Membrane Cholesterol Is a Critical Determinant for Hippocampal Neuronal Polarity.

Mini Jose,Chaitra Channakeshava,Aiswarya Sivanand

doi:10.3389/fnmol.2021.746211

Mini Jose, Chaitra Channakeshava + Show 1 more

Open Access

https://doi.org/10.3389/fnmol.2021.746211

Copy DOI

Abstract

Maintaining a normal cholesterol balance is crucial for the functioning of a healthy brain. Dysregulation in cholesterol metabolism and homeostasis in the brain have been correlated to various neurological disorders. The majority of previous studies in primary cultures focus on the role of cholesterol balance in neuronal development after polarity has been established. Here we have investigated how transient alteration of membrane lipids, specifically cholesterol, affects neuronal development and polarity in developing hippocampal neurons prior to polarity establishment, soon after initiation of neurite outgrowth. We observed that temporary cholesterol perturbation affects axonal and dendritic development differentially in an opposing manner. Transient membrane cholesterol deficiency increased neuronal population with a single neurite, simultaneously generating a second population of neurons with supernumerary axons. Brief replenishment of cholesterol immediately after cholesterol sequestering rescued neuronal development defects and restored polarity. The results showed a small window of cholesterol concentration to be complementing neurite outgrowth, polarity reestablishment, and in determining the normal neuronal morphology, emphasizing the critical role of precise membrane lipid balance in defining the neuronal architecture. Membrane cholesterol enhancement modified neurite outgrowth but did not significantly alter polarity. Cholesterol sequestering at later stages of development has shown to enhance neurite outgrowth, whereas distinct effects for neurite development and polarity were observed at early developmental stages, signifying the relevance of precise membrane cholesterol balance in altering neuronal physiology. Our results confirm cholesterol to be a key determinant for axo-dendritic specification and neuronal architecture and emphasize the possibility to reverse neuronal developmental defects caused by cholesterol deficiency by modulating membrane cholesterol during the early developmental stages.

Highlights

The axo-dendritic specification is a defining feature for the unique architecture of neurons
We have addressed the role of membrane lipid regulation, cholesterol, in regulating neurite outgrowth and development and in determining the axo-dendritic specification at very early stages of neurite growth
A gallery of low magnification images of cells at each developmental stage is presented in Supplementary Figure 1. 3D image stacks of total volume thickness of 3 μm of Tau and Map2 labeled neurons at different stages were acquired at higher magnification (Figure 1)

Summary

Introduction

The axo-dendritic specification is a defining feature for the unique architecture of neurons. Dysregulation in the lipid balance has been correlated to diverse neurodegenerative conditions including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, Niemann Pick type C disease, and recently to cancer (Vance, 2012; Wang and Song, 2012; Leoni and Caccia, 2015; Hussain et al, 2019; Vona et al, 2021) Proteins such as amyloid precursor protein (APP) vital in the pathological outcome of neurological disorders such as AD have been recently shown to be critically involved in the cholesterol turnover for neuronal activity, supporting the importance of cholesterol homeostasis in a wider context (Pierrot et al, 2013; Grimm et al, 2017; Cho et al, 2020)

Methods

Results

Conclusion