Translatomic analysis of regenerating and degenerating spinal motor neurons in injury and ALS

Abstract

Summary The neuromuscular junction is a synapse critical for muscle strength and coordinated motor function. Unlike CNS injuries, motor neurons mount robust regenerative responses after peripheral nerve injuries. Conversely, motor neurons selectively degenerate in diseases such as amyotrophic lateral sclerosis (ALS). To assess how these insults affect motor neurons in vivo , we performed ribosomal profiling of mouse motor neurons. Motor neuron-specific transcripts were isolated from spinal cords following sciatic nerve crush, a model of acute injury and regeneration, and in the SOD1 G93A ALS model. Of the 267 transcripts upregulated after nerve crush, 38% were also upregulated in SOD1 G93A motor neurons. However, most upregulated genes in injured and ALS motor neurons were context specific. Some of the most significantly upregulated transcripts in both paradigms were chemokines such as Ccl2 and Ccl7 , suggesting an important role for neuroimmune modulation. Collectively these data will aid in defining pro-regenerative and pro-degenerative mechanisms in motor neurons.

Deciphering the dynamic niches and regeneration-associated transcriptional program of motoneurons following peripheral nerve injury

“…We investigated six timepoints post-SNC and the naive rat with approximately a single MN resolution (a motor neuron was contained in a sample). Comparison with another study ( Shadrach et al., 2021 ) in gene expression of injured MNs and our immunostaining indicated the high quality of our data in reproducibility and accuracy. In the SNC rodent model, not all dorsal root ganglion (DRG) neurons or motoneurons are axotomized (∼50%) ( Holland et al., 2019 ; Shadrach et al., 2021 ).…”

“…Comparison with another study ( Shadrach et al., 2021 ) in gene expression of injured MNs and our immunostaining indicated the high quality of our data in reproducibility and accuracy. In the SNC rodent model, not all dorsal root ganglion (DRG) neurons or motoneurons are axotomized (∼50%) ( Holland et al., 2019 ; Shadrach et al., 2021 ). Based on clustering analysis and expression of neuronal injury marker ( Atf3 ), we could well distinguish “intact” and “injured” MNs at 1, 3, and 7 days and estimated axotomized MNs ratio were approximated to previous studies ( Holland et al., 2019 ; Shadrach et al., 2021 ).…”

“…macrophage), vascular cells, and extracellular matrix homeostasis ( Lei et al., 2012 ; Scheib and Hoke, 2013 ). A pioneering study has explored molecular change under translating in MNs using RiboTag; ChAT Cre mouse model at 7 days post-SNC ( Shadrach et al., 2021 ). However, this only covered limited mRNA forming their protein products and dynamic gene expression at the genome-wide level in MNs in the first seven days when undergoing dramatic change in gliosis and angiogenesis ( Milich et al., 2021 ; Yu et al., 2019 ) after injury is still unknown.…”

“…In the SNC rodent model, not all dorsal root ganglion (DRG) neurons or motoneurons are axotomized (∼50%) ( Holland et al., 2019 ; Shadrach et al., 2021 ). Based on clustering analysis and expression of neuronal injury marker ( Atf3 ), we could well distinguish “intact” and “injured” MNs at 1, 3, and 7 days and estimated axotomized MNs ratio were approximated to previous studies ( Holland et al., 2019 ; Shadrach et al., 2021 ). We found numerous robustly differentially expressed genes (DEGs) reported as regeneration-associated genes (RAGs) in DRG after PNI was robustly upregulated in “injured and regenerating” MNs by comparison with the naive and “intact” MNs.…”

The Role of Metals in the Neuroregenerative Action of BDNF, GDNF, NGF and Other Neurotrophic Factors

“…On the contrary, regeneration after severe acute trauma or chronic neurodegeneration from underlying neurodegenerative disease is often irreversible with a profound impact on neuromuscular functions. Thus, amyotrophic lateral sclerosis (ALS), a disease that shows selective motor neuron degeneration with typical signs including axonal damage, mitochondrial dysfunction, cytoskeletal deterioration, and muscle denervation, gave a further model system for studies on motoneurons pathophysiology [ 2 ].…”