Characterizing the nanoscale organization of the actin/spectrin membrane-associated periodic skeleton in rodent nerves using 3d-storm microscopy

NG GAZAL; AM SZALAI; G ESCALANTE; LF LOPEZ; E GOROSTIZA; FD STEFANI; N UNSAIN

Santa Cruz

Congreso; IUBMB EMBO Workshop Emerging Concepts of the Neuronal Cytoskeleton. Santa Cruz, Chile; 2023

EMBO

It has been recently discovered that axons and dendrites possess a particular arrangement of theircortical skeleton, referred to as the Membrane-associated actin/spectrin Periodic Skeleton (MPS). TheMPS is a periodic protein structure consisting of actin “rings” located transversely to the axon andseparated every 190 nm by α/β-spectrin tetramers “spacers”. The MPS can only be described usingsuper-resolution (SR) microscopy approaches, since its spatial features lay below the diffraction limit oflight. Most of published studies describe the MPS in vitro (in cultured neurons) and the preciseorganization of the spectrin “spacers” within each period has not been investigated in detail. We havethus begun a project to shed light into this in rodent nerve sections, that is, in situ, using 3D-STORMSR microscopy. We have first established a protocol for the examination of mouse optic and sciaticnerves preparations suitable for them by 3D-STORM. We have preliminary evidence for a model inwhich spectrin tetramers are arranged in each period at regular and fixed distances irrespective ofaxonal identity. In this sense, the number of spectrin tetramers scales with axon diameter. We have alsoevidenced that the localization of a spectrin tetramer in one period is correlated with the position oftetramers in neighboring periods, suggesting a structural constrain for their interaction with actin rings.We believe that describing the MPS at the nanometer scale in situ will provide meaningful insights intoits possible structural components and its function.