey et a!., 1994), these have not been observed so far in isolated total myelin membrane. The presence of ionic channels in the myelin membrane has been investigated in several studies (Morell et al, 1990;Sedzik and Blaurock, 1995) and is supported by morphological data (Livingston et al, 1973) and by the ionophoric properties of certain myelin proteins (Cózar et al, 1987). Thus, myelin proteolipids have been shown to enable voltage-dependent conductances in lipid bilayers (Ting-Beall et a!., 1979;Helynck et al, 1983).…”

“…required to allow access of patch-clamp micropipettes. Although some authors have proposed methods to obtain myelin vesicles, none has proved to be completely successful (Sedzik and Blaurock, 1995).…”