ALS Along the Axons – Expression of Coding and Noncoding RNA Differs in Axons of ALS models

Abstract

Amyotrophic lateral sclerosis (ALS) is a multifactorial lethal motor neuron disease with no known treatment. Although the basic mechanism of its degenerative pathogenesis remains poorly understood, a subcellular spatial alteration in RNA metabolism is thought to play a key role. The nature of these RNAs remains elusive, and a comprehensive characterization of the axonal RNAs involved in maintaining neuronal health has yet to be described. Here, using cultured spinal cord (SC) neurons grown using a compartmented platform followed by next-generation sequencing (NGS) technology, we find that RNA expression differs between the somatic and axonal compartments of the neuron, for both mRNA and microRNA (miRNA). Further, the introduction of SOD1G93A and TDP43A315T, established ALS-related mutations, changed the subcellular expression and localization of RNAs within the neurons, showing a spatial specificity to either the soma or the axon. Altogether, we provide here the first combined inclusive profile of mRNA and miRNA expression in two ALS models at the subcellular level. These data provide an important resource for studies on the roles of local protein synthesis and axon degeneration in ALS and can serve as a possible target pool for ALS treatment.

Microglial activation in an amyotrophic lateral sclerosis-like model caused by Ranbp2 loss and nucleocytoplasmic transport impairment in retinal ganglion neurons

“…Notably, little transcriptional overlap existed between the spinal cord and human iPSC-derived motor neurons [90]. Cultured spinal motoneurons expressing mutations in SOD1 G93A and TDP43 A315T showed few alterations in transcriptional expression and an overlap of only 20 transcripts that encoded proteins mainly with predicted extracellular localization [91]. Lumbar spinal motor and oculomotor neurons, which control eye movement and are spared in ALS, showed differences in broad transcriptional profiles of over 1,700 genes some of which presumably indicate a reduced vulnerability of oculomotor neurons to excitotoxicity by enhanced GABAergic transmission [92].…”

Axon-seq decodes the motor axon transcriptome and its modulation in response to ALS

“…While these are excellent tools for separating axons from somas, residual crosscontamination between the compartments still occurs. In this way, RNA-sequencing efforts aimed at isolating an axonal transcriptome profile (Briese et al, 2016;Gumy et al, 2011;Minis et al, 2014;Rotem et al, 2017;Saal et al, 2014;Taylor et al, 2009) can be easily undermined by a failure to carefully examine the purity of axonal fractions. Due to unappreciated technical difficulties, which are not always acknowledged, axonal fractions can be contaminated with other cellular components or non-neuronal cells.…”

To the end of the line: Axonal mRNA transport and local translation in health and neurodegenerative disease

“…In a recent study, RNA‐Seq of mutant TDP‐43 (TDP‐43 A315T ) motor neuron axonal samples identified numerous dysregulated mRNAs. Similar to changes seen when SMN protein is lost, TDP‐43 mutation driven alterations in the axonal transcriptome resulted in depletion of mRNAs encoding proteins involved in synapse assembly and axon extension (Rotem et al, ). This similarity in axonal transcriptome changes mirrors the similarity in disease pathology between SMA and ALS.…”