Modeling Motor Neuron Resilience in ALS Using Stem Cells

Abstract

Summary Oculomotor neurons, which regulate eye movement, are resilient to degeneration in the lethal motor neuron disease amyotrophic lateral sclerosis (ALS). It would be highly advantageous if motor neuron resilience could be modeled in vitro . Toward this goal, we generated a high proportion of oculomotor neurons from mouse embryonic stem cells through temporal overexpression of PHOX2A in neuronal progenitors. We demonstrate, using electrophysiology, immunocytochemistry, and RNA sequencing, that in vitro- generated neurons are bona fide oculomotor neurons based on their cellular properties and similarity to their in vivo counterpart in rodent and man. We also show that in vitro- generated oculomotor neurons display a robust activation of survival-promoting Akt signaling and are more resilient to the ALS-like toxicity of kainic acid than spinal motor neurons. Thus, we can generate bona fide oculomotor neurons in vitro that display a resilience similar to that seen in vivo .

Synaptotagmin 13 is neuroprotective across motor neuron diseases

“…ALS and SMA are characterized by a selective loss of motor neurons, but OMNs that control extraocular muscles (EOMs) are resistant to degeneration in these fatal diseases [11,24,29,32,55]. Even stem cell-derived OMNs show an increased resilience to ALS-like toxicity compared to in vitro derived spinal motor neurons [3]. Identification of the cell intrinsic mechanisms responsible for this differential vulnerability could allow the development of therapies to prevent or slow down the progressive motor neuron loss.…”

Omics Approach to Axonal Dysfunction of Motor Neurons in Amyotrophic Lateral Sclerosis (ALS)

“…Among these, Nrp1 and Dbn1 are involved in axonal function, and Nek1 is a known ALS-causative gene (Brenner et al, 2016;Kenna et al, 2016;Nijssen et al, 2018). Axon-seq is an advanced technique for sequencing the RNA in axons, and thus can provide enhanced knowledge about peripheral nerve biology to explain the vulnerability/resilience of MN (Nijssen et al, 2017;Allodi et al, 2019) and to identify the treatment of MN diseases.…”

The Dual Nature of Onuf’s Nucleus: Neuroanatomical Features and Peculiarities, in Health and Disease

“…Indeed, given the peculiar characteristics of Onuf's and oculomotor MNs described above (up/down regulation of specific genes compared to spinal MNs as showed in Kaplan et al, 2014;Allodi et al, 2019), it is not surprising that these neurons respond differently in ALS compared to the other MNs, remaining resistant to degeneration until the later stages of the disease. For instance, as stated, it has been demonstrated that MMP9 is highly expressed by ALS-affected spinal MNs, whereas its expression is absent in Onuf's neurons; on the contrary, the protein OPN is selectively expressed by ALS-resistant pool, while downregulated in vulnerable MNs (Kaplan et al, 2014).…”

“…The differential vulnerability of Onuf's neurons has been initially attributed to their cytoarchitecture, connectivity, and metabolic rate (Onuf, 1899;Schrøder, 1981;Gibson et al, 1988;Shaw and Eggett, 2000). Only recently, in the XXI century, it has been evaluated by more sophisticated genetic and molecular analyses (Kaplan et al, 2014;Allodi et al, 2019).…”

“…The common pathways could underlie the joint resilience of Onuf's and oculomotor nuclei in spinal neurodegenerative diseases. For instance, MIF (macrophage migration inhibitory factor), which has been demonstrated to be neuroprotective in ALS (Shvil et al, 2018), showed a high expression both in Onuf's and oculomotor nuclei compared to the other spinal MNs (Allodi et al, 2019). Instead, among the 14 opposite-regulated genes, some are involved in neurogenesis and apoptosis regulation (Ephrin type-A receptor 7, sparc/osteonectin1), in the regulation of proteins associated with the cytoskeleton (PDZ and LIM Domain 1), in the degradation of transmembrane proteins (Rasrelated protein RAB12), in the stabilization of cell membrane potential and maintenance of intracellular pH (CLIC1) and in receptor assembly and activity (e.g., Progestin and AdipoQ Receptor Family Member 8, gamma-aminobutyric acid type A receptor alpha1 subunit, Gamma-Aminobutyric Acid Type A Receptor Subunit β1; Allodi et al, 2019).…”