Membrane Cholesterol Is a Critical Determinant for Hippocampal Neuronal Polarity

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.

Altered NRG1/ErbB4 signaling and cholesterol metabolism dysregulation are key pathomechanisms in VRK1-related motor neuropathies and motor neuron diseases

“…These receptors are located in specialized raft membrane microdomains with a precise lipid composition, cholesterol being one of its major components. Therefore, any disruption in cholesterol metabolism, might have consequences on axonal growth and survival, by perturbating the precise membrane lipid balance necessary to define neuronal architecture (Jose, Sivanand, & Channakeshava, 2021; Modol-Caballero et al, 2017; Rosello-Busquets et al, 2019).…”

Lipid Rafts: The Maestros of Normal Brain Development

“…Specific treatments can be applied, and the behaviour of individual cells in response to the treatment can be observed in real time. Jose et al determined the importance of cholesterol during the development and polarisation of rat hippocampal neurons [ 235 ]. Methylbetacyclodextrin (MβCD) was used to transiently deplete cholesterol from neurons in the early developmental stage.…”

“…The reduction in the length and number of neurites corresponded to the applied concentration of MβCD. On the other hand, transient replenishment with cholesterol partially reversed the effects of MβCD treatment [ 235 ]. This effect of cholesterol on neuronal polarisation could only be observed in neurons that are not in direct contact with the surrounding neurons and, thus, are not affected by synaptic signalling.…”